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Title: Pleasant Ways in Science
Author: Proctor, Richard A. (Richard Anthony)
Language: English
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PLEASANT WAYS IN SCIENCE.
WORKS BY RICHARD A. PROCTOR.
LIGHT SCIENCE FOR LEISURE HOURS: Familiar Essays on Scientific
Subjects. Crown 8vo, 3_s._ 6_d._
THE ORBS AROUND US: A Series of Essays on the Moon and Planets,
Meteors and Comets. With Charts and Diagrams. Crown 8vo, 3_s._
6_d._
OTHER WORLDS THAN OURS: The Plurality of Worlds Studied under the
Light of Recent Scientific Researches. With 14 Illustrations.
Crown 8vo, 3_s._ 6_d._
OTHER SUNS THAN OURS: A Series of Essays on Suns—Old, Young, and
Dead. With other Science Gleanings. Two Essays on Whist, and
Correspondence with Sir John Herschel. With 9 Star Maps and
Diagrams. Cr. 8vo, 3_s._ 6_d._
THE MOON: Her Motions, Aspects, Scenery, and Physical Condition.
With Plates, Charts, Woodcuts, &c. Crown 8vo, 3_s._ 6_d._
UNIVERSE OF STARS: Presenting Researches into and New Views
respecting the Constitution of the Heavens. With 22 Charts and
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LARGER STAR ATLAS for the Library, in 12 Circular Maps, with
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HALF-HOURS WITH THE STARS: A Plain and Easy Guide to the
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throughout the Year. With Introduction and a separate
Explanation of each Map. True for every Year. 4to, 3_s._ net.
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THE STARS IN THEIR SEASONS: An Easy Guide to a Knowledge of the
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THE SOUTHERN SKIES: A Plain and Easy Guide to the Constellations
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ROUGH WAYS MADE SMOOTH: Familiar Essays on Scientific Subjects.
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OUR PLACE AMONG INFINITIES: A Series of Essays contrasting our
Little Abode in Space and Time with the Infinities around us.
Crown 8vo, 3_s._ 6_d._
THE EXPANSE OF HEAVEN: Essays on the Wonders of the Firmament.
Crown 8vo, 3s. 6_d._
THE GREAT PYRAMID: OBSERVATORY, TOMB, AND TEMPLE. With
Illustrations. Crown 8vo, 5_s._
PLEASANT WAYS IN SCIENCE. Crown 8vo, 3_s._ 6_d._
MYTHS AND MARVELS OF ASTRONOMY. Crown 8vo, 3_s._ 6_d._
NATURE STUDIES. By GRANT ALLEN, A. WILSON, T. FOSTER, E. CLODD,
and R. A. PROCTOR. Crown 8vo, 3_s._ 6_d._
LEISURE READINGS. By E. CLODD, A. WILSON, T. FOSTER, A. C.
RANYARD, and R. A. PROCTOR. Crown 8vo, 5_s._ Cheap Edition,
3_s._ 6_d._
STRENGTH: How to Get Strong and Keep Strong. With Chapters
on Rowing and Swimming, Fat, Age, and the Waist. With 9
Illustrations. Crown 8vo, 2_s._
CHANCE AND LUCK: A Discussion of the Laws of Luck, Coincidences,
Wagers, Lotteries, and the Fallacies of Gambling, &c. Crown
8vo, 2_s._ 6_d._
HOW TO PLAY WHIST: With the Laws and Etiquette of Whist. Crown
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HOME WHIST: An Easy Guide to Correct Play. 16mo, 1_s._
LONDON: LONGMANS, GREEN, & CO.
PLEASANT WAYS
IN SCIENCE
BY
RICHARD A. PROCTOR
AUTHOR OF
“ROUGH WAYS MADE SMOOTH,” “THE EXPANSE OF HEAVEN,” “OUR PLACE
AMONG INFINITIES,” “MYTHS AND MARVELS OF ASTRONOMY,”
ETC. ETC.
_NEW IMPRESSION_
LONGMANS, GREEN, AND CO.
39 PATERNOSTER ROW, LONDON
NEW YORK AND BOMBAY
1905
CONTENTS.
PAGE
OXYGEN IN THE SUN 1
SUN-SPOT, STORM, AND FAMINE 28
NEW WAYS OF MEASURING THE SUN’S DISTANCE 56
DRIFTING LIGHT WAVES 77
THE NEW STAR WHICH FADED INTO STAR-MIST 106
STAR-GROUPING, STAR-DRIFT, AND STAR-MIST 136
MALLET’S THEORY OF VOLCANOES 151
TOWARDS THE NORTH POLE 156
A MIGHTY SEA-WAVE 178
STRANGE SEA CREATURES 199
ON SOME MARVELS IN TELEGRAPHY 232
THE PHONOGRAPH, OR VOICE-RECORDER 274
THE GORILLA AND OTHER APES 296
THE USE AND ABUSE OF FOOD 330
OZONE 347
DEW 357
THE LEVELLING POWER OF RAIN 367
ANCIENT BABYLONIAN ASTROGONY 388
PREFACE.
It is very necessary that all who desire to become really proficient in
any department of science should follow the beaten track, toiling more
or less painfully over the difficult parts of the high road which is
their only trustworthy approach to the learning they desire to attain.
But there are many who wish to learn about scientific discoveries
without this special labour, for which some have, perhaps, little
taste, while many have scant leisure. My purpose in the present work,
as in my “Light Science for Leisure Hours,” the “Myths and Marvels of
Astronomy,” the “Borderland of Science,” and “Science Byways,” has been
to provide paths of easy access to the knowledge of some of the more
interesting discoveries, researches, or inquiries of the science of
the day. I wish it to be distinctly understood that my purpose is to
interest rather than to instruct, in the strict sense of the word. But
I may add that it seems to me even more necessary to be cautious, and
accurate in such a work as the present than in advanced treatises. For
in a scientific work the reasoning which accompanies the statements
of fact affords the means of testing and sometimes of correcting
such statements. In a work like the present, where explanation and
description take the place of reasoning, there is no such check. For
this reason I have been very careful in the accounts which I have given
of the subjects here dealt with. I have been particularly careful not
to present, as established truths, such views as are at present only
matters of opinion.
The essays in the present volume are taken chiefly from the
_Contemporary Review_, the _Gentleman’s Magazine_, the _Cornhill
Magazine_, _Belgravia_, and _Chambers’ Journal_. The sixth, however,
presents the substance (and official report) of a lecture which I
delivered at the Royal Institution in May, 1870. It was then that I
first publicly enunciated the views respecting the stellar universe
which I afterwards more fully stated in my “Universe of Stars.” The
same views have also been submitted to the Paris Academy of Science, as
the results of his own investigations, by M. Flammarion, in words which
read almost like translations of passages in the above-mentioned essay.
RICHARD A. PROCTOR.
PLEASANT WAYS IN SCIENCE.
_OXYGEN IN THE SUN._
The most promising result of solar research since Kirchhoff in 1859
interpreted the dark lines of the sun’s spectrum has recently been
announced from America. Interesting in itself, the discovery just made
is doubly interesting in what it seems to promise in the future. Just
as Kirchhoff’s great discovery, that a certain double dark line in the
solar spectrum is due to the vapour of sodium in the sun’s atmosphere,
was but the first of a long series of results which the spectroscopic
analysis of the sun was to reveal, so the discovery just announced that
a certain important gas—the oxygen present in our air and the chief
chemical constituent of water—shows its presence in the sun by bright
lines instead of dark, will in all probability turn out to be but the
firstfruits of a new method of examining the solar spectrum. As its
author, Dr. Henry Draper, of New York, remarks, further investigation
in the direction he has pursued will lead to the discovery of other
elements in the sun, but it was not “proper to conceal, for the sake
of personal advantage, the principle on which such researches are to
be conducted.” It may well happen, though I anticipate otherwise, that
by thus at once describing his method of observation, Dr. Draper may
enable others to add to the list of known solar elements some which
yet remain to be detected; but if Dr. Draper should thus have added but
one element to that list, he will ever be regarded as the physicist
to whose acumen the method was due by which all were detected, and to
whom, therefore, the chief credit of their discovery must certainly be
attributed.
I propose briefly to consider the circumstances which preceded the
great discovery which it is now my pleasing duty to describe, in order
that the reader may the more readily follow the remarks by which I
shall endeavour to indicate some of the results which seem to follow
from the discovery, as well as the line along which, in my opinion, the
new method may most hopefully be followed.
It is generally known that what is called the spectroscopic method
of analyzing the sun’s substance had its origin in Kirchhoff’s
interpretation of the dark lines in the solar spectrum. Until
1859 these dark lines had not been supposed to have any special
significance, or rather it had not been supposed that their
significance, whatever it might be, could be interpreted. A physicist
of some eminence spoke of these phenomena in 1858 in a tone which ought
by the way seldom to be adopted by the man of science. “The phenomena
defy, as we have seen,” he said, “all attempts hitherto to reduce them
within empirical laws, and no complete explanation or theory of them is
possible. All that theory can be expected to do is this—it may explain
how dark lines of any sort may arise within the spectrum.” Kirchhoff,
in 1859, showed not only how dark lines of any sort may appear, but how
and why they do appear, and precisely what they mean. He found that
the dark lines of the solar spectrum are due to the vapours of various
elements in the sun’s atmosphere, and that the nature of such elements
may be determined from the observed position of the dark lines. Thus
when iron is raised by the passage of the electric spark to so intense
a degree of heat that it is vaporized, the light of the glowing
vapour of iron is found to give a multitude of bright lines along the
whole length of the spectrum—that is, some red, some orange, some
yellow, and so on. In the solar spectrum corresponding dark lines are
found along the whole length of the spectrum—that is, some in the
red, some in the orange, yellow, etc., and precisely in those parts
of these various spectral regions which the bright lines of glowing
iron would occupy. Multitudes of other dark lines exist of course in
the solar spectrum. But those corresponding to the bright lines of
glowing iron are unquestionably there. They are by no means lost in
the multitude, as might be expected; but, owing to the peculiarity of
their arrangement, strength, etc., they are perfectly recognizable as
the iron lines reversed, that is, dark instead of bright. Kirchhoff’s
researches showed how this is to be interpreted. It means that the
vapour of iron exists in the atmosphere of the sun, glowing necessarily
with an intensely bright light; _but_, being cooler (however intensely
hot) than the general mass of the sun within, the iron vapour absorbs
more light than it emits, and the result is that the iron lines,
instead of appearing bright, as they would if the iron vapour alone
were shining, appear relatively dark on the bright rainbow-tinted
background of the solar spectrum.
Thus was it shown that in the atmosphere of the sun there is the
glowing vapour of the familiar metal, iron; and in like manner other
metals, and one element (hydrogen) which is not ordinarily regarded as
a metal, were shown to be present in the sun’s atmosphere. In saying
that they are present in the sun’s atmosphere, I am, in point of fact,
saying that they are present in the sun; for the solar atmosphere is,
in fact, the outer part of the sun himself, since a very large part,
if not by far the greater part, of the sun’s mass must be vaporous.
But no other elements, except the metals iron, sodium, barium,
calcium, magnesium, aluminium, manganese, chromium, cobalt, nickel,
zinc, copper, and titanium, and the element hydrogen, were shown
to be present in the sun, by this method of observing directly the
solar dark lines. In passing, I may note that there are reasons for
regarding hydrogen as a metallic element, strange though the idea may
seem to those who regard hardness, brightness, malleability, ductility,
plasticity, and the like, as the characteristic properties of metals,
and necessarily fail to comprehend how a gas far rarer, under the
same conditions, than the air we breathe, and which cannot possibly
be malleable, ductile, or the like, can conceivably be regarded as a
metal. But there is in reality no necessary connection between any one
of the above properties and the metallic nature; many of the fifty-five
metals are wanting in all of these properties; nor is there any reason
why, as we have in mercury a metal which at ordinary temperatures is a
liquid, so we might have in hydrogen a metal which, at all obtainable
temperatures, and under all obtainable conditions of pressure, is
gaseous. It was shown by the late Professor Graham (aided in his
researches most effectively by Dr. Chandler Roberts) that hydrogen will
enter into such combination with the metal palladium that it may be
regarded as forming, for the time, with the palladium, an alloy; and
as alloys can only be regarded as compounds of two or more metals, the
inference is that hydrogen is in reality a metallic element.
Fourteen only of the elements known to us, or less than a quarter
of the total number, were thus found to be present in the sun’s
constitution; and of these all were metals, if we regard hydrogen as
metallic. Neither gold nor silver shows any trace of its presence,
nor can any sign be seen of platinum, lead, and mercury. But, most
remarkable of all, and most perplexing, was the absence of all trace
of oxygen and nitrogen, two gases which could not be supposed wanting
in the substance of the great ruling centre of the planetary system.
It might well be believed, indeed, that none of the five metals just
named are absent from the sun, and indeed that every one of the
forty metals not recognized by the spectroscopic method nevertheless
exists in the sun. For according to the nebular hypothesis of the
origin of our solar system, the sun might be expected to contain all
the elements which exist in our earth. Some of these elements might
indeed escape discovery, because existing only in small quantities;
and others (as platinum, gold, and lead, for example), because but a
small portion of their vaporous substance rose above the level of that
glowing surface which is called the photosphere. But that oxygen, which
constitutes so large a portion of the solid, liquid, and vaporous mass
of our earth, should not exist in enormous quantities, and its presence
be very readily discernable, seemed amazing indeed. Nitrogen, also,
might well be expected to be recognizable in the sun. Carbon, again,
is so important a constituent of the earth, that we should expect to
discover clear traces of its existence in the sun. In less degree,
similar considerations apply to sulphur, boron, silicon, and the other
non-metallic elements.
It was not supposed, however, by any one at all competent to form an
opinion on the subject, that oxygen, nitrogen, and carbon are absent
from the sun. It was perceived that an element might exist in enormous
quantities in the substance of the sun, and yet fail to give any
evidence of its presence, or only give such evidence as might readily
escape recognition. If we remember how the dark lines are really
caused, we shall perceive that this is so. A glowing vapour in the
atmosphere of the sun absorbs rays of the same colour as it emits. If
then, it is cooler than the glowing mass of the sun which it enwraps,
and if, notwithstanding the heat received from this mass, it remains
cooler, then it suffers none of those rays to pass earthwards.[1] It
emits rays of the same kind (that is, of the same _colour_) itself,
but, being cooler, the rays thus coming from it are feebler; or, to
speak more correctly, the ethereal waves thus originated are feebler
than those of the same order which _would_ have travelled earthwards
from the sun but for the interposed screen of vapour. Hence the
corresponding parts of the solar spectrum are less brilliant, and
contrasted with the rainbow-tinted streak of light, on which they lie
as on a background, they appear dark.
In order, then, that any element may be detected by its dark lines, it
is necessary that it should lie as a vaporous screen between the more
intensely heated mass of the sun and the eye of the observer on earth.
It must then form an enclosing envelope cooler than the sun within it.
Or rather, some part of the vapour must be thus situated. For enormous
masses of the vapour might be within the photospheric surface of the
sun at a much higher temperature, which yet, being enclosed in the
cooler vaporous shell of the same substance, would not be able to send
its light rays earthwards. One may compare the state of things, so
far as that particular element is concerned, to what is presented in
the case of a metallic globe cooled on the outside but intensely hot
within. The cool outside of such a globe is what determines the light
and heat received from it, so long as the more heated mass within has
not yet (by conduction) warmed the exterior shell. So in the case of
a vapour permeating the entire mass, perhaps, of the sun, and at as
high a temperature as the sun everywhere except on the outside: it is
the temperature of the outermost part of such a vaporous mass which
determines the intensity of the rays received from it—or in other
words, determines whether the corresponding parts of the spectrum shall
be darker or not than the rest of the spectrum. If the vapour does
not rise above the photosphere of the sun in sufficient quantity to
exercise a recognizable absorptive effect, its presence in the sun will
not be indicated by any dark lines.
I dwell here on the question of quantity, which is sometimes overlooked
in considering the spectroscopic evidence of the sun’s condition, but
is in reality a very important factor in determining the nature of the
evidence relating to each element in the solar mass. In some cases,
the quantity of a material necessary to give unmistakable spectroscopic
evidence is singularly small; insomuch that new elements, as thallium,
cæsium, rubidium, and gallium, have been actually first recognized
by their spectral lines when existing in such minute quantities in
the substances examined as to give no other trace whatever of their
existence. But it would be altogether a mistake to suppose that some
element existing in exceedingly small quantities, or, more correctly,
existing in the form of an exceedingly rare vapour in the sun’s
atmosphere, would be detected by means of its dark lines, or _by any
other method depending on the study of the solar spectrum_. When we
place a small portion of some substance in the space between the carbon
points of an electric lamp, and volatilize that substance in the
voltaic arc, we obtain a spectrum including all the bright lines of the
various elements contained in the substance; and if some element is
contained in it in exceedingly small quantity, we may yet perceive its
distinctive bright lines among the others (many of them far brighter)
belonging to the elements present in greater quantities. But if we have
(for example) a great mass of molten iron, the rainbow-tinted spectrum
of whose light we examine from a great distance, and if a small
quantity of sodium, or other substance which vaporizes at moderate
temperatures, be cast into the molten iron so that the vapour of the
added element presently rises above the glowing surface of the iron,
no trace of the presence of this vapour would be shown in the spectrum
observed from a distance. The part of the spectrum where the dark lines
of sodium usually appear would, undoubtedly, be less brilliant than
before, in the same sense that the sun may be said to be less brilliant
when the air is in the least degree moist than when it is perfectly
dry; but the loss of brilliancy is as utterly imperceptible in the one
case as it is in the other. In like manner, a vapour might exist in
the atmosphere of the sun (above the photosphere, that is), of whose
presence not a trace would be afforded in the spectroscope, for the
simple reason that the absorptive action of the vapour, though exerted
to reduce the brightness of particular solar rays or tints, would not
affect those rays sufficiently for the spectroscopist to recognize any
diminution of their lustre.
There is another consideration, which, so far as I know, has not
hitherto received much attention, but should certainly be taken into
account in the attempt to interpret the real meaning of the solar
spectrum. Some of the metals which are vaporized by the sun’s heat
below the photosphere may become liquid or even solid at or near the
level of the photosphere. Even though the heat at the level of the
photosphere may be such that, under ordinary conditions of pressure and
so forth, such metals would be vaporous, the enormous pressure which
must exist not far below the level of the photosphere may make the
heat necessary for complete vaporization far greater than the actual
heat at that level. In that case the vapour will in part condense into
liquid globules, or, if the heat is considerably less than is necessary
to keep the substance in the form of vapour, then it may in part be
solidified, the tiny globules of liquid metal becoming tiny crystals
of solid metal. We see both conditions fulfilled within the limits of
our own air in the case of the vapour of water. Low down the water
is present in the air (ordinarily) in the form of pure vapour; at a
higher level the vapour is condensed by cold into liquid drops forming
visible clouds (cumulus clouds), and yet higher, where the cold is
still greater, the minute water-drops turn into ice-crystals, forming
those light fleecy clouds called cirrus clouds by the meteorologist.
Now true clouds of either sort may exist in the solar atmosphere even
above that photospheric level which forms the boundary of the sun we
see. It may be said that the spectroscope, applied to examine matter
outside the photosphere, has given evidence only of vaporous cloud
masses. The ruddy prominences which tower tens of thousands of miles
above the surface of the sun, and the sierra (or as it is sometimes
unclassically called, the chromosphere) which covers usually the
whole of the photosphere to a depth of about eight thousand miles,
show only, under spectroscopic scrutiny, the bright lines indicating
gaseity. But though this is perfectly true, it is also true that we
have not here a particle of evidence to show that clouds of liquid
particles, and of tiny crystals, may not float over the sun’s surface,
or even that the ruddy clouds shown by the spectroscope to shine with
light indicative of gaseity may not also contain liquid and crystalline
particles. For in point of fact, the very principle on which our
recognition of the bright lines depends involves the inference that
matter whose light would _not_ be resolved into bright lines would
not be recognizable at all. The bright lines are seen, because by
means of a spectroscope we can throw them far apart, without reducing
their lustre, while the background of rainbow-tinted spectrum has its
various portions similarly thrown further apart and correspondingly
weakened. One may compare the process (the comparison, I believe, has
not hitherto been employed) to the dilution of a dense liquid in which
solid masses have been floating: the more we increase the quantity of
the liquid in diluting it with water, the more transparent it becomes,
but the solid masses in it are not changed, so that we only have to
dilute the liquid sufficiently to see these masses. _But_ if there were
in the interstices of the solid masses particles of some substance
which dissolved in the water, we should not recognize the presence of
this substance by any increase in its visibility; for the very same
process which thinned the liquid would thin this soluble substance in
the same degree. In like manner, by dispersing and correspondingly
weakening the sun’s light more and more, we can recognize the light of
the gaseous matter in the prominences, for this is not weakened; but if
the prominences also contain matter in the solid or liquid form (that
is, drops or crystals), the spectroscopic method will not indicate the
presence of such matter, for the spectrum of matter of this sort will
be weakened by dispersion in precisely the same degree that the solar
spectrum itself is weakened.
It is easy to see how the evidence of the presence of any element
which behaved in this way would be weakened, if we consider what would
happen in the case of our own earth, according as the air were simply
moist but without clouds, or loaded with cumulus masses but without
cirrus clouds, or loaded with cirrus clouds. For although there is not
in the case of the earth a central glowing mass like the sun’s, on
whose rainbow-tinted spectrum the dark lines caused by the absorptive
action of our atmosphere could be seen by the inhabitant of some
distant planet studying the earth from without, yet the sun’s light
reflected from the surface of the earth plays in reality a similar
part. It does not give a simple rainbow-tinted spectrum; for, being
sunlight, it shows all the dark lines of the solar spectrum: but the
addition of new dark lines to these, in consequence of the absorptive
action of the earth’s atmosphere, could very readily be determined. In
fact, we do thus recognize in the spectra of Mars, Venus, and other
planets, the presence of aqueous vapour in their atmosphere, despite
the fact that our own air, containing also aqueous vapour, naturally
renders so much the more difficult the detection of that vapour in the
atmosphere of remote planets necessarily seen through our own air.
Now, a distant observer examining the light of our own earth on a day
when, though the air was moist, there were no clouds, would have ample
evidence of the presence of the vapour of water; for the light which he
examined would have gone twice through our earth’s atmosphere, from its
outermost thinnest parts to the densest layers close to the surface,
then back again through the entire thickness of the air. But if the
air were heavily laden with cumulus clouds (without any cirrus clouds
at a higher layer), although _we_ should know that there was abundant
moisture in the air, and indeed much more moisture then there had been
when there had been no clouds, our imagined observer would either
perceive no traces at all of this moisture, or he would perceive traces
so much fainter than when the air was clear that he would be apt to
infer that the air was either quite dry, or at least very much drier
than it had been in that case. For the light which he would receive
from the earth would not in this case have passed through the entire
depth of moisture-laden air twice, but twice only through that portion
of the air which lay above the clouds, at whose surface the sun’s light
would be reflected. The whole of the moisture-laden layer of the air
would be snugly concealed under the cloud-layer, and would exercise
no absorptive action whatever on the light which the remote observer
would examine. If from the upper surface of the layer of cumulus clouds
aqueous vapour rose still higher, and were converted in the cold upper
regions of the atmosphere into clouds of ice-crystals, the distant
observer would have still less chance of recognizing the presence of
moisture in our atmosphere. For the layer of air between the cumulus
clouds and the cirrus clouds would be unable to exert any absorptive
action on the light which reached the observer. All such light would
come to him after reflection from the layer of cirrus clouds. He would
be apt to infer that there was no moisture at all in the air of our
planet, at the very time when in fact there was so much moisture that
not one layer only, but two layers of clouds enveloped the earth, the
innermost layer consisting of particles of liquid water, the outermost
of particles of frozen water. Using the words ice, water, and steam,
to represent the solid, liquid, and vaporous states of water, we may
fairly say that ice and water, by hiding steam, would persuade the
remote observer that there was no water at all on the earth—at least
if he trusted solely to the spectroscopic evidence then obtained.[2]
We might in like manner fail to obtain any spectroscopic evidence of
the presence of particular elements in the sun, because they do not
exist in sufficient quantity in the vaporous form in those outer layers
which the spectroscope can alone deal with.
In passing, I must note a circumstance in which some of those who have
dealt with this special part of the spectroscopic evidence have erred.
It is true in one sense that some elements may be of such a nature that
their vapours cannot rise so high in the solar atmosphere as those of
other elements. But it must not be supposed that the denser vapours
seek a lower level, the lighter vapours rising higher. According to
the known laws of gaseous diffusion, a gas or vapour diffuses itself
throughout a space occupied by another gas or several other gases,
in the same way as though the space were not occupied at all. If we
introduce into a vessel full of common air a quantity of carbonic
acid gas (I follow the older and more familiar nomenclature), this
gas, although of much higher specific gravity than either oxygen or
nitrogen, does not take its place at the bottom of the vessel, but so
diffuses itself that the air of the upper part of the vessel contains
exactly the same quantity of carbonic acid gas as the air of the
lower part. Similarly, if hydrogen is introduced, it does not seek
the upper part of the vessel, but diffuses itself uniformly throughout
the vessel. If we enclose the carbonic acid gas in a light silken
covering, and the hydrogen in another (at the same pressure as the air
in the vessel) one little balloon will sink and the other will rise;
but this is simply because diffusion is prevented. It may be asked
how this agrees with what I have said above, that some elements may
not exist in sufficient quantity or in suitable condition above the
sun’s photospheric level to give any spectroscope evidence of their
nature. As to quantity, indeed, the answer is obvious: if there is only
a small quantity of any given element in the entire mass of the sun,
only a very small quantity can under any circumstances exist outside
the photosphere. As regards condition, it must be remembered that the
vessel of my illustrative case was supposed to contain air at a given
temperature and pressure throughout. If the vessel was so large that
in different parts of it the temperature and pressure were different,
the diffusion would, indeed, still be perfect, because at all ordinary
temperatures and pressures hydrogen and carbonic acid gas remain
gaseous. But if the vapour introduced is of such a nature that at
moderate temperatures and pressures it condenses, wholly or in part, or
liquefies, the diffusion will not take place with the same uniformity.
We need not go further for illustration than to the case of our own
atmosphere as it actually exists. The vapour of water spreads uniformly
through each layer of the atmosphere which is at such a temperature
and pressure as to permit of such diffusion; but where the temperature
is too low for complete diffusion (at the actual pressure) the aqueous
vapour is condensed into visible cloud, diffusion being checked at
this point as at an impassable boundary. In the case of the sun, as
in the case of our own earth, it is not the density of an element
when in a vaporous form which limits its diffusion, but the value
of the temperature at which its vapour at given pressure condenses
into liquid particles. It is in this way only that any separation can
be effected between the various elements which exist in the sun’s
substance. A separation of this sort is unquestionably competent to
modify the spectroscopic evidence respecting different elements. But
it would be a mistake to suppose that any such separation could occur
as has been imagined by some—a separation causing in remote times
the planets supposed to have been thrown off by the sun to be rarest
on the outskirts of the solar system and densest close to the sun.
The small densities of the outer family of planets, as compared with
the densities of the so-called terrestrial planets, must certainly be
otherwise explained.
But undoubtedly the chief circumstance likely to operate in veiling
the existence of important constituents of the solar mass must be that
which has so long prevented spectroscopists from detecting the presence
of oxygen in the sun. An element may exist in such a condition, either
over particular parts of the photosphere, or over the entire surface
of the sun, that instead of causing dark lines in the solar spectrum
it may produce bright lines. Such lines may be conspicuous, or they
may be so little brighter than the background of the spectrum as to be
scarcely perceptible or quite imperceptible.
In passing, I would notice that this interpretation of the want of all
spectroscopic evidence of the presence of oxygen, carbon, and other
elements in the sun, is not an _ex post facto_ explanation. As will
presently appear, it is now absolutely certain that oxygen, though
really existing, and doubtless, in enormous quantities, in the sun, has
been concealed from recognition in this way. But that this might be so
was perceived long ago. I myself, in the first edition of my treatise
on “The Sun,” pointed out, in 1870, with special reference to nitrogen
and oxygen, that an element “may be in a condition enabling it to
radiate as much light as it absorbs, or else very little more or very
little less; so that it either obliterates all signs of its existence,
or else gives lines so little brighter or darker than the surrounding
parts of the spectrum that we can detect no trace of its existence.”
I had still earlier given a similar explanation of the absence of all
spectroscopic evidence of hydrogen in the case of the bright star
Betelgeux.[3]
Let us more closely consider the significance of what we learn from
the spectral evidence respecting the gas hydrogen. We know that when
the total light of the sun is dealt with, the presence of hydrogen is
constantly indicated by dark lines. In other words, regarding the sun
as a whole, hydrogen constantly reduces the emission of rays of those
special tints which correspond to the light of this element. When we
examine the light of other suns than ours, we find that in many cases,
probably in by far the greater number of cases, hydrogen acts a similar
part. But not in every case. In the spectra of some stars, notably in
those of Betelgeux and Alpha Herculis, the lines of hydrogen are not
visible at all; while in yet others, as Gamma Cassiopeiæ, the middle
star of the five which form the straggling W of this constellation,
the lines of hydrogen show bright upon the relatively dark background
of the spectrum. When we examine closely the sun himself, we find that
although his light as a whole gives a spectrum in which the lines of
hydrogen appear dark, the light of particular parts of his surface,
if separately examined, occasionally shows the hydrogen lines bright
as in the spectrum of Gamma Cassiopeiæ, while sometimes the light of
particular parts gives, like the light of Betelgeux, no spectroscopic
evidence whatever of the presence of hydrogen. Manifestly, if the whole
surface of the sun were in the condition of the portions which give
bright hydrogen lines, the spectrum of the sun would resemble that of
Gamma Cassiopeiæ; while if the whole surface were in the condition of
those parts which show no lines of hydrogen, the spectrum of the sun
would resemble that of Betelgeux. Now if there were any reason for
supposing that the parts of the sun which give no lines of hydrogen
are those from which the hydrogen has been temporarily removed in some
way, we might reasonably infer that in the stars whose spectra show no
hydrogen lines there is no hydrogen. But the fact that the hydrogen
lines are sometimes seen bright renders this supposition untenable.
For we cannot suppose that the lines of hydrogen change from dark
to bright or from bright to dark (both which changes certainly take
place) without passing through a stage in which they are neither bright
nor dark; in other words, we are compelled to assume that there is
an intermediate condition in which the hydrogen lines, though really
existent, are invisible because they are of precisely the same lustre
as the adjacent parts of the spectrum. Hence the evanescence of the
hydrogen lines affords no reason for supposing that hydrogen has become
even reduced in quantity where the lines are not seen. And therefore
it follows that the invisibility of the hydrogen lines in the spectrum
of Betelgeux is no proof that hydrogen does not exist in that star in
quantities resembling those in which it is present in the sun. And
this, being demonstrated in the case of one gas, must be regarded as
at least probable in the case of other gases. Wherefore the absence of
the lines of oxygen from the spectrum of any star affords no sufficient
reason for believing that oxygen is not present in that star, or that
it may not be as plentifully present as hydrogen, or even far more
plentifully present.
There are other considerations which have to be taken into account, as
well in dealing with the difficulty arising from the absence of the
lines of particular elements from the solar spectrum as in weighing the
extremely important discovery which has just been effected by Dr. H.
Draper.
I would specially call attention now to a point which I thus presented
seven years ago:—“The great difficulty of interpreting the results
of the spectroscopic analysis of the sun arises from the circumstance
that we have no means of learning whence that part of the light comes
which gives the continuous spectrum. When we recognize certain dark
lines, we know certainly that the corresponding element exists in the
gaseous form at a lower temperature than the substance which gives the
continuous spectrum. But as regards that continuous spectrum itself
we can form no such exact opinion.” It might, for instance, have
its origin in glowing liquid or solid matter; but it might also be
compounded of many spectra, each containing a large number of bands,
the bands of one spectrum filling up the spaces which would be left
dark between the bands of another spectrum, and so on until the entire
range from the extreme visible red to the extreme visible violet were
occupied by what appeared as a continuous rainbow-tinted streak. “We
have, in fact, in the sun,” as I pointed out, “a vast agglomeration
of elements, subject to two giant influences, producing in some sort
opposing effects—viz., a temperature far surpassing any we can form
any conception of, and a pressure (throughout nearly the whole of
the sun’s globe) which is perhaps even more disproportionate to the
phenomena of our experience. Each known element would be vaporized by
the solar temperature at known pressures; each (there can be little
question) would be solidified by the vast pressures, did these arise
at known temperatures. Now whether, under these circumstances, the
laws of gaseous diffusion prevail where the elements _are_ gaseous in
the solar globe; whether, where liquid matter exists it is in general
bounded in a definite manner from the neighbouring gaseous matter;
whether any elements at all are solid, and if so under what conditions
their solidity is maintained and the limits of the solid matter
defined—all these are questions which _must_ be answered before we
can form a satisfactory idea of the solar constitution; yet they are
questions which we have at present no means of answering.” Again, we
require to know whether any process resembling combustion can under
any circumstances take place in the sun’s globe. If we could assume
that some general resemblance exists between the processes at work upon
the sun and those we are acquainted with, we might imagine that the
various elements ordinarily exist in the sun’s globe in the gaseous
form (chiefly) to certain levels, to others chiefly in the liquid form,
and to yet others chiefly in the solid form. But even then that part
of each element which is gaseous may exist in two forms, having widely
different spectra (in reality in five, but I consider only the extreme
forms). The light of one part is capable of giving characteristic
spectra of lines or bands (which will be different according to
pressure and may appear either dark or bright); that of the other is
capable of giving a spectrum nearly or quite continuous.
It will be seen that Dr. H. Draper’s discovery supplies an answer to
one of the questions, or rather to one of the sets of questions, thus
indicated. I give his discovery as far as possible in his own words.
“_Oxygen discloses itself_,” he says, “_by bright lines or bands in
the solar spectrum_, and does not give dark absorption-lines like the
metals. We must therefore change our theory of the solar spectrum,
and no longer regard it merely as a continuous spectrum with certain
rays absorbed by a layer of ignited metallic vapours, but as having
also bright lines and bands superposed on the background of continuous
spectrum. Such a conception not only opens the way to the discovery
of others of the non-metals, sulphur, phosphorus, selenium, chlorine,
bromine, iodine, fluorine, carbon, etc., but also may account for some
of the so-called dark lines, by regarding them as intervals between
bright lines. It must be distinctly understood that in speaking of the
solar spectrum here, I do not mean the spectrum of any limited area
upon the disc or margin of the sun, but the spectrum of light from the
whole disc.”
In support of the important statement here advanced, Dr. Draper submits
a photograph of part of the solar spectrum with a comparison spectrum
of air, and also with some of the lines of iron and aluminium. The
photograph itself, a copy of which, kindly sent to me by Dr. Draper,
lies before me as I write, fully bears out Dr. Draper’s statement. It
is absolutely free from handwork or retouching, except that reference
letters have been added in the negative. It shows the part of the solar
spectrum between the well-known Fraunhofer lines G and H, of which G
(an iron line) lies in the indigo, and H (a line of hydrogen) in the
violet, so that the portion photographed belongs to that region of
the spectrum whose chemical or actinic energy is strongest. Adjacent
to this lies the photograph of the air lines, showing nine or ten
well-defined oxygen lines or groups of lines, and two nitrogen bands.
The exact agreement of the two spectra in position is indicated by
the coincidence of bright lines of iron and aluminium included in the
air spectrum with the dark lines of the same elements in the solar
spectrum. “No close observation,” as Dr. Draper truly remarks, “is
needed to demonstrate to even the most casual observer” (of this
photograph) “that the oxygen lines are found in the sun as bright
lines.” There is in particular one quadruple group of oxygen lines in
the air spectrum, the coincidence of which with a group of bright lines
in the solar spectrum is unmistakable.
“This oxygen group alone is almost sufficient,” says Dr. Draper, “to
prove the presence of oxygen in the sun, for not only does each of
the four components have a representative in the solar group, but the
relative strength and the general aspect of the lines in each case is
similar.[4] I shall not attempt at this time,” he proceeds, “to give
a complete list of the oxygen lines, ... and it will be noticed that
some lines in the air spectrum which have bright anologues in the sun
are not marked with the symbol of oxygen. This is because there has not
yet been an opportunity to make the necessary detailed comparisons. In
order to be certain that a line belongs to oxygen, I have compared,
under various pressures, the spectra of air, oxygen, nitrogen, carbonic
acid, carburetted hydrogen, hydrogen, and cyanogen.
“As to the spectrum of nitrogen and the existence of this element in
the sun there is not yet certainty. Nevertheless, even by comparing
the diffused nitrogen lines of this particular photograph, in which
nitrogen has been sacrificed to get the best effect for oxygen, the
character of the evidence appears. There is a triple band somewhat
diffused in the photograph belonging to nitrogen, which has its
appropriate representative in the solar spectrum, and another band of
nitrogen is similarly represented.” Dr. Draper states that “in another
photograph a heavy nitrogen line which in the present one lies opposite
an insufficiently exposed part of the solar spectrum, corresponds to a
comparison band in the sun.”
But one of the most remarkable points in Dr. Draper’s paper is what
he tells us respecting the visibility of these lines in the spectrum
itself. They fall, as I have mentioned, in a part of the spectrum where
the actinic energy is great but the luminosity small; in fact, while
this part of the spectrum is the very strongest for photography, it is
close to the region of the visible spectrum,
“Where the last gleamings of refracted light
Die in the fainting violet away.”
It is therefore to be expected that those, if any, of the bright lines
of oxygen, will be least favourably shown for direct vision, and most
favourably for what might almost be called photographic vision, where
we see what photography records for us. Yet Dr. Draper states that
these bright lines of oxygen can be readily seen. “The bright lines
of oxygen in the spectrum of the solar disc have not been hitherto
perceived, probably from the fact that in eye-observation bright lines
on a less bright background do not make the impression on the mind that
dark lines do. When attention is called to their presence they are
readily enough seen, even without the aid of a reference spectrum. The
photograph, however, brings them into greater prominence.” As the lines
of oxygen are not confined to the indigo and violet, we may fairly hope
that the bright lines in other parts of the spectrum of oxygen may be
detected in the spectrum of the sun, now that spectroscopists know that
bright lines and not dark lines are to be looked for.
Dr. Draper remarks that from purely theoretic considerations derived
from terrestrial chemistry, and the nebular hypothesis, the presence of
oxygen in the sun might have been strongly suspected; for this element
is currently stated to form eight-ninths of the water of the globe,
one-third of the crust of the earth, and one-fifth of the air, and
should therefore probably be a large constituent of every member of the
solar system. On the other hand, the discovery of oxygen, and probably
other non-metals, in the sun gives increased strength to the nebular
hypothesis, because to many persons the absence of this important group
has presented a considerable difficulty. I have already remarked on the
circumstance that we cannot, according to the known laws of gaseous
diffusion, accept the reasoning of those who have endeavoured to
explain the small density of the outer planets by the supposition that
the lighter gases were left behind by the great contracting nebulous
mass, out of which, on the nebular hypothesis, the solar system is
supposed to have been formed. It is important to notice, now, that if
on the one hand we find in the community of structure between the sun
and our earth, as confirmed by the discovery of oxygen and nitrogen
in the sun, evidence favouring the theory according to which all the
members of that system were formed out of what was originally a single
mass, we do not find evidence against the theory (as those who have
advanced the explanation above referred to may be disposed to imagine)
in the recognition in the sun’s mass of enormous quantities of one
of these elements which, according to their view, ought to be found
chiefly in the outer members of the solar system. If those who believe
in the nebular hypothesis (generally, that is, for many of the details
of the hypothesis as advanced by Laplace are entirely untenable in
the present position of physical science) had accepted the attempted
explanation of the supposed absence of the non-metallic elements in the
sun, they would now find themselves in a somewhat awkward position.
They would, in fact, be almost bound logically to reject the nebular
hypothesis, seeing that one of the asserted results of the formation of
our system, according to that hypothesis, would have been disproved.
But so far as I know no supporter of the nebular hypothesis possessing
sufficient knowledge of astronomical facts and physical laws to render
his opinion of any weight, has ever given in his adhesion to the
unsatisfactory explanation referred to.
The view which I have long entertained respecting the growth of the
solar system—viz., that it had its origin, not in contraction only or
chiefly, but in combined processes of contraction and accretion—seems
to me to be very strongly confirmed by Dr. Draper’s discovery. This
would not be the place for a full discussion of the reasons on which
this opinion is based. But I may remark that I believe no one who
applies the laws of physics, _as at present known_, to the theory of
the simple contraction of a great nebulous mass formerly extending
far beyond the orbit of Neptune, till, when planet after planet had
been thrown off, the sun was left in his present form and condition
in the centre, will fail to perceive enormous difficulties in the
hypothesis, or to recognize in Dr. Draper’s discovery a difficulty
added to those affecting the hypothesis _so presented_. Has it ever
occurred, I often wonder, to those who glibly quote the nebular theory
as originally propounded, to inquire how far some of the processes
suggested by Laplace are in accordance with the now known laws of
physics? To begin with, the original nebulous mass extending to a
distance exceeding the earth’s distance from the sun more than thirty
times (this being only the distance of Neptune), if we assign to it a
degree of compression making its axial diameter half its equatorial
diameter, would have had a volume exceeding the sun’s (roughly) about
120,000,000,000 times, and in this degree its mean density would have
been less than the sun’s. This would correspond to a density equal
(roughly) to about one-400,000th part of the density of hydrogen gas at
atmospheric pressure. To suppose that a great mass of matter, having
this exceedingly small mean density, and extending to a distance of
three or four thousand millions of miles from its centre, could under
any circumstances rotate as a whole, or behave in other respects after
the fashion attributed to the gaseous embryon of the solar system
in ordinary descriptions of the nebular hypothesis, is altogether
inconsistent with correct ideas of physical and dynamical laws. It is
absolutely a necessity of any nebular hypothesis of the solar system,
that from the very beginning a central nucleus and subordinate nuclei
should form in it, and grow according to the results of the motions (at
first to all intents and purposes independent) of its various parts.
Granting this state of things, we arrive, by considering the combined
effects of accretion and contraction, at a process of development
according fully as well as that ordinarily described with the general
relations described by Laplace, and accounting also (in a general way)
for certain peculiarities which are in no degree explained by the
ordinary theory. Amongst these may specially be noted the arrangement
and distribution of the masses within the solar system, and the fact
that so far as spectroscopic evidence enables us to judge, a general
similarity of structure exists throughout the whole of the system.
Inquiring as to the significance of his discovery, Dr. Draper remarks
that it seems rather difficult “at first sight to believe that an
ignited[5] gas in the solar atmosphere should not be indicated by dark
lines in the solar spectrum, and should appear not to act under the
law, ‘a gas when ignited absorbs rays of the same refrangibility as
those it emits.’ But, in fact, the substances hitherto investigated in
the sun are really metallic vapours, hydrogen probably coming under
that rule. The non-metals obviously may behave differently. It is easy
to speculate on the causes of such behaviour; and it may be suggested
that the reason of the non-appearance of a dark line may be that
the intensity of the light from a great thickness of ignited oxygen
overpowers the effect of the photosphere, just as, if a person were to
look at a candle-flame through a yard thickness of sodium vapour, he
would only see bright sodium lines, and no dark absorption.”
The reasoning here is not altogether satisfactory (or else is not
quite correctly expressed). In the first place, the difficulty dealt
with has no real existence. The law that a gas when glowing absorbs
rays of the same refrangibility as it emits, does not imply that a
gas between a source of light and the observer will show its presence
by spectroscopic dark lines. A gas so placed _does_ receive from the
source of light rays corresponding to those which it emits itself, if
it is cooler than the source of light; and it absorbs them, being in
fact heated by means of them, though the gain of temperature may be
dissipated as fast as received; but if the gas is hotter, it emits more
of those rays than it absorbs, and will make its presence known by its
bright lines. This is not a matter of speculation, but of experiment.
On the other hand, the experiment suggested by Dr. Draper would not
have the effect he supposes, if it were correctly made. Doubtless,
if the light from a considerable area of dully glowing sodium vapour
were received by the spectroscope at the same time as the light of a
candle-flame seen through the sodium vapour, the light of the sodium
vapour overcoming that of the candle-flame would indicate its presence
by bright lines; but if light were received only from that portion of
the sodium vapour which lay between the eye and the candle-flame, then
I apprehend that the dark lines of sodium would not only be seen, but
would be conspicuous by their darkness.
It is in no cavilling spirit that I indicate what appears to me
erroneous in a portion of Dr. Draper’s reasoning on his great
discovery. The entire significance of the discovery depends on the
meaning attached to it, and therefore it is most desirable to ascertain
what this meaning really is. There can be no doubt, I think, that we
are to look for the true interpretation of the brightness of the oxygen
lines in the higher temperature of the oxygen, not in the great depth
of oxygen above the photospheric level. The oxygen which produces
these bright lines need not necessarily be above the photosphere at
all. (In fact, I may remark here that Dr. Draper, in a communication
addressed to myself, mentions that he has found no traces at present
of oxygen above the photosphere, though I had not this circumstance
in my thoughts in reasoning down to the conclusion that the part of
the oxygen effective in showing these bright lines lies probably below
the visible photosphere.) Of course, if the photosphere were really
composed of glowing solid and liquid matter, or of masses of gas so
compressed and so intensely heated as to give a continuous spectrum,
no gas existing below the photosphere could send its light through,
nor could its presence, therefore, be indicated in any spectroscopic
manner. But the investigations which have been made into the structure
of the photosphere as revealed by the telescope, and in particular the
observations made by Professor Langley, of the Alleghany Observatory,
show that we have not in the photosphere a definite bounding envelope
of the sun, but receive light from many different depths below that
spherical surface, 425,000 miles from the sun’s centre, which we call
the photospheric level. We receive more light from the centre of
the solar disc, I feel satisfied, not solely because the absorptive
layer through which we there see the sun is shallower, but partly,
and perhaps chiefly, because we there receive light from some of the
interior and more intensely heated parts of the sun.[6] Should this
prove to be the case, it may be found possible to do what heretofore
astronomers have supposed to be impossible—to ascertain in some degree
how far and in what way the constitution of the sun varies below the
photosphere, which, so far as ordinary telescopic observation is
concerned, seems to present a limit below which researches cannot be
pursued.
I hope we shall soon obtain news from Dr. Huggins’s Observatory that
the oxygen lines have been photographed, and possibly the bright lines
of other elements recognized in the solar spectrum. Mr. Lockyer also,
we may hope, will exercise that observing skill which enabled him early
to recognize the presence of bright hydrogen lines in the spectrum
of portions of the sun’s surface, to examine that spectrum for other
bright lines.
I do not remember any time within the last twenty years when the
prospects of fresh solar discoveries seemed more hopeful than they do
at present. The interest which has of late years been drawn to the
subject has had the effect of enlisting fresh recruits in the work of
observation, and many of these may before long be heard of as among
those who have employed Dr. Draper’s method successfully.
But I would specially call attention to the interest which attaches
to Dr. Draper’s discovery and to the researches likely to follow from
it, in connection with a branch of research which is becoming more
and more closely connected year by year with solar investigations—I
mean stellar spectroscopy. We have seen the stars divided into orders
according to their constitution. We recognize evidence tending to show
that these various orders depend in part upon age—not absolute but
relative age. There are among the suns which people space some younger
by far than our sun, others far older, and some in a late stage of
stellar decrepitude. Whether as yet spectroscopists have perfectly
succeeded in classifying these stellar orders in such sort that the
connection between a star’s spectrum and the star’s age can be at
once determined, may be doubtful. But certainly there are reasons for
hoping that before long this will be done. Amongst the stars, and
(strange to say) among celestial objects which are not stars, there
are suns in every conceivable stage of development, from embryon
masses not as yet justly to be regarded as suns, to masses which have
ceased to fulfil the duties of suns. Among the more pressing duties of
spectroscopic analysis at the present time is the proper classification
of these various orders of stars. Whensoever that task shall have been
accomplished, strong light, I venture to predict, will be thrown on our
sun’s present condition, as well as on his past history, and on that
future fate upon which depends the future of our earth.
_SUN-SPOT, STORM, AND FAMINE._
During the last five or six years a section of the scientific world
has been exercised with the question how far the condition of the
sun’s surface with regard to spots affects our earth’s condition as to
weather, and therefore as to those circumstances which are more or less
dependent on weather. Unfortunately, the question thus raised has not
presented itself alone, but in company with another not so strictly
scientific, in fact, regarded by most men of science as closely related
to personal considerations—the question, namely, whether certain
indicated persons should or should not be commissioned to undertake the
inquiry into the scientific problem. But the scientific question itself
ought not to be less interesting to us because it has been associated,
correctly or not, with the wants and wishes of those who advocate
the endowment of science. I propose here to consider the subject in
its scientific aspect only, and apart from any bias suggested by the
appeals which have been addressed to the administrators of the public
funds.
It is hardly necessary to point out, in the first place, that all
the phenomena of weather are directly referable to the sun as their
governing cause. His rays poured upon our air cause the more important
atmospheric currents directly. Indirectly they cause modifications
of these currents, because where they fall on water or on moist
surfaces they raise aqueous vapour into the air, which, when it
returns to the liquid form as cloud, gives up to the surrounding air
the heat which had originally vaporized the water. In these ways,
directly or indirectly, various degrees of pressure and temperature
are brought about in the atmospheric envelope of the earth, and,
speaking generally, all air currents, from the gentlest zephyr to the
fiercest tornado, are the movements by which the equilibrium of the
air is restored. Like other movements tending to restore equilibrium,
the atmospheric motions are oscillatory. Precisely as when a spring
has been bent one way, it flies not back only, but beyond the mean
position, till it is almost equally bent the other way, so the current
of air which rushes in towards a place of unduly diminished pressure
does more than restore the mean pressure, so that presently a return
current carries off the excess of air thus carried in. We may say,
indeed, that the mean pressure at any place scarcely ever exists, and
when it exists for a time the resulting calm is of short duration.
Just as the usual condition of the sea surface is one of disturbance,
greater or less, so the usual condition of the air at every spot on
the earth’s surface is one of motion not of quiescence. Every movement
of the air, thus almost constantly perturbed, is due directly or
indirectly to the sun.
So also every drop of rain or snow, every particle of liquid or of
frozen water in mist or in cloud, owes its birth to the sun. The
questions addressed of old to Job, “Hath the rain a father? or who
hath begotten the drops of dew? out of whose womb came the ice? and
the hoary frost of heaven, who hath gendered it?” have been answered
by modern science, and to every question the answer is, The Sun. He
is parent of the snow and hail, as he is of the moist warm rains of
summer, of the ice which crowns the everlasting hills, and of the mist
which rises from the valleys beneath his morning rays.
Since, then, the snow that clothes the earth in winter as with a
garment, and the clouds that in due season drop fatness on the earth,
are alike gendered by the sun; since every movement in our air, from
the health-bringing breeze to the most destructive hurricane, owns him
as its parent; we must at the outset admit, that if there is any body
external to the earth whose varying aspect or condition can inform us
beforehand of changes which the weather is to undergo, the sun is that
body. That for countless ages the moon should have been regarded as
the great weather-breeder, shows only how prone men are to recognize
in apparent changes the true cause of real changes, and how slight
the evidence is on which they will base laws of association which
have no real foundation in fact. Every one can see when the moon is
full, or horned, or gibbous, or half-full; when her horns are directed
upwards, or downwards, or sideways. And as the weather is always
changing, even as the moon is always changing, it must needs happen
that from time to time changes of weather so closely follow changes
of the moon as to suggest that the two orders of change stand to each
other in the relation of cause and effect. Thus rough rules (such as
those which Aratus has handed down to us) came to be formed, and as
(to use Bacon’s expression) men mark when such rules hit, and never
mark when they miss, a system of weather lore gradually comes into
being, which, while in one sense based on facts, has not in reality a
particle of true evidence in its favour—every single fact noted for
each relation having been contradicted by several unnoted facts opposed
to the relation. There could be no more instructive illustration of
men’s habits in such matters than the system of lunar weather wisdom in
vogue to this day among seamen, though long since utterly disproved by
science. But let it be remarked in passing, that in leaving the moon,
which has no direct influence, and scarcely any indirect influence, on
the weather, for the sun, which is all-powerful, we have not got rid of
the mental habits which led men so far astray in former times. We shall
have to be specially careful lest it lead us astray yet once more,
perhaps all the more readily because of the confidence with which we
feel that, at the outset anyway, we are on the right road.
I suppose there must have been a time when men were not altogether
certain whether the varying apparent path of the sun, as he travels
from east to west every day, has any special effect on the weather.
It seems so natural to us to recognize in the sun’s greater mid-day
elevation and longer continuance above the horizon in summer, the cause
of the greater warmth which then commonly prevails, that we find it
difficult to believe that men could ever have been in doubt on this
subject. Yet it is probable that a long time passed after the position
of the sun as ruler of the day had been noticed, before his power as
ruler of the seasons was recognized. I cannot at this moment recall
any passage in the Bible, for example, in which direct reference is
made to the sun’s special influence in bringing about the seasons, or
any passage in very ancient writings referring definitely to the fact
that the weather changes with the changing position of the sun in the
skies (as distinguished from the star-sphere), and with the changing
length of the day. “While the earth remaineth,” we are told in Genesis,
“seed-time and harvest, and cold and heat, and summer and winter, and
day and night, shall not cease;” but there is no reference to the sun’s
aspect as determining summer and winter. We find no mention of any of
the celestial signs of the seasons anywhere in the Bible, I think, but
such signs as are mentioned in the parable of the fig tree—“When his
branch is yet tender, and putteth forth leaves, ye know that summer is
nigh.” Whether this indicates or not that the terrestrial, rather than
the celestial signs of the progress of the year were chiefly noted by
men in those times, it is tolerably certain that in the beginning a
long interval must have elapsed between the recognition of the seasons
themselves, and the recognition of their origin in the changes of the
sun’s apparent motions.
When this discovery was effected, men made the most important and, I
think, the most satisfactory step towards the determination of cyclic
associations between solar and terrestrial phenomena. It is for that
reason that I refer specially to the point. In reality, it does not
appertain to my subject, for seasons and sun-spots are not associated.
But it admirably illustrates the value of cyclic relations. Men might
have gone on for centuries, we may conceive, noting the recurrence
of seed-time and harvest-time, summer and winter, recognizing the
periodical returns of heat and cold, and (in some regions) of dry
seasons and wet seasons, of calm and storm, and so forth, without
perceiving that the sun runs through his changes of diurnal motion in
the same cyclic period. We can imagine that some few who might notice
the connection between the two orders of celestial phenomena would
be anxious to spread their faith in the association among their less
observant brethren. They might maintain that observatories for watching
the motions of the sun would demonstrate either that their belief
was just or that it was not so, would in fact dispose finally of the
question. It is giving the most advantageous possible position to those
who now advocate the erection of solar observatories for determining
what connection, if any, may exist between sun-spots and terrestrial
phenomena, thus to compare them to observers who had noted a relation
which unquestionably exists. But it is worthy of notice that if those
whom I have imagined thus urging the erection of an observatory for
solving the question whether the sun rules the seasons, and to some
degree regulates the recurrence of dry or rainy, and of calm or
stormy weather, had promised results of material value from their
observations, they would have promised more than they could possibly
have performed. Even in this most favourable case, where the sun is,
beyond all question, the efficient ruling body, where the nature of
the cyclic change is most exactly determinable, and where even the way
in which the sun acts can be exactly ascertained, no direct benefit
accrues from the knowledge. The exact determination of the sun’s
apparent motions has its value, and this value is great, but it is most
certainly not derived from any power of predicting the recurrence of
those phenomena which nevertheless depend directly on the sun’s action.
The farmer who in any given year knows from the almanac the exact
duration of daylight, and the exact mid-day elevation of the sun for
every day in the year, is not one whit better able to protect his crops
or his herds against storm or flood than the tiller of the soil or the
tender of flocks a hundred thousand years or so ago, who knew only when
seed-time and summer and harvest-time and winter were at hand or in
progress.
The evidence thus afforded is by no means promising, then, so far as
the prediction of special storms, or floods, or droughts is concerned.
It would seem that if past experience can afford any evidence in such
matters, men may expect to recognize cycles of weather change long
before they recognize corresponding solar cycles (presuming always that
such cycles exist), and that they may expect to find the recognition
of such association utterly barren, so far as the possibility of
predicting definite weather changes is concerned. It would seem that
there is no likelihood of anything better than what Sir J. Herschel
said _might_ be hoped for hereafter. “A lucky hit may be made; nay,
some rude approach to the perception of a ‘cycle of seasons’ may
_possibly_ be obtainable. But no person in his senses would alter
his plans of conduct for six months in advance in the most trifling
particular on the faith of any special prediction of a warm or a cold,
a wet or a dry, a calm or a stormy, summer or winter”—far less of a
great storm or flood announced for any special day.
But let us see what the cycle association between solar spots and
terrestrial weather actually is, or rather of what nature it promises
to be, for as yet the true nature of the association has not been made
out.
It has been found that in a period of about eleven years the sun’s
surface is affected by what may be described as a wave of sun-spots.
There is a short time—a year or so—during which scarce any spots are
seen; they become more and more numerous during the next four or five
years, until they attain a maximum of frequency and size; after this
they wane in number and dimensions, until at length, about eleven years
from the time when he had before been freest from spots, he attains
again a similar condition. After this the spots begin to return,
gradually attain to a maximum, then gradually diminish, until after
eleven more years have elapsed few or none are seen. It must not be
supposed that the sun is always free from spots at the time of minimum
spot frequency, or that he always shows many and large spots at the
time of maximum spot frequency. Occasionally several very large spots,
and sometimes singularly large spots, have been seen in the very heart
of the minimum spot season, and again there have been occasions when
scarcely any spots have been seen for several days in the very heart
of the maximum spot season. But, taking the average of each year,
the progression of the spots in number and frequency from minimum
to maximum, and their decline from maximum to minimum, are quite
unmistakeable.
Now there are some terrestrial phenomena which we might expect to
respond in greater or less degree to the sun’s changes of condition
with respect to spots. We cannot doubt that the emission both of light
and of heat is affected by the presence of spots. It is not altogether
clear in what way the emission is affected. We cannot at once assume
that because the spots are dark the quantity of sunlight must be less
when the spots are numerous; for it may well be that the rest of the
sun’s surface may at such times be notably brighter than usual, and the
total emission of light may be greater on the whole instead of less.
Similarly of the emission of heat. It is certain that when there are
many spots the surface of the sun is far less uniform in brightness
than at other times. The increase of brightness all round the spots is
obvious to the eye when the sun’s image, duly enlarged, is received
upon a screen in a darkened room. Whether the total emission of light
is increased or diminished has not yet been put to the test. Professor
Langley, of the Alleghany Observatory, near Pittsburg, U.S., has
carefully measured the diminution of the sun’s emission of light and
heat on the assumption that the portion of the surface not marked by
spots remains unchanged in lustre. But until the total emission of
light and heat at the times of maximum and minimum has been measured,
without any assumption of the kind, we cannot decide the question.
More satisfactory would seem to be the measurements which have been
made by Professor Piazzi Smyth, at Edinburgh, and later by the
Astronomer Royal at Greenwich, into the underground temperature of
the earth. By examining the temperature deep down below the surface,
all local and temporary causes of change are eliminated, and causes
external to the earth can alone be regarded as effective in producing
systematic changes. “The effect is very slight,” I wrote a few years
ago, “indeed barely recognizable. I have before me as I write Professor
Smyth’s sheet of the quarterly temperatures from 1837 to 1869 at
depths of 3, 6, 12, and 24 French feet. Of course the most remarkable
feature, even at the depth of 24 feet, is the alternate rise and fall
with the seasons. But it is seen that, while the range of rise and fall
remains very nearly constant, the crests and troughs of the waves lie
at varying levels.” After describing in the essay above referred to,
which appears in my “Science Byways,” the actual configuration of the
curves of temperature both for seasons and for years, and the chart in
which the sun-spot waves and the temperature waves are brought into
comparison, I was obliged to admit that the alleged association between
the sun-spot period and the changes of underground temperature did
not seem to me very clearly made out. It appears, however, there is a
slight increase of temperature at the time when the sun-spots are least
numerous.
That the earth’s magnetism is affected by the sun’s condition with
respect to spots, seems to have been more clearly made out, though
it must be noted that the Astronomer Royal considers the Greenwich
magnetic observations inconsistent with this theory. It seems to have
been rendered at least extremely probable that the daily oscillation
of the magnetic needle is greater when spots are numerous than when
there are few spots or none. Magnetic storms are also more numerous at
the time of maximum spot-frequency, and auroras are then more common.
(The reader will not fall into the mistake of supposing that magnetic
storms have the remotest resemblance to hurricanes, or rainstorms, or
hailstorms, or even to thunderstorms, though the thunderstorm is an
electrical phenomenon. What is meant by a magnetic storm is simply such
a condition of the earth’s frame that the magnetic currents traversing
it are unusually strong.)
Thus far, however, we have merely considered relations which we might
fairly expect to find affected by the sun’s condition as to spots.
A slight change in his total brightness and in the total amount of
heat emitted by him may naturally be looked for under circumstances
which visibly affect the emission of light, and presumably affect the
emission of heat also, from portions of his surface. Nor can we wonder
if terrestrial magnetism, which is directly dependent on the sun’s
emission of heat, should be affected by the existence of spots upon his
surface.
It is otherwise with the effects which have recently been associated
with the sun’s condition. It may or may not prove actually to be the
case that wind and rain vary in quantity as the sun-spots vary in
number (at least when we take in both cases the average for a year, or
for two or three years), but it cannot be said that any such relation
was antecedently to be expected. When we consider what the sun actually
does for our earth, it seems unlikely that special effects such as
these should depend on relatively minute peculiarities of the sun’s
surface. There is our earth, with her oceans and continents, turning
around swiftly on her axis, and exposed to his rays as a whole. Or,
inverting the way of viewing matters, there is the sun riding high in
the heavens of any region of the earth, pouring down his rays upon that
region. We can understand how in the one case that rotating orb of the
earth may receive rather more or rather less heat from the sun when
he is spotted than when he is not, or how in the other way of viewing
matters, that orb of the sun may give to any region rather more or
rather less heat according as his surface is more or less spotted.
But that in special regions of that rotating earth storms should be
more or less frequent or rainfall heavier or lighter, as the sun’s
condition changes through the exceedingly small range of variation due
to the formation of spots, seems antecedently altogether unlikely; and
equally unlikely the idea that peculiarities affecting limited regions
of the sun’s surface should affect appreciably the general condition
of the earth. If a somewhat homely comparison may be permitted, we
can well understand how a piece of meat roasting before a fire may
receive a greater or less supply of heat on the whole as the fire
undergoes slight local changes (very slight indeed they must be, that
the illustration may be accurate); but it would be extremely surprising
if, in consequence of such slight changes in the fire, the roasting of
particular portions of the joint were markedly accelerated or delayed,
or affected in any other special manner.
But of course all such considerations as to antecedent probabilities
must give way before the actual evidence of observed facts. Utterly
inconsistent with all that is yet known of the sun’s physical action,
as it may seem, on _à priori_ grounds, to suppose that spots, currents,
or other local disturbances of the sun’s surface could produce any but
general effects on the earth as a whole, yet if we shall find that
particular effects are produced in special regions of the earth’s
surface in cycles unmistakably synchronizing with the solar-spot-cycle,
we must accept the fact, whether we can explain it or not. Only let it
be remembered at the outset that the earth is a large place, and the
variations of wind and calm, rain and drought, are many and various in
different regions. Whatever place we select for examining the rainfall,
for example, we are likely to find, in running over the records of the
last thirty years or so, some seemingly oscillatory changes; in the
records of the winds, again, we are likely to find other seemingly
oscillatory changes; if none of these records provide anything which
seems in any way to correspond with the solar spot-cycle, we may
perchance find some such cycle in the relative rainfall of particular
months, or in the varying wetness or dryness of particular winds, and
so forth. Or, if we utterly fail to find any such relation in one
place we may find it in another, or not improbably in half-a-dozen
places among the hundreds which are available for the search. If we
are content with imperfect correspondence between some meteorological
process or another and the solar-spot cycle, we shall be exceedingly
unfortunate indeed if we fail to find a score of illustrative
instances. And if we only record these, without noticing any of the
cases where we fail to find any association whatever—in other words,
as Bacon puts it, if “we note when we hit and never note when we
miss,” we shall be able to make what will seem a very strong case
indeed. But this is not exactly the scientific method in such cases.
By following such a course, indeed, we might prove almost anything. If
we take, for instance, a pack of cards, and regard the cards in order
as corresponding to the years 1825 to 1877, and note their colours as
dealt _once_, we shall find it very difficult to show that there is any
connection whatever between the colours of the cards corresponding to
particular years and the number of spots on the sun’s face. But if we
repeat the process a thousand times, we shall find certain instances
among the number, in which red suits correspond to all the years when
there are many spots on the sun, and black suits to all the years
when there are few spots on the sun. If now we were to publish all
such deals, without mentioning anything at all about the others which
showed no such association, we should go far to convince a certain
section of the public that the condition of the sun as to spots might
hereafter be foretold by the cards; whence, if the public were already
satisfied that the condition of the sun specially affects the weather
of particular places, it would follow that the future weather of these
places might also be foretold by the cards.
I mention this matter at the outset, because many who are anxious to
find some such cycle of seasons as Sir John Herschel thought might be
discovered, have somewhat overlooked the fact that we must not hunt
down such a cycle _per fas et nefas_. “Surely in meteorology as in
astronomy,” Mr. Lockyer writes, for instance, “the thing to hunt down
is a cycle, and if that is not to be found in the temperate zone, then
go to the frigid zones or the torrid zone to look for it; and if found,
then above all things and in whatever manner, lay hold of, study, and
read it, and see what it means.” There can be no doubt that this is the
way to find a cycle, or at least to find what looks like a cycle, but
the worth of a cycle found in this way will be very questionable.[7]
I would not have it understood, however, that I consider all the cycles
now to be referred to as unreal, or even that the supposed connection
between them and the solar cycle has no existence. I only note that
there are thousands, if not tens of thousands, of relations among
which cycles may be looked for, and that there are perhaps twenty or
thirty cases in which some sort of cyclic association between certain
meteorological relations and the period of the solar spots presents
itself. According to the recognized laws of probability, some at least
amongst these cases must be regarded as accidental. Some, however, may
still remain which are not accidental.
Among the earliest published instances may be mentioned Mr. Baxendell’s
recognition of the fact that during a certain series of years, about
thirty, I think, the amount of rainfall at Oxford was greater under
west and south-west winds than under south and south-east winds when
sun-spots were most numerous, whereas the reverse held in years when
there were no spots or few. Examining the meteorological records of
St. Petersburg, he found that a contrary state of things prevailed
there.
The Rev. Mr. Main, Director of the Radcliffe Observatory at Oxford,
found that westerly winds were slightly more common (as compared with
other winds) when sun-spots were numerous than when they were few.
Mr. Meldrum, of Mauritius, has made a series of statistical inquiries
into the records of cyclones which have traversed the Indian Ocean
between the equator and 34 degrees south latitude, in each year from
1856 to 1877, noting the total distances traversed by each, the sums
of their radii and areas, their duration in days, the sums of their
total areas, and their relative areas. His researches, be it marked
in passing, are of extreme interest and value, whether the suggested
connection between sun-spots and cyclones (in the region specified)
be eventually found to be a real one or not. The following are his
results, as described in _Nature_ by a writer who manifestly favours
very strongly the doctrine that an intimate association exists between
solar maculation (or spottiness) and terrestrial meteorological
phenomena:—
“The period embraces two complete, or all but complete, sun-spot
periods, the former beginning with 1856 and ending in 1867, and the
latter extending from 1867 to about the present time [1877]. The broad
result is that the number of cyclones, the length and duration of
their courses, and the extent of the earth’s surface covered by them
all, reach the maximum in each sun-spot period during the years of
maximum maculation, and fall to the minimum during the years of minimum
maculation. The peculiar value of these results lies in the fact that
the portion of the earth’s surface over which this investigation
extends, is, from its geographical position and what may be termed
its meteorological homogeneity, singularly well fitted to bring out
prominently any connection that may exist between the condition of the
sun’s surface and atmospheric phenomena.”
The writer proceeds to describe an instance in which Mr. Meldrum
predicted future meteorological phenomena, though without specifying
the exact extent to which Mr. Meldrum’s anticipations were fulfilled or
the reverse. “A drought commenced in Mauritius early in November,” he
says, “and Mr. Meldrum ventured (on December 21) to express publicly
his opinion that probably the drought would not break up till towards
the end of January, and that it might last till the middle of February,
adding that up to these dates the rainfall of the island would probably
not exceed 50 per cent. of the mean fall. This opinion was an inference
grounded on past observations, which show that former droughts have
lasted from about three to three and a half months, and that these
droughts have occurred in the years of minimum sun-spots, or, at all
events, in years when the spots were far below the average, such as
1842, 1843, 1855, 1856, 1864, 1866, and 1867, and that now we are
near the minimum epoch of sun-spots. It was further stated that the
probability of rains being brought earlier by a cyclone was but slight,
seeing that the season for cyclones is not till February or March, and
that no cyclone whatever visited Mauritius during 1853–56 and 1864–67,
the years of minimum sun-spots. From the immense practical importance
of this application of the connection between sun-spots and weather
to the prediction of the character of the weather of the ensuing
season, we shall look forward with the liveliest interest to a detailed
statement of the weather which actually occurred in that part of the
Indian Ocean from November to March last [1876].”
It was natural that the great Indian famine, occurring at a time
when sun-spots were nearly at a minimum, should by some be directly
associated with a deficiency of sun-spots. In this country, indeed,
we have had little reason, during the last two or three years of few
sun-spots, to consider that drought is one of the special consequences
to be attributed to deficient solar maculation. But in India it may
be different, or at least it may be different in Madras, for it has
been satisfactorily proved that in some parts of India the rainfall
increases in inverse, not in direct proportion, to the extent of
solar maculation. Dr. Hunter has shown to the satisfaction of many
that at Madras there is “a cycle of rainfall corresponding with the
period of solar maculation.” But Mr. E. D. Archibald, who is also
thoroughly satisfied that the sun-spots affect the weather, remarks
that Dr. Hunter has been somewhat hasty in arguing that the same
conditions apply throughout the whole of Southern India. “This hasty
generalization from the results of one station situated in a vast
continent, the rainfall of which varies completely, both in amount and
the season in which it falls, according to locality, has been strongly
contested by Mr. Blanford, the Government Meteorologist, who, in making
a careful comparison of the rainfalls of seven stations, three of which
(Madras, Bangalore, and Mysore) are in Southern India, the others
being Bombay, Najpore, Jubbulpore, and Calcutta, finds that, with the
exception of Najpore in Central India, which shows some slight approach
to the same cyclical variation which is so distinctly marked in the
Madras registers, the rest of the stations form complete exceptions
to the rule adduced for Madras, in many of them the hypothetical
order of relation being reversed. Mr. Blanford, however, shows that,
underlying the above irregularities, a certain cyclical variation
exists on the average at all the stations, the amount, nevertheless,
being so insignificant (not more than 9 per cent. of the total falls)
that it could not be considered of sufficient magnitude to become a
direct factor in the production of famine. It thus appears that the
cycle of rainfall which is considered to be the most important element
in causing periodic famines has only been proved satisfactorily for
the town of Madras. It may perhaps hold for the Carnatic and Northern
Siccars, the country immediately surrounding Madras, though perhaps,
owing to the want of rainfall registers in these districts, evidence
with regard to this part is still wanting.” On this Mr. Archibald
proceeds to remark that, though Dr. Hunter has been only partially
successful, the value of his able pamphlet is not diminished in any
way, “an indirect effect of which has been to stimulate meteorological
inquiry and research in the same direction throughout India. The
meteorology of this country (India), from its peculiar and tropical
position, is in such complete unison with any changes that may
arise from oscillations in the amount of solar radiation, and their
effects upon the velocity and direction of the vapour-bearing winds,
that a careful study of it cannot fail to discover meteorological
periodicities in close connection with corresponding periods of solar
disturbance.” So, indeed, it would seem.
The hope that famines may be abated, or, at least, some of their most
grievous consequences forestalled by means of solar observatories, does
not appear very clearly made out. Rather it would seem that the proper
thing to do is to investigate the meteorological records of different
Indian regions, and consider the resulting evidence of cyclic changes
without any special reference to sun-spots; for if sun-spots may cause
drought in one place, heavy rainfall in another, winds here and calms
there, it seems conceivable that the effects of sun-spots may differ at
different times, as they manifestly do in different places.
Let us turn, however, from famines to shipwrecks. Perhaps, if we admit
that cyclones are more numerous, and blow more fiercely, and range
more widely, even though it be over one large oceanic region only, in
the sun-spot seasons than at other times, we may be assured, without
further research, that shipwrecks will, on the whole, be more numerous
near the time of sun-spot maxima than near the time of sun-spot minima.
The idea that this may be so was vaguely shadowed forth in a poem of
many stanzas, called “The Meteorology of the Future: a Vision,” which
appeared in _Nature_ for July 5, 1877. I do not profess to understand
precisely what the object of this poem may have been-—I mean, whether
it is intended to support or not the theory that sun-spots influence
the weather. Several stanzas are very humorous, but the object of the
humour is not manifest. The part referred to above is as follows:—Poor
Jack lies at the bottom of the sea in 1881, and is asked in a spiritual
way various questions as to the cause of his thus coming to grief. This
he attributed to the rottenness of the ship in which he sailed, to
the jobbery of the inspector, to the failure of the system of weather
telegraphing, and so forth. But, says the questioner, there was one
“In fame to none will yield,
He led the band who reaped renown
On India’s famine field.
“Was he the man to see thee die?
Thou wilt not tax him—come?
The dead man groaned—‘_I met my death
Through a sun-spot maximum_.’”
The first definite enunciation, however, of a relation between
sun-spots and shipwrecks appeared in September, 1876. Mr. Henry
Jeula, in the _Times_ for September 19, stated that Dr. Hunter’s
researches into the Madras rainfall had led him to throw together the
scanty materials available relating to losses posted on Lloyd’s loss
book, to ascertain if any coincidences existed between the varying
number of such losses and Dr. Hunter’s results. “For,” he proceeds,
“since the cycle of rainfall at Madras coincides, I am informed, with
the periodicity of the cyclones in the adjoining Bay of Bengal” (a
relation which is more than doubtful) “as worked out by the Government
Astronomer at Mauritius” (whose researches, however, as we have seen,
related to a region remote from the Bay of Bengal), “some coincidence
between maritime casualties, rainfalls, and sun-spots appeared at
least possible.” In passing, I may note that if any such relation were
established, it would be only an extension of the significance of
the cycle of cyclones, and could have no independent value. It would
certainly follow, if the cycle of cyclones is made out, that shipwrecks
being more numerous, merchants would suffer, and we should have the
influence of the solar spots asserting itself in the _Gazette_. From
the cyclic derangement of monetary and mercantile matters, again,
other relations also cyclic in character would arise. But as all these
may be inferred from the cycle of cyclones once this is established,
we could scarcely find in their occurrence fresh evidence of the
necessity of that much begged-for solar observatory. The last great
monetary panic in this country, by the way, occurred in 1866, at a
time of minimum solar maculation. Have we here a decisive proof that
the sun rules the money market, the bank rate of discount rising to a
maximum as the sun-spots sink to a minimum, and _vice versâ_? The idea
is strengthened by the fact that the American panic in 1873 occurred
when spots were very numerous, and its effects have steadily subsided
as the spots have diminished in number; for this shows that the sun
rules the money market in America on a principle diametrically opposed
to that on which he (manifestly) rules the money market in England,
precisely as the spots cause drought in Calcutta and plenteous rainfall
at Madras, wet south-westers and dry south-westers at Oxford, and wet
south-easters and dry south-easters at St. Petersburg. Surely it would
be unreasonable to refuse to recognize the weight of evidence which
thus tells on both sides at once.
To return, however, to the sun’s influence upon shipwrecks.
Mr. Jeula was “only able to obtain data for two complete cycles of
eleven years, namely, from 1855 to 1876 inclusive, while the period
investigated by Dr. Hunter extended from 1813 to 1876, and his
observations related to Madras and its neighbourhood only, while the
losses posted at Lloyd’s occurred to vessels of various countries, and
happened in different parts of the world. It was necessary to bring
these losses to some common basis of comparison, and the only available
one was the number of ‘British registered vessels of the United Kingdom
and Channel Islands’—manifestly an arbitrary one. I consequently
cast out the percentage of losses posted each year upon the number of
registered vessels for the same year, and also the percentage of losses
posted in each of the eleven years of the two cycles upon the total
posted in each complete cycle, thus obtaining two bases of comparison
independent of each other.”
The results may be thus presented:—
Taking the four years of each cycle when sun-spots were least in
number, Mr. Jeula found the mean percentage of losses in registered
vessels of the United Kingdom and Channel Islands to be 11·13, and the
mean percentage of losses in the total posted in the entire cycle of
eleven years to be 8·64.
In the four years when sun-spots were intermediate in number, that
is in two years following the minimum and in two years preceding the
minimum, the respective percentages were 11·91 and 9·21.
Lastly, in the three years when sun-spots were most numerous, these
percentages were, respectively, 12·49 and 9·53.
That the reader may more clearly understand what is meant here by
percentages, I explain that while the numbers 11·13, 11·91 and 12·49
simply indicate the average number of wrecks (per hundred of all
the ships registered) which occurred in the several years of the
eleven-years cycle, the other numbers, 8·64, 19·21, and 9·53, indicate
the average number of wrecks (per hundred of wrecks recorded) during
eleven successive years, which occurred in the several years of the
cycle. The latter numbers seem more directly to the purpose; and as the
two sets agree pretty closely, we may limit our attention to them.
Now I would in the first place point out that it would have been well
if the actual number or percentage had been indicated for each year of
the cycle, instead of for periods of four years, four years, and three
years. Two eleven-year cycles give in any case but meagre evidence,
and it would have been well if the evidence had been given as fully
as possible. If we had a hundred eleven-yearly cycles, and took the
averages of wrecks for the four years of minimum solar maculation, the
four intermediate years, and the three years of maximum maculation,
we might rely with considerable confidence on the result, because
accidental peculiarities one way or the other could be eliminated. But
in two cycles only, such peculiarities may entirely mask any cyclic
relation really existing, and appear to indicate a relation which has
no real existence. If the percentages had been given for each year,
the effect of such peculiarities would doubtless still remain, and the
final result would not be more trustworthy than before; but we should
have a chance of deciding whether such peculiarities really exist or
not, and also of determining what their nature may be. As an instance
in point, let me cite a case where, having only the results of a
single cycle, we can so arrange them as to appear to indicate a cyclic
association between sun-spots and rainfall, while, when we give them
year by year, such an association is discredited, to say the least.
The total rainfall at Port Louis, between the years 1855 and 1868
inclusive, is as follows:—
In _Rainfall._ _Condition of Sun._
1855 42·665 inches Sun-spot minimum.
1856 46·230 „
1857 43·445 „
1858 35·506 „
1859 56·875 „
1860 45·166 „ Sun-spot maximum.
1861 68·733 „
1862 28·397 „
1863 33·420 „
1864 24·147 „
1865 44·730 „
1866 20·571 „ Sun-spot minimum.
1867 35·970 „
1868 64·180 „
[Illustration]
I think no one, looking at these numbers as they stand, can recognize
any evidence of a cyclic tendency. If we represent the rainfall by
ordinates we get the accompanying figure, which shows the rainfall for
eighteen years, and again I think it may be said that a very lively
imagination is required to recognize anything resembling that wave-like
undulation which the fundamental law of statistics requires where
a cycle is to be made out from a single oscillation. Certainly the
agreement between the broken curve of rainfall and the sun-spot curve
indicated by the waved dotted line is not glaringly obvious. But when
we strike an average for the rainfall, in the way adopted by Mr. Jeula
for shipwrecks, how pleasantly is the theory of sun-spot influence
illustrated by the Port Louis rainfall! Here is the result, as quoted
by the high-priest of the new order of diviners, from the papers by Mr.
Meldrum:—
Three minimum years—total rainfall 133·340
Three maximum years—total rainfall 170·774
Three minimum years—total rainfall 120·721
Nothing could be more satisfactory, but nothing, I venture to assert,
more thoroughly inconsistent with the true method of statistical
research.
May it not be that, underlying the broad results presented by Mr.
Jeula, there are similar irregularities?
When we consider that the loss of ships depends, not only on a cause so
irregularly variable (to all seeming) as wind-storms, but also on other
matters liable to constant change, as the variations in the state of
trade, the occurrence of wars and rumours of wars, special events, such
as international exhibitions, and so forth, we perceive that an even
wider range of survey is required to remove the effects of accidental
peculiarities in their case, than in the case of rainfall, cyclones,
or the like. I cannot but think, for instance, that the total number
of ships lost in divers ways during the American war, and especially
in its earlier years (corresponding with two of the three maximum
years of sun-spots) may have been greater, not merely absolutely but
relatively, than in other years. I think it conceivable, again, that
during the depression following the great commercial panic of 1866
(occurring at a time of minimum solar maculation, as already noticed)
the loss of ships may have been to some degree reduced, relatively as
well as absolutely. We know that when trade is unusually active many
ships have sailed, and perhaps may still be allowed to sail (despite
Mr. Plimsoll’s endeavours), which should have been broken up; whereas
in times of trade depression the ships actually afloat are likely
to be, _on the average_, of a better class. So also, when, for some
special reason, passenger traffic at sea is abnormally increased. I
merely mention these as illustrative cases of causes not (probably)
dependent on sun-spots, which may (not improbably) have affected the
results examined by Mr. Jeula. I think it possible that those results,
if presented for each year, would have indicated the operation of such
causes, naturally masked when sets of four years, four years, and three
years are taken instead of single years.
I imagine that considerations such as these will have to be taken into
account and disposed of before it will be unhesitatingly admitted that
sun-spots have any great effect in increasing the number of shipwrecks.
The advocates of the doctrine of sun-spot influence—or, perhaps
it would be more correct to say, the advocates of the endowment of
sun-spot research—think differently on these and other points. Each
one of the somewhat doubtful relations discussed above is constantly
referred to by them as a demonstrated fact, and a demonstrative proof
of the theory they advocate. For instance, Mr. Lockyer, in referring to
Meldrum’s statistical researches into the frequency of cyclones, does
not hesitate to assert that according to these researches “the whole
question of cyclones is merely a question of solar activity, and that
if we wrote down in one column the number of cyclones in any given
year, and in another column the number of sun-spots in any given year,
there will be a strict relation between them—many sun-spots, many
hurricanes; few sun-spots, few hurricanes.” ... And again, “Mr. Meldrum
has since found” (not merely “has since found reason to believe,” but
definitely, “has since found”) “that what is true of the storms which
devastate the Indian Ocean is true of the storms which devastate the
West Indies; and on referring to the storms of the Indian Ocean, Mr.
Meldrum points out that at those years where we have been quietly
mapping the sun-spot maxima, the harbours were filled with wrecks, and
vessels coming in disabled from every part of the Indian Ocean.” Again,
Mr. Balfour Stewart accepts Mr. Jeula’s statistics confidently as
demonstrating that there are most shipwrecks during periods of maximum
solar activity. Nor are the advocates of the new method of prediction
at all doubtful as to the value of these relations in affording the
basis of a system of prediction. They do not tell us precisely _how_ we
are to profit by the fact, if fact it is, that cyclones and shipwrecks
mark the time of maximum solar maculation, and droughts and famine the
time of minimum. “If we can manage to get at these things,” says Mr.
Lockyer, “the power of prediction, that power which would be the most
useful one in meteorology, if we could only get at it, would be within
our grasp.” And Mr. Balfour Stewart, in a letter to the _Times_, says,
“If we are on the track of a discovery which will in time enable
us to foretell the cycle of droughts, public opinion should demand
that the investigation be prosecuted with redoubled vigour and under
better conditions. If forewarned be forearmed, then such research will
ultimately conduce to the saving of life both at times of maximum and
minimum sun-spot frequency.”
If these hopes are really justified by the facts of the case, it would
be well that the matter should be as quickly as possible put to the
test. No one would be so heartless, I think, as to reject, through an
excess of scientific caution, a scheme which might issue in the saving
of many lives from famine or from shipwreck. And on the other hand, no
one, I think, would believe so ill of his fellow-men as to suppose for
one moment that advantage could be taken of the sympathies which have
been aroused by the Indian famine, or which may from time to time be
excited by the record of great disasters by sea and land, to advocate
bottomless schemes merely for purposes of personal advancement. We must
now, perforce, believe that those who advocate the erection of new
observatories and laboratories for studying the physics of the sun,
have the most thorough faith in the scheme which they proffer to save
our Indian population from famine and our seamen from shipwreck.
But they, on the other hand, should now also believe that those who
have described the scheme as entirely hopeless, do really so regard it.
If we exonerate them from the charge of responding to an appeal for
food by offering spectroscopes, they in turn should exonerate us from
the charge of denying spectroscopes to the starving millions of India
though knowing well that the spectroscopic track leads straight to
safety.
I must acknowledge I cannot for my own part see even that small modicum
of hope in the course suggested which would suffice to justify its
being followed. In my opinion, one ounce of rice would be worth more
(simply because it would be worth something) than ten thousand tons of
spectroscopes. For what, in the first place, has been shown as to the
connection between meteorological phenomena and sun-spots? Supposing we
grant, and it is granting a great deal, that all the cycles referred
to have been made out. They one and all affect averages only. The most
marked among them can so little be trusted in detail that while the
maximum of sun-spots agrees _in the main_ with an excess or defect of
rain or wind, or of special rains with special winds, or the like, the
actual year of maximum may present the exact reverse.
Of what use can it be to know, for instance, that the three years of
least solar maculation will probably give a rainfall less than that
for the preceding or following three years, if the middle year of
the three, when the spots are most numerous of all, _may_ haply show
plenteous rainfall? Or it may be the first of the three, or the last,
which is thus well supplied, while a defect in the other two, or in one
of the others, brings the total triennial rainfall below the average.
What provision could possibly be made under such circumstances to meet
a contingency which may occur in any one of three years? or, at least,
what provision could be made which would prove nearly so effective
as an arrangement which could readily be made for keeping sufficient
Government stores at suitable stations (that is, never allowing such
stores to fall at the critical season in each year below a certain
minimum), and sending early telegraphic information of unfavourable
weather? Does any one suppose that the solar rice-grains are better
worth watching for such a purpose than the terrestrial rice-grains, or
that it is not well within the resources of modern science and modern
means of communication and transport, to make sufficient preparation
each year for a calamity always possible in India? And be it noticed
that if, on the one hand, believers in solar safety from famine may
urge that, in thus objecting to their scheme, I am opposing what might,
in some year of great famine and small sun-spots, save the lives of
a greater number than would be saved by any system of terrestrial
watchfulness, I would point out, on the other, that the solar scheme,
if it means anything at all, means special watchfulness at the minimum
sun-spot season, and general confidence (so far as famine is concerned)
at the season of maximum solar maculation; and that while as yet
nothing has been really proved about the connection between sun-spots
and famine, such confidence might prove to be a very dangerous mistake.
Supposing even it were not only proved that sun-spots exert such and
such effects, but that this knowledge can avail to help us to measures
of special precaution, how is the study of the sun going to advance
our knowledge? In passing, let it be remarked that already an enormous
number of workers are engaged in studying the sun in every part of
the world. The sun is watched on every fine day, in every quarter of
the earth, with the telescope, analyzed with the spectroscope, his
prominences counted and measured, his surface photographed, and so
forth. What more ought to be or could be done? But that is not the main
point. If more could be done, what could be added to our knowledge
which would avail in the way of prediction? “At present,” says Mr.
Balfour Stewart, “the problem has not been pursued on a sufficiently
large scale or in a sufficient number of places. If the attack is to
be continued, the skirmishers should give way to heavy guns, and these
should be brought to bear without delay now that the point of attack is
known.” In other words, now that we know, according to the advocates
of these views, that meteorological phenomena follow roughly the great
solar-spot period, we should prosecute the attack in this direction,
in order to find out—what? Minor periods, perhaps, with which
meteorological phenomena may still more roughly synchronize. Other such
periods are already known with which meteorological phenomena have
never yet been associated. New details of the sun’s surface? No one has
yet pretended that any of the details already known, except the spots,
affect terrestrial weather, and the idea that peculiarities so minute
as hitherto to have escaped detection can do so, is as absurd, on the
face of it, as the supposition that minute details in the structure
of a burning coal, such details as could only be detected by close
scrutiny, can affect the general quality and effects of the heat
transmitted by the coal, as part of a large fire, to the further side
of a large room.
Lastly, I would urge this general argument against a theory which seems
to me to have even less to recommend it to acceptance than the faith
in astrology.[8] _If it requires, as we are so strongly assured, the
most costly observations, the employment of the heaviest guns (and
“great guns” are generally expensive), twenty or thirty years of time,
and the closest scrutiny and research, to prove that sun-spots affect
terrestrial relations in a definite manner, effects so extremely
difficult to demonstrate cannot possibly be important enough to be
worth predicting._
_NEW WAYS OF MEASURING THE SUN’S DISTANCE._
It is strange that the problem of determining the sun’s distance, which
for many ages was regarded as altogether insoluble, and which even
during later years had seemed fairly solvable in but one or two ways,
should be found, on closer investigation, to admit of many methods
of solution. If astronomers should only be as fortunate hereafter in
dealing with the problem of determining the distances of the stars,
as they have been with the question of the sun’s distance, we may
hope for knowledge respecting the structure of the universe such as
even the Herschels despaired of our ever gaining. Yet this problem of
determining star-distances does not seem more intractable, now, than
the problem of measuring the sun’s distance appeared only two centuries
ago. If we rightly view the many methods devised for dealing with the
easier task, we must admit that the more difficult—which, by the way,
is in reality infinitely the more interesting—cannot be regarded
as so utterly hopeless as, with our present methods and appliances,
it appears to be. True, we know only the distances of two or three
stars, approximately, and have means of forming a vague opinion
about the distances of only a dozen others, or thereabouts, while at
distances now immeasurable lie six thousand stars visible to the eye,
and twenty millions within range of the telescope. Yet, in Galileo’s
time, men might have argued similarly against all hope of measuring
the proportions of the solar system. “We know only,” they might have
urged, “the distance of the moon, our immediate neighbour,—beyond
her, at distances so great that hers, so far as we can judge, is by
comparison almost as nothing, lie the Sun and Mercury, Venus and Mars;
further away yet lie Jupiter and Saturn, and possibly other planets,
not visible to the naked eye, but within range of that wonderful
instrument, the telescope, which our Galileo and others are using so
successfully. What hope can there be, when the exact measurement of the
moon’s distance has so fully taxed our powers of celestial measurement,
that we can ever obtain exact information respecting the distances of
the sun and planets? By what method is a problem so stupendous to be
attacked?” Yet, within a few years of that time, Kepler had formed
already a rough estimate of the distance of the sun; in 1639, young
Horrocks pointed to a method which has since been successfully applied.
Before the end of the seventeenth century Cassini and Flamsteed had
approached the solution of the problem more nearly, while Hailey had
definitely formulated the method which bears his name. Long before the
end of the eighteenth century it was certainly known that the sun’s
distance lies between 85 millions of miles and 98 millions (Kepler,
Cassini, and Flamsteed had been unable to indicate any superior limit).
And lastly, in our own time, half a score of methods, each subdivisible
into several forms, have been applied to the solution of this
fundamental problem of observational astronomy.
I propose now to sketch some new and very promising methods, which have
been applied already with a degree of success arguing well for the
prospects of future applications of the methods under more favourable
conditions.
In the first place, let us very briefly consider the methods which had
been before employed, in order that the proper position of the new
methods may be more clearly recognized.
The plan obviously suggested at the outset for the solution of the
problem was simply to deal with it as a problem of surveying. It was
in such a manner that the moon’s distance had been found, and the
only difficulty in applying the method to the sun or to any planet
consisted in the delicacy of the observations required. The earth being
the only surveying-ground available to astronomers in dealing with
this problem (in dealing with the problem of the stars’ distances they
have a very much wider field of operations), it was necessary that
a base-line should be measured on this globe of ours,—large enough
compared with our small selves, but utterly insignificant compared
with the dimensions of the solar system. The diameter of the earth
being less than 8000 miles, the longest line which the observers could
take for base scarcely exceeded 6000 miles; since observations of the
same celestial object at opposite ends of a diameter necessarily imply
that the object is in the horizon of _both_ the observing stations
(for precisely the same reason that two cords stretched from the ends
of any diameter of a ball to a distant point touch the ball at those
ends). But the sun’s distance being some 92 millions of miles, a base
of 6000 miles amounts to less than the 15,000th part of the distance
to be measured. Conceive a surveyor endeavouring to determine the
distance of a steeple or rock 15,000 feet, or nearly three miles, from
him, with a base-line _one foot_ in length, and you can conceive the
task of astronomers who should attempt to apply the direct surveying
method to determine the sun’s distance,—at least, you have one of
their difficulties strikingly illustrated, though a number of others
remain which the illustration does not indicate. For, after all, a
base one foot in length, though far too short, is a convenient one in
many respects: the observer can pass from one end to the other without
trouble—he looks at the distant object under almost exactly the same
conditions from each end, and so forth. A base 6000 miles long for
determining the sun’s distance is too short in precisely the same
degree, but it is assuredly not so convenient a base for the observer.
A giant 36,000 miles high would find it as convenient as a surveyor
six feet high would find a one foot base-line; but astronomers, as
a rule, are less than 36,000 miles in height. Accordingly the same
observer cannot work at both ends of the base-line, and they have to
send out expeditions to occupy each station. All the circumstances
of temperature, atmosphere, personal observing qualities, etc., are
unlike at the two ends of the base-line. The task of measuring the
sun’s distance directly is, in fact, at present beyond the power of
observational astronomy, wonderfully though its methods have developed
in accuracy.
We all know how, by observations of Venus in transit, the difficulty
has been so far reduced that trustworthy results have been obtained.
Such observations belong to the surveying method, only Venus’s distance
is made the object of measurement instead of the sun’s. The sun serves
simply as a sort of dial-plate, Venus’s position while in transit
across this celestial dial-plate being more easily measured than when
she is at large upon the sky. The devices by which Halley and Delisle
severally caused _time_ to be the relation observed, instead of
position, do not affect the general principle of the transit method. It
remains dependent on the determination of position. Precisely as by the
change of the _position_ of the hands of a clock on the face we measure
_time_, so by the transit method, as Halley and Delisle respectively
suggested its use, we determine Venus’s position on the sun’s face,
by observing the difference of the time she takes in crossing, or the
difference of the time at which she begins to cross, or passes off, his
face.
Besides the advantage of having a dial-face like the sun’s on which
thus to determine positions, the transit method deals with Venus when
at her nearest, or about 25 million miles from us, instead of the sun
at his greater distance of from 90½ to 93½ millions of miles. Yet we
do not get the entire advantage of this relative proximity of Venus.
For the dial-face—the sun, that is—changes its position too—in less
degree than Venus changes hers, but still so much as largely to reduce
her seeming displacement. The sun being further away as 92 to 25, is
less displaced as 25 to 92. Venus’s displacement is thus diminished by
25/92nds of its full amount, leaving only 67/92nds. Practically, then,
the advantage of observing Venus, so far as distance is concerned, is
the same as though, instead of being at a distance of only 25 million
miles, her distance were greater as 92 to 67, giving as her effective
distance when in transit some 34,300,000 miles.
All the methods of observing Venus in transit are affected in _this_
respect. Astronomers were not content during the recent transit to use
Halley’s and Delisle’s two time methods (which may be conveniently
called the duration method and the epoch method), but endeavoured to
determine the position of Venus on the sun’s face directly, both by
observation and by photography. The heliometer was the instrument
specially used for the former purpose; and as, in one of the new
methods to be presently described, this is the most effective of all
available instruments, a few words as to its construction will not be
out of place.
The heliometer, then, is a telescope whose object-glass (that is,
the large glass at the end towards the object observed) is divided
into two halves along a diameter. When these two halves are exactly
together—that is, in the position they had before the glass was
divided—of course they show any object to which they may be directed
precisely as they would have done before the glass was cut. But if,
without separating the straight edges of the two semicircular glasses,
one be made to slide along the other, the images formed by the two
no longer coincide.[9] Thus, if we are looking at the sun we see
two overlapping discs, and by continuing to turn the screw or other
mechanism which carries our half-circular glass past the other, the
disc-images of the sun may be brought entirely clear of each other.
Then we have two suns in the same field of view, seemingly in contact,
or nearly so. Now, if we have some means of determining how far the
movable half-glass has been carried past the other to bring the two
discs into apparently exact contact, we have, in point of fact, a
measure of the sun’s apparent diameter. We can improve this estimate by
carrying back the movable glass till the images coincide again, then
further back till they separate the other way and finally are brought
into contact on that side. The entire range, from contact on one side
to contact on the other side, gives twice the entire angular span of
the sun’s diameter; and the half of this is more likely to be the true
measure of the diameter, than the range from coincident images to
contact either way, simply because instrumental errors are likely to be
more evenly distributed over the double motion than over the movement
on either side of the central position. The heliometer derived its
name—which signifies sun-measurer—from this particular application of
the instrument.
It is easily seen how the heliometer was made available in determining
the position of Venus at any instant during transit. The observer
could note what displacement of the two half-glasses was necessary to
bring the black disc of Venus on one image of the sun to the edge of
the other image, first touching on the inside and then on the outside.
Then, reversing the motion, he could carry her disc to the opposite
edge of the other image of the sun, first touching on the inside and
then on the outside. Lord Lindsay’s private expedition—one of the
most munificent and also one of the most laborious contributions to
astronomy ever made—was the only English expedition which employed
the heliometer, none of our public observatories possessing such an
instrument, and official astronomers being unwilling to ask Government
to provide instruments so costly. The Germans, however, and the
Russians employed the heliometer very effectively.
Next in order of proximity, for the employment of the direct surveying
method, is the planet Mars when he comes into opposition (or on the
same line as the earth and sun) in the order
Sun____________________________Earth__________Mars,
at a favourable part of his considerably eccentric orbit. His distance
then may be as small as 34½ millions of miles; and we have in his case
to make no reduction for the displacement of the background on which
his place is to be determined. That background is the star sphere,
his place being measured from that of stars near which his apparent
path on the heavens carries him; and the stars are so remote that
the displacement due to a distance of six or seven thousand miles
between two observers on the earth is to all intents and purposes
nothing. The entire span of the earth’s orbit round the sun, though
amounting to 184 millions of miles, is a mere point as seen from all
save ten or twelve stars; how utterly evanescent, then, the span of
the earth’s globe—less than the 23,000th part of her orbital range!
Thus the entire displacement of Mars due to the distance separating
the terrestrial observers comes into effect. So that, in comparing the
observation of Mars in a favourable opposition with that of Venus in
transit, we may fairly say that, so far as surveying considerations are
concerned, the two planets are equally well suited for the astronomer’s
purpose. Venus’s less distance of 25 millions of miles is effectively
increased to 34⅓ millions by the displacement of the solar background
on which we see her when in transit; while Mars’s distance of about
34½ millions of miles remains effectively the same when we measure his
displacement from neighbouring fixed stars.
But in many respects Mars is superior to Venus for the purpose of
determining the sun’s distance. Venus can only be observed at her
nearest when in transit, and transit lasts but a few hours. Mars can
be observed night after night for a fortnight or so, during which his
distance still remains near enough to the least or opposition distance.
Again, Venus being observed on the sun, all the disturbing influences
due to the sun’s heat are at work in rendering the observation
difficult. The air between us and the sun at such a time is disturbed
by undulations due in no small degree to the sun’s action. It is true
that we have not, in the case of Mars, any means of substituting time
measures or time determinations for measures of position, as we have
in Venus’s case, both with Halley’s and Delisle’s methods. But to say
the truth, the advantage of substituting these time observations has
not proved so great as was expected. Venus’s unfortunate deformity of
figure when crossing the sun’s edge renders the determination of the
exact moments of her entry on the sun’s face and of her departure from
it by no means so trustworthy as astronomers could wish. On the whole,
Mars would probably have the advantage even without that point in his
favour which has now to be indicated.
Two methods of observing Mars for determining the sun’s distance are
available, both of which, as they can be employed in applying one of
the new methods, may conveniently be described at this point.
An observer far to the north of the earth’s equator sees Mars at
midnight, when the planet is in opposition, displaced somewhat to
the south of his true position—that is, of the position he would
have as supposed to be seen from the centre of the earth. On the
other hand, an observer far to the south of the equator sees Mars
displaced somewhat to the north of his true position. The difference
may be compared to different views of a distant steeple (projected,
let us suppose, against a much more remote hill), from the uppermost
and lowermost windows of a house corresponding to the northerly and
southerly stations on the earth, and from a window on the middle
story corresponding to a view of Mars from the earth’s centre. By
ascertaining the displacement of the two views of Mars obtained from
a station far to the north and another station far to the south,
the astronomer can infer the distance of the planet, and thence the
dimensions of the solar system. The displacement is determinable by
noticing Mars’s position with respect to stars which chance to be close
to him. For this purpose the heliometer is specially suitable, because,
having first a view of Mars and some companion stars as they actually
are placed, the observer can, by suitably displacing the movable
half-glass, bring the star into apparent contact with the planet, first
on one side of its disc, and then on the other side—the mean of the
two resulting measures giving, of course, the distance between the star
and the centre of the disc.
This method requires that there shall be two observers, one at a
northern station, as Greenwich, or Paris, or Washington, the other at
a southern station, as Cape Town, Cordoba, or Melbourne. The base-line
is practically a north-and-south line; for though the two stations may
not lie in the same, or nearly the same, longitude, the displacement
determined is in reality that due to their difference of latitude only,
a correction being made for their difference of longitude.
The other method depends, not on displacement of two observers north
and south, or difference of latitude, but on displacement east and
west. Moreover, it does not require that there shall be two observers
at stations far apart, but uses the observations made at one and the
same stations at different times. The earth, by turning on her axis,
carries the observer from the west to the east of an imaginary line
joining the earth’s centre and the centre of Mars. When on the west
of that line, or in the early evening, he sees Mars displaced towards
the east of the planet’s true position. After nine or ten hours the
observer is carried as far to the east of that line, and sees Mars
displaced towards the west of his true position. Of course Mars has
moved in the interval. He is, in fact, in the midst of his retrograde
career. But the astronomer knows perfectly well how to take that
motion into account. Thus, by observing the two displacements, or the
total displacement of Mars from east to west on account of the earth’s
rotation, one and the same observer can, in the course of a single
favourable night, determine the sun’s distance. And in passing, it may
be remarked that this is the only general method of which so much can
be said. By some of the others an astronomer can, indeed, estimate the
sun’s distance without leaving his observatory—at least, theoretically
he can do so. But many years of observation would be required before he
would have materials for achieving this result. On the other hand, one
good pair of observations of Mars, in the evening and in the morning,
from a station near the equator, would give a very fair measure of
the sun’s distance. The reason why the station should be near the
equator will be manifest, if we consider that at the poles there
would be no displacement due to rotation; at the equator the observer
would be carried round a circle some twenty-five thousand miles in
circumference; and the nearer his place to the equator the larger
the circle in which he would be carried, and (_cæteris paribus_) the
greater the evening and morning displacement of the planet.
Both these methods have been successfully applied to the problem of
determining the sun’s distance, and both have recently been applied
afresh under circumstances affording exceptionally good prospects of
success, though as yet the results are not known.
It is, however, when we leave the direct surveying method to which
both the observations of Venus in transit and Mars in opposition
belong (in all their varieties), that the most remarkable, and, one
may say, unexpected methods of determining the sun’s distance present
themselves. Were not my subject a wide one, I would willingly descant
at length on the marvellous ingenuity with which astronomers have
availed themselves of every point of vantage whence they might measure
the solar system. But, as matters actually stand, I must be content
to sketch these other methods very roughly, only indicating their
characteristic features.
One of them is in some sense related to the method by actual survey,
only it takes advantage, not of the earth’s dimensions, but of the
dimensions of her orbit round the common centre of gravity of herself
and the moon. This orbit has a diameter of about six thousand miles;
and as the earth travels round it, speeding swiftly onwards all the
time in her path round the sun, the effect is the same as though the
sun, in his apparent circuit round the earth, were constantly circling
once in a lunar month around a small subordinate orbit of precisely the
same size and shape as that small orbit in which the earth circuits
round the moon’s centre of gravity. He appears then sometimes displaced
about 3000 miles on one side, sometimes about 3000 miles on the other
side of the place which he would have if our earth were not thus
perturbed by the moon. But astronomers can note each day where he is,
and thus learn by how much he seems displaced from his mean position.
Knowing that his greatest displacement corresponds to so many miles
exactly, and noting what it seems to be, they learn, in fact, how large
a span of so many miles (about 3000) looks at the sun’s distance.
Thus they learn the sun’s distance precisely as a rifleman learns the
distance of a line of soldiers when he has ascertained their apparent
size—for only at a certain distance can an object of known size have a
certain apparent size.
The moon comes in, in another way, to determine the sun’s distance
for us. We know how far away she is from the earth, and how much,
therefore, she approaches the sun when new, and recedes from him when
full. Calling this distance, roughly, a 390th part of the sun’s, her
distance from him when new, her mean distance, and her distance from
him when full, are as the numbers 389, 390, 391. Now, these numbers
do not quite form a continued proportion, though they do so very
nearly (for 389 is to 390 as 390 to 391-1/400). If they were in exact
proportion, the sun’s disturbing influence on the moon when she is at
her nearest would be exactly equal to his disturbing influence on the
moon when at her furthest from him—or generally, the moon would be
exactly as much disturbed (on the average) in that half of her path
which lies nearer to the sun as in that half which lies further from
him. As matters are, there is a slight difference. Astronomers can
measure this difference; and measuring it, they can ascertain what the
actual numbers are for which I have roughly given the numbers 389, 390,
and 391; in other words, they can ascertain in what degree the sun’s
distance exceeds the moon’s. This is equivalent to determining the
sun’s distance, since the moon’s is already known.
Another way of measuring the sun’s distance has been “favoured”
by Jupiter and his family of satellites. Few would have thought,
when Römer first explained the delay which occurs in the eclipse of
these moons while Jupiter is further from us than his mean distance,
that that explanation would lead up to a determination of the sun’s
distance. But so it happened. Römer showed that the delay is not in the
recurrence of the eclipses, but in the arrival of the news of these
events. From the observed time required by light to traverse the extra
distance when Jupiter is nearly at his furthest from us, the time in
which light crosses the distance separating us from the sun is deduced;
whence, if that distance has been rightly determined, the velocity of
light can be inferred. If this velocity is directly measured in any
way, and found not to be what had been deduced from the adopted measure
of the sun’s distance, the inference is that the sun’s distance has
been incorrectly determined. Or, to put the matter in another way, we
know exactly how many minutes and seconds light takes in travelling to
us from the sun; if, therefore, we can find out how fast light travels
we know how far away the sun is.
But who could hope to measure a velocity approaching 200,000 miles in a
second? At a first view the task seems hopeless. Wheatstone, however,
showed how it might be accomplished, measuring by his method the yet
greater velocity of freely conducted electricity. Foucault and Fizeau
measured the velocity of light; and recently Cornu has made more exact
measurements. Knowing, then, how many miles light travels in a second,
and in how many seconds it comes to us from the sun, we know the sun’s
distance.
The first of the methods which I here describe as new methods must next
be considered. It is one which Leverrier regards as the method of the
future. In fact, so highly does he esteem it, that, on its account, he
may almost be said to have refused to sanction in any way the French
expeditions for observing the transit of Venus in 1874.
The members of the sun’s family perturb each other’s motions in a
degree corresponding with their relative mass, compared with each
other and with the sun. Now, it can be shown (the proof would be
unsuitable to these pages,[10] but I have given it in my treatise
on “The Sun”) that no change in our estimate of the sun’s distance
affects our estimate of his mean density as compared with the earth’s.
His substance has a mean density equal to one-fourth of the earth’s,
whether he be 90 millions or 95 millions of miles from us, or indeed
whether he were ten millions or a million million miles from us
(supposing for a moment our measures did not indicate his real distance
more closely). We should still deduce from calculation the same
unvarying estimate of his mean density. It follows that the nearer
any estimate of his distance places him, and therefore the smaller it
makes his estimated volume, the smaller also it makes his estimated
mass, and in precisely the same degree. The same is true of the planets
also. We determine Jupiter’s mass, for example (at least, this is the
simplest way), by noting how he swerves his moons at their respective
(estimated) distances. If we diminish our estimate of their distances,
we diminish at the same time our estimate of Jupiter’s attractive
power, and in such degree, it may be shown (see note), as precisely to
correspond with our changed estimate of his size, leaving our estimate
of his mean density unaltered. And the same is true for all methods of
determining Jupiter’s mass. Suppose, then, that, adopting a certain
estimate of the scale of the solar system, we find that the resulting
estimate of the masses of the planets and of the sun, _as compared with
the earth’s mass_, from their observed attractive influences on bodies
circling around them or passing near them, accords with their estimated
perturbing action as compared with the earth’s,—then we should infer
that our estimate of the sun’s distance or of the scale of the solar
system was correct. But suppose it appeared, on the contrary, that
the earth took a larger or a smaller part in perturbing the planetary
system than, according to our estimate of her relative mass, she
should do,—then we should infer that the masses of the other members
of the system had been overrated or underrated; or, in other words,
that the scale of the solar system had been overrated or underrated
respectively. Thus we should be able to introduce a correction into our
estimate of the sun’s distance.
Such is the principle of the method by which Leverrier showed that in
the astronomy of the future the scale of the solar system may be very
exactly determined. Of course, the problem is a most delicate one. The
earth plays, in truth, but a small part in perturbing the planetary
system, and her influence can only be distinguished satisfactorily
(at present, at any rate) in the case of the nearer members of the
solar family. Yet the method is one which, unlike others, will have
an accumulative accuracy, the discrepancies which are to test the
result growing larger as time proceeds. The method has already been
to some extent successful. It was, in fact, by observing that the
motions of Mercury are not such as can be satisfactorily explained by
the perturbations of the earth and Venus according to the estimate of
relative masses deducible from the lately discarded value of the sun’s
distance, that Leverrier first set astronomers on the track of the
error affecting that value. He was certainly justified in entertaining
a strong hope that hereafter this method will be exceedingly effective.
We come next to a method which promises to be more quickly if not more
effectively available.
Venus and Mars approach the orbit of our earth more closely than any
other planets, Venus being our nearest neighbour on the one side, and
Mars on the other. Looking beyond Venus, we find only Mercury (and the
mythical Vulcan), and Mercury can give no useful information respecting
the sun’s distance. He could scarcely do so even if we could measure
his position among the stars when he is at his nearest, as we can
that of Mars; but as he can only then be fairly seen when he transits
the sun’s face, and as the sun is nearly as much displaced as Mercury
by change in the observer’s station, the difference between the two
displacements is utterly insufficient for accurate measurement. But,
when we look beyond the orbit of Mars, we find certain bodies which are
well worth considering in connection with the problem of determining
the sun’s distance. I refer to the asteroids, the ring of small planets
travelling between the paths of Mars and Jupiter, but nearer (on the
whole[11]) to the path of Mars than to that of Jupiter.
The asteroids present several important advantages over even Mars and
Venus.
Of course, none of the asteroids approach so near to the earth as Mars
at his nearest. His least distance from the sun being about 127 million
miles, and the earth’s mean distance about 92 millions, with a range of
about a million and a half on either side, owing to the eccentricity of
her orbit, it follows that he _may_ be as near as some 35 million miles
(rather less in reality) from the earth when the sun, earth, and Mars
are nearly in a straight line and in that order. The least distance of
any asteroid from the sun amounts to about 167 million miles, so that
their least distance from the earth cannot at any time be less than
about 73,500,000 miles, even if the earth’s greatest distance from
the sun corresponded with the least distance of one of these closely
approaching asteroids. This, by the way, is not very far from being the
case with the asteroid Ariadne, which comes within about 169 million
miles of the sun at her nearest, her place of nearest approach being
almost exactly in the same direction from the sun as the earth’s place
of greatest recession, reached about the end of June. So that, whenever
it so chances that Ariadne comes into opposition in June, or that the
sun, earth, and Ariadne are thus placed—
Sun________Earth________Ariadne,
Ariadne will be but about 75,500,000 miles from the earth. Probably no
asteroid will ever be discovered which approaches the earth much more
nearly than this; and this approach, be it noticed, is not one which
can occur in the case of Ariadne except at very long intervals.
But though we may consider 80 millions of miles as a fair average
distance at which a few of the most closely approaching asteroids may
be observed, and though this distance seems very great by comparison
with Mars’s occasional opposition distance of 35 million miles, yet
there are two points in which asteroids have the advantage over Mars.
First, they are many, and several among them can be observed under
favourable circumstances; and in the multitude of observations there
is safety. In the second place, which is the great and characteristic
good quality of this method of determining the sun’s distance, they do
not present a disc, like the planet Mars, but a small star-like point.
When we consider the qualities of the heliometric method of measuring
the apparent distance between celestial objects, the advantage of
points of light over discs will be obvious. If we are measuring the
apparent distance between Mars and a star, we must, by shifting the
movable object-glass, bring the star’s image into apparent contact
with the disc-image of Mars, first on one side and then on the other,
taking the mean for the distance between the centres. Whereas, when we
determine the distance between a star and an asteroid, we have to bring
two star-like points (one a star, the other the asteroid) into apparent
coincidence. We can do this in two ways, making the result so much the
more accurate. For consider what we have in the field of view when the
two halves of the object-glass coincide. There is the asteroid and
close by there is the star whose distance we seek to determine in order
to ascertain the position of the asteroid on the celestial sphere.
When the movable half is shifted, the two images of star and asteroid
separate; and by an adjustment they can be made to separate along the
line connecting them. Suppose, then, we first make the movable image
of the asteroid travel away from the fixed image (meaning by movable
and fixed images, respectively, those given by the movable and fixed
halves of the object-glass), towards the fixed image of the star—the
two points, like images, being brought into coincidence, we have the
measure of the distance between star and asteroid. Now reverse the
movement, carrying back the movable images of the asteroid and star
till they coincide again with their fixed images. This movement gives
us a second measure of the distance, which, however, may be regarded as
only a reversed repetition of the preceding. But now, carrying on the
reverse motion, the moving images of star and asteroid separate from
their respective fixed images, the moving image of the star drawing
near to the fixed image of the asteroid and eventually coinciding with
it. Here we have a third measure of the distance, which is independent
of the two former. Reversing the motion, and carrying the moving
images to coincidence with the fixed images, we have a fourth measure,
which is simply the third reversed. These four measures will give a
far more satisfactory determination of the true apparent distance
between the star and the asteroid than can, under any circumstances,
be obtained in the case of Mars and a star. Of course, a much more
exact determination is required to give satisfactory measures of the
asteroid’s real distance from the earth in miles, for a much smaller
error would vitiate the estimate of the asteroid’s distance than would
vitiate to the same degree the estimate of Mars’s distance: for the
apparent displacements of the asteroid as seen either from Northern and
Southern stations, or from stations east and west of the meridian, are
very much less than in the case of Mars, owing to his great proximity.
But, on the whole, there are reasons for believing that the advantage
derived from the nearness of Mars is almost entirely counterbalanced
by the advantage derived from the neatness of the asteroid’s image.
And the number of asteroids, with the consequent power of repeating
such measurements many times for each occasion on which Mars has been
thus observed, seem to make the asteroids—so long regarded as very
unimportant members of the solar system—the bodies from which, after
all, we shall gain our best estimate of the sun’s distance; that is, of
the scale of the solar system.
* * * * *
Since the above pages were written, the results deduced from the
observations made by the British expeditions for observing the transit
of December 9, 1874, have been announced by the Astronomer Royal.
It should be premised that they are not the results deducible from
the entire series of British observations, for many of them can only
be used effectively in combination with observations made by other
nations. For instance, the British observations of the duration of the
transit as seen from Southern stations are only useful when compared
with observations of the duration of the transit as seen from Northern
stations, and no British observations of this kind were taken at
Northern stations, or could be taken at any of the British Northern
stations except one, where chief reliance was placed on photographic
methods. The only British results as yet “worked up” are those which
are of themselves sufficient, theoretically, to indicate the sun’s
distance, viz., those which indicated the epochs of the commencement of
transit as seen from Northern and Southern stations, and those which
indicated the epochs of the end of transit as seen from such stations.
The Northern and Southern epochs of commencement compared together
suffice _of themselves_ to indicate the sun’s distance; so also do the
epochs of the end of transit suffice _of themselves_ for that purpose.
Such observations belong to the Delislean method, which was the subject
of so much controversy for two or three years before the transit took
place. Originally it had been supposed that only observations by that
method were available, and the British plans were formed upon that
assumption. When it was shown that this assumption was altogether
erroneous, there was scarcely time to modify the British plans so that
of themselves they might provide for the other or Halleyan method.
But the Southern stations which were suitable for that method were
strengthened; and as other nations, especially America and Russia,
occupied large numbers of Northern stations, the Halleyan method was,
in point of fact, effectually provided for—a fortunate circumstance,
as will presently be seen.
The British operations, then, thus far dealt with, were based on
Delisle’s method; and as they were carried out with great zeal and
completeness, we may consider that the result affords an excellent
test of the qualities of this method, and may supply a satisfactory
answer to the questions which were under discussion in 1872–74. Sir
George Airy, indeed, considers that the zeal and completeness with
which the British operations were carried out suffice to set the
result obtained from them above all others. But this opinion is based
rather on personal than on strictly scientific grounds. It appears to
me that the questions to be primarily decided are whether the results
are in satisfactory agreement (i) _inter se_ and (ii) with the general
tenor of former researches. In other words, while the Astronomer Royal
considers that the method and the manner of its application must
be considered so satisfactory that the results are to be accepted
unquestionably, it appears to me that the results must be carefully
questioned (as it were) to see whether the method, and the observations
by it, are satisfactory. In the first place, the result obtained
from Northern and Southern observations of the commencement ought to
agree closely with the result obtained from Northern and Southern
observations of the end of transit. Unfortunately, they differ rather
widely. The sun’s distance by the former observations comes out about
one million miles greater than the distance determined by the latter
observations.
This should be decisive, one would suppose. But it is not all.
The mean of the entire series of observations by Delisle’s method
comes out nearly one million miles greater than the mean deduced by
Professor Newcomb from many entire series of observations by six
different methods, all of which may fairly be regarded as equal in
value to Delisle’s, while three are regarded by most astronomers as
unquestionably superior to it. Newcomb considers the probable limits of
error in his evaluation from so many combined series of observations
to be about 100,000 miles. Sir G. Airy will allow no wider limits of
error for the result of the one series his observers have obtained than
200,000 miles. Thus the greatest value admitted by Newcomb falls short
of the least value admitted by Sir G. Airy, by nearly 700,000 miles.
The obvious significance of this result should be, one would suppose,
that Delisle’s method is not quite so effective as Sir G. Airy
supposed; and the wide discordance between the several results, of
which the result thus deduced is the mean, should prove this, one
would imagine, beyond all possibility of question. The Astronomer
Royal thinks differently, however. In his opinion, the wide difference
between his result and the mean of all the most valued results by other
astronomers, indicates the superiority of Delisle’s method, not its
inadequacy to the purpose for which it has been employed.
Time will shortly decide which of these views is correct; but, for my
own part, I do not hesitate to express my own conviction that the sun’s
distance lies very near the limits indicated by Newcomb, and therefore
is several hundred thousand miles less than the minimum distance
allowed by the recently announced results.
DRIFTING LIGHT-WAVES.
The method of measuring the motion of very swiftly travelling bodies
by noting changes in the light-waves which reach us from them—one
of the most remarkable methods of observation ever yet devised by
man—has recently been placed upon its trial, so to speak; with results
exceedingly satisfactory to the students of science who had accepted
the facts established by it. The method will not be unfamiliar to many
of my readers. The principle involved was first noted by M. Doppler,
but not in a form which promised any useful results. The method
actually applied appears to have occurred simultaneously to several
persons, as well theorists as observers. Thus Secchi claimed in March,
1868, to have applied it though unsuccessfully; Huggins in April, 1868,
described his successful use of the method. I myself, wholly unaware
that either of these observers was endeavouring to measure celestial
motions by its means, described the method, in words which I shall
presently quote, in the number of _Fraser’s Magazine_ for January,
1868, two months before the earliest enunciation of its nature by the
physicists just named.
It will be well briefly to describe the principle of this interesting
method, before considering the attack to which it has been recently
subjected, and its triumphant acquittal from defects charged against
it. This brief description will not only be useful to those readers who
chance not to be acquainted with the method, but may serve to remove
objections which suggest themselves, I notice, to many who have had
the principle of the method imperfectly explained to them.
Light travels from every self-luminous body in waves which sweep
through the ether of space at the rate of 185,000 miles per second.
The whole of that region of space over which astronomers have extended
their survey, and doubtless a region many millions of millions of times
more extended, may be compared to a wave-tossed sea, only that instead
of a wave-tossed surface, there is wave-tossed space. At every point,
through every point, along every line, athwart every line, myriads of
light-waves are at all times rushing with the inconceivable velocity
just mentioned.
It is from such waves that we have learned all we know about the
universe outside our own earth. They bring to our shores news from
other worlds, though the news is not always easy to decipher.
Now, seeing that we are thus immersed in an ocean, athwart which
infinite series of waves are continually rushing, and moreover that
we ourselves, and every one of the bodies whence the waves proceed
either directly or after reflection, are travelling with enormous
velocity through this ocean, the idea naturally presents itself that we
may learn something about these motions (as well as about the bodies
themselves whence they proceed), by studying the aspect of the waves
which flow in upon us in all directions.
Suppose a strong swimmer who knew that, were he at rest, a certain
series of waves would cross him at a particular rate—ten, for
instance, in a minute—were to notice that when he was swimming
directly facing them, eleven passed him in a minute: he would be able
at once to compare his rate of swimming with the rate of the waves’
motion. He would know that while ten waves had passed him on account
of the waves’ motion, he had by his own motion caused yet another wave
to pass him, or in other words, had traversed the distance from one
wave-crest to the next Thus he would know that his rate was one-tenth
that of the waves. Similarly if, travelling the same way as the waves,
he found that only nine passed him in a minute, instead of ten.
Again, it is not difficult to see that if an observer were at rest,
and a body in the water, which by certain motions produced waves,
were approaching or receding from the observer, the waves would come
in faster in the former case, slower in the latter, than if the body
were at rest. Suppose, for instance, that some machinery at the bows
of a ship raised waves which, if the ship were at rest, would travel
along at the rate of ten a minute past the observer’s station. Then
clearly, if the ship approached him, each successive wave would have
a shorter distance to travel, and so would reach him sooner than it
otherwise would have done. Suppose, for instance, the ship travelled
one-tenth as fast as the waves, and consider ten waves proceeding from
her bows—the first would have to travel a certain distance before
reaching the observer; the tenth, starting a minute later, instead of
having to travel the same distance, would have to travel this distance
diminished by the space over which the ship had passed in one minute
(which the wave itself passes over in the tenth of a minute); instead,
then, of reaching the observer one minute after the other, it would
reach him nine-tenths of a minute after the first. Thus it would seem
to him as though the waves were coming in faster than when the ship was
at rest, in the proportion of ten to nine, though in reality they would
be travelling at the same rate as before, only arriving in quicker
succession, because of the continual shortening of the distance they
had to travel, on account of the ship’s approach. If he knew precisely
how fast they _would_ arrive if the ship were at rest, and determined
precisely how fast they _did_ arrive, he would be able to determine at
once the rate of the ship’s approach, at least the proportion between
her rate and the rate of the waves’ motion. Similarly if, owing to the
ship’s recession, the apparent rate of the waves’ motion were reduced,
it is obvious that the actual change in the wave motion would not be
a difference of rate; but, in the case of the approaching ship, the
breadth from crest to crest would be reduced, while in the case of a
receding ship the distance from crest to crest would be increased.
If the above explanation should still seem to require closer attention
than the general reader may be disposed to give, the following,
suggested by a friend of mine—a very skilful mathematician—will be
found still simpler: Suppose a stream to flow quite uniformly, and that
at one place on its banks an observer is stationed, while at another
higher up a person throws corks into the water at regular intervals,
say ten corks per minute; then these will float down and pass the other
observer, wherever he may be, at the rate of ten per minute, _if_
the cork-thrower is at rest. But if he saunters either up-stream or
down-stream, the corks will no longer float past the other at the exact
rate of ten per minute. If the thrower is sauntering down-stream, then,
between throwing any cork and the next, he has walked a certain way
down, and the tenth cork, instead of having to travel the same distance
as the first before reaching the observer, has a shorter distance to
travel, and so reaches that observer sooner. Or in fact, which some may
find easier to see, this cork will be nearer to the first cork than it
would have been if the thrower had remained still. The corks will lie
at equal distances from each other, but these equal distances will be
less than they would have been if the observer had been at rest. If, on
the contrary, the cork-thrower saunters up-stream, the corks will be
somewhat further apart than if he had remained at rest. And supposing
the observer to know beforehand that the corks would be thrown in
at the rate of ten a minute, he would know, if they passed him at a
greater rate than ten a minute (or, in other words, at a less distance
from each other than the stream traversed in the tenth of a minute),
that the cork-thrower was travelling down-stream or approaching him;
whereas, if fewer than ten a minute passed him, he would know that the
cork-thrower was travelling away from him, or up-stream. But also, if
the cork-thrower were at rest, and the observer moved up-stream—that
is, towards him—the corks would pass him at a greater rate than ten a
minute; whereas, if the observer were travelling down-stream, or from
the thrower, they would pass him at a slower rate. If both were moving,
it is easily seen that if their movement brought them nearer together,
the number of corks passing the observer per minute would be increased,
whereas if their movements set them further apart, the number passing
him per minute would be diminished.
These illustrations, derived from the motions of water, suffice in
reality for our purpose. The waves which are emitted by luminous
bodies in space travel onwards like the water-waves or the corks of
the preceding illustrations. If the body which emits them is rapidly
approaching us, the waves are set closer together or narrowed; whereas,
if the body is receding, they are thrown further apart or broadened.
And if we can in any way recognize such narrowing or broadening of the
light-waves, we know just as certainly that the source of light is
approaching us or receding from us (as the case may be) as our observer
in the second illustration would know from the distance between the
corks whether his friend, the cork-thrower, was drawing near to him or
travelling away from him.
But it may be convenient to give another illustration, drawn from
waves, which, like those of light, are not themselves discernible
by our senses—I refer to those aerial waves of compression and
rarefaction which produce what we call sound. These waves are not
only in this respect better suited than water-waves to illustrate
our subject, but also because they travel in all directions through
aerial space, not merely along a surface. The waves which produce
a certain note, that is, which excite in our minds, through the
auditory nerve, the impression corresponding to a certain tone, have
a definite length. So long as the observer, and a source of sound
vibrating in one particular period, remain both in the same place,
the note is unchanged in tone, though it may grow louder or fainter
according as the vibrations increase or diminish in amplitude. But if
the source of sound is approaching the hearer, the waves are thrown
closer together and the sound is rendered more acute (the longer waves
giving the deeper sound); and, on the other hand, if the source of
sound is receding from the hearer, the waves are thrown further apart
and the sound is rendered graver. The _rationale_ of these changes is
precisely the same as that of the changes described in the preceding
illustrations. It might, perhaps, appear that in so saying we were
dismissing the illustration from sound, at least as an independent
one, because we are explaining the illustration by preceding
illustrations. But in reality, while there is absolutely nothing
new to be said respecting the increase and diminution of distances
(as between the waves and corks of the preceding illustration),
the illustration from sound has the immense advantage of admitting
readily of experimental tests. It is necessary only that the rate of
approach or recession should bear an appreciable proportion to the
rate at which sound travels. For waves are shortened or lengthened by
approach or recession by an amount which bears to the entire length of
the wave the same proportion which the rate of approach or recession
bears to the rate of the wave’s advance. Now it is not very difficult
to obtain rates of approach or recession fairly comparable with the
velocity of sound—about 364 yards per second. An express train at
full speed travels, let us say, about 1800 yards per minute, or 30
yards per second. Such a velocity would suffice to reduce all the
sound-waves proceeding from a bell or whistle upon the engine, by
about one-twelfth part, for an observer at rest on a station platform
approached by the engine. On the contrary, after the engine had passed
him, the sound-waves proceeding from the same bell or whistle would be
lengthened by one-twelfth. The difference between the two tones would
be almost exactly three semitones. If the hearer, instead of being on
a platform, were in a train carried past the other at the same rate,
the difference between the tone of the bell in approaching and its
tone in receding would be about three tones. It would not be at all
difficult so to arrange matters, that while two bells were sounding the
same note—_Mi_, let us say—one bell on one engine the other on the
other, a traveller by one should hear his own engine’s bell, the bell
of the approaching engine, and the bell of the same engine receding,
as the three notes—_Do_—_Mi_—_Sol_, whose wave-lengths are as the
numbers 15, 12, and 10. We have here differences very easily to be
recognized even by those who are not musicians. Every one who travels
much by train must have noticed how the tone of a whistle changes as
the engine sounding it travels past. The change is not quite sharp,
but very rapid, because the other engine does not approach with a
certain velocity up to a definite moment and then recede with the same
velocity. It could only do this by rushing through the hearer, which
would render the experiment theoretically more exact but practically
unsatisfactory. As it rushes past instead of through him, there is a
brief time during which the rate of approach is rapidly being reduced
to nothing, followed by a similarly brief time during which the rate of
recession gradually increases from nothing up to the actual rate of the
engines’ velocities added together.[12] The change of tone may be thus
illustrated:—
[Illustration]
A B representing the sound of the approaching whistle, B C representing
the rapid degradation of sound as the engine rushes close past the
hearer, and C D representing the sound of the receding whistle. When
a bell is sounded on the engine, as in America, the effect is better
recognized, as I had repeated occasion to notice during my travels in
that country. Probably this is because the tone of a bell is in any
case much more clearly recognized than the tone of a railway whistle.
The change of tone as a clanging bell is carried swiftly past (by the
combined motions of both trains) is not at all of such a nature as to
require close attention for its detection.
However, the apparent variation of sound produced by rapid approach or
recession has been tested by exact experiments. On a railway uniting
Utrecht and Maarsen “were placed,” the late Professor Nichol wrote,
“at intervals of something upwards of a thousand yards, three groups
of musicians, who remained motionless during the requisite period.
Another musician on the railway sounded at intervals one uniform note;
and its effects on the ears of the stationary musicians have been
fully published. From these, certainly—from the recorded changes
between grave and the more acute, and _vice versâ_,—confirming, even
_numerically_, what the relative velocities might have enabled one to
predict, it appears justifiable to conclude that the general theory is
correct; and that the note of any sound may be greatly modified, if
not wholly changed, by the velocity of the individual hearing it,” or,
he should have added, by the velocity of the source of sound: perhaps
more correct than either, is the statement that the note may be altered
by the approach or recession of the source of sound, whether that be
caused by the motion of the sounding body, or of the hearer himself, or
of both.
It is difficult, indeed, to understand how doubt can exist in the
mind of any one competent to form an opinion on the matter, though,
as we shall presently see, some students of science and one or two
mathematicians have raised doubts as to the validity of the reasoning
by which it is shown that a change should occur. That the reasoning is
sound cannot, in reality, be questioned, and after careful examination
of the arguments urged against it by one or two mathematicians, I
can form no other opinion than that these arguments amount really
but to an expression of inability to understand the matter. This
may seem astonishing, but is explained when we remember that some
mathematicians, by devoting their attention too particularly to special
departments, lose, to a surprising degree, the power of dealing with
subjects (even mathematical ones) outside their department. Apart
from the soundness of the reasoning, the facts are unmistakably in
accordance with the conclusion to which the reasoning points. Yet some
few still entertain doubts, a circumstance which may prove a source of
consolation to any who find themselves unable to follow the reasoning
on which the effects of approach and recession on wave-lengths depend.
Let such remember, however, that experiment in the case of the aerial
waves producing sound, accords perfectly with theory, and that the
waves which produce light are perfectly analogous (so far as this
particular point is concerned) with the waves producing sound.
Ordinary white light, and many kinds of coloured light, may be compared
with _noise_—that is, with a multitude of intermixed sounds. But light
of one pure colour may be compared to sound of one determinate note.
As the aerial waves producing the effect of one definite tone are all
of one length, so the ethereal waves producing light of one definite
colour are all of one length. Therefore if we approach or recede from a
source of light emitting such waves, effects will result corresponding
with what has been described above for the case of water-waves and
sound-waves. If we approach the source of light, or if it approaches
us, the waves will be shortened; if we recede from it, or if it
recedes from us, the waves will be lengthened. But the colour of light
depends on its wave-length, precisely as the tone of sound depends on
its wave-length. The waves producing red light are longer than those
producing orange light, these are longer than the waves producing
yellow light; and so the wave-lengths shorten down from yellow to
green, thence to blue, to indigo, and finally to violet. Thus if a body
shining in reality with a pure green colour, approached the observer
with a velocity comparable with that of light, it would seem blue,
indigo, or violet, according to the rate of approach; whereas if it
rapidly receded, it would seem yellow, orange, or red, according to the
rate of recession.
Unfortunately in one sense, though very fortunately in many much more
important respects, the rates of motion among the celestial bodies are
_not_ comparable with the velocity of light, but are always so much
less as to be almost rest by comparison. The velocity of light is about
187,000 miles per second, or, according to the measures of the solar
system at present in vogue (which will shortly have to give place to
somewhat larger measures, the result of observations made upon the
recent transit of Venus), about 185,000 miles per second. The swiftest
celestial motion of which we have ever had direct evidence was that of
the comet of the year 1843, which, at the time of its nearest approach
to the sun, was travelling at the rate of about 350 miles per second.
This, compared with the velocity of light, is as the motion of a person
taking six steps a minute, each less than half a yard long, to the
rush of the swiftest express train. No body within our solar system
can travel faster than this, the motion of a body falling upon the sun
from an infinite distance being only about 370 miles per second when it
reaches his surface. And though swifter motions probably exist among
the bodies travelling around more massive suns than ours, yet of such
motions we can never become cognizant. All the motions taking place
among the stars themselves would appear to be very much less in amount.
The most swiftly moving sun seems to travel but at the rate of about 50
or 60 miles per second.
Now let us consider how far a motion of 100 miles per second might be
expected to modify the colour of pure green light—selecting green as
the middle colour of the spectrum. The waves producing green light
are of such a length, that 47,000 of them scarcely equal in length a
single inch. Draw on paper an inch and divide it carefully into ten
equal parts, or take such parts from a well-divided rule; divide one
of these tenths into ten equal parts, as nearly as the eye will permit
you to judge; then one of these parts, or about half the thickness of
an average pin, would contain 475 of the waves of pure green light.
The same length would equal the length of 440 waves of pure yellow
light, and of 511 waves of pure blue light. (The green, yellow, and
blue, here spoken of, are understood to be of the precise colour of
the middle of the green, yellow, and blue parts of the spectrum.) Thus
the green waves must be increased in the proportion of 475 to 440 to
give yellow light, or reduced in the proportion of 511 to 475 to give
blue light. For the first purpose, the velocity of recession must bear
to the velocity of light the proportion which 30 bears to 475, or
must be equal to rather more than one-sixteenth part of the velocity
of light—say 11,600 miles per second. For the second purpose, the
velocity of approach must bear to the velocity of light the proportion
which 36 bears to 475, or must be nearly equal to one-thirteenth part
of the velocity of light—say 14,300 miles per second. But the motions
of the stars and other celestial bodies, and also the motions of matter
in the sun, and so forth, are very much less than these. Except in the
case of one or two comets (and always dismissing from consideration
the amazing apparent velocities with which comets’ tails _seem_ to
be formed), we may take 100 miles per second as the extreme limit of
velocity with which we have to deal, in considering the application
of our theory to the motions of recession and approach of celestial
bodies. Thus in the case of recession the greatest possible change
of colour in pure green light would be equivalent to the difference
between the medium green of the spectrum, and the colour 1-116th part
of the way from medium green to medium yellow; and in the case of
approach, the change would correspond to the difference between the
medium green and the colour 1-143rd part of the way from medium green
to medium blue. Let any one look at a spectrum of fair length, or even
at a correctly tinted painting of the solar spectrum, and note how
utterly unrecognizable to ordinary vision is the difference of tint for
even the twentieth part of the distance between medium green and medium
yellow on one side or medium blue on the other, and he will recognize
how utterly hopeless it would be to attempt to appreciate the change
of colour due to the approach or recession of a luminous body shining
with pure green light and moving at the tremendous rate of 100 miles
per second. It would be hopeless, even though we had the medium green
colour and the changed colour, either towards yellow or towards blue,
placed side by side for comparison—how much more when the changed
colour would have to be compared with the observer’s recollection of
the medium colour, as seen on some other occasion!
But this is the least important of the difficulties affecting the
application of this method by noting change of colour, as Doppler
originally proposed. Another difficulty, which seems somehow to have
wholly escaped Doppler’s attention, renders the colour test altogether
unavailable. We do not get _pure_ light from any of the celestial
bodies except certain gaseous clouds or nebulæ. From every sun we get,
as from our own sun, all the colours of the rainbow. There may be an
excess of some colours and a deficiency of others in any star, so as
to give the star a tint, or even a very decided colour. But even a
blood-red star, or a deep-blue or violet star, does not shine with
pure light, for the spectroscope shows that the star has other colours
than those producing the prevailing tint, and it is only the great
_excess_ of red rays (all kinds of red, too) or of blue rays (of all
kinds), and so on, which makes the star appear red, or blue, and so on,
to the eye. By far the greater number of stars or suns show all the
colours of the rainbow nearly equally distributed, as in the case of
our own sun. Now imagine for a moment a white sun, which had been at
rest, to begin suddenly to approach us so rapidly (travelling more than
10,000 miles per second) that the red rays became orange, the orange
became yellow, the yellow green, the green blue, the blue indigo, the
indigo violet, while the violet waves became too short to affect the
sense of sight. Then, _if that were all_, that sun, being deprived of
the red part of its light, would shine with a slightly bluish tinge,
owing to the relative superabundance of rays from the violet end of
the spectrum. We should be able to recognize such a change, yet not
nearly so distinctly as if that sun had been shining with a pure green
light, and suddenly beginning to approach us at the enormous rate just
mentioned, changed in colour to full blue. _Though_, if that sun were
all the time approaching us at the enormous rate imagined, we should be
quite unable to tell whether its slightly bluish tinge were due to such
motion of approach or to some inherent blueness in the light emitted by
the star. Similarly, if a white sun suddenly began to recede so rapidly
that its violet rays were turned to indigo, the indigo to blue, and
so on, the orange rays turning to red, and the red rays disappearing
altogether, then, _if that were all_, its light would become slightly
reddish, owing to the relative superabundance of light from the red
end of the spectrum; and we might distinguish the change, yet not so
readily as if a sun shining with pure green light began to recede at
the same enormous rate, and so shone with pure yellow light. _Though_,
if that sun were all the time receding at that enormous rate, we should
be quite unable to tell whether its slightly reddish hue were due to
such motion of recession or to some inherent redness in its own lustre.
_But in neither case would that be all._ In the former, the red rays
would indeed become orange; but the rays beyond the red, which produce
no effect upon vision, would be converted into red rays, and fill up
the part of the spectrum deserted by the rays originally red. In the
latter, the violet rays would indeed become indigo; but the rays beyond
the violet, ordinarily producing no visible effect, would be converted
into violet rays, and fill up the part of the spectrum deserted by the
rays originally violet. Thus, despite the enormous velocity of approach
in one case and of recession in the other, there would be no change
whatever in the colour of the sun in either case. All the colours of
the rainbow would still be present in the sun’s light, and it would
therefore still be a white sun.
Doppler’s method would thus fail utterly, even though the stars were
travelling hither and thither with motions a hundred times greater than
the greatest known stellar motions.
This objection to Doppler’s theory, as originally proposed, was
considered by me in an article on “Coloured Suns” in _Fraser’s
Magazine_ for January, 1868. His theory, indeed, was originally
promulgated not as affording a means of measuring stellar motions, but
as a way of accounting for the colours of double stars. It was thus
presented by Professor Nichol, in a chapter of his “Architecture of the
Heavens,” on this special subject:—“The rapid motion of light reaches
indeed one of those numbers which reason owns, while imagination ceases
to comprehend them; but it is also true that the swiftness with which
certain individuals of the double stars sweep past their perihelias,
or rather their periasters, is amazing; and in this matter of colours,
it must be recollected that the question solely regards the difference
between the velocities of the waves constituent of colours, at those
different stellar positions. Still it is a bold—even a magnificent
idea; and if it can be reconciled with the permanent colours of the
multitude of stars surrounding us—stars which too are moving in great
orbits with immense velocities—it may be hailed almost as a positive
discovery. It must obtain confirmation, or otherwise, so soon as we
can compare with certainty the observed colorific changes of separate
systems with the known fluctuations of their orbital motions.”
That was written a quarter of a century ago, when spectroscopic
analysis, as we now know it, had no existence. Accordingly, while the
fatal objection to Doppler’s original theory is overlooked on the
one hand, the means of applying the principle underlying the theory,
in a much more exact manner than Doppler could have hoped for, is
overlooked on the other. Both points are noted in the article above
referred to, in the same paragraph. “We may dismiss,” I there stated,
“the theory started some years ago by the French astronomer, M.
Doppler.” But, I presently added, “It is quite clear that the effects
of a motion rapid enough to produce such a change” (_i.e._ a change
of tint in a pure colour) “would shift the position of the whole
spectrum—and this change would be readily detected by a reference
to the spectral lines.” This is true, even to the word “readily.”
Velocities which would produce an appreciable change of tint would
produce “readily” detectible changes in the position of the spectral
lines; the velocities actually existing among the star-motions would
produce changes in the position of these lines detectible only with
extreme difficulty, or perhaps in the majority of instances not
detectible at all.
It has been in this way that the spectroscopic method has actually been
applied.
It is easy to perceive the essential difference between this way of
applying the method and that depending on the attempted recognition
of changes of colour. A dark line in the spectrum marks in reality
the place of a missing tint. The tints next to it on either side are
present, but the tint between them is wanting. They are changed in
colour—very slightly, in fact quite inappreciably—by motions of
recession or approach, or, in other words, they are shifted in position
along the spectrum, towards the red end for recession, towards the
violet end for approach; and of course the dark space between is
shifted along with them. One may say that the missing tint is changed.
For in reality that is precisely what would happen. If the light of
a star at rest gave every tint of the spectrum, for instance, except
mid-green alone, and that star approached or receded so swiftly that
its motion would change pure green light to pure yellow in one case,
or pure blue in the other, then the effect on the spectrum of such a
star would be to throw the dark line from the middle of the green part
of the spectrum to the middle of the yellow part in one case, or to
the middle of the blue part in the other. The dark line would be quite
notably shifted in either case. With the actual stellar motions, though
all the lines are more or less shifted, the displacement is always
exceedingly minute, and it becomes a task of extreme difficulty to
recognize, and still more to measure, such displacement.
When I first indicated publicly (January, 1868) the way in which
Doppler’s principle could alone be applied, two physicists, Huggins
in England and Secchi in Italy, were actually endeavouring, with the
excellent spectroscopes in their possession, to apply this method. In
March, 1868, Secchi gave up the effort as useless, publicly announcing
the plan on which he had proceeded and his failure to obtain any
results except negative ones. A month later Huggins also publicly
announced the plan on which he had been working, but was also able
to state that in one case, that of the bright star Sirius, he had
succeeded in measuring a motion in the line of sight, having discovered
that Sirius was receding from the earth at the rate of 41·4 miles per
second. I say was receding, because a part of the recession at the time
of observation was due to the earth’s orbital motion around the sun. I
had, at his request, supplied Huggins with the formula for calculating
the correction due to this cause, and, applying it, he found that
Sirius is receding from the sun at the rate of about 29½ miles per
second, or some 930 millions of miles per annum.
I am not here specially concerned to consider the actual results of the
application of this method since the time of Huggins’s first success;
but the next chapter of the history of the method is one so interesting
to myself personally that I feel tempted briefly to refer to details.
So soon as I had heard of Huggins’s success with Sirius, and that an
instrument was being prepared for him wherewith he might hope to extend
the method to other stars, I ventured to make a prediction as to the
result which he would obtain whensoever he should apply it to five
stars of the seven forming the so-called Plough. I had found reason
to feel assured that these five form a system drifting all together
amid stellar space. Satisfied for my own part as to the validity of
the evidence, I submitted it to Sir J. Herschel, who was struck by
its force. The apparent drift of those stars was, of course, a thwart
drift; but if they really were drifting in space, then their motions in
the line of sight must of necessity be alike. My prediction, then, was
that whensoever Huggins applied to those stars the new method he would
find them either all receding at the same rate, or all approaching at
the same rate, or else that all _alike_ failed to give any evidence at
all either of recession or approach. I had indicated the five in the
first edition of my “Other Worlds”—to wit, the stars of the Plough,
omitting the nearest “pointer” to the pole and the star marking the
third horse (or the tip of the Great Bear’s tail). So soon as Huggins’s
new telescope and its spectroscopic adjuncts were in working order, he
re-examined Sirius, determined the motions of other stars; and at last
on one suitable evening he tested the stars of the Plough. He began
with the nearest pointer, and found that star swiftly approaching the
earth. He turned to the other pointer, and found it rapidly receding
from the earth. Being under the impression that my five included both
pointers, he concluded that my prediction had utterly failed, and so
went on with his observations, altogether unprejudiced in its favour,
to say the least. The next star of the seven he found to be receding
at the same rate as the second pointer; the next at the same rate,
the next, and the next receding still at the same rate, and lastly
the seventh receding at a different rate. Here, then, were five stars
all receding at a common rate, and of the other two one receding at
a different rate, the other swiftly approaching. Turning next to the
work containing my prediction, Huggins found that the five stars thus
receding at a common rate were the five whose community of motion I
had indicated two years before. Thus the first prediction ever made
respecting the motions of the so-called fixed stars was not wanting in
success. I would venture to add that the theory of star-drift, on the
strength of which the prediction was made, was in effect demonstrated
by the result.
The next application of the new method was one of singular interest. I
believe it was Mr. Lockyer who first thought of applying the method to
measure the rate of solar hurricanes as well as the velocities of the
uprush and downrush of vaporous matter in the atmosphere of the sun.
Another spectroscopic method had enabled astronomers to watch the rush
of glowing matter from the edge of the sun, by observing the coloured
flames and their motions; but by the new method it was possible to
determine whether the flames at the edge were swept by solar cyclones
carrying them from or towards the eye of the terrestrial observer,
and also to determine whether glowing vapours over the middle of the
visible disc were subject to motion of uprush, which of course would
carry them towards the eye, or of downrush, which would carry them
from the eye. The result of observations directed to this end was to
show that at least during the time when the sun is most spotted, solar
hurricanes of tremendous violence take place, while the uprushing and
downrushing motions of solar matter sometimes attain a velocity of more
than 100 miles per second.
It was this success on the part of an English spectroscopist which
caused that attack on the new method against which it has but recently
been successfully defended, at least in the eyes of those who are
satisfied only by experimental tests of the validity of a process.
The Padre Secchi had failed, as we have seen, to recognize motions of
recession and approach among the stars by the new method. But he had
taken solar observation by spectroscopic methods under his special
charge, and therefore when the new results reached his ears he felt
bound to confirm or invalidate them. He believed that the apparent
displacement of dark lines in the solar spectrum might be due to the
heat of the sun causing changes in the delicate adjustments of the
instrument—a cause of error against which precautions are certainly
very necessary. He satisfied himself that when sufficient precautions
are taken no displacements take place such as Lockyer, Young, and
others claimed to have seen. But he submitted the matter to a further
test. As the sun is spinning swiftly on his axis, his mighty equator,
more than two and a half millions of miles in girth, circling once
round in about twenty-four days, it is clear that on one side the sun’s
surface is swiftly moving _towards_, and on the other side as swiftly
moving _from_, the observer. By some amazing miscalculation, Secchi
made the rate of this motion 20 miles per second, so that the sum of
the two motions in opposite directions would equal 40 miles per second.
He considered that he ought to be able by the new method, if the new
method is trustworthy at all, to recognize this marked difference
between the state of the sun’s eastern and western edges; he found on
trial that he could not do so; and accordingly he expressed his opinion
that the new method is not trustworthy, and that the arguments urged in
its favour are invalid.
The weak point in his reasoning resided in the circumstance that the
solar equator is only moving at the rate of about 1¼ miles per second,
so that instead of a difference of 40 miles per second between the
two edges, which should be appreciable, the actual difference (that
is, the sum of the two equal motions in opposite directions) amounts
only to 2½ miles per second, which certainly Secchi could not hope to
recognize with the spectroscopic power at his disposal. Nevertheless,
when the error in his reasoning was pointed out, though he admitted
that error, he maintained the justice of his conclusion; just as
Cassini, having mistakenly reasoned that the degrees of latitude should
diminish towards the pole instead of increasing, and having next
mistakenly found, as he supposed, that they do diminish, acknowledged
the error of his reasoning, but insisted on the validity of his
observations,—maintaining thenceforth, as all the world knows, that
the earth is extended instead of flattened at the poles.
Huggins tried to recognize by the new method the effects of the sun’s
rotation, using a much more powerful spectroscope than Secchi’s. The
history of the particular spectroscope he employed is in one respect
specially interesting to myself, as the extension of spectroscopic
power was of my own devising before I had ever used or even seen a
powerful spectroscope. The reader is aware that spectroscopes derive
their light-sifting power from the prisms forming them. The number
of prisms was gradually increased, from Newton’s single prism to
Fraunhofer’s pair, and to Kirchhoff’s battery of four, till six were
used, which bent the light round as far as it would go. Then the idea
occurred of carrying the light to a higher level (by reflections)
and sending it back through the same battery of prisms, doubling the
dispersion. Such a battery, if of six prisms, would spread the spectral
colours twice as widely apart as six used in the ordinary way, and
would thus have a dispersive power of twelve prisms. It occurred
to me that after taking the rays through six prisms, arranged in a
curve like the letter C, an intermediate four-cornered prism of a
particular shape (which I determined) might be made to send the rays
into another battery of six prisms, the entire set forming a double
curve like the letter S, the rays being then carried to a higher level
and back through the double battery. In this way a dispersive power of
nineteen prisms could be secured. My friend, Mr. Browning, the eminent
optician, made a double battery of this kind,[13] which was purchased
by Mr. W. Spottiswoode, and by him lent to Mr. Huggins for the express
purpose of dealing with the task Secchi had set spectroscopists. It
did not, however, afford the required evidence. Huggins considered
the displacement of dark lines due to the sun’s rotation to be
recognizable, but so barely that he could not speak confidently on the
point.
There for a while the matter rested. Vögel made observations confirming
Huggins’s results relative to stellar motions; but Vögel’s instrumental
means were not sufficiently powerful to render his results of much
weight.
But recently two well-directed attacks have been made upon this
problem, one in England, the other in America, and in both cases with
success. Rather, perhaps, seeing that the method had been attacked and
was supposed to require defence, we may say that two well-directed
assaults have been made upon the attacking party, which has been
completely routed.
Arrangements were made not very long ago, by which the astronomical
work of Greenwich Observatory, for a long time directed almost
exclusively to time observations, should include the study of the sun,
stars, planets, and so forth. Amongst other work which was considered
suited to the National Observatory was the application of spectroscopic
analysis to determine motions of recession and approach among the
celestial bodies. Some of these observations, by the way, were made, we
are told, “to test the truth of Doppler’s principle,” though it seems
difficult to suppose for an instant that mathematicians so skilful as
the chief of the Observatory and some of his assistants could entertain
any doubt on that point. Probably it was intended by the words just
quoted to imply simply that some of the observations were made for the
purpose of illustrating the principle of the method. We are not to
suppose that on a point so simple the Greenwich observers have been in
any sort of doubt.
At first their results were not very satisfactory. The difficulties
which had for a long time foiled Huggins, and which Secchi was never
able to master, rendered the first Greenwich measures of stellar
motions in the line of sight wildly inconsistent, not only with
Huggins’s results, but with each other.
Secchi was not slow to note this. He renewed his objections to the new
method of observation, pointing and illustrating them by referring to
the discrepancies among the Greenwich results. But recently a fresh
series of results has been published, showing that the observers
at Greenwich have succeeded in mastering some at least among the
difficulties which they had before experienced. The measurements
of star-motions showed now a satisfactory agreement with Huggins’s
results, and their range of divergence among themselves was greatly
reduced. The chief interest of the new results, however, lay in the
observations made upon bodies known to be in motion in the line of
sight at rates already measured. These observations, though not wanted
as tests of the accuracy of the principle, were very necessary as tests
of the qualities of the instruments used in applying it. It is here and
thus that Secchi’s objections alone required to be met, and here and
thus they have been thoroughly disposed of. Let us consider what means
exist within the solar system for thus testing the new method.
The earth travels along in her orbit at the rate of about 18⅓ miles
in every second of time. Not to enter into niceties which could only
properly be dealt with mathematically, it may be said that with this
full velocity she is at times approaching the remoter planets of the
system, and at times receding from them; so that here at once is a
range of difference amounting to about 37 miles per second, and fairly
within the power of the new method of observation. For it matters
nothing, so far as the new method is concerned, whether the earth is
approaching another orb by her motion, or that orb approaching by its
own motion. Again, the plant Venus travels at the rate of about 21½
miles per second, but as the earth travels only 3 miles a second less
swiftly, and the same way round, only a small portion of Venus’s motion
ever appears as a motion of approach towards or recession from the
earth. Still, Venus is sometimes approaching and sometimes receding
from the earth, at a rate of more than 8 miles per second. Her light
is much brighter than that of Jupiter or Saturn, and accordingly this
smaller rate of motion would be probably more easily recognized than
the greater rate at which the giant planets are sometimes approaching
and at other times receding from the earth. At least, the Greenwich
observers seem to have confined their attention to Venus, so far as
motions of planets in the line of sight are concerned. The moon, as
a body which keeps always at nearly the same distance from us, would
of course be the last in the world to be selected to give positive
evidence in favour of the new method; but she serves to afford a useful
test of the qualities of the instruments employed. If when these were
applied to her they gave evidence of motions of recession or approach
at the rate of several miles per second, when we know as a matter of
fact that the moon’s distance never[14] varies by more than 30,000
miles during the lunar month, her rate of approach or recession thus
averaging about one-fiftieth part of a mile per second, discredit
would be thrown on the new method—not, indeed, as regards its
principle, which no competent reasoner can for a moment question, but
as regards the possibility of practically applying it with our present
instrumental means.
Observations have been made at Greenwich, both on Venus and on the
moon, by the new method, with results entirely satisfactory. The method
shows that Venus is receding when she is known to be receding, and
that she is approaching when she is known to be approaching. Again,
the method shows no signs of approach or recession in the moon’s case.
It is thus in satisfactory agreement with the known facts. Of course
these results are open to the objection that the observers have known
beforehand what to expect, and that expectation often deceives the
mind, especially in cases where the thing to be observed is not at all
easy to recognize. It will presently be seen that the new method has
been more satisfactorily tested, in this respect, in other ways. It may
be partly due to the effect of expectation that in the case of Venus
the motions of approach and recession, tested by the new method, have
always been somewhat too great. A part of the excess may be due to the
use of the measure of the sun’s distance, and therefore the measures
of the dimensions of the solar system, in vogue before the recent
transit. These measures fall short to some degree of those which result
from the observations made in December, 1874, on Venus in transit, the
sun’s distance being estimated at about 91,400,000 miles instead of
92,000,000 miles, which would seem to be nearer the real distance. Of
course all the motions within the solar system would be correspondingly
under-estimated. On the other hand, the new method would give all
velocities with absolute correctness if instrumental difficulties
could be overcome. The difference between the real velocities of Venus
approaching and receding, and those calculated according to the present
inexact estimate of the sun’s distance, is however much less than
the observed discrepancy, doubtless due to the difficulties involved
in the application of this most difficult method. I note the point,
chiefly for the sake of mentioning the circumstance that theoretically
the method affords a new means of measuring the dimensions of the
solar system. Whensoever the practical application of the method has
been so far improved that the rate of approach or recession of Venus,
or Mercury, or Jupiter, or Saturn (any one of these planets), can be
determined on any occasion, with great nicety, we can at once infer
the sun’s distance with corresponding exactness. Considering that
the method has only been invented ten years (setting aside Doppler’s
first vague ideas respecting it), and that spectroscopic analysis as a
method of exact observation is as yet little more than a quarter of
a century old, we may fairly hope that in the years to come the new
method, already successfully applied to measure motions of recession
and approach at the rate of 20 or 30 miles per second, will be employed
successfully in measuring much smaller velocities. Then will it give
us a new method of measuring the great base-line of astronomical
surveying—the distance of our world from the centre of the solar
system.
That this will one day happen is rendered highly probable, in my
opinion, by the successes next to be related.
Besides the motions of the planets around the sun, there are their
motions of rotation, and the rotation of the sun himself upon his
axis. Some among these turning motions are sufficiently rapid to be
dealt with by the new method. The most rapid rotational motion with
which we are acquainted from actual observation is that of the planet
Jupiter. The circuit of his equator amounts to about 267,000 miles,
and he turns once on his axis in a few minutes less than ten hours, so
that his equatorial surface travels at the rate of about 26,700 miles
an hour, or nearly 7½ miles per second. Thus between the advancing and
retreating sides of the equator there is a difference of motion in
the line of sight amounting to nearly 15 miles. But this is not all.
Jupiter shines by reflecting sunlight. Now it is easily seen that where
his turning equator _meets_ the waves of light from the sun, these are
shortened, in the same sense that waves are shortened for a swimmer
travelling to meet them, while these waves, already shortened in this
way, are further shortened when starting from the same advancing
surface of Jupiter, on their journey to us after reflection. In this
way the shortening of the waves is doubled, at least when the earth is
so placed that Jupiter lies in the same direction from us as from the
sun, the very time, in fact, when Jupiter is most favourably placed
for ordinary observation, or is at his highest due south, when the sun
is at his lowest below the northern horizon—that is, at midnight.
The lengthening of the waves is similarly doubled at this most
favourable time for observation; and the actual difference between the
motion of the two sides of Jupiter’s equator being nearly 15 miles
per second, the effect on the light-waves is equivalent to that due
to a difference of nearly 30 miles per second. Thus the new method
may fairly be expected to indicate Jupiter’s motion of rotation. The
Greenwich observers have succeeded in applying it, though Jupiter has
not been favourably situated for observation. Only on one occasion,
says Sir G. Airy, was the spectrum of Jupiter “seen fairly well,”
and on that occasion “measures were obtained which gave a result in
remarkable agreement with the calculated value.” It may well be hoped
that when in the course of a few years Jupiter returns to that part of
his course where he rises high above the horizon, shining more brightly
and through a less perturbed air, the new method will be still more
successfully applied. We may even hope to see it extended to Saturn,
not merely to confirm the measures already made of Saturn’s rotation,
but to resolve the doubts which exist as to the rotation of Saturn’s
ring-system.
Lastly, there remains the rotation of the sun, a movement much more
difficult to detect by the new method, because the actual rate of
motion even at the sun’s equator amounts only to about 1 mile per
second.
In dealing with this very difficult task, the hardest which
spectroscopists have yet attempted, the Greenwich observers have
achieved an undoubted success; but unfortunately for them, though
fortunately for science, another observatory, far smaller and of much
less celebrity, has at the critical moment achieved success still more
complete.
The astronomers at our National Observatory have been able to recognize
by the new method the turning motion of the sun upon his axis. And
here we have not, as in the case of Venus, to record merely that the
observers have seen what they expected to see because of the known
motion of the sun. “Particular care was taken,” says Airy, “to
avoid any bias from previous knowledge of the direction in which a
displacement” (of the spectral lines) “was to be expected,” the side of
the sun under observation not being known by the observer until after
the observation was completed.
But Professor Young, at Dartmouth College, Hanover, N.H., has done much
more than merely obtain evidence by the new method that the sun is
rotating as we already knew. He has succeeded so perfectly in mastering
the instrumental and observational difficulties, as absolutely to be
able to rely on his _measurement_ (as distinguished from the mere
recognition) of the sun’s motion of rotation. The manner in which he
has extended the powers of ordinary spectroscopic analysis, cannot very
readily be described in these pages, simply because the principles on
which the extension depends require for their complete description a
reference to mathematical considerations of some complexity. Let it be
simply noted that what is called the diffraction spectrum, obtained
by using a finely lined plate, results from the dispersive action
of such a plate, or _grating_ as it is technically called, and this
dispersive power can be readily combined with that of a spectroscope
of the ordinary kind. Now Dr. Rutherfurd, of New York, has succeeded
in ruling so many thousand lines on glass within the breadth of a
single inch as to produce a grating of high dispersive power. Availing
himself of this beautiful extension of spectroscopic powers, Professor
Young has succeeded in recognizing effects of much smaller motions
of recession and approach than had before been observable by the new
method. He has thus been able to measure the rotation-rate of the sun’s
equatorial regions. His result exceeds considerably that inferred from
the telescopic observation of the solar spots. For whereas from the
motion of the spots a rotation-rate of about 1¼ mile per second has
been calculated for the sun’s equator, Professor Young obtains from his
spectroscopic observations a rate of rather more than 1⅖ mile, or about
300 yards per second more than the telescopic rate.
If Young had been measuring the motion of the same matter which is
observed with the telescope, there could of course be no doubt that
the telescope was right and the spectroscope wrong. We might add a
few yards per second for the probably greater distance of the sun
resulting from recent transit observations. For of course with an
increase in our estimate of the sun’s distance there comes an increase
in our estimate of the sun’s dimensions, and of the velocity of the
rotational motion of his surface. But only about 12 yards per second
could be allowed on this account; the rest would have to be regarded
as an error due to the difficulties involved in the spectroscopic
method. In reality, however, the telescopist and the spectroscopist
observe different things in determining by their respective methods
the sun’s motion of rotation. The former observes the motion of the
spots belonging to the sun’s visible surface; the latter observes the
motion of the glowing vapours outside that surface, for it is from
these vapours, not from the surface of the sun, that the dark lines
of the spectrum proceed. Now so confident is Professor Young of the
accuracy of his spectroscopic observations, that he is prepared to
regard the seeming difference of velocity between the atmosphere and
surface of the sun as real. He believes that “the solar atmosphere
really sweeps forward over the underlying surface, in the same way
that the equatorial regions outstrip the other parts of the sun’s
surface.” This inference, important and interesting in itself, is far
more important in what it involves. For if we can accept it, it follows
that the spectroscopic method of measuring the velocity of motions in
the line of sight is competent, under favourable conditions, to obtain
results accurate within a few hundred yards per second, or 10 or 12
miles per minute. If this shall really prove to be true for the method
now, less than ten years after it was first successfully applied,
what may we not hope from the method in future years? Spectroscopic
analysis itself is in its infancy, and this method is but a recent
application of spectroscopy. A century or so hence astronomers will
smile (though not disdainfully) at these feeble efforts, much as we
smile now in contemplating the puny telescopes with which Galileo and
his contemporaries studied the star-depths. And we may well believe
that largely as the knowledge gained by telescopists in our own
time surpasses that which Galileo obtained, so will spectroscopists
a few generations hence have gained a far wider and deeper insight
into the constitution and movements of the stellar universe than the
spectroscopists of our own day dare even hope to attain.
I venture confidently to predict that, in that day, astronomers will
recognize in the universe of stars a variety of structure, a complexity
of arrangement, an abundance of every form of cosmical vitality, such
as I have been led by other considerations to suggest, not the mere
cloven lamina of uniformly scattered stars more or less resembling our
sun, and all in nearly the same stage of cosmical development, which
the books of astronomy not many years since agreed in describing. The
history of astronomical progress does not render it probable that the
reasoning already advanced, though in reality demonstrative, will
convince the generality of science students until direct and easily
understood observations have shown the real nature of the constitution
of that part of the universe over which astronomical survey extends.
But the evidence already obtained, though its thorough analysis may
be “_caviare_ to the general,” suffices to show the real nature of
the relations which one day will come within the direct scope of
astronomical observation.
_THE NEW STAR WHICH FADED INTO STAR-MIST._
The appearance of a new star in the constellation of the Swan in the
autumn of 1876 promises to throw even more light than was expected on
some of the most interesting problems with which modern astronomy has
to deal. It was justly regarded as a circumstance of extreme interest
that so soon after the outburst of the star which formed a new gem
in the Northern Crown in May, 1866, another should have shone forth
under seemingly similar conditions. And when, as time went on, it
appeared that in several respects the new star in the Swan differed
from the new star in the Crown, astronomers found fresh interest in
studying, as closely as possible, the changes presented by the former
as it gradually faded from view. But they were not prepared to expect
what has actually taken place, or to recognize so great a difference
of character between these two new stars, that whereas one seemed
throughout its visibility to ordinary eyesight, and even until the
present time, to be justly called a star, the other should so change as
to render it extremely doubtful whether at any time it deserved to be
regarded as a star or sun.
Few astronomical phenomena, even of those observed during this century
(so fruitful in great astronomical discoveries), seem better worthy
of thorough investigation and study than those presented by the two
stars which appeared in the Crown and in the Swan, in 1866 and 1876
respectively. A new era seems indeed to be beginning for those
departments of astronomy which deal with stars and star-cloudlets on
the one hand, and with the evolution of solar systems and stellar
systems on the other.
Let us briefly consider the history of the star of 1866 in the first
place, and then turn our thoughts to the more surprising and probably
more instructive history of the star which shone out in November, 1876.
In the first place, however, I would desire to make a few remarks
on the objections which have been expressed by an observer to whom
astronomy is indebted for very useful work, against the endeavour to
interpret the facts ascertained respecting these so-called new stars.
M. Cornu, who made some among the earliest spectroscopic observations
of the star in Cygnus, after describing his results, proceeded as
follows:—“Grand and seductive though the task may be of endeavouring
to draw from observed facts inductions respecting the physical state of
this new star, respecting its temperature, and the chemical reactions
of which it may be the scene, I shall abstain from all commentary and
all hypothesis on this subject. I think that we do not yet possess
the data necessary for arriving at useful conclusions, or at least at
conclusions capable of being tested: however attractive hypotheses may
be, we must not forget that they are outside the bounds of science,
and that, far from serving science, they seriously endanger its
progress.” This, as I ventured to point out at the time, is utterly
inconsistent with all experience. M. Cornu’s objection to theorizing
when he did not see his way to theorizing justly, is sound enough;
but his general objection to theorizing is, with all deference be it
said, sheerly absurd. It will be noticed that I say theorizing, not
hypothesis-framing; for though he speaks of hypotheses, he in reality
is describing theories. The word hypothesis is too frequently used in
this incorrect sense—perhaps so frequently that we may almost prefer
sanctioning the use to substituting the correct word. But the fact
really is, that many, even among scientific writers, when they hear
the word hypothesis, think immediately of Newton’s famous “hypotheses
non fingo,” a dictum relating to real hypotheses, not to theories. It
would, in fact, be absurd to suppose that Newton, who had advanced,
advocated, and eventually established, the noblest scientific theory
the world has known, would ever have expressed an objection to
theorizing, as he is commonly understood to have done by those who
interpret his “hypotheses non fingo” in the sense which finds favour
with M. Cornu. But apart from this, Newton definitely indicates what he
means by hypotheses. “I frame no hypotheses,” he says, “_for whatever
is not deduced from phenomena is to be called an hypothesis_.” M.
Cornu, it will be seen, rejects the idea of deducing from phenomena
what he calls an hypothesis, but what would not be an hypothesis
according to Newton’s definition: “Malgré tout ce qu’il y aurait de
séduisant et de grandiose à tirer de ce fait des inductions, etc., je
m’abstiendrai de tout commentaire et de toute hypothèse à ce sujet.” It
is not thus that observed scientific facts are to be made fruitful, nor
thus that the points to which closer attention must be given are to be
ascertained.
Since the preceding paragraph was written, my attention has been
attracted to the words of another observer more experienced than M.
Cornu, who has not only expressed the same opinion which I entertain
respecting M. Cornu’s ill-advised remark, but has illustrated in a
very practical way, and in this very case, how science gains from
commentary and theory upon observed facts. Herr Vögel considers “that
the fear that an hypothesis” (he, also, means a theory here) “might do
harm to science is only justifiable in very rare cases: in most cases
it will further science. In the first place, it draws the attention of
the observer to things which but for the hypothesis might have been
neglected. Of course if the observer is so strongly influenced that
in favour of an hypothesis he sees things which do not exist—and
this may happen sometimes—science may for a while be arrested in its
progress, but in that case the observer is far more to blame than
the author of the hypothesis. On the other hand, it is very possible
that an observer may, involuntarily, arrest the progress of science,
even without originating an hypothesis, by pronouncing and publishing
sentences which have a tendency to diminish the general interest in a
question, and which do not place its high significance in the proper
light.” (This is very neatly put.) He is “almost inclined to think that
such an effect might follow from the reading of M. Cornu’s remark, and
that nowhere better than in the present case, where in short periods
colossal changes showed themselves occurring upon a heavenly body,
might the necessary data be obtained for drawing useful conclusions,
and tests be applied to those hypotheses which have been ventured
with regard to the condition of heavenly bodies.” It was, as we shall
presently see, in thus collecting data and applying tests, that Vögel
practically illustrated the justice of his views.
The star which shone out in the Northern Crown in May, 1866, would seem
to have grown to its full brightness very quickly. It is not necessary
that I should here consider the history of the star’s discovery; but
I think all who have examined that history agree in considering that
whereas on the evening of May 12, 1866, a new star was shining in the
Northern Crown with second-magnitude brightness, none had been visible
in the same spot with brightness above that of a fifth-magnitude
star twenty-four hours earlier. On ascertaining, however, the place
of the new star, astronomers found that there had been recorded in
Argelander’s charts and catalogue a star of between the ninth and tenth
magnitude in this spot. The star declined very rapidly in brightness.
On May 13th it appeared of the third magnitude; on May 16th it had
sunk to the fourth magnitude; on the 17th to the fifth; on the 19th to
the seventh; and by the end of the month it shone only as a telescopic
star of the ninth magnitude. It is now certainly not above the tenth
magnitude.
Examined with the spectroscope, this star was found to be in an
abnormal condition. It gave the rainbow-tinted streak crossed by dark
lines, which is usually given by stars (with minor variations, which
enable astronomers to classify the stars into several distinct orders).
But superposed upon this spectrum, or perhaps we should rather say
shining through this spectrum, were seen four brilliant lines, two
of which certainly belonged to glowing hydrogen. These lines were so
bright as to show that the greater part of the light of the star at
the time came from the glowing gas or gases giving these lines. It
appeared, however, that the rainbow-tinted spectrum on which these
lines were seen was considerably brighter than it would otherwise have
been, in consequence of the accession of heat indicated by and probably
derived from the glowing hydrogen.
Unfortunately, we have not accordant accounts of the changes which the
spectrum of this star underwent as the star faded out of view. Wolf
and Rayet, of the Paris Observatory, assert that when there remained
scarcely any trace of the continuous spectrum, the four bright lines
were still quite brilliant. But Huggins affirms that this was not the
case in his observations; he was “able to see the continuous spectrum
when the bright lines could be scarcely distinguished.” As the bright
lines certainly faded out of view eventually, we may reasonably assume
that the French observers were prevented by the brightness of the lines
from recognizing the continuous spectrum at that particular stage of
the diminution of the star’s light when the continuous spectrum had
faded considerably but the hydrogen lines little. Later, the continuous
spectrum ceased to diminish in brightness, while the hydrogen lines
rapidly faded. Thereafter the continuous spectrum could be discerned,
and with greater and greater distinctness as the hydrogen lines faded
out.
Now, in considering the meaning of the observed changes in the
so-called “new star,” we have two general theories to consider.
One of these theories is that to which Dr. Huggins would seem to have
inclined, though he did not definitely adopt it—the theory, namely,
that in consequence of some internal convulsion enormous quantities of
hydrogen and other gases were evolved, which in combining with some
other elements ignited on the surface of the star, and thus enveloped
the whole body suddenly in a sheet of flame.
“The ignited hydrogen gas in burning produced the light corresponding
to the two bright bands in the red and green; the remaining bright
lines were not, however, coincident with those of oxygen, as might have
been expected. According to this theory, the burning hydrogen must have
greatly increased the heat of the solid matter of the photosphere and
brought it into a state of more intense incandescence and luminosity,
which may explain how the formerly faint star could so suddenly assume
such remarkable brilliance; the liberated hydrogen became exhausted,
the flame gradually abated, and with the consequent cooling the
photosphere became less vivid, and the star returned to its original
condition.”
According to the other theory, advanced by Meyer and Klein, the
blazing forth of this new star may have been occasioned by the violent
precipitation of some great mass, perhaps a planet, upon a fixed star,
“by which the momentum of the falling mass would be changed into
molecular motion,” and result in the emission of light and heat.
“It might even be supposed that the new star, through its rapid motion,
may have come in contact with one of the nebulæ which traverse in great
numbers the realms of space in every direction, and which from their
gaseous condition must possess a high temperature; such a collision
would necessarily set the star in a blaze, and occasion the most
vehement ignition of its hydrogen.”
If we regard these two theories in their more general aspect,
considering one as the theory that the origin of disturbance was within
the star, and the other as the theory that the origin of disturbance
was outside the star, they seem to include all possible interpretations
of the observed phenomena. But, as actually advanced, neither seems
satisfactory. The sudden pouring forth of hydrogen from the interior,
in quantities sufficient to explain the outburst, seems altogether
improbable. On the other hand, as I have pointed out elsewhere, there
are reasons for rejecting the theory that the cause of the heat which
suddenly affected this star was either the downfall of a planet on
the star or the collision of the star with a star-cloudlet or nebula,
traversing space in one direction, while the star rushed onwards in
another.
A planet could not very well come into final conflict with its sun at
one fell swoop. It would gradually draw nearer and nearer, not by the
narrowing of its path, but by the change of the path’s shape. The path
would, in fact, become more and more eccentric; until at length, at its
point of nearest approach, the planet would graze its primary, exciting
an intense heat where it struck, but escaping actual destruction that
time. The planet would make another circuit, and again graze the sun,
at or near the same part of the planet’s path. For several circuits
this would continue, the grazes not becoming more and more effective
each time, but rather less. The interval between them, however, would
grow continually less and less; at last the time would come when
the planet’s path would be reduced to the circular form, its globe
touching the sun’s all the way round, and then the planet would very
quickly be reduced to vapour and partly burned up, its substance being
absorbed by its sun. But all successive grazes would be indicated to
us by accessions of lustre, the period between each seeming outburst
being only a few months at first, and gradually becoming less and less
(during a long course of years, perhaps even of centuries) until the
planet was finally destroyed. Nothing of this sort has happened in the
case of any so-called new star. As for the rush of a star through a
nebulous mass, that is a theory which would scarcely be entertained by
any one acquainted with the enormous distances separating the gaseous
star-clouds properly called nebulæ. There may be small clouds of the
same sort scattered much more freely through space; but we have not a
particle of evidence that this is actually the case. All we certainly
_know_ about star-cloudlets suggests that the distances separating them
from each other are comparable with those which separate star from
star, in which case the idea of a star coming into collision with a
star-cloudlet, and still more the idea of this occurring several times
in a century, is wild in the extreme.
But while thus advancing objections, which seem to me irrefragable,
against the theory that either a planet or a nebula (still less another
small star) had come into collision with the orb in Corona which shone
out so splendidly for a while, I advanced another view which seemed
to me then and seems now to correspond well with phenomena, and to
render the theory of action from without on the whole preferable to the
theory of outburst from within. I suggested that, far more probably,
an enormous flight of large meteoric masses travelling around the
star had come into partial collision with it in the same way that the
flight of November meteors comes into collision with our earth thrice
in each century, and that other meteoric flights may occasionally come
into collision with our sun, producing the disturbances which occasion
the sun-spots. As I pointed out, in conceiving this we are imagining
nothing new. A meteoric flight capable of producing the suggested
effects would differ only in kind from meteoric flights which are known
to circle around our own sun. The meteors which produce the November
displays of falling stars follow in the track of a comet barely visible
to the naked eye.
“May we not reasonably assume that those glorious comets which have not
only been visible but conspicuous, shining even in the day-time, and
brandishing around tails, which like that of the ‘wonder in heaven, the
great dragon,’ seemed to ‘draw the third part of the stars of heaven,’
are followed by much denser flights of much more massive meteors?
Some of these giant comets have paths which carry them very close to
our sun. Newton’s comet, with its tail a hundred millions of miles in
length, all but grazed the sun’s globe. The comet of 1843, whose tail,
says Sir John Herschel, ‘stretched half-way across the sky,’ must
actually have grazed the sun, though but lightly, for its nucleus was
within 80,000 miles of his surface, and its head was more than 160,000
miles in diameter. And these are only two among the few comets whose
paths are known. At any time we might be visited by a comet mightier
than either, travelling in an orbit intersecting the sun’s surface,
followed by flights of meteoric masses enormous in size and many in
number, which, falling on the sun’s globe with enormous velocity
corresponding to their vast orbital range and their near approach to
the sun—a velocity of some 360 miles per second—would, beyond all
doubt, excite his whole frame, and especially his surface regions, to a
degree of heat far exceeding what he now emits.”
This theory corresponds far better also with observed facts than the
theory of Meyer and Klein, in other respects than simply in antecedent
probability. It can easily be shown that if a planet fell upon a
sun in such sort as to become part of his mass, or if a nebula in a
state of intense heat excited the whole frame of a star to a similar
degree of heat, the effects would be of longer duration than the
observed accession of heat and light in the case of all the so-called
“new stars.” It has been calculated by Mr. Croll (the well-known
mathematician to whom we owe the most complete investigations yet made
into the effect of the varying eccentricity of the earth’s orbit on the
climate of the earth) that if two suns, each equal in mass to one-half
of our sun, came into collision with a velocity of 476 miles per
second, light and heat would be produced which would cover the present
rate of the sun’s radiation for fifty million years. Now although it
certainly does not follow from this that such a collision would result
in the steady emission of so much light and heat as our sun gives out,
for a period of fifty million years, but is, on the contrary, certain
that there would be a far greater emission at first and a far smaller
emission afterwards, yet it manifestly must be admitted that such a
collision could not possibly produce so short-lived an effect as we see
in the case of every one of the so-called new stars. The diminution
in the emission of light and heat from the maximum to one-half the
maximum would not occupy fifty millions of years, or perhaps even five
million or five hundred thousand years; but it would certainly require
thousands of years; whereas we have seen that the new stars in the
Crown and in the Swan have lost not one-half but ninety-nine hundredths
of their maximum lustre in a few months.
This has been urged as an objection even to the term star as applied to
these suddenly appearing orbs. But the objection is not valid; because
there is no reason whatever for supposing that even our own sun might
not be excited by the downfall of meteoric or cometic matter upon it
to a sudden and short-lasting intensity of splendour and of heat. Mr.
Lockyer remarks that, if any star, properly so called, were to become
a “a world on fire,” or “burst into flames,” or, in less poetical
language, were to be driven either into a condition of incandescence
absolutely, or to have its incandescence increased, there can be little
doubt that thousands or millions of years would be necessary for the
reduction of its light to its original intensity. This must, however,
have been written in forgetfulness of some facts which have been
ascertained respecting our sun, and which indicate pretty clearly that
the sun’s surface might be roused to a temporary intensity of splendour
and heat without any corresponding increase in the internal heat, or in
the activity of the causes, whatever they may be, to which the sun’s
_steady_ emissions of light and heat are due.
For instance, most of my readers are doubtless familiar with the
account (an oft-told tale, at any rate) of the sudden increase in
the splendour of a small portion of the sun’s surface on September
1, 1859, observed by two astronomers independently. The appearances
described corresponded exactly with what we should expect if two large
meteoric masses travelling side by side had rushed, with a velocity
originally amounting to two or three hundred miles per second, through
the portions of the solar atmosphere lying just above, at, and just
below the visible photosphere. The actual rate of motion was measured
at 120 miles per second as the minimum, but may, if the direction of
motion was considerably inclined to the line of sight, have amounted
to more than 200 miles per second. The effect was such, that the parts
of the sun thus suddenly excited to an increased emission of light and
heat appeared like bright stars upon the background of the glowing
photosphere itself. One of the observers, Carrington, supposed for a
moment that the dark glass screen used to protect the eye had broken.
The increase of splendour was exceedingly limited in area, and lasted
only for a few minutes—fortunately for the inhabitants of earth. As
it was, the whole frame of the earth sympathized with the sun. Vivid
auroras were seen, not only in both hemispheres, but in latitudes where
auroras are seldom seen. They were accompanied by unusually great
electro-magnetic disturbances.
“In many places,” says Sir J. Herschel, “the telegraph wires struck
work. At Washington and Philadelphia, the electric signalmen received
severe electric shocks. At a station in Norway, the telegraphic
apparatus was set fire to, and at Boston, in North America, a flame of
fire followed the pen of Bain’s electric telegraph, which writes down
the message upon chemically prepared paper.”
We see, then, that most certainly the sun can be locally excited to
increased emission of light and heat, which nevertheless may last but
for a very short time; and we have good reason for believing that the
actual cause of the sudden change in his condition was the downfall
of meteoric matter upon a portion of his surface. We may well believe
that, whatever the cause may have been, it was one which might in the
case of other suns, or even in our sun’s own case, affect a much larger
portion of the photosphere. If this happened there would be just
such an accession of splendour as we recognize in the case of the new
stars. And as the small local accession of brilliancy lasted only a few
minutes, we can well believe that an increase of surface brilliancy
affecting a much larger portion of the photosphere, or even the entire
photosphere, might last but for a few days or weeks.
All that can be said in the way of negative evidence, so far as our
own sun is concerned, is that we have no reason for believing that
our sun has, at any time within many thousands of years, been excited
to emit even for a few hours a much greater amount of light and heat
than usual; so that it has afforded no direct evidence in favour of
the belief that other suns may be roused to many times their normal
splendour, and yet very quickly resume that usual lustre. But we know
that our sun, whether because of his situation in space, or of his
position in time (that is, the stage of solar development to which he
has at present attained), belongs to the class of stars which shine
with steady lustre. He does not vary like Betelgeux, for example, which
is not only a sun like him as to general character, but notably a
larger and more massive orb. Still less is he like Mira, the Wonderful
Star; or like that more wonderful variable star, Eta Argûs, which at
one time shines with a lustre nearly equalling that of the bright
Sirius, and anon fades away almost into utter invisibility. He _is_ a
variable sun, for we cannot suppose that the waxing and waning of the
sun-spot period leaves his lustre, as a whole, altogether unaffected.
But his variation is so slight that, with all ordinary methods of
photometric measurement by observers stationed on worlds which circle
around other suns, it must be absolutely undiscernible. We do not,
however, reject Betelgeux, or Mira, or even Eta Argûs, from among stars
because they vary in lustre. We recognize the fact that, as in glory,
so in condition and in changes of condition, one star differeth from
another.
Doubtless there are excellent reasons for rejecting the theory that a
massive body like a planet, or a nebulous mass like those which are
found among the star-depths (the least of which would exceed many
times in volume a sphere filling the entire space of the orbit of
Neptune), fell on some remote sun in the Northern Crown. But there are
no sufficient reasons for rejecting or even doubting the theory that
a comet, bearing in its train a flight of many millions of meteoric
masses, falling directly upon such a sun, might cause it to shine
with many times its ordinary lustre, but only for a short time, a few
months or weeks, or a few days, or even hours. In the article entitled
“Suns in Flames,” in my “Myths and Marvels of Astronomy,” before the
startling evidence recently obtained from the star in Cygnus had
been thought of, I thus indicated the probable effects of such an
event:—“When the earth has passed through the richer portions (not the
actual nuclei be it remembered) of meteor systems, the meteors visible
from even a single station have been counted by tens of thousands, and
it has been computed that millions must have fallen upon the whole
earth. These were meteors following in the trains of very small comets.
If a very large comet followed by no denser a flight of meteors, but
each meteoric mass much larger, fell directly upon the sun, it would
not be the outskirts but the nucleus of the meteoric train which would
impinge upon him. They would number thousands of millions. The velocity
of downfall of each mass would be more than 360 miles per second. And
they would continue to pour in upon him for several days in succession,
millions falling every hour. It seems not improbable that under this
tremendous and long-continued meteoric hail, his whole surface would
be caused to glow as intensely as that small part whose brilliancy
was so surprising in the observation made by Carrington and Hodgson.
In that case our sun, seen from some remote star whence ordinarily he
is invisible, would shine out as a new sun for a few days, while all
things living, on our earth and whatever other members of the solar
system are the abodes of life, would inevitably be destroyed.”
There are, indeed, reasons for believing, not only, as I have already
indicated, that the outburst in the sun was caused by the downfall of
meteoric masses, but that those masses were following in the train of
a known comet, precisely as the November meteors follow in the train of
Tempel’s comet (II., 1866). For we know that November meteoric displays
have been witnessed for five or six years after the passage of Tempel’s
comet, in its thirty-three year orbit, while the August meteoric
displays have been witnessed fully one hundred and twenty years
after the passage of their comet (II., 1862).[15] Now only sixteen
years before the solar outburst witnessed by Carrington and Hodgson,
a magnificent comet had passed even closer to the sun than either
Tempel’s comet or the second comet of 1862 approached the earth’s
orbit. That was the famous comet of the year 1843. Many of us remember
that wonderful object. I was but a child myself when it appeared, but
I can well remember its amazing tail, which in March, 1843, stretched
half-way across the sky.
“Of all the comets on record,” says Sir J. Herschel, “that approached
nearest the sun; indeed, it was at first supposed that it had actually
grazed the sun’s surface, but it proved to have just missed by an
interval of not more than 80,000 miles—about a third of the distance
of the moon from the earth, which (in such a matter) is a very close
shave indeed to get clear off.”
We can well believe that the two meteors which produced the remarkable
outburst of 1859 may have been stragglers from the main body following
after that glorious comet. I do not insist upon the connection. In
fact, I rather incline to the belief that the disturbance in 1859,
occurring as it did about the time of maximum sun-spot frequency, was
caused by meteors following in the train of some as yet undiscovered
comet, circuiting the sun in about eleven years, the spots themselves
being, I believe, due in the main to meteoric downfalls. There is
greater reason for believing that the great sun-spot which appeared
in June, 1843, was caused by the comet which three months before had
grazed the sun’s surface. As Professor Kirkwood, of Bloomington,
Indiana, justly remarks, had this comet approached a little nearer,
the resistance of the solar atmosphere would probably have brought
the comet’s entire mass to the solar surface. Even at its actual
distance, it must have produced considerable atmospheric disturbance.
But the recent discovery that a number of comets are associated
with meteoric matter travelling in nearly the same orbits, suggests
the inquiry whether an enormous meteorite following in the comet’s
train, and having a somewhat less perihelion distance, may not have
been precipitated upon the sun, thus producing the great disturbance
observed so shortly after the comet’s perihelion passage.
Let us consider now the evidence obtained from the star in Cygnus,
noting especially in what points it resembles, and in what points it
differs from, the evidence afforded by the star in the Crown.
The new star was first seen by Professor Schmidt at a quarter to six
on the evening of November 24. It was then shining as a star of the
third magnitude, in the constellation of the Swan, not very far from
the famous but faint star 61 Cygni—which first of all the stars in the
northern heavens had its distance determined by astronomers. The three
previous nights had unfortunately been dark; but Schmidt is certain
that on November 20 the star was not visible. At midnight, November
24, its light was very yellow, and it was somewhat brighter than the
well-known star Eta Pegasi, which marks the forearm of the Flying
Horse. Schmidt sent news of the discovery to Leverrier, at Paris;
but neither he nor Leverrier telegraphed the news, as they should
have done, to Greenwich, Berlin, or the United States. Many precious
opportunities for observing the spectrum of the new-comer at the time
of its greatest brilliancy were thus lost.
The observers at Paris did their best to observe the spectrum of the
star and the all-important changes in the spectrum. But they had
unfavourable weather. It was not till December 2 that the star was
observed at Paris, by which time the colour, which had been very yellow
on November 24, had become “greenish, almost blue.” The star had also
then sunk from the third to far below the fourth magnitude. It is
seldom that science has to regret a more important loss of opportunity
than this. What we want specially to know is the nature of the spectrum
given by this star when its light was yellow; and this we can now never
know. Nor are the outbursts of new stars so common that we may quickly
expect another similar opportunity, even if any number of other new
stars should present the same series of phenomena as the star in Cygnus.
On December 2, the spectrum, as observed by M. Cornu, consisted almost
entirely of bright lines. On December 5, he determined the position of
these lines, though clouds still greatly interfered with his labours.
He found three bright lines of hydrogen, the strong double sodium line
in the orange-yellow, the triple magnesium line in the yellow-green,
and two other lines—one of which seemed to agree exactly in position
with a bright line belonging to the solar corona. All these lines were
shining upon the rainbow-tinted background of the spectrum, which was
relatively faint. He drew the conclusion that in chemical constitution
the atmosphere of the new star was constituted exactly like the solar
sierra.
Herr Vögel’s observations commenced on December 5, and were continued
at intervals until March 10, when the star had sunk to below the eighth
magnitude.
Vögel’s earlier observations agreed well with Cornu’s. He remarks,
however, that Cornu’s opinion as to the exact resemblance of the
chemical constitution of the star’s atmosphere with that of the sierra
is not just, for both Cornu and himself noticed one line which did not
correspond with any line belonging to the solar sierra; and this line
eventually became the brightest line of the whole spectrum. Comparing
his own observations with those of Cornu, Vögel points out that they
agree perfectly with regard to the presence of the three hydrogen
lines, and that of the brightest line of the air spectrum (belonging to
nitrogen),—which is the principal line of the spectrum of nebulæ. This
is the line which has no analogue in the spectrum of the sierra.
We have also observations by F. Secchi, at Rome, Mr. Copeland, at
Dunecht, and Mr. Backhouse, of Sunderland, all agreeing in the main
with the observations made by Vögel and Cornu. In particular, Mr.
Backhouse observed, as Vögel had done, that whereas in December the
greenish-blue line of hydrogen, F, was brighter than the nitrogen line
(also in the green-blue, but nearer the red end than F), on January 6
the nitrogen line was the brightest of all the lines in the spectrum of
the new star.
Vögel, commenting on the results of his observations up to March 10,
makes the following interesting remarks (I quote, with slight verbal
alterations, from a paraphrase in a weekly scientific journal):—“A
stellar spectrum with _bright_ lines is always a highly interesting
phenomenon for any one acquainted with stellar spectrum analysis,
and well worthy of deep consideration. Although in the chromosphere
(sierra) of our sun, near the limb, we see numerous bright lines, yet
only dark lines appear in the spectrum whenever we produce a small
star-like image of the sun, and examine it through the spectroscope. It
is generally believed that the bright lines in some few star-spectra
result from gases which break forth from the interior of the luminous
body, the temperature of which is higher than that of the surface of
the body—that is, the phenomenon is the same sometimes observed in
the spectra of solar spots, where incandescent hydrogen rushing out
of the hot interior becomes visible above the cooler spots through
the hydrogen lines turning bright. But this is not the only possible
explanation. We may also suppose that the atmosphere of a star,
consisting of incandescent gases, as is the case with our own sun, is
on the whole cooler than the nucleus, but with regard to the latter is
extremely large. I cannot well imagine how the phenomenon can last for
any long period of time if the former hypothesis be correct. The gas
breaking forth from the hot interior of the body will impart a portion
of its heat to the surface of the body, and thus raise the temperature
of the latter; consequently, the difference of temperature between the
incandescent gas and the surface of the body will soon be insufficient
to produce bright lines; and these will disappear from the spectrum.
This view applies perfectly to stars which suddenly appear and soon
disappear again, or at least increase considerably in intensity—that
is, it applies perfectly to so-called new stars in the spectra of
which bright lines are apparent, _if_ the hypothesis presently to be
mentioned is admitted for their explanation. For a more stable state
of things the second hypothesis seems to be far better adapted. Stars
like Beta Lyræ, Gamma Cassiopeiæ, and others, which show the hydrogen
lines and the sierra D line bright on a continuous spectrum, with
only slight changes of intensity, possess, according to this theory,
atmospheres very large relatively to their own volume—the atmospheres
consisting of hydrogen and that unknown element which produces the
D line.[16] With regard to the new star, Zöllner, long before the
progress lately made in stellar physics by means of spectrum analysis,
deduced from Tycho’s observations of the star called after him, that
on the surface of a star, through the constant emission of heat, the
products of cooling, which in the case of our sun we call sun-spots,
accumulate: so that finally the whole surface of the body is covered
with a colder stratum, which gives much less light or none at all.
Through a sudden and violent tearing up of this stratum, the interior
incandescent materials which it encloses must naturally break forth,
and must in consequence, according to the extent of their eruption,
cause larger or smaller patches of the dark envelope of the body to
become luminous again. To a distant observer such an eruption from the
hot and still incandescent interior of a heavenly body must appear as
the sudden flashing-up of a new star. That this evolution of light
may under certain conditions be an extremely powerful one, could be
explained by the circumstance that all the chemical compounds which,
under the influence of a lower temperature, had already formed upon the
surface, are again decomposed through the sudden eruption of these hot
materials; and that this decomposition, as in the case of terrestrial
substances, takes place under evolution of light and heat. Thus the
bright flashing-up is not only ascribed to the parts of the surface
which through the eruption of the incandescent matter have again become
luminous, but also to a simultaneous process of combustion, which is
initiated through the colder compounds coming into contact with the
incandescent matter.”
Vögel considers that Zöllner’s hypothesis has been confirmed in its
essential points by the application of spectrum analysis to the stars.
We can recognize from the spectrum different stages in the process
of cooling, and in some of the fainter stars we perceive indeed that
chemical compounds have already formed, and still exist. As to new
stars, again, says Vögel, Zöllner’s theory seems in nowise contradicted
“by the spectral observations made on the two new stars of 1866 and
1876. The bright continuous spectrum, and the bright lines only
slightly exceeding it at first” (a description, however, applying
correctly only to the star of 1876), “could not be well explained if we
only suppose a violent eruption from the interior, which again rendered
the surface wholly or partially luminous; but are easily explained
if we suppose that the quantity of light is considerably augmented
through a simultaneous process of combustion. If this process is of
short duration, then the continuous spectrum, as was the case with the
new star of 1876, will very quickly decrease in intensity down to a
certain limit, while the bright lines in the spectrum, which result
from the incandescent gases that have emanated in enormous quantities
from the interior, will continue for some time.”
It thus appears that Herr Vögel regarded the observations which had
been made on this remarkable star up to March 10 as indicating that
first there had been an outburst of glowing gaseous matter from the
interior, producing the part of the light which gave the bright
lines indicative of gaseity, and that then there had followed, as a
consequence, the combustion of a portion of the solid and relatively
cool crust, causing the continuous part of the spectrum. We may
compare what had taken place, on this hypothesis, with the outburst of
intensely hot gases from the interior of a volcanic crater, and the
incandescence of the lips of the crater in consequence of the intense
heat of the out-rushing gases. Any one viewing such a crater from a
distance, with a spectroscope, would see the bright lines belonging
to the out-rushing gases superposed upon the continuous spectrum due
to the crater’s burning lips. Vögel further supposes that the burning
parts of the star soon cooled, the majority of the remaining light (or
at any rate the part of the remaining light spectroscopically most
effective) being that which came from the glowing gases which had
emanated in vast quantities from the star’s interior.
“The observations of the spectrum show, beyond doubt,” he says, “that
the decrease in the light of the star corresponds with the cooling
of its surface. The violet and blue parts decreased more rapidly in
intensity than the other parts; and the absorption-bands which crossed
the spectrum have gradually become darker and darker.”
The reasoning, however, if not altogether unsatisfactory, is by no
means so conclusive as Herr Vögel appears to think. It is not clear how
the incandescent portion of the surface could possibly cool in any
great degree while enormous quantities of gas more intensely heated (by
the hypothesis) remained around the star. The more rapid decrease in
the violet and blue parts of the spectrum than in the red and orange
is explicable as an effect of absorption, at least as readily as by
the hypothesis that burning solid or liquid matter had cooled. Vögel
himself could only regard the other bands which crossed the spectrum
as absorption-bands. And the absorption of light from the continuous
spectrum in these parts (that is, not where the bright lines belonging
to the gaseous matter lay) could not possibly result from absorption
produced by those gases. If other gases were in question, gases which,
by cooling with the cooling surface, had become capable of thus
absorbing light from special parts of the spectrum, how is it that
before, when these gases were presumably intensely heated, they did not
indicate their presence by bright bands? Bright bands, indeed, were
seen, which eventually faded out of view, but these bright bands did
not occupy the position where, later on, absorption-bands appeared.
The natural explanation of what had thus far been observed is different
from that advanced by Vögel, though we must not assume that because
it is the natural, it is necessarily the true explanation. It is
this—that the source of that part of the star’s light which gave the
bright-line spectrum, or the spectrum indicative of gaseity, belongs
to the normal condition of the star, and not to gases poured forth,
in consequence of some abnormal state of things, from the sun’s
interior. We should infer naturally, though again I say not _therefore_
correctly, that if a star spectroscope had been directed upon the
place occupied by the new star before it began to shine with unusual
splendour, the bright-line spectrum would have been observed. Some
exceptional cause would then seem to have aroused the entire surface
of the star to shine with a more intense brightness, the matter thus
(presumably) more intensely heated being such as would give out the
combined continuous and bright-line spectrum, including the bright
lines which, instead of fading out, shone with at least relatively
superior brightness as the star faded from view. The theory that, on
the contrary, the matter giving these more persistent lines was that
whose emission caused the star’s increase of lustre, seems at least not
proven, and I would go so far as to say that it accords ill with the
evidence.
The question, be it noted, is simply whether we should regard the kind
of light which lasts longest in this star as it fades out of view as
more probably belonging to the star’s abnormal brightness or to its
normal luminosity. It seems to me there can be little doubt that the
persistence of this part of the star’s light points to the latter
rather than to the former view.
Let it also be noticed that the changes which had been observed thus
far were altogether unlike those which had been observed in the case of
the star in the Northern Crown, and therefore cannot justly be regarded
as pointing to the same explanation. As the star in the Crown faded
from view, the bright lines indicative of glowing hydrogen died out,
and only the ordinary stellar spectrum remained. In the case of the
star in the Swan, the part of the spectrum corresponding to stellar
light faded gradually from view, and bright lines only were left, at
least as conspicuous parts of the star’s spectrum. So that whereas one
orb seemed to have faded into a faint star, the other seemed fading
out into a nebula—not merely passing into such a condition as to
shine with light indicative of gaseity, but actually so changing as
to shine with light of the very tints (or, more strictly, of the very
wave-lengths) observed in all the gaseous nebulæ.
The strange eventful history of the new star in Cygnus did not end
here, however. We may even say, indeed, that it has not ended yet. But
another chapter can already be written.
Vögel ceased from observing the star in March, precisely when
observation seemed to promise the most interesting results. At most
other observatories, also, no observations were made for about half
a year. At the Dunecht Observatory[17] pressure of work relating to
Mars interfered with the prosecution of those observations which
had been commenced early in the year. But on September 3, Lord
Lindsay’s 15-inch reflector was directed upon the star. A star was
still shining where the new star’s yellow lustre had been displayed
in November, 1876; but now the star shone with a faint blue colour.
Under spectroscopic examination, however, the light from this seeming
blue star was found not to be starlight, properly speaking, at all.
It formed no rainbow-tinted spectrum, but gave light of only a single
colour. The single line now seen was that which at the time of Vögel’s
latest observation had become the strongest of the bright lines of
the originally complex spectrum of the so-called new star. It is the
brightest of the lines given by the gaseous nebulæ. In fact, if nothing
had been known about this body before the spectroscopic observation
of September 3 was made, the inference from the spectrum given by the
blue star would undoubtedly have been that the object is in reality a
small nebula of the planetary sort, very similar to that one close by
the pole of the ecliptic, which gave Huggins the first evidence of the
gaseity of nebulæ, but very much smaller. I would specially direct the
reader’s attention, in fact, to Huggins’s account of his observation
of that planetary nebula in the Dragon. “On August 19, 1864,” he says,
“I directed the telescope armed with the spectrum apparatus to this
nebula. At first I suspected some derangement of the instrument had
taken place, for no spectrum was seen, but only” a single line of
light. “I then found that the light of this nebula, unlike any other
extra-terrestrial light which had yet been subjected by me to prismatic
analysis, was not composed of light of different refrangibilities, and
therefore could not form a spectrum. A great part of the light from
this nebula is monochromatic, and after passing through the prisms
remains concentrated in a bright line.” A more careful examination
showed that not far from the bright line was a much fainter line;
and beyond this, again, a third exceedingly faint line was seen. The
brightest of the three lines was a line of nitrogen corresponding in
position with the brightest of the lines in the spectrum of our own
air. The faintest corresponded in position with a line of hydrogen. The
other has not yet been associated with a known line of any element.
Besides the faint lines, Dr. Huggins perceived an exceedingly faint
continuous spectrum on both sides of the group of bright lines; he
suspected, however, that this faint spectrum was not continuous, but
crossed by dark spaces. Later observations on other nebulæ induced him
to regard this faint continuous spectrum as due to the solid or liquid
matter of the nucleus, and as quite distinct from the bright lines into
which nearly the whole of the light from the nebula is concentrated.
The fainter parts of the spectrum of the gaseous nebulæ, in fact,
correspond to those parts of the spectrum of the “new star” in Cygnus
which last remained visible, before the light assumed its present
monochromatic colour.
Now let us consider the significance of the evidence afforded by this
discovery—not perhaps hoping at once to perceive the full meaning of
the discovery, but endeavouring to advance as far as we safely can in
the direction in which it seems to point.
We have, then, these broad facts: where no star had been known, an
object has for a while shone with stellar lustre, in this sense, that
its light gave a rainbow-tinted spectrum not unlike that which is given
by a certain order of stars; this object has gradually parted with its
new lustre, and in so doing the character of its spectrum has slowly
altered, the continuous portion becoming fainter, and the chief lustre
of the bright-line portion shifting from the hydrogen lines to a line
which, there is every reason to believe, is absolutely identical with
the nebula nitrogen line: and lastly, the object has ceased to give
any perceptible light, other than that belonging to this nitrogen line.
Now it cannot, I think, be doubted that, accompanying the loss of
lustre in this orb, there has been a corresponding loss of heat. The
theory that all the solid and liquid materials of the orb have been
vaporized by intense heat, and that this vaporization has caused the
loss of the star’s light (as a lime-light might die out with the
consumption of the lime, though the flame remained as hot as ever),
is opposed by many considerations. It seems sufficient to mention
this, that if a mass of solid matter, like a dead sun or planet, were
exposed to an intense heat, first raising it to incandescence, and
eventually altogether vaporizing its materials, although quite possibly
the time of its intensest lustre might precede the completion of the
vaporization, yet certainly so soon as the vaporization was complete,
the spectrum of the newly vaporized mass would show multitudinous
bright lines corresponding to the variety of material existing in the
body. No known fact of spectroscopic analysis lends countenance to the
belief that a solid or liquid mass, vaporized by intense heat, would
shine thenceforth with monochromatic light.
Again, I think we are definitely compelled to abandon Vögel’s
explanation of the phenomena by Zöllner’s theory. The reasons which
I have urged above are not only strengthened severally by the change
which has taken place in the spectrum of the new star since Vögel
observed it, but an additional argument of overwhelming force has
been introduced. If any one of the suns died out, a crust forming
over its surface and this crust being either absolutely dark or only
shining with very feeble lustre, the sun would still in one respect
resemble all the suns which are spread over the heavens—it would show
no visible disc, however great the telescopic power used in observing
it. If the nearest of all the stars were as large, or even a hundred
times as large, as Sirius, and were observed with a telescope of ten
times greater magnifying power than any yet directed to the heavens,
it would appear only as a point of light. If it lost the best part of
its lustre, it would appear only as a dull point of light. Now the
planetary nebulæ show discs, sometimes of considerable breadth. Sir
J. Herschel, to whom and to Sir W. Herschel we owe the discovery and
observation of nearly all these objects, remarks that “the planetary
nebulæ have, as their name imports, a near, in some instances a
perfect, resemblance to planets, presenting discs round, or slightly
oval, in some quite sharply terminated, in others a little hazy or
softened at the borders....” Among the most remarkable may be specified
one near the Cross, whose light is about equal to that of a star just
visible to the naked eye, “its diameter about twelve seconds, its
disc circular or very slightly elliptic, and with a clear, sharp,
well-defined outline, having exactly the appearance of a planet, with
the exception of its colour, which is a fine and full blue, verging
somewhat upon green.” But the largest of these planetary nebulæ, not
far from the southernmost of the two stars called the Pointers, has
a diameter of 2⅔ minutes of arc, “which, supposing it placed at a
distance from us not greater than that of the nearest known star of our
northern heavens, would imply a linear diameter seven times greater
than that of the orbit of Neptune.” The actual volume of this object,
on this assumption, would exceed our sun’s ten million million times.
No one supposes that this planetary nebula, shining with a light
indicative of gaseity, has a mass exceeding our sun’s in this enormous
degree. It probably has so small a mean density as not greatly to
exceed, or perhaps barely to equal, our sun in mass. Now though the
“new star” in Cygnus presented no measurable disc, and still shines
as a mere blue point in the largest telescope, yet inasmuch as its
spectrum associated it with the planetary and gaseous nebulæ, which
we know to be much larger bodies than the stars, it must be regarded,
in its present condition, as a planetary nebula, though a small one;
and since we cannot for a moment imagine that the monstrous planetary
nebulæ just described are bodies which once were suns, but whose crust
has now become non-luminous, while around the crust masses of gas shine
with a faint luminosity, so are we precluded from believing that this
smaller member of the same family is in that condition.
It _is_ conceivable (and the possibility must be taken into account
in any attempt to interpret the phenomena of the new star) that when
shining as a star, the new orb, so far as this unusual lustre was
concerned, was of sunlike dimensions. For we cannot tell whether the
surface which gave the strong light was less or greater than, or equal
to, that which is now shining with monochromatic light. Very likely,
if we had been placed where we could have seen the full dimensions of
the planetary nebula as it at present exists, we should have found
only its nuclear part glowing suddenly with increased lustre, which,
after very rapidly attaining its maximum, gradually died out again,
leaving the nebula as it had been before. But that the mass now shining
with monochromatic light is, I will not say enormously large, but
of exceedingly small mean density, so that it is enormously large
compared with the dimensions it would have if its entire substance were
compressed till it had the same mean density as our own sun, must be
regarded as, to all intents and purposes, certain.
We certainly have not here, then, the case of a sun which has grown
old and dead and dark save at the surface, but within whose interior
fire has still remained, only waiting some disturbing cause to enable
it for a while to rush forth. If we could suppose that in such a case
there _could_ be such changes as the spectroscope has indicated—that
the bright lines of the gaseous outbursting matter would, during the
earlier period of the outburst, show on a bright continuous background,
due to the glowing lips of the opening through which the matter had
rushed, but later would shine alone, becoming also fewer in number,
till at last only one was left,—we should find ourselves confronted
with the stupendous difficulty that that single remaining line is the
bright line of the planetary and other gaseous nebulæ. Any hypothesis
accounting for its existence in the spectrum of the faint blue starlike
object into which the star in Cygnus has faded ought to be competent
to explain its existence in the spectrum of those nebulæ. But _this_
hypothesis certainly does not so explain its existence in the nebular
spectrum. The nebulæ cannot be suns which have died out save for the
light of gaseous matter surrounding them, for they are millions, or
rather millions of millions, of times too large. If, for instance, a
nebula, like the one above described as lying near the southernmost
Pointer, were a mass of this kind, having the same mean density as
the sun, and lying only at the distance of the nearest of the stars
from us, then not only would it have the utterly monstrous dimensions
stated by Sir J. Herschel, but it would in the most effective way
perturb the whole solar system. With a diameter exceeding seven times
that of the orbit of Neptune, it would have a volume, and therefore a
mass, exceeding our sun’s volume and mass more than eleven millions
of millions of times. But its distance on this assumption would be
only about two hundred thousand times the sun’s, and its attraction
reduced, as compared with his, on this account only forty thousand
millions of times. So that its attraction on the sun and on the earth
would be greater than his attraction on the earth, in the same degree
that eleven millions are greater than forty thousand—or two hundred
and seventy-five times. The sun, despite his enormous distance from
such a mass, would be compelled to fall very quickly into it, unless
he circuited (with all his family) around it in about one-sixteenth of
a year, which most certainly he does not do. Nor would increasing the
distance at which we assume the star to lie have any effect to save
the sun from being thus perturbed, but the reverse. If we double for
instance our estimate of the nebula’s distance, we increase eightfold
our estimate of its mass, while we only diminish its attraction on
our sun fourfold on account of increased distance; so that now its
attraction on our sun would be one-fourth its former attraction
multiplied by eight, or twice our former estimate. We cannot suppose
the nebula to be much nearer than the nearest star. Again, we cannot
suppose that the light of these gaseous nebulæ comes from some bright
orb within them of only starlike apparent dimensions, for in that case
we should constantly recognize such starlike nucleus, which is not the
case. Moreover, the bright-line spectrum from one of these nebulæ comes
from the whole nebula, as is proved by the fact that if the slit of the
spectroscope be opened it becomes possible to see three spectroscopic
images of the nebula itself, not merely the three bright lines.
So that, if we assume the so-called star in Cygnus to be now like other
objects giving the same monochromatic spectrum—and this seems the only
legitimate assumption—we are compelled to believe that the light now
reaching us comes from a nebulous mass, not from the faintly luminous
envelope of a dead sun. Yet, remembering that when at its brightest
this orb gave a spectrum resembling in general characteristics that of
other stars or suns, and closely resembling even in details that of
stars like Gamma Cassiopeiæ, we are compelled by parity of reasoning
to infer that when the so-called new star was so shining, the greater
part of its light came from a sunlike mass. Thus, then, we are led
to the conclusion that in the case of this body we have a nucleus or
central mass, and that around this central mass there is a quantity of
gaseous matter, resembling in constitution that which forms the bulk
of the other gaseous nebulæ. The denser nucleus ordinarily shines with
so faint a lustre that the continuous spectrum from its light is too
faint to be discerned with the same spectroscopic means by which the
bright lines of the gaseous portion are shown; and the gaseous portion
ordinarily shines with so faint a lustre that its bright lines would
not be discernible on the continuous background of a stellar spectrum.
Through some cause unknown—possibly (as suggested in an article on
the earlier history of this same star in my “Myths and Marvels of
Astronomy”) the rush of a rich and dense flight of meteors upon the
central mass—the nucleus was roused to a degree of heat far surpassing
its ordinary temperature. Thus for a time it glowed as a sun. At the
same time the denser central portions of the nebulous matter were
also aroused to intenser heat, and the bright lines which ordinarily
(and certainly at present) would not stand out bright against the
rainbow-tinted background of a stellar spectrum, showed brightly upon
the continuous spectrum of the new star. Then as the rush of meteors
upon the nucleus and on the surrounding nebulous matter ceased—if
that be the true explanation of the orb’s accession of lustre—or as
the cause of the increase of brightness, whatever that cause may have
been, ceased to act, the central orb slowly returned to its usual
temperature, the nebulous matter also cooling, the continuous spectrum
slowly fading out, the denser parts of the nebulous matter exercising
also a selective absorption (explaining the bands seen in the spectrum
at this stage) which gradually became a continuous absorption—that
is, affected the entire spectrum. Those component gases, also, of the
nebulous portion which had for a while been excited to sufficient heat
to show their bright lines, cooled until their lines disappeared, and
none remained visible except for a while the three usual nebular lines,
and latterly (owing to still further cooling) only the single line
corresponding to the monochromatic light of the fainter gaseous nebulæ.
_STAR-GROUPING, STAR-DRIFT, AND STAR-MIST._
_A Lecture delivered at the Royal Institution on May 6, 1870._
Nearly a century has passed since the greatest astronomer the world has
ever known—the Newton of observational astronomy, as he has justly
been called by Arago—conceived the daring thought that he would gauge
the celestial depths. And because in his day, as indeed in our own,
very little was certainly known respecting the distribution of the
stars, he was forced to found his researches upon a guess. He supposed
that the stars, not only those visible to the naked eye, but all that
are seen in the most powerful telescopes, are suns, distributed with
a certain general uniformity throughout space. It is my purpose to
attempt to prove that—as Sir Wm. Herschel was himself led to suspect
during the progress of his researches—this guess was a mistaken one;
that but a small proportion of the stars can be regarded as real suns;
and that in place of the uniformity of distribution conceived by Sir
Wm. Herschel, the chief characteristic of the sidereal system is
_infinite variety_.
In order that the arguments on which these views are based may be
clearly apprehended, it will be necessary to recall the main results of
Sir Wm. Herschel’s system of star-grouping.
Directing one of his 20-feet reflectors to different parts of the
heavens, he counted the stars seen in the field of view. Assuming that
the telescope really reached the limits of the sidereal system, it is
clear that the number of stars seen in any direction affords a means
of estimating the relative extension of the system in that direction,
provided always that the stars are really distributed throughout the
system with a certain approach to uniformity. Where many stars are
seen, there the system has its greatest extension; where few, there the
limits of the system must be nearest to us.
Sir Wm. Herschel was led by this process of star-grouping to the
conclusion that the sidereal system has the figure of a cloven disc.
The stars visible to the naked eye lie far within the limits of
this disc. Stars outside the relatively narrow limits of the sphere
including all the visible stars, are separately invisible. But where
the system has its greatest extension these orbs produce collectively
the diffused light which forms the Milky Way.
Sir John Herschel, applying a similar series of researches to the
southern heavens, was led to a very similar conclusion. His view of the
sidereal system differs chiefly in this respect from his father’s, that
he considered the stars within certain limits of distance from the sun
to be spread less richly through space than those whose united lustre
produces the milky light of the galaxy.
Now it is clear that if the supposition on which these views are based
is just, the three following results are to be looked for.
In the first place, the stars visible to the naked eye would be
distributed with a certain general uniformity over the celestial
sphere; so that if on the contrary we find certain extensive regions
over which such stars are strewn much more richly than over the rest of
the heavens, we must abandon Sir Wm. Herschel’s fundamental hypothesis
and all the conclusions which have been based upon it.
In the second place, we ought to find no signs of the aggregation
of lucid stars into streams or clustering groups. If we should find
such associated groups, we must abandon the hypothesis of uniform
distribution and all the conclusions founded on it.
Thirdly, and most obviously of all, the lucid stars ought not to be
associated in a marked manner with the figure of the Milky Way. To
take an illustrative instance. When we look through a glass window at
a distant landscape we do not find that the specks in the substance
of the glass seem to follow the outline of valleys, hills, trees, or
whatever features the landscape may present. In like manner, regarding
the sphere of the lucid stars as in a sense the window through which we
view the Milky Way, we ought not to find these stars, which are so near
to us, associated with the figure of the Milky Way, whose light comes
from distances so enormously exceeding those which separate us from the
lucid stars. Here again, then, if there should appear signs of such
association, we must abandon the theory that the sidereal system is
constituted as Sir Wm. Herschel supposed.
It should further be remarked that the three arguments derived from
these relations are independent of each other. They are not as three
links of a chain, any one of which being broken the chain is broken.
They are as three strands of a triple cord. If one strand holds, the
cord holds. It may be shown that all three are to be trusted.
It is not to be expected, however, that the stars as actually seen
should exhibit these relations, since far the larger number are but
faintly visible; so that the eye would look in vain for the signs of
law among them, even though law may be there. What is necessary is that
maps should be constructed on a uniform and intelligible plan, and that
in these maps the faint stars should be made bright, and the bright
stars brighter.
The maps exhibited during this discourse [since published as my
“Library Atlas”] have been devised for this purpose amongst others.
There are twelve of them, but they overlap, so that in effect each
covers a tenth part of the heavens. There is first a north-polar map,
then five maps symmetrically placed around it; again, there is a
south-polar map, and five maps symmetrically placed round that map; and
these five so fit in with the first five as to complete the enclosure
of the whole sphere. In effect, every map of the twelve has five maps
symmetrically placed around it and overlapping it.
Since the whole heavens contain but 5932 stars visible to the naked
eye, each of the maps should contain on the average about 593 stars.
But instead of this being the case, some of the maps contain many more
than their just proportion of stars, while in others the number as
greatly falls short of the average. One recognizes, by combining these
indications, the existence of a roughly circular region, rich in stars,
in the northern heavens, and of another, larger and richer, in the
southern hemisphere.
To show the influence of these rich regions, it is only necessary to
exhibit the numerical relations presented by the maps.
The north-polar map, in which the largest part of the northern rich
region falls, contains no less than 693 lucid stars, of which upwards
of 400 fall within the half corresponding to the rich region. Of the
adjacent maps, two contain upwards of 500 stars, while the remaining
three contain about 400 each. Passing to the southern hemisphere, we
find that the south-polar map, which falls wholly within a rich region,
contains no less than 1132 stars! One of the adjacent maps contains 834
stars, and the four others exhibit numbers ranging from 527 to 595.
It is wholly impossible not to recognize so unequal a distribution as
exhibiting the existence of special laws of stellar aggregation.
It is noteworthy, too, that the greater Magellanic cloud falls in
the heart of the southern rich region. Were there not other signs
that this wonderful object is really associated with the sidereal
system, it might be rash to recognize this relation as indicating the
existence of a physical connection between the Nubecula Major and
the southern region rich in stars. Astronomers have indeed so long
regarded the Nubeculæ as belonging neither to the sidereal nor to the
nebular systems, that they are not likely to recognize very readily
the existence of any such connection. Yet how strangely perverse is
the reasoning which has led astronomers so to regard these amazing
objects. Presented fairly, that reasoning amounts simply to this: The
Magellanic clouds contain stars and they contain nebulæ; therefore
they are neither nebular nor stellar. Can perversity of reasoning be
pushed further? Is not the obvious conclusion this, that since nebulæ
and stars are _seen_ to be intermixed in the Nubeculæ, the nebular and
stellar systems form in reality but one complex system?
As to the existence of star-streams and clustering aggregations, we
have also evidence of a decisive character. There is a well-marked
stream of stars running from near Capella towards Monoceros. Beyond
this lies a long dark rift altogether bare of lucid orbs, beyond which
again lies an extensive range of stars, covering Gemini, Cancer, and
the southern parts of Leo. This vast system of stars resembles a
gigantic sidereal billow flowing towards the Milky Way as towards some
mighty shore-line. Nor is this description altogether fanciful; since
one of the most marked instances of star-drift presently to be adduced
refers to this very region. These associated stars _are_ urging their
way towards the galaxy, and that at a rate which, though seemingly slow
when viewed from beyond so enormous a gap as separates us from this
system, must in reality be estimated by millions of miles in every year.
Other streams and clustering aggregations there are which need not
here be specially described. But it is worth noticing that all the
well-marked streams recognized by the ancients seem closely associated
with the southern rich region already referred to. This is true of the
stars forming the River Eridanus, the serpent Hydra, and the streams
from the water-can of Aquarius. It is also noteworthy that in each
instance a portion of the stream lies outside the rich region, the rest
within it; while all the streams which lie on the same side of the
galaxy tend towards the two Magellanic clouds.
Most intimate signs of association between lucid stars and the galaxy
can be recognized—(i.) in the part extending from Cygnus to Aquila;
(ii.) in the part from Perseus to Monoceros; (iii.) over the ship Argo;
and (iv.) near Crux and the feet of Centaurus.
Before proceeding to the subject of Star-drift, three broad facts may
be stated. They are, I believe, now recognized for the first time, and
seem decisive of the existence of special laws of distribution among
the stars:—
First, the rich southern region, though covering but a sixth part of
the heavens, contains one-third of all the lucid stars, leaving only
two-thirds for the remaining five-sixths of the heavens.
Secondly, if the two rich regions and the Milky Way be considered as
one part of the heavens, the rest as another, then the former part is
three times as richly strewn with lucid stars as the second.
Thirdly, the southern hemisphere contains one thousand more lucid
stars than the northern, a fact which cannot but be regarded as most
striking when it is remembered that the total number of stars visible
to ordinary eyesight in both hemispheres falls short of 6000.
Two or three years ago, the idea suggested itself to me that if
the proper motions of the stars were examined, they would be found
to convey clear information respecting the existence of variety of
structure, and special laws of distribution within the sidereal system.
In the first place, the mere amount of a star’s apparent motion must
be regarded as affording a means of estimating the star’s distance.
The nearer a moving object is, the faster it will seem to move, and
_vice versâ_. Of course in individual instances little reliance can be
placed on this indication; but by taking the average proper motions of
a set of stars, a trustworthy measure may be obtained of their average
distance, as compared with the average distance of another set.
For example, we have in this process the means of settling the question
whether the apparent brightness of a star is indeed a test of relative
nearness. According to accepted theories the sixth-magnitude stars
are ten or twelve times as far off as those of the first magnitude.
Hence their motions should, on the average, be correspondingly small.
Now, to make assurance doubly sure, I divided the stars into two sets,
the first including the stars of the 1st, 2nd, and 3rd, the second
including those of the 4th, 5th, and 6th magnitude. According to
accepted views, the average proper motion for the first set should be
about five times as great as that for the second. I was prepared to
find it about three times as great; that is, not so much greater as
the accepted theories require, but still considerably greater. To my
surprise, I found that the average proper motion of the brighter orders
of stars is barely equal to that of the three lower orders.
This proves beyond all possibility of question that by far the greater
number of the fainter orders of stars (I refer here throughout to lucid
stars) owe their faintness not to vastness of distance, but to real
relative minuteness.
To pass over a number of other modes of research, the actual mapping of
the stellar motions, and the discovery of the peculiarity to which I
have given the name of star-drift, remain to be considered.
In catalogues it is not easy to recognize any instances of community of
motion which may exist among the stars, owing to the method in which
the stars are arranged. What is wanted in this case (as in many others
which yet remain to be dealt with) is the adoption of a plan by which
such relations may be rendered obvious to the eye. The plan I adopted
was to attach to each star in my maps a small arrow, indicating the
amount and direction of that star’s apparent motion in 36,000 years
(the time-interval being purposely lengthened, as otherwise most of the
arrows would have been too small to be recognized). When this was done,
several well-marked instances of community of motion could immediately
be recognized.
It is necessary to premise, however, that before the experiment was
tried, there were reasons for feeling very doubtful whether it would
succeed. A system of stars might really be drifting athwart the
heavens, and yet the drift might be rendered unrecognizable through
the intermixture of more distant or nearer systems having motions of
another sort and seen accidentally in the same general direction.
This was found to be the case, indeed, in several instances. Thus the
stars in the constellation Ursa Major, and neighbouring stars in Draco,
exhibit two well-marked directions of drift. The stars β, γ, δ, ε, and
ζ of the Great Bear, besides two companions of the last-named star,
are travelling in one direction, with equal velocity, and clearly form
one system. The remaining stars in the neighbourhood are travelling in
a direction almost exactly the reverse. But even this relation, thus
recognized in a region of diverse motions, is full of interest. Baron
Mädler, the well-known German astronomer, recognizing the community
of motion between ζ Ursæ and its companions, calculated the cyclic
revolution of the system to be certainly not less than 7000 years. But
when the complete system of stars showing this motion is considered,
we get a cyclic period so enormous, that not only the life of man,
but the life of the human race, the existence of our earth, nay, even
the existence of the solar system, must be regarded as a mere day in
comparison with that tremendous cycle.
Then there are other instances of star-drift where, though two
directions of motion are not intermixed, the drifting nature of the
motion is not at once recognized, because of the various distances at
which the associated stars lie from the eye.
A case of this kind is to be met with in the stars forming the
constellation Taurus. It was here that Mädler recognized a community
of motion among the stars, but he did not interpret this as I do. He
had formed the idea that the whole of the sidereal system must be in
motion around some central point; and for reasons which need not here
be considered, he was led to believe that in whatever direction the
centre of motion may lie, the stars seen in that general direction
would exhibit a community of motion. Then, that he might not have to
examine the proper motions all over the heavens, he inquired in what
direction (in all probability) the centre of motion may be supposed
to lie. Coming to the conclusion that it must lie towards Taurus,
he examined the proper motions in that constellation, and found a
community of motion which led him to regard Alcyone, the chief star of
the Pleiades, as the centre around which the sidereal system is moving.
Had he examined further he would have found more marked instances of
community of motion in other parts of the heavens, a circumstance which
would have at once compelled him to abandon his hypothesis of a central
sun in the Pleiades, or at least to lay no stress on the evidence
derivable from the community of motion in Taurus.
Perhaps the most remarkable instance of star-drift is that observed in
the constellations Gemini and Cancer. Here the stars seem to set bodily
towards the neighbouring part of the Milky Way. The general drift
in that direction is too marked, and affects too many stars, to be
regarded as by any possibility referable to accidental coincidence.
It is worthy of note that if the community of star-drift should be
recognized (or I prefer to say, _when_ it is recognized), astronomers
will have the means of determining the relative distances of the
stars of a drifting system. For differences in the apparent direction
and amount of motion can be due but to differences of distance and
position, and the determination of these differences becomes merely a
question of perspective.[18]
Before long it is likely that the theory of star-drift will be
subjected to a crucial test, since spectroscopic analysis affords the
means of determining the stellar motions of recess or approach. The
task is a very difficult one, but astronomers have full confidence that
in the able hands of Mr. Huggins it will be successfully accomplished.
I await the result with full confidence that it will confirm my views.
(See pages 92–94 for the result.)
* * * * *
Turning to the subject of Star-mist, under which head I include all
orders of nebulæ, I propose to deal with but a small proportion of the
evidence I have collected to prove that none of the nebulæ are external
galaxies. That evidence has indeed become exceedingly voluminous.
I shall dwell, therefore, on three points only.
First, as to the distribution of the nebulæ:—They are not spread with
any approach to uniformity over the heavens, but are gathered into
streams and clusters. The one great law which characterizes their
distribution is an avoidance of the Milky Way and its neighbourhood.
This peculiarity has, strangely enough, been regarded by astronomers
as showing that there is no association between the nebulæ and the
sidereal system. They have forgotten that marked contrast is as clear
a sign of association as marked resemblance, and has always been so
regarded by logicians.
Secondly, there are in the southern heavens two well-marked streams of
nebulæ. Each of these streams is associated with an equally well-marked
stream of stars. Each intermixed stream directs its course towards a
Magellanic Cloud, one towards the Nubecula Minor, the other towards the
Nubecula Major. To these great clusters they flow, like rivers towards
some mighty lake. And within these clusters, which are doubtless
roughly spherical in form, there are found intermixed in wonderful
profusion, stars, star-clusters, and all the orders of nebulæ. Can
these coincidences be regarded as accidental? And if not accidental,
is not the lesson they clearly teach us this, that nebulæ form but
portions of the sidereal system, associating themselves with stars on
terms of equality (if one may so speak), even if single stars be not
more important objects in the scale of creation than these nebulous
masses, which have been so long regarded as equalling, if not outvying,
the sidereal system itself in extent?
The third point to which I wish to invite attention is the way in which
in many nebulæ stars of considerable relative brightness, and belonging
obviously to the sidereal system, are so associated with nebulous
masses as to leave no doubt whatever that these masses really cling
around them. The association is in many instances far too marked to be
regarded as the effect of accident.
Among other instances[19] may be cited the nebula round the stars _c_¹
and _c_² in Orion. In this object two remarkable nebulous nodules
centrally surround two double stars. Admitting the association here to
be real (and no other explanation can reasonably be admitted), we are
led to interesting conclusions respecting the whole of that wonderful
nebulous region which surrounds the sword of Orion. We are led to
believe that the other nebulæ in that region are really associated with
the fixed stars there; that it is not a mere coincidence, for instance,
that the middle star in the belt of Orion is involved in nebula, or
that the lowest star of the sword is similarly circumstanced. It is
a legitimate inference from the evidence that all the nebulæ in this
region belong to one great nebulous group, which extends its branches
to these stars. As a mighty hand, this nebulous region seems to gather
the stars here into close association, showing us, in a way there is no
misinterpreting, that these stars form one system.
The nebula around the strange variable star, Eta Argûs, is another
remarkable instance of this sort. More than two years ago I ventured
to make two predictions about this object. The first was a tolerably
safe one. I expressed my belief that the nebula would be found to be
gaseous. After Mr. Huggins’s discovery that the great Orion nebula is
gaseous, it was not difficult to see that the Argo nebula must be
so too. At any rate, this has been established by Captain Herschel’s
spectroscopic researches. The other prediction was more venturesome.
Sir John Herschel, whose opinion on such points one would always
prefer to share, had expressed his belief that the nebula lies far out
in space beyond the stars seen in the same field of view. I ventured
to express the opinion that those stars are involved in the nebula.
Lately there came news from Australia that Mr. Le Sueur, with the
great reflector erected at Melbourne, has found that the nebula has
changed largely in shape since Sir John Herschel observed it. Mr. Le
Sueur accordingly expressed his belief that the nebula lies _nearer_ to
us than the fixed stars seen in the same field of view. More lately,
however, he has found that the star Eta Argûs is shining with the
light of burning hydrogen, and he expresses his belief that the star
has consumed the nebulous matter near it. Without agreeing with this
view, I recognize in it a proof that Mr. Le Sueur now considers the
nebula to be really associated with the stars around it. My belief is
that as the star recovers its brilliancy observation will show that the
nebula in its immediate neighbourhood becomes brighter (_not_ fainter
through being consumed as fuel). In fact, I am disposed to regard the
variations of the nebula as systematic, and due to orbital motions
among its various portions around neighbouring stars.
As indicative of other laws of association bearing on the relations I
have been dealing with, I may mention the circumstance that red stars
and variable stars affect the neighbourhood of the Milky Way or of
well-marked star-streams. The constellation Orion is singularly rich in
objects of this class. It is here that the strange “variable” Betelgeux
lies. At present this star shows no sign of variation, but a few years
ago it exhibited remarkable changes. One is invited to believe that
the star may have been carried by its proper motion into regions where
there is a more uniform distribution of the material whence this orb
recruits its fires. It may be that in the consideration of such causes
of variation affecting our sun in long past ages a more satisfactory
explanation than any yet obtained may be found of the problem
geologists find so perplexing—the former existence of a tropical
climate in places within the temperate zone, or even near the Arctic
regions.[20]
* * * * *
It remains that I should exhibit the general results to which I have
been led. It has seemed to many that my views tend largely to diminish
our estimate of the extent of the sidereal system. The exact reverse
is the case. According to accepted views there lie within the range of
our most powerful telescopes millions of millions of suns. According
to mine the primary suns within the range of our telescopes must be
counted by tens of thousands, or by hundreds of thousands at the
outside. What does this diminution of numbers imply but that the space
separating sun from sun is enormously greater than accepted theories
would permit? And this increase implies an enormous increase in the
estimate we are to form of the vital energies of individual suns. For
the vitality of a sun, if one may be permitted the expression, is
measured not merely by the amount of matter over which it exercises
control, but by the extent of space within which that matter is
distributed. Take an orb a thousand times vaster than our sun, and
spread over its surface an amount of matter exceeding a thousandfold
the combined mass of all the planets of the solar system:—So far as
living force is concerned, the result is—_nil_. But distribute that
matter throughout a vast space all round the orb:—That orb becomes
at once fit to be the centre of a host of dependent worlds. Again,
according to accepted theories, when the astronomer has succeeded in
resolving the milky light of a portion of the galaxy into stars, he
has in that direction, at any rate, reached the limits of the sidereal
system. According to my views, what he has really done has been but to
analyze a definite aggregation of stars, a mere corner of that great
system. Yet once more, according to accepted views, thousands and
thousands of galaxies, external to the sidereal system, can be seen
with powerful telescopes. If I am right, the external star-systems lie
far beyond the reach of the most powerful telescope man has yet been
able to construct, insomuch that perchance the nearest of the outlying
galaxies may lie a million times beyond the range even of the mighty
mirror of the great Rosse telescope.
But this is little. Wonderful as is the extent of the sidereal system
as thus viewed, even more wonderful is its infinite variety. We know
how largely modern discoveries have increased our estimate of the
complexity of the planetary system. Where the ancients recognized
but a few planets, we now see, besides the planets, the families of
satellites; we see the rings of Saturn, in which minute satellites must
be as the sands on the sea-shore for multitude; the wonderful zone
of asteroids; myriads on myriads of comets; millions on millions of
meteor-systems, gathering more and more richly around the sun, until
in his neighbourhood they form the crown of glory which bursts into
view when he is totally eclipsed. But wonderful as is the variety seen
within the planetary system, the variety within the sidereal system is
infinitely more amazing. Besides the single suns, there are groups and
systems and streams of primary suns; there are whole galaxies of minor
orbs; there are clustering stellar aggregations, showing every variety
of richness, of figure, and of distribution; there are all the various
forms of nebulæ, resolvable and irresolvable, circular, elliptical,
and spiral; and lastly, there are irregular masses of luminous gas,
clinging in fantastic convolutions around stars and star-systems. Nor
is it unsafe to assert that other forms and variety of structure will
yet be discovered, or that hundreds more exist which we may never hope
to recognize.
But lastly, even more wonderful than the infinite variety of the
sidereal system, is its amazing vitality. Instead of millions of inert
masses, we see the whole heavens instinct with energy—astir with busy
life. The great masses of luminous vapour, though occupying countless
millions of cubic miles of space, are moved by unknown forces like
clouds before the summer breeze; star-mist is condensing into clusters;
star-clusters are forming into suns; streams and clusters of minor orbs
are swayed by unknown attractive energies; and primary suns singly or
in systems are pursuing their stately path through space, rejoicing as
giants to run their course, extending on all sides the mighty arm of
their attraction, gathering from ever-new regions of space supplies of
motive energy, to be transformed into the various forms of force—light
and heat and electricity—and distributed in lavish abundance to the
worlds which circle round them.
Truly may I say, in conclusion, that whether we regard its vast extent,
its infinite variety, or the amazing vitality which pervades its every
portion, the sidereal system is, of all the subjects man can study,
the most imposing and the most stupendous. It is as a book full of
mighty problems—of problems which are as yet almost untouched by man,
of problems which it might seem hopeless for him to attempt to solve.
But those problems are given to him for solution, and he _will_ solve
them, whenever he dares attempt to decipher aright the records of that
wondrous volume.
_MALLET’S THEORY OF VOLCANOES._
There are few subjects less satisfactorily treated in scientific
treatises than that which Humboldt calls the Reaction of the Earth’s
Interior. We find, not merely in the configuration of the earth’s
crust, but in actual and very remarkable phenomena, evidence of
subterranean forces of great activity; and the problems suggested seem
in no sense impracticable: yet no theory of the earth’s volcanic energy
has yet gained general acceptance. While the astronomer tells us of the
constitution of orbs millions of times further away than our own sun,
the geologist has hitherto been unable to give an account of the forces
which agitate the crust of the orb on which we live.
The theory put forward respecting volcanic energy, however, by the
eminent seismologist Mallet, promises not merely to take the place
of all others, but to gain a degree of acceptance which has not been
accorded to any theory previously enunciated. It is, in principle,
exceedingly simple, though many of the details (into which I do not
propose to enter) involve questions of considerable difficulty.
Let us, in the first place, consider briefly the various explanations
which had been already advanced.
There was first the chemical theory of volcanic energy, the favourite
theory of Sir Humphry Davy. It is possible to produce on a small scale
nearly all the phenomena due to subterranean activity, by simply
bringing together certain substances, and leaving them to undergo
the chemical changes due to their association. As a familiar instance
of explosive action thus occasioned, we need only mention the results
experienced when any one unfamiliar with the methods of treating
lime endeavours over hastily to “slake” or “slack” it with water.
Indeed, one of the strong points of the chemical theory consisted in
the circumstance that volcanoes only occur where water can reach the
subterranean regions—or, as Mallet expresses it, that “without water
there is no volcano.” But the theory is disposed of by the fact, now
generally admitted, that the chemical energies of our earth’s materials
were almost wholly exhausted before the surface was consolidated.
Another inviting theory is that according to which the earth is
regarded as a mere shell of solid matter surrounding a molten nucleus.
There is every reason to believe that the whole interior of the earth
is in a state of intense heat; and if the increase of heat with depth
(as shown in our mines) is supposed to continue uniformly, we find that
at very moderate depths a degree of heat must prevail sufficient to
liquefy any known solids under ordinary conditions. But the conditions
under which matter exists a few miles only below the surface of the
earth are not ordinary. The pressure enormously exceeds any which our
physicists can obtain experimentally. The ordinary distinction between
solids and liquids cannot exist at that enormous pressure. A mass
of cold steel could be as plastic as any of the glutinous liquids,
while the structural change which a solid undergoes in the process
of liquefying could not take place under such pressure even at an
enormously high temperature. It is now generally admitted that if the
earth really has a molten nucleus, the solid crust must, nevertheless,
be far too thick to be in any way disturbed by changes affecting the
liquid matter beneath.
Yet another theory has found advocates. The mathematician Hopkins,
whose analysis of the molten-nucleus theory was mainly effective in
showing that theory to be untenable, suggested that there may be
isolated subterranean lakes of fiery matter, and that these may be the
true seat of volcanic energy. But such lakes could not maintain their
heat for ages, if surrounded (as the theory requires) by cooler solid
matter, especially as the theory also requires that water should have
access to them. It will be observed also that none of the theories just
described affords any direct account of those various features of the
earth’s surface—mountain ranges, table-lands, volcanic regions, and so
on—which are undoubtedly due to the action of subterranean forces. The
theory advanced by Mr. Mallet is open to none of these objections. It
seems, indeed, competent to explain all the facts which have hitherto
appeared most perplexing.
It is recognized by physicists that our earth is gradually parting with
its heat. As it cools it contracts. Now if this process of contraction
took place uniformly, no subterranean action would result. But if the
interior contracts more quickly than the crust, the latter must in some
way or other force its way down to the retreating nucleus. Mr. Mallet
shows that the hotter internal portion must contract faster than the
relatively cool crust; and then he shows that the shrinkage of the
crust is competent to occasion all the known phenomena of volcanic
action. In the distant ages when the earth was still fashioning, the
shrinkage produced the _irregularities of level_ which we recognize in
the elevation of the land and the depression of the ocean-bed. Then
came the period when as the crust shrank it formed _corrugations_, in
other words, when the foldings and elevations of the somewhat thickened
crust gave rise to the mountain-ranges of the earth. Lastly, as the
globe gradually lost its extremely high temperature, the continuance
of the same process of shrinkage led no longer to the formation of
ridges and table-lands, but to local crushing-down and dislocation.
This process is still going on, and Mr. Mallet not only recognizes here
the origin of earthquakes, and of the changes of level now in progress,
but the true cause of volcanic heat. The modern theory of heat as
a form of motion here comes into play. As the solid crust closes in
upon the shrinking nucleus, the work expended in crushing down and
dislocating the parts of the crust is transformed into heat, by which,
at the places where the process goes on with greatest energy, “the
materials of the rock so crushed and of that adjacent to it are heated
even to fusion. The access of water to such points determines volcanic
eruption.”
Now all this is not mere theorising. Mr. Mallet does not come before
the scientific world with an ingenious speculation, which may or may
not be confirmed by observation and experiment. He has measured and
weighed the forces of which he speaks. He is able to tell precisely
what proportion of the actual energy which must be developed as the
earth contracts is necessary for the production of observed volcanic
phenomena. It is probable that nine-tenths of those who have read
these lines would be disposed to think that the contraction of the
earth must be far too slow to produce effects so stupendous as those
which we recognize in the volcano and the earthquake. But Mr. Mallet
is able to show, by calculations which cannot be disputed, that less
than one-fourth of the heat at present annually lost by the earth is
sufficient to account for the total annual volcanic action, according
to the best data at present in our possession.
As I have said, I do not propose to follow out Mr. Mallet’s admirable
theory into all its details. I content myself with pointing out how
excellently it accounts for certain peculiarities of the earth’s
surface configuration. Few that have studied carefully drawn charts
of the chief mountain-ranges can have failed to notice that the
arrangement of these ranges does not accord with the idea of upheaval
through the action of internal forces. But it will be at once
recognized that the aspect of the mountain-ranges accords exactly with
what would be expected to result from such a process of contraction
as Mr. Mallet has indicated. The shrivelled skin of an apple affords
no inapt representation of the corrugated surface of our earth,
and according to the new theory, the shrivelling of such a skin is
precisely analogous to the processes at work upon the earth when
mountain-ranges were being formed. Again, there are few students of
geology who have not found a source of perplexity in the foldings and
overlappings of strata in mountainous regions. No forces of upheaval
seem competent to produce this arrangement. But by the new theory this
feature of the earth’s surface is at once explained; indeed, no other
arrangement could be looked for.
It is worthy of notice that Mr. Mallet’s theory of Volcanic energy
is completely opposed to ordinary ideas respecting earthquakes and
volcanoes. We have been accustomed vaguely to regard these phenomena
as due to the eruptive outbursting power of the earth’s interior; we
shall now have to consider them as due to the subsidence and shrinkage
of the earth’s exterior. Mountains have not been upheaved, but valleys
have sunk down. And in another respect the new theory tends to modify
views which have been generally entertained in recent times. Our
most eminent geologists have taught that the earth’s internal forces
may be as active now as in the epochs when the mountain-ranges were
formed. But Mr. Mallet’s theory tends to show that the volcanic energy
of the earth is a declining force. Its chief action had already been
exerted when mountains began to be formed; what remains now is but
the minutest fraction of the volcanic energy of the mountain-forming
era; and each year, as the earth parts with more and more of its
internal heat, the sources of her subterranean energy are more and more
exhausted. The thought once entertained by astronomers that the earth
might explode like a bomb, her scattered fragments producing a ring of
bodies resembling the zone of asteroids, seems further than ever from
probability; if ever there was any danger of such a catastrophe, the
danger has long since passed away.
_TOWARDS THE NORTH POLE._
The Arctic Expedition which returned to our shores in the autumn of
1876 may be regarded as having finally decided the question whether
the North Pole of the earth is accessible by the route through Smith’s
Sound—a route which may conveniently and properly be called the
American route. Attacks may hereafter be made on the Polar fastness
from other directions; but it is exceedingly unlikely that this
country, at any rate, will again attempt to reach the Pole along
the line of attack followed by Captain Nares’s expedition. I may be
forgiven, perhaps, for regarding Arctic voyages made by the seamen
of other nations as less likely to be successful than those made by
my own countrymen. It is not mere national prejudice which suggests
this opinion. It is the simple fact that hitherto the most successful
approaches towards both the Northern and the Southern Poles have been
made by British sailors. Nearly a quarter of a century has passed since
Sir E. Parry made the nearest approach to the North Pole recorded up
to that time; and although, in the interval between Parry’s expedition
and Nares’s, no expedition had been sent out from our shores with
the object of advancing towards the Pole, while America, Sweden,
Russia, and Germany sent out several, Parry’s attempt still remained
unsurpassed and unequalled. At length it has been surpassed, but it has
been by his own countrymen. In like manner, no nation has yet succeeded
in approaching the Antarctic Pole so nearly, within many miles, as did
Captain Sir J. C. Ross in 1844. Considering these circumstances, and
remembering the success which rewarded the efforts of Great Britain
in the search for the North-West Passage, it cannot be regarded as
national prejudice to assert that events indicate the seamen of this
country as exceptionally fitted to contend successfully against the
difficulties and the dangers of Arctic exploration. Should England,
then, give up the attempt to reach the North Pole by way of Smith’s
Sound and its northerly prolongation, it may fairly be considered
unlikely that the Pole will ever be reached in that direction.
It may be well to examine the relative probable chances of success
along other routes which have either not been so thoroughly tried, or
have been tried under less favourable conditions.
Passing over the unfortunate expedition under Hugh Willoughby in 1553,
the first attempt to penetrate within the Polar domain was made by
Henry Hudson in 1607. The route selected was one which many regard
(and I believe correctly) as the one on which there is the best chance
of success; namely, the route across the sea lying to the west of
Spitzbergen. That Hudson, in the clumsy galleons of Elizabeth’s time,
should have penetrated to within eight degrees and a half of the Pole,
or to a distance only exceeding Nares’s nearest approach by about 130
miles, proves conclusively, we think, that with modern ships, and
especially with the aid of steam, this route might be followed with
much better prospect of success than that which was adopted for Nares’s
expedition. If the reader will examine a map of the Arctic regions he
will find that the western shores of Spitzbergen and the north-eastern
shores of Greenland, as far as they have been yet explored, are
separated by about 33 degrees of longitude, equivalent on the 80th
parallel of latitude to about 335 miles. Across the whole breadth of
this sea Arctic voyagers have attempted to sail northwards beyond the
80th parallel, but no one has yet succeeded in the attempt except on
the eastern side of that sea. It was here that Hudson—fortunately for
him—directed his attack; and he passed a hundred miles to the north
of the 80th parallel, being impeded and finally stopped by the packed
ice around the north-western shores of Spitzbergen.
Let us consider the fortunes of other attempts which have been made to
approach the Pole in this direction.
In 1827 Captain (afterwards Sir Edward) Parry, who had already four
times passed beyond the Arctic Circle—viz., in 1818, 1819, 1821–23,
and 1824–25—made an attempt to reach the North Pole by way of
Spitzbergen. His plan was to follow Hudson’s route until stopped by
ice; then to leave his ship, and cross the ice-field with sledges
drawn by Esquimaux dogs, and, taking boats along with the party, to
cross whatever open water they might find. In this way he succeeded
in reaching latitude 82° 45´ north, the highest ever attained until
Nares’s expedition succeeded in crossing the 83rd parallel. Parry found
that the whole of the ice-field over which his party were laboriously
travelling northwards was being carried bodily southwards, and that at
length the distance they were able to travel in a day was equalled by
the southerly daily drift of the ice-field, so that they made no real
progress. He gave up further contest, and returned to his ship the
_Hecla_.
It is important to inquire whether the southerly drift which stopped
Parry was due to northerly winds or to a southerly current; and if
to the latter cause, whether this current probably affects the whole
extent of the sea in which Parry’s ice-field was drifting. We know
that his party were exposed, during the greater part of their advance
from Spitzbergen, to northerly winds. Now the real velocity of these
winds must have been greater than their apparent velocity, because the
ice-field was moving southwards. Had this not been the case, or had the
ice-field been suddenly stopped, the wind would have seemed stronger;
precisely as it seems stronger to passengers on board a sailing vessel
when, after being before the wind for a time, she is brought across
the wind. The ice-field was clearly travelling before the wind, but
not nearly so fast as the wind; and therefore there is good reason
for believing that the motion of the ice-field was due to the wind
alone. If we suppose this to have been really the case, then, as there
is no reason for believing that northerly winds prevail uniformly in
the Arctic regions, we must regard Parry’s defeat as due to mischance.
Another explorer might have southerly instead of northerly winds, and
so might be assisted instead of impeded in his advance towards the
Pole. Had this been Parry’s fortune, or even if the winds had proved
neutral, he would have approached nearer to the Pole than Nares. For
Parry reckoned that he had lost more than a hundred miles by the
southerly drift of the ice-field, by which amount at least he would
have advanced further north. But that was not all; for there can be
little doubt that he would have continued his efforts longer but for
the Sisyphæan nature of the struggle. It is true he was nearer home
when he turned back than he would have been but for the drift, and one
of his reasons for turning back was the consideration of the distance
which his men had to travel in returning. But he was chiefly influenced
(so far as the return journey was concerned) by the danger caused by
the movable nature of the ice-field, which might at any time begin to
travel northwards, or eastwards, or westwards.
If we suppose that not the wind but Arctic currents carried the
ice-field southwards, we must yet admit the probability—nay, almost
the certainty—that such currents are only local, and occupy but a part
of the breadth of the North Atlantic seas in those high latitudes. The
general drift of the North Atlantic surface-water is unquestionably
not towards the south but towards the north; and whatever part we
suppose the Arctic ice to perform in regulating the system of oceanic
circulation—whether, with Carpenter, we consider the descent of
the cooled water as the great moving cause of the entire system of
circulation, or assign to that motion a less important office (which
seems to me the juster opinion)—we must in any case regard the Arctic
seas as a region of surface indraught. The current flowing from those
seas, which caused (on the hypothesis we are for the moment adopting)
the southwardly motion of Parry’s ice-field, must therefore be regarded
as in all probability an exceptional phenomenon of those seas. By
making the advance from a more eastwardly or more westwardly part of
Spitzbergen, a northerly current would probably be met with; or rather,
the motion of the ice-field would indicate the presence of such a
current, for I question very much whether open water would anywhere be
found north of the 83rd parallel. In that case, a party might advance
in one longitude and return in another, selecting for their return
the longitude in which (always according to our present hypothesis
that currents caused the drift) Parry found that a southerly current
underlay his route across the ice. On the whole, however, it appears to
me more probable that winds, not currents, caused the southerly drift
of Parry’s ice-field.
In 1868, a German expedition, under Captain Koldewey, made the first
visit to the seas west of Spitzbergen in a steamship, the small but
powerful screw steamer _Germania_ (126 tons), advancing northwards
a little beyond the 81st parallel. But this voyage can scarcely be
regarded as an attempt to approach the Pole on that course; for
Koldewey’s instructions were, “to explore the eastern coast of
Greenland northwards; and, if he found success in that direction
impossible, to make for the mysterious Island of Gilles on the east of
Spitzbergen.”
Scoresby in 1806 had made thus far the most northerly voyage in a ship
on Hudson’s route, but in 1868 a Swedish expedition attained higher
latitudes than had ever or have ever been reached by a ship in that
direction. The steamship _Sofia_, strongly built of Swedish iron, and
originally intended for winter voyages in the Baltic, was selected for
the voyage. Owing to a number of unfortunate delays, it was not until
September, 1868, that the _Sofia_ reached the most northerly part of
her journey, attaining a point nearly fifteen miles further north than
Hudson had reached. To the north broken ice was still found, but it was
so closely packed that not even a boat could pass through. Two months
earlier in the season the voyagers might have waited for a change of
wind and the breaking up of the ice; but in the middle of September
this would have been very dangerous. The temperature was already
sixteen degrees below the freezing-point, and there was every prospect
that in a few weeks, or even days, the seas over which they had reached
their present position would be icebound. They turned back from that
advanced position; but, with courage worthy of the old Vikings, they
made another attack a fortnight later. They were foiled again, as was
to be expected, for by this time the sun was already on the wintry side
of the equator. They had, indeed, a narrow escape from destruction.
“An ice-block with which they came into collision opened a large leak
in the ship’s side, and when, after great exertions, they reached the
land, the water already stood two feet over the cabin floor.”[21]
On the western side of the North Atlantic Channel—so to term the part
lying between Greenland and Spitzbergen—the nearest approach towards
the Pole was made by the Dutch in 1670, nearly all the more recent
attempts to reach high northern latitudes in this direction having
hitherto ended in failure more or less complete.
We have already seen that Captain Koldewey was charged to explore the
eastern coast of Greenland in the _Germania_ in 1868. In 1869 the
_Germania_ was again despatched under his command from Bremerhaven,
in company with the _Hansa_, a sailing vessel. Lieutenant Payer and
other Austrian _savants_ accompanied Captain Koldewey. The attack was
again made along the eastern shores of Greenland. As far as the 74th
degree the two vessels kept company; but at this stage it happened
unfortunately that a signal from the _Germania_ was misinterpreted,
and the _Hansa_ left her. Soon after, the _Hansa_ was crushed by masses
of drifting ice, and her crew and passengers took refuge on an immense
ice-floe seven miles in circumference. Here they built a hut, which was
in its turn crushed. Winds and currents carried their icy home about,
and at length broke it up. Fortunately they had saved their boats, and
were able to reach Friedrichsthal, a missionary station in the south of
Greenland, whence they were conveyed to Copenhagen in September, 1870.
Returning to the _Germania_, we find that she had a less unfortunate
experience. She entered the labyrinth of sinuous fjords, separated
by lofty promontories, and girt round by gigantic glaciers, which
characterize the eastern coast of Greenland to the north of Scoresby
Sound. In August the channels by which she had entered were closed,
and the _Germania_ was imprisoned. So soon as the ice would bear
them, Koldewey and his companions made sledging excursions to various
points around their ship. But in November the darkness of the polar
winter settled down upon them, and these excursions ceased. The polar
winter of 1869–70 was “characterized by a series of violent northerly
tempests, one of which continued more than 100 hours, with a velocity
(measured by the anemometer) of no less than sixty miles an hour”—a
velocity often surpassed, indeed, but which must have caused intense
suffering to all who left the shelter of the ship; for it is to be
remembered that the air which thus swept along at the rate of a mile
a minute was the bitter air of the Arctic regions. The thermometer
did not, however, descend lower than 26° below zero, or 58° below the
freezing-point—a cold often surpassed in parts of the United States. I
have myself experienced a cold of more than 30° below zero, at Niagara.
“With proper precautions as regards shelter and clothing,” proceeds
the narrative, “even extreme cold need not cause great suffering to
those who winter in such regions. One of the worst things to be endured
is the physical and moral weariness of being cut off from external
observations during the long night of some ninety days, relieved only
by the strange Northern Lights. The ice accumulates all round with
pressure, and assumes peculiar and fantastic forms, emitting ever and
anon ominous noises. Fortunately, the _Germania_ lay well sheltered
in a harbour opening southwards, and, being protected by a rampart of
hills on the north, was able to resist the shock of the elements. The
sun appearing once more about the beginning of February, the scientific
work of exploration began.... The pioneers of the _Germania_ advanced
as far as the 77th degree of latitude, in longitude 18° 50´ west from
Greenwich. There was no sign of an open sea towards the Pole. _Had it
not been for want of provisions, the party could have prolonged their
sledge journey indefinitely._ The bank of ice, without remarkable
protuberances, extends to about two leagues from the shore, which
from this extreme point seems to trend towards the north-west, where
the view was bounded by lofty mountains.” As the expedition was only
equipped for one winter, it returned to Europe in September, 1870,
without having crossed the 78th parallel of north latitude.
Captain Koldewey was convinced, by the results of his exploration,
that there is no continuous channel northwards along the eastern coast
of Greenland. It does not seem to me that his expedition proved this
beyond all possibility of question. Still, it seems clear that the
eastern side of the North Atlantic is less suited than the western for
the attempt to reach the North Pole. The prevailing ocean-currents are
southerly on that side, just as they are northerly on the western side.
The cold also is greater, the lines of equal temperature lying almost
exactly in the direction of the channel itself—that is, nearly north
and south—and the cold increasing athwart that direction, towards the
west. The nearer to Greenland the greater is the cold.[22]
The next route to be considered in order of time would be the American
route; but I prefer to leave this to the last, as the latest results
relate to that route. I take next, therefore, a route which some regard
as the most promising of all—that, namely, which passes between
Spitzbergen and the Scandinavian peninsula.
It will be remembered that Lieutenant Payer, of the Austrian navy, had
accompanied Captain Koldewey’s first expedition. When driven back from
the attempt to advance along the eastern shores of Greenland, that
commander crossed over to Spitzbergen, and tried to find the Land of
Gilles. He also accompanied Koldewey’s later expedition, and shared his
belief that there is no continuous channel northwards on the western
side of the North Atlantic channel. Believing still, however, with
Dr. Petermann, the geographer, that there is an open Polar sea beyond
the ice-barrier, Payer set out in 1871, in company with Weyprecht,
towards the Land of Gilles. They did not find this mysterious land,
but succeeded in passing 150 miles further north, after rounding the
south-eastern shores of Spitzbergen, than any Arctic voyagers who had
before penetrated into the region lying between Spitzbergen and Novaia
Zemlia. Here they found, beyond the 76th parallel, and between 42° and
60° east longitude, an open sea, and a temperature of between 5° and 7°
above the freezing-point. Unfortunately, they had not enough provisions
with them to be able safely to travel further north, and were thus
compelled to return. The season seems to have been an unusually open
one; and it is much to be regretted that the expedition was not better
supplied with provisions—a defect which appears to be not uncommon
with German expeditions.
Soon after their return, Payer and Weyprecht began to prepare for a new
expedition; and this time their preparations were thorough, and adapted
for a long stay in Arctic regions. “The chief aim of this expedition,”
says the _Revue des Deux Mondes_, in an interesting account of recent
Polar researches, “was to investigate the unknown regions of the Polar
seas to the north of Siberia, and to try to reach Behring’s Straits
by this route.” It was only if after two winters and three summers
they failed to double the extreme promontory of Asia, that they were
to direct their course towards the Pole. The voyagers, numbering
twenty-four persons, left the Norwegian port of Tromsoë, in the steamer
_Tegethoff_, on July 14, 1872. Count Wilczek followed shortly after
in a yacht, which was to convey coals and provisions to an eastern
point of the Arctic Ocean, for the benefit of the _Tegethoff_. At
a point between Novaia Zemlia and the mouth of the Petschora, the
yacht lost sight of the steamer, and nothing was heard of the latter
for twenty-five months. General anxiety was felt for the fate of the
expedition, and various efforts were made by Austria, England, and
Russia to obtain news of it. In September, 1874, the voyagers suddenly
turned up at another port, and soon after entered Vienna amid great
enthusiasm. Their story was a strange one.
It appears that when the _Tegethoff_ was lost sight of (August 21,
1872), she had been surrounded by vast masses of ice, which crushed
her hull. For nearly half a year the deadly embrace of the ice
continued; and when at length pressure ceased, the ship remained
fixed in the ice, several miles from open water. During the whole
summer the voyagers tried to release their ship, but in vain. They had
not, however, remained motionless all this time. The yacht had lost
sight of them at a spot between Novaia Zemlia and Malaia Zemlia (in
North Russia) in about 71° north latitude, and they were imprisoned
not far north of this spot. But the ice-field was driven hither
and thither by the winds, until they found themselves, on the last
day of August, 1873, only 6´ or about seven miles south of the 80th
parallel of latitude. Only fourteen miles from them, on the north,
they saw “a mass of mountainous land, with numerous glaciers.” They
could not reach it until the end of October, however, and then they
had to house themselves in preparation for the long winter night.
This land they called Francis Joseph Land. It lies north of Novaia
Zemlia, and on the Polar side of the 80th parallel of latitude. The
winter was stormy and bitterly cold, the thermometer descending on one
occasion to 72° below zero—very nearly as low as during the greatest
cold experienced by Nares’s party. In February, 1874, “the sun having
reappeared, Lieutenant Payer began to prepare sledge excursions to
ascertain the configuration of the land.... In the second excursion
the voyagers entered Austria Sound, which bounds Francis Joseph Island
on the east and north, and found themselves, after emerging from it,
in the midst of a large basin, surrounded by several large islands.
The extreme northern point reached by the expedition was a cape on one
of these islands, which they named Prince Rodolph’s Land, calling the
point Cape Fligely. It lies a little beyond the 81st parallel. They
saw land further north beyond the 83rd degree of latitude, and named
it Petermann’s Land. The archipelago thus discovered is comparable
in extent to that of which Spitzbergen is the chief island.” The
voyagers were compelled now to return, as the firm ice did not extend
further north. They had a long, difficult, and dangerous journey
southwards—sometimes on open water, in small boats, sometimes on
ice, with sledges—impeded part of the time by contrary winds, and
with starvation staring them in the face during the last fortnight of
their journey. Fortunately, they reached Novaia Zemlia before their
provisions quite failed them, and were thence conveyed to Wardhoë by a
Russian trading ship.
We have now only to consider the attempts which have been made to
approach the North Pole by the American route. For, though Collinson
in 1850 reached high latitudes to the north of Behring’s Straits, while
Wrangel and other Russian voyagers have attempted to travel northwards
across the ice which bounds the northern shores of Siberia, it can
hardly be said that either route has been followed with the definite
purpose of reaching the North Pole. I shall presently, however, have
occasion to consider the probable value of the Behring’s Straits route,
which about twelve years ago was advocated by the Frenchman Lambert.
Dr. Kane’s expedition in 1853–55 was one of those sent out in search
of Sir John Franklin. It was fitted out at the expense of the United
States Government, and the route selected was that along Smith’s Sound,
the northerly prolongation of Baffin’s Bay. Kane wintered in 1853 and
1854 in Van Reusselaer’s Inlet, on the western coast of Greenland, in
latitude 78° 43´ north. Leaving his ship, the _Advance_, he made a
boat-journey to Upernavik, 6° further south. He next traced Kennedy
Channel, the northerly prolongation of Smith’s Sound, reaching latitude
81° 22´ north. He named heights visible yet further to the north,
Parry Mountains; and at the time—that is, twenty-two years ago—the
land so named was the highest northerly land yet seen. Hayes, who had
accompanied Kane in this voyage, succeeded in reaching a still higher
latitude in sledges drawn by Esquimaux dogs. Both Kane and Hayes agreed
in announcing that where the shores of Greenland trend off eastwards
from Kennedy Channel, there is an open sea, “rolling,” as Captain Maury
magniloquently says, “with the swell of a boundless ocean.” It was in
particular noticed that the tides ebbed and flowed in this sea. On this
circumstance Captain Maury based his conclusion that there is an open
sea to the north of Greenland. After showing that the tidal wave could
not well have travelled along the narrow and icebound straits between
Baffin’s Bay and the region reached by Kane and Hayes, Maury says:
“Those tides must have been born in that cold sea, having their cradle
about the North Pole.” The context shows, however, that he really
intended to signify that the waves were formed in seas around the North
Pole, and thence reached the place where they were seen; so that, as
birth usually precedes cradling, Maury would more correctly have said
that these tides are cradled in that cold sea, having their birth about
the North Pole.
The observations of Kane and Hayes afford no reason, however, for
supposing that there is open water around the North Pole. They have
been rendered somewhat doubtful, be it remarked in passing, by the
results of Captain Nares’s expedition; and it has been proved beyond
all question that there is not an open sea directly communicating with
the place where Kane and Hayes observed tidal changes. But, apart
from direct evidence of this kind, two serious errors affect Maury’s
reasoning, as I pointed out eleven years since. In the first place,
a tidal wave would be propagated quite freely along an ice-covered
sea, no matter how thick the ice might be, so long as the sea was not
absolutely icebound. Even if the latter condition could exist for a
time, the tidal wave would burst the icy fetters that bound the sea,
unless the sea were frozen to the very bottom; which, of course, can
never happen with any sea properly so called. It must be remembered
that, even in the coldest winter of the coldest Polar regions, ice
of only a moderate thickness can form in open sea in a single day;
but the tidal wave does not allow ice to form for a single hour in
such sort as to bind the great ice-fields and the shore-ice into one
mighty mass. At low tide, for a very short time, ice may form in the
spaces between the shore-ice and the floating ice, and again between
the various masses of floating ice, small or large (up to many square
miles in extent); but as the tidal wave returns it breaks through these
bonds as easily as the Jewish Hercules burst the withes with which the
Philistines had bound his mighty limbs. It is probable that if solid
ice as thick as the thickest which Nares’s party found floating in the
Palæocrystic Sea—ice 200 feet thick—reached from shore to shore of
the North Atlantic channel, the tidal wave would burst the barrier as
easily as a rivulet rising but a few inches bursts the thin coating
which has formed over it on the first cold night of autumn. But no such
massive barriers have to be broken through, for the tidal wave never
gives the ice an hour’s rest Maury reasons that “the tidal wave from
the Atlantic can no more pass under the icy barrier to be propagated
in the seas beyond, than the vibrations of a musical string can pass
with its notes a fret on which the musician has placed his finger.” But
the circumstances are totally different. The ice shares the motion of
the tidal wave, which has not to pass under the ice, but to lift it.
This, of course, it does quite as readily as though there were no ice,
but only the same weight of water. The mere weight of the ice counts
simply for nothing. The tidal wave would rise as easily in the British
Channel if a million Great Easterns were floating there as if there was
not even a cock-boat; and the weight of ice, no matter how thick or
extensive, would be similarly ineffective to restrain the great wave
which the sun and moon send coursing twice a day athwart our oceans.
Maury’s other mistake was even more important so far as this question
of an open sea is concerned. “No one,” as I wrote in 1867, “who is
familiar with the astronomical doctrine of the tides, can believe for
a moment that tides could be generated in a land-locked ocean, so
limited in extent as the North Polar sea (assuming its existence) must
necessarily be.” To raise a tidal wave the sun and moon require not
merely an ocean of wide extent to act upon, but an ocean so placed that
there is a great diversity in their pull on various parts of it; for it
is the difference between the pull exerted on various parts, and not
the pull itself, which creates the tidal wave. Now the Polar sea has
not the required extent, and is not in the proper position, for this
diversity of pull to exist in sufficient degree to produce a tidal wave
which could be recognized. It is certain, in fact, that, whether there
is open water or not near the Pole, the tides observed by Kane and
Hayes must have come from the Atlantic, and most probably by the North
Atlantic channel.
Captain Hall’s expedition in the _Polaris_ (really under the command
of Buddington), in 1871–72, will be probably in the recollection of
most of my readers. Leaving Newfoundland on June 29, 1871, it sailed up
Smith’s Sound, and by the end of August had reached the 80th parallel.
Thence it proceeded up Kennedy Channel, and penetrated into Robeson
Channel, the northerly prolongation of Kennedy Channel, and only 13
miles wide. Captain Hall followed this passage as far as 82° 16´ north
latitude, reaching his extreme northerly point on September 3. From it
he saw “a vast expanse of open sea, which he called Lincoln Sea, and
beyond that another ocean or gulf; while on the west there appeared,
as far as the eye could reach, the contours of coast. This region he
called Grant Land.” So far as appears, there was no reason at that time
why the expedition should not have gone still further north, the season
apparently having been exceptionally open. But the naval commander of
the expedition, Captain Buddington, does not seem to have had his heart
in the work, and, to the disappointment of Hall, the _Polaris_ returned
to winter in Robeson Channel, a little beyond the 81st degree. In the
same month, September, 1871, Captain Hall died, under circumstances
which suggested to many of the crew and officers the suspicion that
he had been poisoned.[23] In the spring of 1870 the _Polaris_ resumed
her course homewards. They were greatly impeded by the ice. A party
which got separated from those on board were unfortunately unable to
regain the ship, and remained on an ice-field for 240 days, suffering
fearfully. The ice-field, like that on which the crew of the _Hansa_
had to take up their abode, drifted southwards, and was gradually
diminishing, when fortunately a passing steamer observed the prisoners
(April 30, 1872) and rescued them. The _Polaris_ herself was so injured
by the ice that her crew had to leave her, wintering on Lyttelton
Island. They left this spot in the early summer of 1872, in two boats,
and were eventually picked up by a Scotch whaler.
Captain Nares’s expedition followed Hall’s route. I do not propose to
enter here into any of the details of the voyage, with which my readers
are no doubt familiar. The general history of the expedition must be
sketched, however, in order to bring it duly into its place here. The
_Alert_ and _Discovery_ sailed under Captains Nares and Stephenson, in
May, 1875. Their struggle with the ice did not fairly commence until
they were nearing the 79th parallel, where Baffin’s Bay merges into
Smith’s Sound. Thence, through Smith’s Sound, Kennedy Channel, and
Robeson Channel, they had a constant and sometimes almost desperate
struggle with the ice, until they had reached the north end of Robeson
Channel. Here the _Discovery_ took up her winter quarters, in north
latitude 81° 44´, a few miles north of Captain Hall’s wintering-place,
but on the opposite (or westerly) side of Robeson Channel. The _Alert_
still struggled northwards, rounding the north-east point of Grant
Land, and there finding, not, as was expected, a continuous coast-line
on the west, but a vast icebound sea. No harbour could be found, and
the ship was secured on the inside of a barrier of grounded ice, in
latitude 82° 31´, in the most northerly wintering-place ever yet
occupied by man. The ice met with on this sea is described as “of most
unusual age and thickness, resembling in a marked degree, both in
appearance and formation, low floating icebergs rather than ordinary
salt-water ice. Whereas ordinary ice is from 2 feet to 10 feet in
thickness, that in this Polar sea has gradually increased in age and
thickness until it measures from 80 feet to 120 feet, floating with
its surface at the lower part 15 feet above the water-line. In some
places the ice reaches a thickness of from 150 to 200 feet, and the
general impression among the officers of the expedition seems to have
been that the ice of this Palæocrystic Sea is the accumulation of many
years, if not of centuries; “that the sea is never free of it and never
open; and that progress to the Pole through it or over it is impossible
with our present resources.”
The winter which followed was the bitterest ever known by man. For
142 days the sun was not seen; the mercury was frozen during nearly
nine weeks. On one occasion the thermometer showed 104° below the
freezing-point, and during one terrible fortnight the mean temperature
was 91° below freezing!
As soon as the sun reappeared sledge-exploration began, each ship being
left with only half-a-dozen men and officers on board. Expeditions were
sent east and west, one to explore the northern coast of Greenland, the
other to explore the coast of Grant Land. Captain Stephenson crossed
over from the _Discovery’s_ wintering-place to Polaris Bay, and there
placed over Hall’s grave a tablet, prepared in England, bearing the
following inscription: “Sacred to the memory of Captain C. F. Hall, of
U.S. _Polaris_, who sacrificed his life in the advancement of science,
on November 8, 1871. This tablet has been erected by the British Polar
Expedition of 1875, who, following in his footsteps, have profited by
his experience”—a graceful acknowledgment (which might, however, have
been better expressed). The party which travelled westwards traced
the shores of Grant Land as far as west longitude 86° 30´, the most
northerly cape being in latitude 83° 7´, and longitude 70° 30´ west.
This cape they named Cape Columbia.
The coast of Greenland was explored as far east as longitude 50° 40´
(west), land being seen as far as 82° 54´ north, longitude 48° 33´
west. Lastly, a party under Commander Markham and Lieutenant Parr
pushed northwards. They were absent ten weeks, but had not travelled
so far north in the time as was expected, having encountered great
difficulties. On May 12, 1876, they reached their most northerly point,
planting the British flag in latitude 83° 20´ 26´´ north. “Owing to
the extraordinary nature of the pressed-up ice, a roadway had to be
formed by pickaxes for nearly half the distance travelled, before any
advance could be safely made, even with light loads; this rendered it
always necessary to drag the sledge-loads forward by instalments, and
therefore to journey over the same road several times. The advance was
consequently very slow, and only averaged about a mile and a quarter
daily—much the same rate as was attained by Sir Edward Parry during
the summer of 1827. The greatest journey made in any one day amounted
only to two miles and three quarters. Although the distance made good
was only 73 miles from the ship, 276 miles were travelled over to
accomplish it.” It is justly remarked, in the narrative from which I
have made this extract, that no body of men could have surpassed in
praiseworthy perseverance this gallant party, whose arduous struggle
over the roughest and most monotonous road imaginable, may fairly be
regarded as surpassing all former exploits of the kind. (The narrator
says that it has “eclipsed” all former ones, which can scarcely be
intended to be taken _au pied de la lettre_.) The expedition reached
the highest latitude ever yet attained under any conditions, carried
a ship to higher latitudes than any ship had before reached, and
wintered in higher latitudes than had ever before been dwelt in during
the darkness of a Polar winter. They explored the most northerly
coast-line yet traversed, and this both on the east and west of their
route northwards. They have ascertained the limits of human habitation
upon this earth, and have even passed beyond the regions which animals
occupy, though nearly to the most northerly limit of the voyage they
found signs of the occasional visits of warm-blooded animals. Last, but
not least, they have demonstrated, as it appears to me (though possibly
Americans will adopt a different opinion), that by whatever route the
Pole is to be reached, it is not by that which I have here called
the American route, at least with the present means of transit over
icebound seas. The country may well be satisfied with such results
(apart altogether from the scientific observations, which are the
best fruits of the expedition), even though the Pole has not yet been
reached.
Must we conclude, however, that the North Pole is really inaccessible?
It appears to me that the annals of Arctic research justify no such
conclusion. The attempt which has just been made, although supposed at
the outset to have been directed along the most promising of all the
routes heretofore tried, turned out to be one of the most difficult
and dangerous. Had there been land extending northwards (as Sherard
Osborn and others opined), on the western side of the sea into which
Robeson Channel opens, a successful advance might have been made along
its shore by sledging. M’Clintock, in 1853, travelled 1220 miles in 105
days; Richards 1012 miles in 102 days; Mecham 1203 miles; Richards and
Osborn 1093 miles; Hamilton 1150 miles with a dog-sledge and one man.
In 1854 Mecham travelled 1157 miles in only 70 days; Young travelled
1150 miles and M’Clintock 1330 miles. But these journeys were made
either over land or over unmoving ice close to a shore-line. Over an
icebound sea journeys of the kind are quite impracticable. But the
conditions, while not more favourable in respect of the existence of
land, were in other respects altogether less favourable along the
American route than along any of the others I have considered in this
brief sketch of the attempts hitherto made to reach the Pole.
The recent expedition wintered as near as possible to the region of
maximum winter cold in the western hemisphere, and pushed their journey
northwards athwart the region of maximum summer cold. Along the course
pursued by Parry’s route the cold is far less intense, in corresponding
latitudes, than along the American route; and cold is the real enemy
which bars the way towards the Pole. All the difficulties and dangers
of the journey either have their origin (as directly as the ice itself)
in the bitter Arctic cold, or are rendered effective and intensified
by the cold. The course to be pursued, therefore, is that indicated
by the temperature. Where the July isotherms, or lines of equal summer
heat, run northwards, a weak place is indicated in the Arctic barrier;
where they trend southwards, that barrier is strongest. Now there are
two longitudes in which the July Arctic isotherms run far northward
of their average latitude. One passes through the Parry Islands, and
indicates the sea north-east of Behring’s Straits as a suitable region
for attack; the other passes through Spitzbergen, and indicates the
course along which Sir E. Parry’s attack was made. The latter is
slightly the more promising line of the two, so far as temperature is
concerned, the isotherm of 36° Fahrenheit (in July) running here as
far north as the 77th parallel, whereas its highest northerly range in
the longitude of the Parry Islands is but about 76°. The difference,
however, is neither great nor altogether certain; and the fact that
Parry found the ice drifting southwards, suggests the possibility that
that _may_ be the usual course of oceanic currents in that region.
North of the Parry Islands the drift may be northwardly, like that
which Payer and Weyprecht experienced to the north of Novaia Zemlia.
There is one great attraction for men of science in the route by the
Parry Islands. The magnetic pole has almost certainly travelled into
that region. Sir J. Ross found it, indeed, to be near Boothia Gulf,
far to the east of the Parry Islands, in 1837. But the variations of
the needle all over the world since then, indicate unmistakably that
the magnetic poles have been travelling round towards the west, and at
such a rate that the northern magnetic pole has probably nearly reached
by this time the longitude of Behring’s Straits. The determination of
the exact present position of the Pole would be a much more important
achievement, so far as science is concerned, than a voyage to the pole
of rotation.
There is one point which suggests itself very forcibly in reading the
account of the sledging expedition from the _Alert_ towards the north.
In his official report, Captain Nares says that “half of each day was
spent in dragging the sledges in that painful fashion—face toward the
boat—in which the sailors drag a boat from the sea on to the sand;”
and again he speaks of the “toilsome dragging of the sledges over
ice-ridges which resembled a stormy sea suddenly frozen.” In doing
this “276 miles were toiled over in travelling only 73 miles.” Is it
altogether clear that the sledges were worth the trouble? One usually
regards a sledge as intended to carry travellers and their provisions,
etc., over ice and snow, and as useful when so employed; but when the
travellers have to take along the sledge, going four times as far and
working ten times as hard as if they were without it, the question
suggests itself whether all necessary shelter, provisions, and utensils
might not have been much more readily conveyed by using a much smaller
and lighter sledge, and by distributing a large part of the luggage
among the members of the expedition. The parts of a small hut could,
with a little ingenuity, be so constructed as to admit of being used as
levers, crowbars, carrying-poles, and so forth, and a large portion of
the luggage absolutely necessary for the expedition could be carried by
their help; while a small, light sledge for the rest could be helped
along and occasionally lifted bodily over obstructions by levers and
beams forming part of the very material which by the usual arrangement
forms part of the load. I am not suggesting, be it noticed, that by any
devices of this sort a journey over the rough ice of Arctic regions
could be made easy. But it does seem to me that if a party could go
back and forth over 276 miles, pickaxing a way for a sledge, and
eventually dragging it along over the path thus pioneered for it, and
making only an average of 1¼ mile of real progress per day, or 73 miles
in all, the same men could with less labour (though still, doubtless,
with great toil and trouble) make six or seven miles a day by reducing
their _impedimenta_ to what could be carried directly along with them.
Whether use might not be made of the lifting power of buoyant gas, is
a question which only experienced aëronauts and Arctic voyagers could
answer. I believe that the employment of imprisoned balloon-power for
many purposes, especially in time of war, has received as yet much less
attention than it deserves. Of course I am aware that in Arctic regions
many difficulties would present themselves; and the idea of ordinary
ballooning over the Arctic ice-fields may be regarded as altogether
wild in the present condition of the science of aëronautics. But the
use of balloon-power as an auxiliary, however impracticable at present,
is by no means to be despaired of as science advances.
After all, however, the advance upon the Pole itself, however
interesting to the general public, is far less important to science
than other objects which Arctic travellers have had in view. The
inquiry into the phenomena of terrestrial magnetism within the Arctic
regions; the investigation of oceanic movements there; of the laws
according to which low temperatures are related to latitude and
geographical conditions; the study of aerial phenomena; of the limits
of plant life and animal life; the examination of the mysterious
phenomena of the Aurora Borealis—these and many other interesting
subjects of investigation have been as yet but incompletely dealt with.
In the Polar regions, as Maury well remarked, “the icebergs are framed
and glaciers launched; there the tides have their cradle, the whales
their nursery; there the winds complete their circuit, and the currents
of the sea their round, in the wonderful system of oceanic circulation;
there the Aurora is lighted up, and the trembling needle brought to
rest; and there, too, in the mazes of that mystic circle, terrestrial
forces of occult power and of vast influence upon the well-being of man
are continually at work. It is a circle of mysteries; and the desire to
enter it, to explore its untrodden wastes and secret chambers, and to
study its physical aspects, has grown into a longing. Noble daring has
made Arctic ice and snow-clad seas classic ground.”
_A MIGHTY SEA-WAVE._
On May 10th, 1876, a tremendous wave swept the Pacific Ocean from Peru
northwards, westwards, and southwards, travelling at a rate many times
greater than that of the swiftest express train. For reasons best known
to themselves, writers in the newspapers have by almost common consent
called this phenomenon a tidal-wave. But the tides had nothing to do
with it. Unquestionably the wave resulted from the upheaval of the bed
of the ocean in some part of that angle of the Pacific Ocean which is
bounded by the shores of Peru and Chili. This region has long been
celebrated for tremendous submarine and subterranean upheavals. The
opinions of geologists and geographers have been divided as to the real
origin of the disturbances by which at one time the land, at another
time the sea, and at yet other times (oftener, in fact, than either
of the others) both land and sea have been shaken as by some mighty
imprisoned giant, struggling, like Prometheus, to cast from his limbs
the mountain masses which hold them down. Some consider that the seat
of the Vulcanian forces lies deep below that part of the chain of the
Andes which lies at the apex of the angle just mentioned, and that the
direction of their action varies according to the varying conditions
under which the imprisoned gases find vent. Others consider that there
are two if not several seats of subterranean activity. Yet others
suppose that the real seat of disturbance lies beneath the ocean
itself, a view which seems to find support in several phenomena of
recent Peruvian earthquakes.
Although we have not full information concerning the great wave which
in May, 1876, swept across the Pacific, and northwards and southwards
along the shores of the two Americas, it may be interesting to consider
some of the more striking features of this great disturbance of the
so-called peaceful ocean, and to compare them with those which have
characterized former disturbances of a similar kind. We may thus,
perhaps, find some evidence by which an opinion may be formed as to the
real seat of subterranean activity in this region.
At the outset it may be necessary to explain why I have asserted
somewhat confidently that the tides have nothing whatever to do with
this great oceanic wave. It is of course well known to every reader
that the highest or spring tides occur always two or three days after
new moon and after full moon, the lowest (or rather the tides having
least range above and below the mean level) occurring two or three days
after the first and third quarters of the lunar month. The sun and moon
combine, indeed, to sway the ocean most strongly at full and new, while
they pull contrariwise at the first and third quarters; but the full
effect of their combined effort is only felt a few days later than when
it is made, while the full effect of their opposition to each other,
in diminishing the range of the oceanic oscillation, is also only felt
after two or three days. Thus in May, 1876, the tidal wave had its
greatest range on or about May 16, new moon occurring at half-past five
on the morning of May 13; and the tidal wave had its least range on or
about May 8, the moon passing her third quarter a little after eleven
on the morning of May 4. Accordingly the disturbance which affected the
waters of the Pacific so mightily on May 10, occurred two days after
the lowest or neap tides, and five days before the highest or spring
tides. Manifestly that was not a time when a tidal wave of exceptional
height could be expected, or, indeed, could possibly occur. Such a
wave as actually disturbed the Pacific on that day could not in any
case have been produced by tidal action, even though the winds had
assisted to their utmost, and all the circumstances which help to make
high tides had combined—as the greatest proximity of moon to earth,
the conjunction of moon and sun near the celestial equator, and (of
course) the exact coincidence of the time of the tidal disturbance
with that when the combined pull of the sun and moon is strongest. As,
instead, the sun was nearly eighteen degrees from the equator, the moon
more than nine, and as the moon was a full week’s motion from the part
of her path where she is nearest to the earth, while, as we have seen,
only two days had passed from the time of absolutely lowest tides, it
will be seen how utterly unable the tidal-wave must have been on the
day of the great disturbance to produce the effects presently to be
described.
It may seem strange, in dealing with the case of a wave which
apparently had its origin in or near Peru on May 9, to consider the
behaviour of a volcano, distant 5000 miles from this region, a week
before the disturbance took place. But although the coincidence may
possibly have been accidental, yet in endeavouring to ascertain
the true seat of disturbance we must overlook no evidence, however
seemingly remote, which may throw light on that point; and as the
sea-wave generated by the disturbance reached very quickly the distant
region referred to, it is by no means unlikely that the subterranean
excitement which the disturbance relieved may have manifested its
effects beforehand at the same remote volcanic region. Be this as
it may, it is certain that on May 1 the great crater of Kilauea, in
the island of Hawaii, became active, and on the 4th severe shocks of
earthquake were felt at the Volcano House. At three in the afternoon a
jet of lava was thrown up to a height of about 100 feet, and afterwards
some fifty jets came into action. Subsequently jets of steam issued
along the line formed by a fissure four miles in length down the
mountain-side. The disturbance lessened considerably on the 5th, and an
observing party examined the crater. They found that a rounded hill,
700 feet in height, and 1400 feet in diameter, had been thrown up on
the plain which forms the floor of the crater. Fire and scoria spouted
up in various places.
Before rejecting utterly the belief that the activity thus exhibited in
the Hawaii volcano had its origin in the same subterrene or submarine
region as the Peruvian earthquake, we should remember that other
regions scarcely less remote have been regarded as forming part of the
same Vulcanian district. The violent earthquakes which occurred at
New Madrid, in Missouri, in 1812, took place at the same time as the
earthquake of Caraccas, the West Indian volcanoes being simultaneously
active; and earthquakes had been felt in South Carolina for several
months before the destruction of Caraccas and La Guayra. Now we have
abundant evidence to show that the West Indian volcanoes are connected
with the Peruvian and Chilian regions of Vulcanian energy, and the
Chilian region is about as far from New Madrid as Arica in Peru from
the Sandwich Isles.
It was not, however, until about half-past eight on the evening of May
9 that the Peruvian earthquake began. A severe shock, lasting from
four to five minutes, was felt along the entire southern coast, even
reaching Antofagasta. The shock was so severe that it was impossible,
in many places, to stand upright. It was succeeded by several others of
less intensity.
While the land was thus disturbed, the sea was observed to be gradually
receding, a movement which former experiences have taught the Peruvians
to regard with even more terror than the disturbance of the earth
itself. The waters which had thus withdrawn, as if concentrating their
energies to leap more fiercely on their prey, presently returned in
a mighty wave, which swept past Callao, travelling southwards with
fearful velocity, while in its train followed wave after wave, until
no less than eight had taken their part in the work of destruction.
At Mollendo the railway was torn up by the sea for a distance of 300
feet. A violent hurricane which set in afterwards from the south
prevented all vessels from approaching, and unroofed most of the houses
in the town. At Arica the people were busily engaged in preparing
temporary fortifications to repel a threatened assault of the rebel ram
_Huiscar_, at the moment when the roar of the earthquake was heard.
The shocks here were very numerous, and caused immense damage in the
town, the people flying to the Morro for safety. The sea was suddenly
perceived to recede from the beach, and a wave from ten feet to fifteen
feet in height rolled in upon the shore, carrying before it all that it
met. Eight times was this assault of the ocean repeated. The earthquake
had levelled to the ground a portion of the custom-house, the railway
station, the submarine cable office, the hotel, the British Consulate,
the steamship agency, and many private dwellings. Owing to the early
hour of the evening, and the excitement attendant on the proposed
attack of the _Huiscar_, every one was out and stirring; but the only
loss of life which was reported was that of three little children who
were overtaken by the water. The progress of the wave was only stopped
at the foot of the hill on which the church stands, which point is
further inland than that reached in August, 1868. Four miles of the
embankment of the railway were swept away like sand before the wind.
Locomotives, cars, and rails, were hurled about by the sea like so many
playthings, and left in a tumbled mass of rubbish.
The account proceeds to say that the United States steamer _Waters_,
stranded by the bore of 1868, was lifted up bodily by the wave at
Arica, and floated two miles north of her former position. The
reference is no doubt to the double-ender _Watertree_, not stranded by
a bore (a term utterly inapplicable to any kind of sea-wave at Arica,
where there is no large river), but carried in by the great wave which
followed the earthquake of August 13. The description of the wave at
Arica on that occasion should be compared with that of the wave of
May, 1876. About twenty minutes after the first earth shock, the sea
was seen to retire, as if about to leave the shores wholly dry; but
presently its waters returned with tremendous force. A mighty wave,
whose length seemed immeasurable, was seen advancing like a dark wall
upon the unfortunate town, a large part of which was overwhelmed by
it. Two ships, the Peruvian corvette _America_, and the American
double-ender _Watertree_, were carried nearly half a mile to the north
of Arica, beyond the railroad which runs to Tacna, and there left
stranded high and dry. As the English vice-consul at Arica estimated
the height of this enormous wave at fully fifty feet, it would not seem
that the account of the wave of May, 1876, has been exaggerated, for a
much less height is, as we have seen, attributed to it, though, as it
carried the _Watertree_ still further inland, it must have been higher.
The small loss of life can be easily understood when we consider that
the earthquake was not followed instantly by the sea-wave. Warned by
the experience of the earthquake of 1868, which most of them must have
remembered, the inhabitants sought safety on the higher grounds until
the great wave and its successors had flowed in. We read that the
damage done was greater than that caused by the previous calamity, the
new buildings erected since 1868 being of a more costly and substantial
class. Merchandise from the custom-house and stores was carried by the
water to a point on the beach five miles distant.
At Iquique, in 1868, the great wave was estimated at fifty feet in
height. We are told that it was black with the mud and slime of the sea
bottom. “Those who witnessed its progress from the upper balconies of
their houses, and presently saw its black mass rushing close beneath
their feet, looked on their safety as a miracle. Many buildings were,
indeed, washed away, and in the low-lying parts of the town there was a
terrible loss of life.” In May, 1876, the greatest mischief at Iquique
would seem to have been caused by the earthquake, not by the sea-wave,
though this also was destructive in its own way. “Iquique,” we are
told, “is in ruins. The movement was experienced there at the same time
and with the same force [as at Arica]. Its duration was exactly four
minutes and a third. It proceeded from the south-east, exactly from the
direction of Ilaga.” The houses built of wood and cane tumbled down at
the first attacks, lamps were broken, and the burning oil spread over
and set fire to the ruins. Three companies of firemen, German, Italian,
and Peruvian, were instantly at their posts, although it was difficult
to maintain an upright position, shock following shock with dreadful
rapidity. Nearly 400,000 quintals of nitrate in the stores at Iquique
and the adjacent ports of Molle and Pisagua were destroyed. The British
barque _Caprera_ and a German barque sank, and all the coasting craft
and small boats in the harbour were broken to pieces and drifted about
in every direction.
At Chanavaya, a small town at the guano-loading dépôt known as Pabellon
de Pica, only two houses were left standing out of four hundred. Here
the earthquake shock was specially severe. In some places the earth
opened in crevices seventeen yards deep and the whole surface of the
ground was changed.
At Punta de Eobos two vessels were lost, and fourteen ships more
or less damaged, by the wave. Antofagasta, Mexillones, Tocopilla,
and Cobigo, on the Bolivian coast, suffered simultaneously from the
earthquake and the sea-wave. The sea completely swept the business
portion of Antofagasta during four hours. Here a singular phenomenon
was noticed. For some time the atmosphere was illuminated with a ruddy
glow. It was supposed that this light came from the volcano of San
Pedro de Atacama, a few leagues inland from Antofagasta. A somewhat
similar phenomenon was noticed at Tacna during the earthquake of
August, 1868. About three hours after the earthquake an intensely
brilliant light made its appearance above the neighbouring mountains.
It lasted fully half an hour, and was ascribed to the eruption of some
as yet unknown volcano.
As to the height of the great wave along this part of the shore-line
of South America, the accounts vary. According to those which are best
authenticated, it would seem as though the wave exceeded considerably
in height that which flowed along the Peruvian, Bolivian, and Chilian
shores in August, 1868. At Huaniles the wave was estimated at sixty
feet in height, at Mexillones, where the wave, as it passed southwards,
ran into Mexillones Bay, it reached a height of sixty-five feet.
Two-thirds of the town were completely obliterated, wharves, railway
stations, distilleries, etc., all swallowed up by the sea.
The shipping along the Peruvian and Bolivian coast suffered terribly.
The list of vessels lost or badly injured at Pabellon de Pica alone,
reads like the list of a fleet.
I have been particular in thus describing the effects produced by the
earthquake and sea-wave on the shores of South America, in order that
the reader may recognize in the disturbance produced there the real
origin of the great wave which a few hours later reached the Sandwich
Isles, 5000 miles away. Doubt has been entertained respecting the
possibility of a wave, other than the tidal-wave, being transmitted
right across the Pacific. Although in August, 1868, the course of the
great wave which swept from some region near Peru, not only across
the Pacific, but in all directions over the entire ocean, could be
clearly traced, there were some who considered the connection between
the oceanic phenomena and the Peruvian earthquake a mere coincidence.
It is on this account perhaps chiefly that the evidence obtained in
May, 1876, is most important. It is interesting, indeed, as showing
how tremendous was the disturbance which the earth’s frame must
then have undergone. It would have been possible, however, had we
no other evidence, for some to have maintained that the wave which
came in upon the shores of the Sandwich Isles a few hours after the
earthquake and sea disturbance in South America was in reality an
entirely independent phenomenon. But when we compare the events which
happened in May, 1876, with those of August, 1868, and perceive their
exact similarity, we can no longer reasonably entertain any doubt of
the really stupendous fact that _the throes of the earth in and near
Peru are of sufficient energy to send oceanic waves right across the
Pacific_,—waves, too, of such enormous height at starting, that,
after travelling with necessarily diminishing height the whole way
to Hawaii, they still rose and fell through thirty-six feet The real
significance of this amazing oceanic disturbance is exemplified by the
wave circles which spread around the spot where a stone has fallen into
a smooth lake. We know how, as the circles widen, the height of the
wave grows less and less, until, at no great distance from the centre
of disturbance, the wave can no longer be discerned, so slight is the
slope of its advancing and following faces. How tremendous, then, must
have been the upheaval of the bed of ocean by which wave-circles were
sent across the Pacific, retaining, after travelling 5000 miles from
the centre of disturbance, the height of a two-storied house! In 1868,
indeed, we know that the wave travelled very much further, reaching the
shores of Japan, of New Zealand, and of Australia, even if it did not
make its way through the East Indian Archipelago to the Indian Ocean,
as some observations seem to show. Although no news has been received
which would justify us in believing that the wave of May, 1876,
produced corresponding effects at such great distances from the centre
of disturbance, it must be remembered that the dimensions of the wave
when it reached the Sandwich Isles fell far short of those of the great
wave of August 13–14, 1868.
It will be well to make a direct comparison between the waves of May,
1876, and August, 1868, in this respect, as also with regard to the
rate at which they would seem to have traversed the distance between
Peru and Hawaii. On this last point, however, it must be noted that
we cannot form an exact opinion until we have ascertained the real
region of Vulcanian disturbance on each occasion. It is possible that
a careful comparison of times, and of the direction in which the wave
front advanced upon different shores, might serve to show where this
region lay. I should not be greatly surprised to learn that it was far
from the continent of South America.
The great wave reached the Sandwich Isles between four and five on the
morning of May 10, corresponding to about five hours later of Peruvian
time. An oscillation only was first observed at Hilo, on the east coast
of the great southern island of Hawaii, the wave itself not reaching
the village till about a quarter before five. The greatest difference
between the crest and trough of the wave was found to be thirty-six
feet here; but at the opposite side of the island, in Kealakekua Bay
(where Captain Cook was killed), amounted only to thirty feet. In
other places the difference was much less, being in some only three
feet, a circumstance doubtless due to interference, waves which have
reached the same spot along different courses chancing so to arrive
that the crest of one corresponded with the trough of the other, so
that the resulting wave was only the difference of the two. We must
explain, however, in the same way, the highest waves of thirty-six to
forty feet, which were doubtless due to similar interference, crest
agreeing with crest and trough with trough, so that the resulting wave
was the sum of the two which had been divided, and had reached the
same spot along different courses. It would follow that the higher of
the two waves was about twenty-one feet high, the lower about eighteen
feet high; but as some height would be lost in the encounter with the
shore-line, wherever it lay, on which the waves divided, we may fairly
assume that in the open ocean, before reaching the Sandwich group, the
wave had a height of nearly thirty feet from trough to crest. We read,
in accordance with this explanation, that “the regurgitations of the
sea were violent and complex, and continued through the day.”
The wave, regarded as a whole, seems to have reached all the islands at
the same time. Since this has not been contradicted by later accounts,
we are compelled to conclude that the wave reached the group with its
front parallel to the length of the group, so that it must have come
(arriving as it did from the side towards which Hilo lies) from the
north-east It was, then, not the direct wave from Peru, but the wave
reflected from the shores of California, which produced the most marked
effects. We can understand well, this being so, that the regurgitations
of the sea were complex. Any one who has watched the inflow of waves
on a beach so lying within an angle of the line that while one set of
waves comes straight in from the sea, another thwart set comes from the
shore forming the other side of the angle, will understand how such
waves differ from a set of ordinary rollers. The crests of the two
sets form a sort of network, ever changing as each set rolls on; and
considering any one of the four-cornered meshes of this wave-net, the
observer will notice that while the middle of the raised sides rises
little above the surrounding level, because here the crests of one set
cross the troughs of the other, the corners of each quadrangle are
higher than they would be in either set taken separately, while the
middle of the four-cornered space is correspondingly depressed. The
reason is that at the corners of the wave-net crests join with crests
to raise the water surface, while in the middle of the net (not the
middle of the sides, but the middle of the space enclosed by the four
sides) trough joins with trough to depress the water surface.[24]
We must take into account the circumstance that the wave which reached
Hawaii in May, 1876, was probably reflected from the Californian coast,
when we endeavour to determine the rate at which the sea disturbance
was propagated across the Atlantic. The direct wave would have come
sooner, and may have escaped notice because arriving in the night-time,
as it would necessarily have done if a wave which travelled to
California, and thence, after reflection, to the Sandwich group arrived
there at a quarter before five in the morning following the Peruvian
earthquake. We shall be better able to form an opinion on this point
after considering what happened in August, 1868.
The earth-throe on that occasion was felt in Peru about five minutes
past five on the evening of August 13. Twelve hours later, or shortly
before midnight, August 13, Sandwich Island time (corresponding to
5 p.m., August 14, Peruvian time), the sea round the group of the
Sandwich Isles rose in a surprising manner, “insomuch that many thought
the islands were sinking, and would shortly subside altogether beneath
the waves. Some of the smaller islands were for a time completely
submerged. Before long, however, the sea fell again, and as it did so
the observers found it impossible to resist the impression that the
islands were rising bodily out of the water. For no less than three
days this strange oscillation of the sea continued to be experienced,
the most remarkable ebbs and floods being noticed at Honolulu, on the
island of Woahoo.”
The distance between Honolulu and Arica is about 6300 statute miles;
so that, if the wave travelled directly from the shores of Peru to the
Sandwich Isles, it must have advanced at an average rate of about 525
miles an hour (about 450 knots an hour). This is nearly half the rate
at which the earth’s surface near the equator is carried round by the
earth’s rotation, or is about the rate at which parts in latitude 62 or
63 degrees north are carried round by rotation; so that the motion of
the great wave in 1868 was fairly comparable with one of the movements
which we are accustomed to regard as cosmical. I shall presently have
something more to say on this point.
Now in May, 1876, as we have seen, the wave reached Hawaii at about a
quarter to five in the morning, corresponding to about ten, Peruvian
time. Since, then, the earthquake was felt in Peru at half-past eight
on the previous evening, it follows that the wave, if it travelled
directly from Peru, must have taken about 13½ hours—or an hour and a
half longer, in travelling from Peru to the Sandwich Isles, than it
took in August, 1868. This is unlikely, because ocean-waves travel
nearly at the same rate in the same parts of the ocean, whatever
their dimensions, so only that they are large. We have, then, in the
difference of time occupied by the wave in May, 1876, and in August,
1868, in reaching Hawaii, some confirmation of the result to which we
were led by the arrival of the wave simultaneously at all the islands
of the Sandwich group—the inference, namely, that the observed wave
had reached these islands after reflection from the Californian
shore-line. As the hour when the direct wave probably reached Hawaii
was about a quarter past three in the morning, when not only was it
night-time but also a time when few would be awake to notice the rise
and fall of the sea, it seems not at all improbable that the direct
wave escaped notice, and that the wave actually observed was the
reflected wave from California. The direction, also, in which the
oscillation was first observed corresponds well with this explanation.
It is clear that the wave which traversed the Pacific in May, 1876,
was somewhat inferior in size to that of August, 1868, which therefore
still deserves to be called (as I then called it) the greatest sea-wave
ever known. The earthquake, indeed, which preceded the oceanic
disturbance of 1868 was far more destructive than that of May, 1876,
and the waves which came in upon the Peruvian and Bolivian shores were
larger. Nevertheless, the wave of May, 1876, was not so far inferior to
that of August, 1868, but that its course could be traced athwart the
entire extent of the Pacific Ocean.
When we consider the characteristic features of the Peruvian and
Chilian earthquakes, and especially when we note how wide is the extent
of the region over which their action is felt in one way or another,
it can scarcely be doubted that the earth’s Vulcanian energies are at
present more actively at work throughout that region than in any other.
There is nothing so remarkable, one may even say so stupendous, in
the history of subterranean disturbance as the alternation of mighty
earth-throes by which, at one time, the whole of the Chilian Andes seem
disturbed and anon the whole of the Peruvian Andes. In Chili scarcely
a year ever passes without earthquakes, and the same may be said of
Peru; but so far as great earthquakes are concerned the activity of the
Peruvian region seems to synchronize with the comparative quiescence
of the Chilian region, and _vice versâ_. Thus, in 1797, the terrible
earthquake occurred which is known as the earthquake of Riobamba, which
affected the entire Peruvian earthquake region. Thirty years later
a series of tremendous throes shook the whole of Chili, permanently
elevating its long line of coast to the height of several feet. During
the last twelve years the Peruvian region has in turn been disturbed by
great earthquakes. It should be added that between Chili and Peru there
is a region about five hundred miles in length in which scarcely any
volcanic action has been observed. And singularly enough, “this very
portion of the Andes, to which one would imagine that the Peruvians and
Chilians would fly as to a region of safety, is the part most thinly
inhabited; insomuch that, as Von Buch observes, it is in some places
entirely deserted.”
One can readily understand that this enormous double region of
earthquakes, whose oscillations on either side of the central region
of comparative rest may be compared to the swaying of a mighty see-saw
on either side of its point of support, should be capable of giving
birth to throes propelling sea-waves across the Pacific Ocean. The
throe actually experienced at any given place is relatively but an
insignificant phenomenon: it is the disturbance of the entire region
over which the throe is felt which must be considered in attempting
to estimate the energy of the disturbing cause. The region shaken by
the earthquake of 1868, for instance, was equal to at least a fourth
of Europe, and probably to fully one-half. From Quito southwards as
far as Iquique—or along a full third part of the length of the South
American Andes—the shock produced destructive effects. It was also
distinctly felt far to the north of Quito, far to the south of Iquique,
and inland to enormous distances. The disturbing forces which thus
shook 1,000,000 square miles of the earth’s surface must have been of
almost inconceivable energy. If directed entirely to the upheaval of a
land region no larger than England, those forces would have sufficed
to have destroyed utterly every city, town, and village within such a
region; if directed entirely to the upheaval of an oceanic region, they
would have been capable of raising a wave which would have been felt
on every shore-line of the whole earth. Divided even between the ocean
on the one side and a land region larger than Russia in Europe on the
other, those Vulcanian forces shook the whole of the land region, and
sent athwart the largest of our earth’s oceans a wave which ran in upon
shores 10,000 miles from the centre of disturbance with a crest thirty
feet high. Forces such as these may fairly be regarded as cosmical;
they show unmistakably that the earth has by no means settled down into
that condition of repose in which some geologists still believe. We
may ask with the late Sir Charles Lyell whether, after contemplating
the tremendous energy thus displayed by the earth, any geologist will
continue to assert that the changes of relative level of land and sea,
so common in former ages of the world, have now ceased? and agree
with him that if, in the face of such evidence, a geologist persists
in maintaining this favourite dogma, it would be vain to hope, by
accumulating proofs of similar convulsions during a series of ages, to
shake the tenacity of his conviction—
“Si fractus illabatur orbis,
Impavidum ferient ruinæ.”
But there is one aspect in which such mighty sea-waves as, in 1868 and
again in May, 1876, have swept over the surface of our terrestrial
oceans, remains yet to be considered.
The oceans and continents of our earth must be clearly discernible from
her nearer neighbours among the planets—from Venus and Mercury on the
inner side of her path around the sun, and from Mars (though under
less favourable conditions) from the outer side. When we consider,
indeed, that the lands and seas of Mars can be clearly discerned with
telescopic aid from our earth at a distance of forty millions of miles,
we perceive that our earth, seen from Venus at little more than half
this distance, must present a very interesting appearance. Enlarged,
owing to greater proximity, nearly fourfold, having a diameter nearly
twice as great as that of Mars, so that at the same distance her disc
would seem more than three times as large, more brightly illuminated
by the sun in the proportion of about five to two, she would shine
with a lustre exceeding that of Mars, when in full brightness in the
midnight sky, about thirty times; and all her features would of course
be seen with correspondingly increased distinctness. Moreover, the
oceans of our earth are so much larger in relative extent than those
of Mars, covering nearly three-fourths instead of barely one-half of
the surface of the world they belong to, that they would appeal as far
more marked and characteristic features than the seas and lakes of
Mars. When the Pacific Ocean, indeed, occupies centrally the disc of
the earth which at the moment is turned towards any planet, nearly the
whole of that disc must appear to be covered by the ocean. Under such
circumstances the passage of a wide-spreading series of waves over the
Pacific, at the rate of about 500 miles an hour, is a phenomenon which
could scarcely fail to be discernible from Venus or Mercury, if either
planet chanced to be favourably placed for the observation of the
earth—always supposing there were observers in Mercury or Venus, and
that these observers were provided with powerful telescopes.
It must be remembered that the waves which spread over the Pacific
on August 13–14, 1868, and again on May 9–10, 1876, were not only of
enormous range in length (measured along crest or trough), but also
of enormous breadth (measured from crest to crest, or from trough
to trough). Were it otherwise, indeed, the progress of a wave forty
or fifty feet high (at starting, and thirty-five feet high after
travelling 6000 miles), at the rate of 500 miles per hour, must
have proved destructive to ships in the open ocean as well as along
the shore-line. Suppose, for instance, the breadth of the wave from
crest to crest one mile, then, in passing under a ship at the rate
of 500 miles per hour, the wave would raise the ship from trough to
crest—that is, through a height of forty feet—in one-thousandth
part of an hour (for the distance from trough to crest is but half
the breadth of the wave), or in less than four seconds, lowering it
again in the same short interval of time, lifting and lowering it
at the same rate several successive times. The velocity with which
the ship would travel upwards and downwards would be greatest when
she was midway in her ascent and descent, and would then be equal to
about the velocity with which a body strikes the ground after falling
from a height of four yards. It is hardly necessary to say that small
vessels subjected to such tossing as this would inevitably be swamped.
On even the largest ships the effect of such motion would be most
unpleasantly obvious. Now, as a matter of fact, the passage of the
great sea-wave in 1868 was not noticed at all on board ships in open
sea. Even within sight of the shore of Peru, where the oscillation of
the sea was most marked, the motion was such that its effects were
referred to the shore. We are told that observers on the deck of a
United States’ war steamer distinctly saw the “peaks of the mountains
in the chain of the Cordilleras wave to and fro like reeds in a storm;”
the fact really being that the deck on which they stood was swayed to
and fro. This, too, was in a part of the sea where the great wave had
not attained its open sea form, but was a rolling wave, because of the
shallowness of the water. In the open sea, we read that the passage
of the great sea-wave was no more noticed than is the passage of the
tidal-wave itself. “Among the hundreds of ships which were sailing upon
the Pacific when its length and breadth were traversed by the great
sea-wave, there was not one in which any unusual motion was perceived.”
The inference is clear, that the slope of the advancing and following
faces of the great wave was very much less than in the case above
imagined; in other words, that the breadth of the wave greatly exceeded
one mile—amounting, in fact, to many miles.
Where the interval between the passage of successive wave-crests was
noted, we can tell the actual breadth of the wave. Thus, at the Samoan
Isles, in 1868, the crests succeeded each other at intervals of sixteen
minutes, corresponding to eight minutes between crest and trough.
But we have seen, that if the waves were one mile in breadth, the
corresponding interval would be only four seconds, or only one 120th
part of eight minutes: it follows, then, that the breadth of the great
wave, where it reached the Samoan Isles in 1868, was about 120 miles.
Now a wave extending right athwart the Pacific Ocean, and having a
cross breadth of more than 120 miles, would be discernible as a marked
feature of the disc of our earth, seen under the conditions described
above, either from Mercury or Venus. It is true that the slope of
the wave’s advancing and following surfaces would be but slight, yet
the difference of the illumination under the sun’s rays would be
recognizable. Then, also, it is to be remembered that there was not
merely a single wave, but a succession of many waves. These travelled
also with enormous velocity; and though at the distance of even the
nearest planet, the apparent motion of the great wave, swift though
it was in reality, would be so far reduced that it would have to be
estimated rather than actually seen, yet there would be no difficulty
in thus perceiving it with the mind’s eye. The rate of motion indeed
would almost be exactly the same as that of the equatorial part of the
surface of Mars, in consequence of the planet’s rotation; and this
(as is well known to telescopists), though not discernible directly,
produces, even in a few minutes, changes which a good eye can clearly
recognize. We can scarcely doubt then that if our earth were so
situated at any time when one of the great waves generated by Peruvian
earthquakes in traversing the Pacific, that the hemisphere containing
this ocean were turned fully illuminated towards Venus (favourably
placed for observing her), the disturbance of the Pacific could be
observed and measured by telescopists on that planet.
Unfortunately there is little chance that terrestrial observers will
ever be able to watch the progress of great waves athwart the oceans of
Mars, and still less that any disturbance of the frame of Venus should
become discernible to us by its effects. We can scarce even be assured
that there are lands and seas on Venus, so far as direct observation is
concerned, so unfavourably is she always placed for observation; and
though we see Mars under much more favourable conditions, his seas are
too small and would seem to be too shallow (compared with our own) for
great waves to traverse them such as could be discerned from the earth.
Yet it is well to remember the possibility that changes may at times
take place in the nearer planets—the terrestrial planets, as they
are commonly called, Mars, Venus, and Mercury—such as telescopic
observation under favourable conditions might detect. Telescopists
have, indeed, described apparent changes, lasting only for a short
time, in the appearance of one of these planets, Mars, which may fairly
be attributed to disturbances affecting its surface in no greater
degree than the great Peruvian earthquakes have affected for a time the
surface of our earth. For instance, the American astronomer Mitchel
says that on the night of July 12, 1845, bright polar snows of Mars
exhibited an appearance never noticed at any preceding or succeeding
observation. In the very centre of the white surface appeared a
dark spot, which retained its position during several hours: on the
following evening not a trace of the spot could be seen. Again the same
observer says that on the evening of August 30, 1845, he observed for
the first time a small bright spot, nearly or quite round, projecting
out of the lower side of the polar spot. “In the early part of the
evening,” he says, “the small bright spot seemed to be partly buried
in the large one. After the lapse of an hour or more my attention was
again directed to the planet, when I was astonished to find a manifest
change in the position of the small bright spot. It had apparently
separated from the large spot, and the edges alone of the two were now
in contact, whereas when first seen they overlapped by an amount quite
equal to one-third of the diameter of the small one. This, however,
was merely an optical phenomenon, for on the next evening the spots
went through the same apparent changes as the planet went through the
corresponding part of its rotation. But it showed the spots to be real
ice masses. The strange part of the story is that in the course of a
few days the smaller spot, which must have been a mass of snow and ice
as large as Novaia Zemlia, gradually disappeared. Probably some great
shock had separated an enormous field of ice from the polar snows, and
it had eventually been broken up and its fragments carried away from
the Arctic regions by currents in the Martian oceans. It appears to
me that the study of our own earth, and of the changes and occasional
convulsions which affect its surface, gives to the observation of such
phenomena as I have just described a new interest. Or rather, perhaps,
it is not too much to say that the telescopic observations of the
planets derive their only real interest from such considerations.
I may note in conclusion, that while on the one hand we cannot doubt
that the earth is slowly parting with its internal heat, and thus
losing century by century a portion of its Vulcanian energy, such
phenomena as the Peruvian earthquakes show that the loss of energy is
taking place so slowly that the diminution during many ages is almost
imperceptible. As I have elsewhere remarked, “When we see that while
mountain ranges were being upheaved or valleys depressed to their
present position, race after race and type after type lived out on the
earth the long lives which belong to races and to types, we recognize
the great work which the earth’s subterranean forces are still engaged
upon. Even now continents are being slowly depressed or upheaved, even
now mountain ranges are being raised to a different level, table-lands
are being formed, great valleys are being gradually scooped out; old
shore-lines shift their place, old soundings vary; the sea advances in
one place and retires in another; on every side nature’s plastic hand
is still at work, modelling and remodelling the earth, and making it
constantly a fit abode for those who dwell upon it.”
_STRANGE SEA CREATURES._
“We ought to make up our minds to dismiss as idle prejudices,
or, at least, suspend as premature, any preconceived notion of
what _might_, or what _ought to_, _be_ the order of nature, and
content ourselves with observing, as a plain matter of fact, what
_is_.”—Sir J. HERSCHEL, “Prelim. Disc.” page 79.
The fancies of men have peopled three of the four so-called elements,
earth, air, water, and fire, with strange forms of life, and have even
found in the salamander an inhabitant for the fourth. On land the
centaur and the unicorn, in the air the dragon and the roc, in the
water tritons and mermaids, may be named as instances among many of the
fabulous creatures which have been not only imagined but believed in
by men of old times. Although it may be doubted whether men have ever
invented any absolutely imaginary forms of life, yet the possibility
of combining known forms into imaginary, and even impossible, forms,
must be admitted as an important element in any inquiry into the origin
of ideas respecting such creatures as I have named. One need only look
through an illuminated manuscript of the Middle Ages to recognize the
readiness with which imaginary creatures can be formed by combining,
or by exaggerating, the characteristics of known animals. Probably
the combined knowledge and genius of all the greatest zoologists of
our time would not suffice for the invention of an entirely new form
of animal which yet should be zoologically possible; but to combine
the qualities of several existent animals in a single one, or to
conceive an animal with some peculiarity abnormally developed, is
within the capacity of persons very little acquainted with zoology,
nay, is perhaps far easier to such persons than it would be to an
Owen, a Huxley, or a Darwin. In nearly every case, however, the purely
imaginary being is to be recognized by the utter impossibility of
its actual existence. If it be a winged man, arms and wings are both
provided, but the pectoral muscles are left unchanged. A winged horse,
in like manner, is provided with wings, without any means of working
them. A centaur, as in the noble sculptures of Phidias, has the upper
part of the trunk of a man superadded, not to the hind quarters of a
horse or other quadruped, but to the entire trunk of such an animal,
so that the abdomen of the human figure lies _between_ the upper half
of the human trunk and the corresponding part of the horse’s trunk,
an arrangement anatomically preposterous. Without saying that every
fabulous animal which was anatomically and zoologically possible, had a
real antitype, exaggerated though the fabulous form may have been, we
must yet admit that errors so gross marked the conception of all the
really imaginary animals of antiquity, that any fabulous animal found
to accord fairly well with zoological possibilities may be regarded,
with extreme probability, as simply the exaggerated presentation of
some really existent animal. The inventors of centaurs, winged and
man-faced bulls, many-headed dogs, harpies, and so forth, were utterly
unable to invent a possible new animal, save by the merest chance, the
probability of which was so small that it may fairly be disregarded.
This view of the so-called fabulous animals of antiquity has been
confirmed by the results of modern zoological research. The merman,
zoologically possible (not in all details, of course, but generally),
has found its antitype in the dugong and the manatee; the roc in the
condor, or perhaps in those extinct species whose bones attest their
monstrous proportions; the unicorn in the rhinoceros; even the dragon
in the pterodactyl of the green-sand; while the centaur, the minotaur,
the winged horse, and so forth, have become recognized as purely
imaginary creatures, which had their origin simply in the fanciful
combination of known forms, no existent creatures having even suggested
these monstrosities.
It is not to be wondered at that the sea should have been more prolific
in monstrosities and in forms whose real nature has been misunderstood.
Land animals cannot long escape close observation. Even the most
powerful and ferocious beasts must succumb in the long run to man, and
in former ages, when the struggle was still undecided between some race
of animals and savage man, individual specimens of the race must often
have been killed, and the true appearance of the animal determined.
Powerful winged animals might for a longer time remain comparatively
mysterious creatures even to those whom they attacked, or whose flocks
they ravaged. A mighty bird, or a pterodactylian creature (a late
survivor of a race then fast dying out), might swoop down on his prey
and disappear with it too swiftly to be made the subject of close
scrutiny, still less of exact scientific observation. Yet the general
characteristics even of such creatures would before long be known.
From time to time the strange winged monster would be seen hovering
over the places where his prey was to be found. Occasionally it would
be possible to pierce one of the race with an arrow or a javelin; and
thus, even in those remote periods when the savage progenitors of the
present races of man had to carry on a difficult contest with animals
now extinct or greatly reduced in power, it would become possible to
determine accurately the nature of the winged enemy. But with sea
creatures, monstrous, or otherwise, the case would be very different.
To this day we remain ignorant of much that is hidden beneath the
waves of the “hollow-sounding and mysterious main.” Of far the greater
number of sea creatures, it may truly be said that we never see any
specimens except by accident, and never obtain the body of any except
by very rare accident. Those creatures of the deep sea which we are
best acquainted with, are either those which are at once very numerous
and very useful as food or in some other way, or else those which are
very rapacious and thus expose themselves, by their attacks on men,
to counter-attack and capture or destruction. In remote times, when
men were less able to traverse the wide seas, when, on the one hand,
attacks from great sea creatures were more apt to be successful,
while, on the other, counter-attack was much more dangerous, still
less would be known about the monsters of the deep. Seen only for a
few moments as he seized his prey, and then sinking back into the
depths, a sea monster would probably remain a mystery even to those
who had witnessed his attack, while their imperfect account of what
they had seen would be modified at each repetition of the story, until
there would remain little by which the creature could be identified,
even if at some subsequent period its true nature were recognized. We
can readily understand, then, that among the fabulous creatures of
antiquity, even of those which represented actually existent races
incorrectly described, the most remarkable, and those zoologically
the least intelligible, would be the monsters of the deep sea. We can
also understand that even the accounts which originally corresponded
best with the truth would have undergone modifications much more
noteworthy than those affecting descriptions of land animals or winged
creatures—simply because there would be small chance of any errors
thus introduced being corrected by the study of freshly discovered
specimens.
We may, perhaps, explain in this way the strange account given by
Berosus of the creature which came up from the Red Sea, having the body
of a fish but the front and head of a man. We may well believe that
this animal was no other than a dugong, or halicore (a word signifying
sea-maiden), a creature inhabiting the Indian Ocean to this day, and
which might readily find its way into the Red Sea. But the account of
the creature has been strangely altered from the original narrative,
if at least the original narrative was correct. For, according to
Berosus, the animal had two human feet which projected from each side
of the tail; and, still stranger, it had a human voice and human
language. “This strange monster sojourned among the rude people during
the day, taking no food, but retiring to the sea again at night, and
continued for some time teaching them the arts of civilized life.” A
picture of this stranger is said to have been preserved at Babylon
for many centuries. With a probable substratum of truth, the story in
its latest form is as fabulous as Autolycus’s “ballad of a fish that
appeared upon the coast, on Wednesday the fourscore of April, forty
thousand fathoms above water, and sang a ballad against the hard hearts
of maids.”
It is singular, by the way, how commonly the power of speech, or at
least of producing sounds resembling speech or musical notes, was
attributed to the creature which imagination converted into a man-fish
or woman-fish. Dugongs and manatees make a kind of lowing noise, which
could scarcely be mistaken under ordinary conditions for the sound of
the human voice. Yet, not only is this peculiarity ascribed to the
mermaid and siren (the merman and triton having even the supposed power
of blowing on conch-shells), but in more recent accounts of encounters
with creatures presumably of the seal tribe and allied races, the same
feature is to be noticed. The following account, quoted by Mr. Gosse
from a narrative by Captain Weddell, the well-known geographer, is
interesting for this reason amongst others. It also illustrates well
the mixture of erroneous details (the offspring, doubtless, of an
excited imagination) with the correct description of a sea creature
actually seen:—“A boat’s crew were employed on Hall’s Island, when
one of the crew, left to take care of some produce, saw an animal
whose voice was musical. The sailor had lain down, and at ten o’clock
he heard a noise resembling human cries, and as daylight in these
latitudes never disappears at this season” (the Antarctic summer),
“he rose and looked around, but, on seeing no person, returned to
bed. Presently he heard the noise again; he rose a second time, but
still saw nothing. Conceiving, however, the possibility of a boat
being upset, and that some of the crew might be clinging to detached
rocks, he walked along the beach a few steps and heard the noise more
distinctly but in a musical strain. Upon searching around, he saw an
object lying on a rock a dozen yards from the shore, at which he was
somewhat frightened. The face and shoulders appeared of human form and
of a reddish colour; over the shoulders hung long green hair; the tail
resembled that of the seal, but the extremities of the arms he could
not see distinctly. The creature continued to make a musical noise
while he gazed about two minutes, and on perceiving him it disappeared
in an instant. Immediately, when the man saw his officer, he told this
wild tale, and to add weight to his testimony (being a Romanist) he
made a cross on the sand, which he kissed, as making oath to the truth
of his statement. When I saw him he told the story in so clear and
positive a manner, making oath to its truth, that I concluded he must
really have seen the animal he described, or that it must have been the
effects of a disturbed imagination.”
In this story all is consistent with the belief that the sailor saw
an animal belonging to the seal family (of a species unknown to him),
except the green hair. But the hour was not very favourable to the
discerning of colour, though daylight had not quite passed away, and as
Gosse points out, since golden-yellow fur and black fur are found among
Antarctic seals, the colours may be intermingled in some individuals,
producing an olive-green tint, which, by contrast with the reddish
skin, might be mistaken for a full green. Considering that the man had
been roused from sleep and was somewhat frightened, he would not be
likely to make very exact observations. It will be noticed that it was
only at first that he mistook the sounds made by the creature for human
cries; afterwards he heard only the same _noise_, but in a musical
strain. Now with regard to the musical sounds said to have been uttered
by this creature, and commonly attributed to creatures belonging to
families closely allied to the seals, I do not know that any attempt
has yet been made to show that these families possess the power of
emitting sounds which can properly be described as musical. It is quite
possible that the Romanist sailor’s ears were not very nice, and that
any sound softer than a bellow seemed musical to him. Still, the idea
suggests itself that possibly seals, like some other animals, possess a
note not commonly used, but only as a signal to their mates, and never
uttered when men or other animals are known to be near. It appears
to me that this is rendered probable by the circumstance that seals
are fond of music. Darwin refers to this in his treatise on Sexual
Selection (published with his “Descent of Man”), and quotes a statement
to the effect that the fondness of seals for music “was well known to
the ancients, and is often taken advantage of by hunters to the present
day.” The significance of this will be understood from Darwin’s remark
immediately following, that “with all these animals, the males of which
during the season of courtship incessantly produce musical notes or
mere rhythmical sounds, we must believe that the females are able to
appreciate them.”
The remark about the creature’s arms seems strongly to favour the
belief that the sailor intended his narrative to be strictly truthful.
Had he wished to excite the interest of his comrades by a marvellous
story, he certainly would have described the creature as having
well-developed human hands.
Less trustworthy by far seem some of the stories which have been told
of animals resembling the mermaid of antiquity. It must always be
remembered, however, that in all probability we know very few among the
species of seals and allied races, and that some of these species may
present, in certain respects and perhaps at a certain age, much closer
resemblance to the human form than the sea-lion, seal, manatee, or
dugong.
We cannot, for instance, attach much weight to the following story
related by Hudson, the famous navigator:—“One of our company, looking
overboard, saw a mermaid and calling up some of the company to see her,
one more came up, and by that time she was come close to the ship’s
side, looking earnestly on the men. A little after a sea came and
overturned her. From the navel upward her back and breasts were like a
woman’s, as they say that saw her; her body as big as one of us; her
skin very white; and long hair hanging down behind, of colour black. In
her going down they saw her tail, which was like the tail of a porpoise
and speckled like a mackerel.” If Hudson himself had seen and thus
described the creature it would have been possible to regard the story
with some degree of credence; but his account of what Thomas Hilles and
Robert Rayner, men about whose character for veracity we know nothing,
_said_ they saw, is of little weight. The skin very white, and long
hair hanging down behind, are especially suspicious features of the
narrative; and were probably introduced to dispose of the idea, which
others of the crew may have advanced, that the creature was only some
kind of seal after all. The female seal (_Phoca Greenlandica_ is the
pretty name of the animal) is not, however, like the male, tawny grey,
but dusky white, or yellowish straw-colour, with a tawny tint on the
back. The young alone could be called “very white.” They are so white
in fact as scarcely to be distinguishable when lying on ice and snow,
a circumstance which, as Darwin considers, serves as a protection for
these little fellows.
The following story, quoted by Gosse from Dr. Robert Hamilton’s able
“History of the Whales and Seals,” compares favourably in some respects
with the last narrative:—“It was reported that a fishing-boat off the
island of Yell, one of the Shetland group, had captured a mermaid by
its getting entangled in the lines! The statement is, that the animal
is about three feet long, the upper part of the body resembling the
human, with protuberant mammæ like a woman; the face, the forehead,
and neck, were short, and resembling those of a monkey; the arms,
which were small, were kept folded across the breast; the fingers were
distinct, not webbed; a few stiff long bristles were on the top of
the head, extending down to the shoulders, and these it could erect
and depress at pleasure, something like a crest. The inferior part of
the body was like a fish. The skin was smooth and of a grey colour.
It offered no resistance, nor attempted to bite, but uttered a low,
plaintive sound. The crew, six in number, took it within their boat;
but superstition getting the better of curiosity, they carefully
disentangled it from the lines and a hook which had accidentally
fastened in the body, and returned it to its native element. It
instantly dived, descending in a perpendicular direction.” “They had
the animal for three hours within the boat; the body was without scales
or hair; of a silvery grey colour above, and white below, like the
human skin; no gills were observed, nor fins on the back or belly. The
tail was like that of the dog-fish; the mammæ were about as large as
those of a woman; the mouth and lips were very distinct, and resembled
the human.”
This account, if accepted in all its details, would certainly indicate
that an animal of some species before unknown had been captured. But it
is doubtful how much reliance can be placed on the description of the
animal. Mr. Gosse, commenting upon the case, says that the fishermen
cannot have been affected by fear in such sort that their imagination
exaggerated the resemblance of the creature to the human form. “For the
mermaid,” he says, “is not an object of terror to the fishermen; it
is rather a welcome guest, and danger is to be apprehended only from
its experiencing bad treatment.” But then this creature had not been
treated as a specially welcome guest. The crew had captured it; and
probably not without some degree of violence; for though it offered
no resistance it uttered a plaintive cry. And that hook which “had
accidentally fastened in the body” has a very suspicious look. If the
animal could have given its own account of the capture, probably the
hook would not have been found to have fastened in the body altogether
by accident. Be this as it may, the fishermen were so far frightened
that superstition got the better of curiosity; so that, as they were
evidently very foolish fellows, their evidence is scarcely worth much.
There are, however, only two points in their narrative which do not
seem easily reconciled with the belief that they had captured a rather
young female of a species closely allied to the common seal—the
distinct unwebbed fingers and the small arms folded across the breast.
Other points in their description suggest marked differences in
degree from the usual characteristics of the female seal; but these
two alone seem to differ absolutely in kind. Considering all the
circumstances of the narrative, we may perhaps agree with Mr. Gosse to
this extent, that, combined with other statements, the story induces a
strong suspicion that the northern seas may hold forms of life as yet
uncatalogued by science.
The stories which have been related about monstrous cuttle-fish
have only been fabulous in regard to the dimensions which they have
attributed to these creatures. Even in this respect it has been shown,
quite recently, that some of the accounts formerly regarded as fabulous
fell even short of the truth. Pliny relates, for instance, that the
body of a monstrous cuttle-fish, of a kind known on the Spanish coast,
weighed, when captured, 700 lbs., the head the same, the arms being 30
feet in length. The entire weight would probably have amounted to about
2000 lbs. But we shall presently see that this weight has been largely
exceeded by modern specimens. It was, however, in the Middle Ages that
the really fabulous cuttle-fish flourished—the gigantic kraken, “liker
an island than an animal,” according to credulous Bishop Pontoppidan,
and able to destroy in its mighty arms the largest galleons and war
ships of the fourteenth and fifteenth centuries.
It is natural that animals really monstrous should be magnified by the
fears of those who have seen or encountered them, and still further
magnified afterwards by tradition. Some specimens of cuttle-fish which
have been captured wholly, or in part, indicate that this creature
sometimes attains such dimensions that but little magnifying would
be needed to suggest even the tremendous proportions of the fabulous
kraken. In 1861, the French war-steamer _Alecton_ encountered a
monstrous cuttle, on the surface of the sea, about 120 miles north-east
of Teneriffe. The crew succeeded in slipping a noose round the body,
but unfortunately the rope slipped, and, being arrested by the tail
fin, pulled off the tail. This was hauled on board, and found to weigh
over 40 lbs. From a drawing of the animal, the total length without
the arms was estimated at 50 feet, and the weight at 4000 lbs., nearly
twice the weight of Pliny’s monstrous cuttle-fish, long regarded as
fabulous. In one respect this creature seems to have been imperfect,
the two long arms usually possessed by cuttle-fish of the kind being
wanting. Probably it had lost these long tentacles in a recent
encounter with some sea enemy, perhaps one of its own species. Quite
possibly it may have been such recent mutilation which exposed this
cuttle-fish to successful attack by the crew of the _Alecton_.
A cuttle-fish of about the same dimensions was encountered by two
fishermen in 1873, in Conception Bay, Newfoundland. When they attacked
it, the creature threw its long arms across the boat, but the fishermen
with an axe cut off these tentacles, on which the cephalopod withdrew
in some haste. One of the arms was preserved, after it had lost about
6 feet of its length. Even thus reduced it measured 19 feet; and as
the fishermen estimate that the arm was struck off about 10 feet from
the body, it follows that the entire length of the limb must have
been about 35 feet. They estimated the body at 60 feet in length and
5 feet in diameter—a monstrous creature! It was fortunate for these
fishermen that they had an axe handy for its obtrusive tentacles, as
with so great a mass and the great propulsive power possessed by all
cephalopods, it might readily have upset their small boat. Once in the
water, they would have been at the creature’s mercy—a quality which,
by all accounts, the cuttle-fish does not possess to any remarkable
extent.
Turn we, however, from the half fabulous woman-fish, and the
exaggeratedly monstrous cuttle-fish, to the famous sea-serpent, held
by many to be the most utterly fabulous of all fabled creatures, while
a few, including some naturalists of distinction, stoutly maintain
that the creature has a real existence, though whether it be rightly
called a sea-serpent or not is a point about which even believers are
extremely doubtful.
It may be well, in the first place, to remark that in weighing the
evidence for and against the existence of this creature, and bearing
on the question of its nature (if its existence be admitted), we ought
not to be influenced by the manifest falsity of a number of stories
relating to supposed encounters with this animal. It is probable
that, but for these absurd stories, the well-authenticated narratives
relating to the creature, whatever it may be, which has been called
the sea-serpent, would have received much more attention than has
heretofore been given to them. It is also possible that some narratives
would have been published which have been kept back from the fear
lest a truthful (though possibly mistaken) account should be classed
with the undoubted untruths which have been told respecting the great
sea-serpent. It cannot be denied that in the main the inventions and
hoaxes about the sea-serpent have come chiefly from American sources.
It is unfortunately supposed by too many of the less cultured sons of
America that (to use Mr. Gosse’s expression) “there is somewhat of wit
in gross exaggerations or hoaxing inventions.” Of course an American
gentleman—using the word “in that sense in which every man may be
a gentleman,” as Twemlow hath it—would as soon think of uttering a
base coin as a deliberate untruth or foolish hoax. But it is thought
clever, by not a few in America who know no better, to take any one in
by an invention. Some, perhaps but a small number, of the newspapers
set a specially bad example in this respect, giving room in their
columns for pretended discoveries in various departments of science,
elaborate accounts of newly discovered animals, living or extinct, and
other untruths which would be regarded as very disgraceful indeed by
English editors. Such was the famous “lunar hoax,” published in the
New York _Sun_ some forty years ago; such the narrative, in 1873, of a
monstrous fissure which had been discerned in the body of the moon, and
threatened to increase until the moon should be cloven into two unequal
parts; such the fables which have from time to time appeared respecting
the sea-serpent. But it would be as unreasonable to reject, because
of these last-named fables, the narratives which have been related by
quiet, truth-loving folk, and have borne close and careful scrutiny, as
it would be to reject the evidence given by the spectroscope respecting
the existence of iron and other metals in the sun because an absurd
story had told how creatures in the moon had been observed to make use
of metal utensils or to adorn the roofs of their temples with metallic
imitations of wreathed flames.
The oldest accounts on record of the appearance of a great sea creature
resembling a serpent are those quoted by Bishop Pontoppidan, in his
description of the natural history of his native country, Norway.
Amongst these was one confirmed by oath taken before a magistrate
by two of the crew of a ship commanded by Captain de Ferry, of the
Norwegian navy. The captain and eight men saw the animal, near Molde,
in August, 1747. They described it as of the general form of a serpent,
stretched on the surface in receding coils (meaning, probably, the
shape assumed by the neck of a swan when the head is drawn back). The
head, which resembled that of a horse, was raised two feet above the
water.
In August, 1817, a large marine animal, supposed to be a serpent, was
seen near Cape Ann, Massachusetts. Eleven witnesses of good reputation
gave evidence on oath before magistrates. One of these magistrates had
himself seen the creature, and corroborated the most important points
of the evidence given by the eleven witnesses. The creature had the
appearance of a serpent, dark brown in colour (some said mottled),
with white under the head and neck. Its length was estimated at from
50 to 100 feet. The head was in shape like a serpent’s, but as large
as a horse’s. No mane was noticed. Five of the witnesses deposed
to protuberances on the back; four said the back was straight; the
other two gave no opinion on this point. The magistrate who had seen
the animal considered the appearance of protuberances was due to the
bendings of the body while in rapid motion.
In 1848, when the captain of the British frigate _Dædalus_ had
published an account of a similar animal seen by him and several of his
officers and crew, the Hon. Colonel T. H. Perkins, of Boston, who had
seen the animal on the occasion just mentioned in 1817, gave an account
(copied from a letter written in 1820) of what he had witnessed. It
is needless to quote those points which correspond with what has
been already stated. Colonel Perkins noticed “an appearance in the
front of the head like a single horn, about nine inches to a foot in
length, shaped like a marlinspike, which will presently be explained.
I left the place,” he proceeds, “fully satisfied that the reports in
circulation, though differing in details, were essentially correct.”
He relates how a person named Mansfield, “one of the most respectable
inhabitants of the town, who had been such an unbeliever in the
existence of this monster that he had not given himself the trouble to
go from his house to the harbour when the report was first made,” saw
the animal from a bank overlooking the harbour. Mr. Mansfield and his
wife agreed in estimating the creature’s length at 100 feet. Several
crews of coasting vessels saw the animal, _in some instances within a
few yards_. “Captain Tappan,” proceeds Colonel Perkins, “a person well
known to me, saw him with his head above water two or three feet, at
times moving with great rapidity, at others slowly. He also saw what
explained the appearance which I have described of a horn on the front
of the head. This was doubtless what was observed by Captain Tappan to
be the tongue, thrown in an upright position from the mouth, and having
the appearance which I have given to it. One of the revenue cutters,
whilst in the neighbourhood of Cape Ann, had an excellent view of him
at a few yards’ distance; he moved slowly, and upon the appearance of
the vessel sank and was seen no more.”
Fifteen years later, in May 1833, five British officers—Captain
Sullivan, Lieutenants Maclachlan and Malcolm of the Rifle Brigade,
Lieutenant Lyster of the Artillery, and Mr. Snee of the Ordnance—when
cruising in a small yacht off Margaret’s Bay, not far from Halifax,
“saw the head and neck of some denizen of the deep, precisely like
those of a common snake, in the act of swimming, the head so elevated
and thrown forward by the curve of the neck as to enable us to see
the water under and beyond it.” They judged its length to exceed
80 feet. “There could be no mistake nor delusion, and we were all
perfectly satisfied that we had been favoured with a view of the ‘true
and veritable sea-serpent,’ which had been generally considered to
have existed only in the brain of some Yankee skipper, and treated
as a tale not entitled to belief.” Dowling, a man-of-war’s man they
had along with them, made the following unscientific but noteworthy
comment: “Well, I’ve sailed in all parts of the world, and have seen
rum sights too in my time, but this is the queerest thing I ever
see.” “And surely,” adds Captain Sullivan, “Jack Dowling was right.”
The description of the animal agrees in all essential respects with
previous accounts, but the head was estimated at about six feet in
length—considerably larger, therefore, than a horse’s head.
But unquestionably the account of the sea-serpent which has commanded
most attention was that given by the captain, officers, and crew of
the British frigate _Dædalus_, Captain M’Quhæ, in 1848. The _Times_
published on October 9, 1848, a paragraph stating that the sea-serpent
had been seen by the captain and most of the officers and crew of this
ship, on her passage home from the East Indies. The Admiralty inquired
at once into the truth of the statement, and the following is abridged
from Captain M’Quhæ’s official reply, addressed to Admiral Sir W. H.
Gage.
“Sir,—In reply to your letter, requiring information as to the truth
of a statement published in the _Times_ newspaper, of a sea-serpent of
extraordinary dimensions having been seen from the _Dædalus_, I have
the honour to inform you that at 5 p.m., August 6 last, in latitude 24°
44´ S., longitude 9° 22´ E., the weather dark and cloudy, wind fresh
from N.W., with long ocean swell from S.W., the ship on the port tack,
heading N.E. by N., Mr. Sartoris, midshipman, reported to Lieutenant
E. Drummond (with whom, and Mr. W. Barrett, the master, I was walking
the quarter-deck) something very unusual rapidly approaching the ship
from before the beam. The object was seen to be an enormous serpent,
with head and shoulders kept about four feet constantly above the
surface of the sea, as nearly as we could judge; at least 60 feet of
the animal was on the surface, no part of which length was used, so
far as we could see, in propelling the animal either by vertical or
horizontal undulation. It passed quietly, _but so closely under our lee
quarter that, had it been a man of my acquaintance, I should easily
have recognized his features with the naked eye_. It did not, while
visible, deviate from its course to the S.W., which it held on at the
pace of from 12 to 15 miles per hour, as if on some determined purpose.
The diameter of the serpent was from 15 to 16 inches behind the head,
which was, without any doubt, that of a snake. Its colour was a dark
brown, with yellowish white about the throat. It did not once, while
within the range of view from our glasses, sink below the surface. It
had no fins, but something like the mane of a horse, or rather a bunch
of sea-weed, washed about its back. It was seen by the quarter-master,
the boatswain’s mate, and the man at the wheel, in addition to myself
and the officers above-mentioned. I am having a drawing of the serpent
made from a sketch taken immediately after it was seen, which I hope to
have ready for my Lords Commissioners of the Admiralty by to-morrow’s
post.—Peter M’Quhæ, Captain.”
The drawing here mentioned was published in the _Illustrated London
News_ for October 28, 1848, being there described as made “under the
supervision of Captain M’Quhæ, and his approval of the authenticity of
the details as to position and form.”
The correspondence and controversy elicited by the statement of Captain
M’Quhæ were exceedingly interesting. It is noteworthy, at the outset,
that few, perhaps none, who had read the original statement, suggested
the idea of illusion, while it need hardly perhaps be said that no one
expressed the slightest doubt as to the _bona fides_ of Captain M’Quhæ
and his fellow-witnesses. These points deserve attention, because,
in recent times, the subject of the sea-serpent has been frequently
mentioned in public journals and elsewhere as though no accounts of
the creature had ever been given which had been entitled to credence.
I proceed to summarise the correspondence which followed M’Quhæ’s
announcement. The full particulars will be found in Mr. Gosse’s
interesting work, the “Romance of Natural History,” where, however, as
it seems to me, the full force of the evidence is a little weakened,
for all save naturalists, by the introduction of particulars not
bearing directly on the questions at issue.
Among the earliest communications was one from Mr. J. D. M. Stirling,
a gentleman who, during a long residence in Norway, had heard repeated
accounts of the sea-serpent in Norwegian seas, and had himself seen a
fish or reptile at a distance of a quarter of a mile, which, examined
through a telescope, corresponded in appearance with the sea-serpent as
usually described. This communication was chiefly interesting, however,
as advancing the theory that the supposed sea-serpent is not a serpent
at all, but a long-necked plesiosaurian. This idea had been advanced
earlier, but without his knowledge, by Mr. E. Newman, the editor of
the _Zoologist_. Let us briefly inquire into the circumstances which
suggest the belief.
If we consider the usual account of the sea-serpent, we find one
constant feature, which seems entirely inconsistent with the belief
that the creature can be a serpent. The animal has always shown a
large portion of its length, from 20 to 60 feet, above the surface
of the water, and without any evident signs of undulation, either
vertically or horizontally. Now, apart from all zoological evidence,
our knowledge of physical laws will not permit us to believe that the
portion thus visible above the surface was propelled by the undulations
of a portion concealed below the surface, unless this latter portion
largely exceeded the former in bulk. A true fish does not swim for any
length of time with any but a very small portion of its body above
water; probably large eels never show even a head or fin above water
for more than a few seconds when not at rest. Cetaceans, owing to the
layers of blubber which float them up, remain often for a long time
with a portion of their bulk out of the water, and the larger sort
often swim long distances with the head and fore-part out of water.
But, even then, the greater part of the creature’s bulk is under water,
and the driving apparatus, the anterior fins and the mighty tail, are
constantly under water (when the animal is urging its way horizontally,
be it understood). A sea creature, in fact, whatever its nature, which
keeps any considerable volume of its body out of water constantly,
while travelling a long distance, must of necessity have a much greater
volume all the time under water, and must have its propelling apparatus
under water. Moreover, if the propulsion is not effected by fins,
paddles, a great flat tail, or these combined, but by the undulations
of the animal’s own body, then the part out of water must of necessity
be affected by these undulations, unless it is very small in volume
and length compared with the part under water. I assert both these
points as matters depending on physical laws, and without fear that the
best-informed zoologist can adduce any instances to the contrary. It
is in fact physically impossible that such instances should exist.
It would not be saying too much to assert that if the so-called
sea-serpent were really a serpent, its entire length must be nearer
1000 than 100 feet. This, of course, is utterly incredible. We are,
therefore, forced to the belief that the creature is not a serpent.
If it were a long-necked reptile, with a concealed body much bulkier
than the neck, the requirements of floatation would be satisfied; if
to that body there were attached powerful paddles, the requirements
of propulsion would be satisfied. The theory, then, suggested, first
by Mr. Newman, later but independently by Mr. Stirling, and advocated
since by several naturalists of repute, is simply that the so-called
sea-serpent is a modern representative of the long-necked plesiosaurian
reptile to which has been given the name of the _enaliosaurus_.
Creatures of this kind prevailed in that era when what is called the
lias was formed, a fossiliferous stratum belonging to the secondary or
mesozoic rocks. They are not found in the later or tertiary rocks, and
thereon an argument might be deduced against their possible existence
in the present, or post-tertiary, period; but, as will presently be
shown, this argument is far from being conclusive. The enaliosaurian
reptiles were “extraordinary,” says Lyell, “for their number, size, and
structure.” Like the ichthyosauri, or fish-lizards, the enaliosauri
(or serpent-turtles, as they might almost be called) were carnivorous,
their skeletons often enclosing the fossilized remains of half-digested
fishes. They had extremely long necks, with heads very small compared
with the body. They are supposed to have lived chiefly in narrow seas
and estuaries, and to have breathed air like the modern whales and
other aquatic mammals. Some of them were of formidable dimensions,
though none of the skeletons yet discovered indicate a length of more
than 35 feet. It is not, however, at all likely that the few skeletons
known indicate the full size attained by these creatures. Probably,
indeed, we have the remains of only a few out of many species, and
some species existing in the mesozoic period may have as largely
exceeded those whose skeletons have been found, as the boa-constrictor
exceeds the common ringed snake. It is also altogether probable that
in the struggle for existence during which the enaliosaurian reptiles
have become _almost_ extinct (according to the hypothesis we are
considering), none but the largest and strongest had any chance, in
which case the present representatives of the family would largely
exceed in bulk their progenitors of the mesozoic period.
A writer in the _Times_ of November 2, 1848, under the signature
F. G. S., pointed out how many of the external characters of the
creature seen from the _Dædalus_ corresponded with the belief that it
was a long-necked plesiosaurus. “Geologists,” he said, “are agreed in
the inference that the plesiosauri carried their necks, which must
have resembled the bodies of serpents, above the water, while their
propulsion was effected by large paddles working beneath, the short but
stout tail acting the part of a rudder.... In the letter and drawing
of Captain M’Quhæ ... we have ... the short head, the serpent-like
neck, carried several feet above the water. Even the bristly mane in
certain parts of the back, so unlike anything found in serpents, has
its analogue in the iguana, to which animal the plesiosaurus has been
compared by some geologists. But I would most of all insist upon the
peculiarity of the animal’s progression, which could only have been
effected with the evenness and at the rate described by an apparatus of
fins or paddles, not possessed by serpents, but existing in the highest
perfection in the plesiosaurus.”
At this stage a very eminent naturalist entered the field—Professor
Owen. He dwelt first on a certain characteristic of Captain M’Quhæ’s
letter which no student of science could fail to notice—the definite
statement that the creature _was_ so and so, where a scientific
observer would simply have said that the creature presented such and
such characteristics. “No sooner was the captain’s attention called to
the object,” says Professor Owen, “than ‘it was discovered to be an
enormous serpent,’” though in reality the true nature of the creature
could not be determined even from the observations made during the
whole time that it remained visible. Taking, however, “the more certain
characters,” the “head with a convex, moderately capacious cranium,
short, obtuse muzzle, gape not extending further than to beneath the
eye, which (the eye) is rather small, round, filling closely the
palpebral aperture” (that is, the eyelids fit closely[25]); “colour and
surface as stated; nostrils indicated in the drawing by a crescentic
mark at the end of the nose or muzzle. All these,” proceeds Owen,
“are the characters of the head of a warm-blooded mammal, none of
them those of a cold-blooded reptile or fish. Body long, dark brown,
not undulating, without dorsal or other apparent fins, ‘but something
like the mane of a horse, or rather a bunch of sea-weed, washed about
its back.’” He infers that the creature had hair, showing only where
longest on the back, and therefore that the animal was not a mammal
of the whale species but rather a great seal. He then shows that the
sea-elephant, or _Phoca proboscidea_, which attains the length of
from 20 to 30 feet, was the most probable member of the seal family
to be found about 300 miles from the western shore of the southern
end of Africa, in latitude 24° 44´. Such a creature, accidentally
carried from its natural domain by a floating iceberg, would have
(after its iceberg had melted) to urge its way steadily southwards,
as the supposed sea-serpent was doing; and probably the creature
approached the _Dædalus_ to scan her “capabilities as a resting-place,
as it paddled its long, stiff body past the ship.” “In so doing it
would raise a head of the form and colour described and delineated
by Captain M’Quhæ”—its head only, be it remarked, corresponding
with the captain’s description. The neck also would be of the right
diameter. The thick neck, passing into an inflexible trunk, the longer
and coarser hair on the upper part of which would give rise to the
idea “explained by the similes above cited” (of a mane or bunch of
sea-weed), the paddles would be out of sight; and the long eddy and
wake created by the propelling action of the tail would account for the
idea of a long serpentine body, at least for this idea occurring to one
“looking at the strange phenomenon with a sea-serpent in his mind’s
eye.” “It is very probable that not one on board the _Dædalus_ ever
before beheld a gigantic seal freely swimming in the open ocean.” The
excitement produced by the strange spectacle, and the recollection of
“old Pontoppidan’s sea-serpent with the mane,” would suffice, Professor
Owen considered, to account for the metamorphosis of a sea-elephant
into a maned sea-serpent.
This was not the whole of Professor Owen’s argument; but it may be well
to pause here, to consider the corrections immediately made by Captain
M’Quhæ; it may be noticed, first, that Professor Owen’s argument
seems sufficiently to dispose of the belief that the creature really
was a sea-serpent, or any cold-blooded reptile. And this view of the
matter has been confirmed by later observations. But few, I imagine,
can readily accept the belief that Captain M’Quhæ and his officers
had mistaken a sea-elephant for a creature such as they describe and
picture. To begin with, although it might be probable enough that
no one on board the _Dædalus_ had ever seen a gigantic seal freely
swimming in the open ocean—a sight which Professor Owen himself had
certainly never seen—yet we can hardly suppose they would not have
known a sea-elephant under such circumstances. Even if they had never
seen a sea-elephant at all, they would surely know what such an animal
is like. No one could mistake a sea-elephant for any other living
creature, even though his acquaintance with the animal were limited to
museum specimens or pictures in books. The supposition that the entire
animal, that is, its entire length, should be mistaken for 30 or 40
feet of the length of a serpentine neck, seems, in my judgment, as
startling as the ingenious theory thrown out by some naturalists when
they first heard of the giraffe—to the effect that some one of lively
imagination had mistaken the entire body of a short-horned antelope for
the neck of a much larger animal!
Captain M’Quhæ immediately replied:—“I assert that neither was it
a common seal nor a sea-elephant; its great length and its totally
different physiognomy precluding the possibility of its being a _Phoca_
of any species. The head was flat, and not a capacious vaulted cranium;
nor had it a stiff, inflexible trunk—a conclusion to which Professor
Owen has jumped, most certainly not justified by my simple statement,
that ‘no portion of the 60 feet seen by us was used in propelling it
through the water, either by vertical or horizontal undulation.’”
He explained that the calculation of the creature’s length was made
before, not after, the idea had been entertained that the animal was
a serpent, and that he and his officers were “too well accustomed
to judge of lengths and breadths of objects in the sea to mistake a
real substance and an actual living body, coolly and dispassionately
contemplated, at so short a distance too, for the ‘eddy caused by
the action of the deeply immersed fins and tail of a rapidly moving,
gigantic seal raising its head above the water,’ as Professor Owen
imagines, in quest of its lost iceberg.” He next disposed of Owen’s
assertion that the idea of clothing the serpent with a mane had been
suggested by old Pontoppidan’s story, simply because he had never seen
Pontoppidan’s account or heard of Pontoppidan’s sea-serpent, until
he had told his own tale in London. Finally, he added, “I deny the
existence of excitement, or the possibility of optical illusion. I
adhere to the statement as to form, colour, and dimensions, contained
in my report to the Admiralty.”
A narrative which appeared in the _Times_ early in 1849 must be
referred to in this place, as not being readily explicable by Professor
Owen’s hypothesis. It was written by Mr. R. Davidson, superintending
surgeon, Najpore Subsidiary Force Kamptee, and was to the following
effect (I abridge it considerably):—When at a considerable distance
south-west of the Cape of Good Hope, Mr. Davidson, Captain Petrie, of
the _Royal Saxon_, a steerage passenger, and the man at the wheel, saw
“an animal of which no more correct description could be given than
that by Captain M’Quhæ. It passed within 35 yards of the ship, without
altering its course in the least; but as it came right abreast of us it
slowly turned its head towards us.” About one-third of the upper part
of its body was above water, “in nearly its whole length; and we could
see the water curling up on its breast as it moved along, but by what
means it moved we could not perceive.” They _saw this creature in its
whole length_ with the exception of a small portion of the tail which
was under water; and by comparing its length with that of the _Royal
Saxon_, 600 feet, when exactly alongside in passing, they calculated it
to be in length as well as in other dimensions greater than the animal
described by Captain M’Quhæ.
In the year 1852 two statements were made, one by Captain Steele, 9th
Lancers, the other by one of the officers of the ship _Barham_ (India
merchantman), to the effect that an animal of a serpentine appearance
had been seen about 500 yards from that ship (in longitude 40° E. and
37° 16´ S., that is, east of the south-eastern corner of Africa). “We
saw him,” said the former, “about 16 or 20 feet out of the water, and
he _spouted_ a long way from his head”—that is, I suppose, he spouted
to some distance, not, as the words really imply, at a part of his neck
far removed from the head. “Down his back he had a crest like a cock’s
comb, and was going very slowly through the water, but left a wake of
about 50 or 60 feet, as if dragging a long body after him. The captain
put the ship off her course to run down to him, but as we approached
him he went down. His colour was green with light spots. He was seen by
every one on board.” The other witness gives a similar account, adding
that the creature kept moving his head up and down, and was surrounded
by hundreds of birds. “We at first thought it was a dead whale....
When we were within 100 yards he slowly sank into the depths of the
sea; while we were at dinner he was seen again.” Mr. Alfred Newton,
the well-known naturalist, guarantees his personal acquaintance with
one of the recipients of the letters just quoted from. But such a
guarantee is, of course, no sufficient guarantee of the authenticity
of the narrative. Even if the narrative be accepted, the case seems a
very doubtful one. The birds form a suspicious element in the story.
Why should birds cluster around a living sea creature? It seems to
me probable that the sea-weed theory, presently to be noticed, gives
the best explanation of this case. Possibly some great aggregation of
sea-weed was there, in which were entangled divers objects desirable
to birds and to fishes. These last may have dragged the mass under
water when the ship approached, being perhaps more or less entangled
in it—and it floated up again afterwards. The spouting may have been
simply the play of water over the part mistaken for the head.
The sea-weed theory of the sea-serpent was broached in February, 1849,
and supported by a narrative not unlike the last. When the British
ship _Brazilian_ was becalmed almost exactly in the spot where M’Quhæ
had seen his monster, Mr. Herriman, the commander, perceived something
right abeam, about half a mile to the westward, “stretched along the
water to the length of about 25 or 30 feet, and perceptibly moving from
the ship with a steady, sinuous motion. The head, which seemed to be
lifted several feet above the waters, had something resembling a mane,
running down to the floating portion, and within about 6 feet of the
tail it forked out into a sort of double fin.” Mr. Herriman, his first
mate, Mr. Long, and several of the passengers, after surveying the
object for some time, came to the unanimous conclusion that it must be
the sea-serpent seen by Captain M’Quhæ. “As the _Brazilian_ was making
no headway, Mr. Herriman, determining to bring all doubts to an issue,
had a boat lowered down, and taking two hands on board, together with
Mr. Boyd, of Peterhead, near Aberdeen, one of the passengers, who
acted as steersman under the direction of the captain, they approached
the monster, Captain Herriman standing on the bow of the boat, armed
with a harpoon to commence the onslaught. The combat, however, was
not attended with the danger which those on board apprehended; for
on coming close to the object it was found to be nothing more than
an immense piece of sea-weed, evidently detached from a coral reef
and drifting with the current, which sets constantly to the westward
in this latitude, and which, together with the swell left by the
subsidence of the gale, gave it the sinuous, snake-like motion.”
A statement was published by Captain Harrington in the _Times_ of
February, 1858, to the effect that from his ship _Castilian_, then
distant ten miles from the north-east end of St. Helena, he and
his officers had seen a huge marine animal within 20 yards of the
ship; that it disappeared for about half a minute, and then made its
appearance in the same manner again, showing distinctly its neck and
head about 10 or 12 feet out of the water. “Its head was shaped like
a long nun-buoy,” proceeds Captain Harrington, “and I suppose the
diameter to have been 7 or 8 feet in the largest part, with a kind of
scroll, or tuft, of loose skin encircling it about 2 feet from the top;
the water was discoloured for several hundred feet from its head....
From what we saw from the deck, we conclude that it must have been over
200 feet long. The boatswain and several of the crew who observed it
from the top-gallant forecastle,[26] (query, cross-trees?) state that
it was more than double the length of the ship, in which case it must
have been 500 feet. Be that as it may, I am convinced that it belonged
to the serpent tribe; it was of a dark colour about the head, and was
covered with several white spots.”
This immediately called out a statement from Captain F. Smith, of
the ship _Pekin_, that on December 28, not far from the place where
the _Dædalus_ had encountered the supposed sea-serpent, he had seen,
at a distance of about half a mile, a creature which was declared by
all hands to be the great sea-serpent, but proved eventually to be a
piece of gigantic sea-weed. “I have no doubt,” he says, that the great
sea-serpent seen from the _Dædalus_ “was a piece of the same weed.”
It will have been noticed that the sea-weed sea-serpents, seen by
Captain F. Smith and by Captain Herriman, were both at a distance
of half a mile, at which distance one can readily understand that a
piece of sea-weed might be mistaken for a living creature. This is
rather different from the case of the _Dædalus_ sea-serpent, which
passed so near that had it been a man of the captain’s acquaintance
he could have recognized that man’s features with the naked eye. The
case, too, of Captain Harrington’s sea-serpent, seen within 20 yards
of the _Castilian_, can hardly be compared to those cases in which
sea-weed, more than 800 yards from the ship, was mistaken for a living
animal. An officer of the _Dædalus_ thus disposed of Captain Smith’s
imputation:—“The object seen from the ship was beyond all question a
living animal, moving rapidly through the water against a cross sea,
and within five points of a fresh breeze, with such velocity that
the water was surging against its chest as it passed along at a rate
probably of ten miles per hour. Captain M’Quhæ’s first impulse was to
tack in pursuit, but he reflected that we could neither lay up for it
nor overhaul it in speed. There was nothing to be done, therefore, but
to observe it as accurately as we could with our glasses as it came up
under our lee quarter and passed away to windward, being at its nearest
position not more than 200 yards from us; _the eye, the mouth, the
nostril, the colour, and the form, all being most distinctly visible
to us_.... My impression was that it was rather of a lizard than a
serpentine character, as its movement was steady and uniform, _as if
propelled by fins_, not by any undulatory power.”
But all the evidence heretofore obtained respecting the sea-serpent,
although regarded by many naturalists, Gosse, Newman, Wilson, and
others, as demonstrating the existence of some as yet unclassified
monster of the deep, seems altogether indecisive by comparison with
that which has recently been given by the captain, mates, and crew
of the ship _Pauline_. In this case, assuredly, we have not to deal
with a mass of sea-weed, the floating trunk of a tree, a sea-elephant
hastening to his home amid the icebergs, or with any of the other more
or less ingenious explanations of observations previously made. We have
either the case of an actual living animal, monstrous, fierce, and
carnivorous, or else the five men who deposed on oath to the stated
facts devised the story between them, and wilfully perjured themselves
for no conceivable purpose—that, too, not as men have been known to
perjure themselves under the belief that none could know of their
infamy, but with the certainty on the part of each that four others
(any one of whom might one day shame him and the rest by confessing)
knew the real facts of the case.
The story of the _Pauline_ sea-serpent ran simply as follows, as
attested at the Liverpool police-court:—“We, the undersigned, captain,
officers, and crew of the bark _Pauline_, of London, do solemnly
and sincerely declare, that on July 8, 1875, in latitude 5° 13´ S.,
longitude 35° W., we observed three large sperm whales, and one of
them was gripped round the body with two turns of what appeared to be
a huge serpent. The head and tail appeared to have a length beyond
the coils of about 30 feet, and its girth 8 or 9 feet. The serpent
whirled its victim round and round for about fifteen minutes, and then
suddenly dragged the whale to the bottom, head first.—George Drevat,
master; Horatio Thompson, chief mate; John H. Landells, second mate;
William Lewarn, steward; Owen Baker, A.B. Again on the 13th July a
similar serpent was seen about 200 yards off, shooting itself along the
surface, head and neck being out of the water several feet. This was
seen only by the captain and an ordinary seaman.—George Drevat. A few
moments afterwards it was seen elevated some 60 feet perpendicularly
in the air by the chief officer and two seamen, whose signatures are
affixed.—Horatio Thompson, Owen Baker, William Lewarn.”
The usual length of the cachalot or sperm whale is about 70 feet, and
its girth about 50 feet. If we assign to the unfortunate whale which
was captured on this occasion, a length of only 50 feet, and a girth
of only 35 feet, we should still have for the entire length of the
supposed serpent about 100 feet. This can hardly exceed the truth,
since the three whales are called large sperm whales. With a length of
100 feet and a girth of about 9 feet, however, a serpent would have
no chance in an attempt to capture a sperm whale 50 feet long and 35
feet in girth, for the simple reason that the whale would be a good
deal heavier than its opponent. In a contest in open sea, where one
animal seeks to capture another bodily, weight is all-important. We
can hardly suppose the whale could be so compassed by the coils of his
enemy as to be rendered powerless; in fact, the contest lasted fifteen
minutes, during the whole of which time the so-called serpent was
whirling its victim round, though more massive than itself, through
the water. On the whole, it seems reasonable to conclude—in fact, the
opinion is almost forced upon us—that besides the serpentine portion
of its bulk, which was revealed to view, the creature, thus whirling
round a large sperm whale, had a massive concealed body, provided with
propelling paddles of enormous power. _These_ were at work all the time
the struggle went on, enabling the creature to whirl round its enemy
easily, whereas a serpentine form, with two-thirds of its length, at
least, coiled close round another body, would have had no propulsive
power left, or very little, in the remaining 30 feet of its length,
including both the head and tail ends beyond the coils. Such a creature
as an enaliosaurus _could_ no doubt have done what a serpent of twice
the supposed length would have attempted in vain—viz., dragged down
into the depths of the sea the mighty bulk of a cachalot whale.
When all the evidence is carefully weighed, we appear led to the
conclusion that at least one large marine animal exists which has not
as yet been classified among the known species of the present era. It
would appear that this animal has certainly a serpentine neck, and a
head small compared with its body, but large compared with the diameter
of the neck. It is probably an air-breather and warm-blooded, and
certainly carnivorous. Its propulsive power is great and apparently
independent of undulations of its body, wherefore it presumably
has powerful concealed paddles. All these circumstances correspond
with the belief that it is a modern representative of the long-neck
plesiosaurians of the great secondary or mesozoic era, a member of that
strange family of animals whose figure has been compared to that which
would be formed by drawing a serpent through the body of a sea-turtle.
Against this view sundry objections have been raised, which must now be
briefly considered.
In the first place, Professor Owen pointed out that the sea-saurians
of the secondary period have been replaced in the tertiary and present
seas by the whales and allied races. No whales are found in the
secondary strata, no saurians in the tertiary. “It seems to me less
probable,” he says, “that no part of the carcase of such reptiles
should have ever been discovered in a recent unfossilized state, than
that men should have been deceived by a cursory view of a partly
submerged and rapidly moving animal which might only be strange to
themselves. In other words, I regard the negative evidence from the
utter absence of any of the recent remains of great sea-serpents,
krakens, or enaliosauria, as stronger against their actual existence,
than the positive statements which have hitherto weighed with the
public mind in favour of their existence. A larger body of evidence
from eye-witnesses might be got together in proof of ghosts than of the
sea-serpent.”
To this it has been replied that genera are now known to exist, as the
_Chimæra_, the long-necked river tortoise, and the iguana, which are
closely related to forms which existed in the secondary era, while no
traces have been found of them in any of the intermediate or tertiary
strata. The chimæra is a case precisely analogous to the supposed case
of the enaliosaurus, for the chimæra is but rarely seen, like the
supposed enaliosaurus, is found in the same and absent from the same
fossiliferous strata. Agassiz is quoted in the _Zoologist_, page 2395,
as saying that it would be in precise conformity with analogy that such
an animal as the enaliosaurus should exist in the American seas, as
he had found numerous instances in which the fossil forms of the Old
World were represented by living types in the New. In close conformity
with this opinion is a statement made by Captain the Hon. George Hope,
that when in the British ship _Fly_, in the Gulf of California, the
sea being perfectly calm and transparent, he saw at the bottom a large
marine animal, with the head and general figure of an alligator, but
the neck much longer, and with four large paddles instead of legs.
Here, then, unless this officer was altogether deceived, which seems
quite unlikely under the circumstances, was a veritable enaliosaurus,
though of a far smaller species, probably, than the creature mistaken
for a sea-serpent.
As for the absence of remains, Mr. Darwin has pointed out that
the fossils we possess are but fragments accidentally preserved
by favouring circumstances in an almost total wreck. We have many
instances of existent creatures, even such as would have a far better
chance of floating after death, and so getting stranded where their
bones might be found, which have left no trace of their existence. A
whale possessing two dorsal fins was said to have been seen by Smaltz,
a Sicilian naturalist; but the statement was rejected, until a shoal
of these whales were seen by two eminent French zoologists, MM. Quoy
and Gaimard. No carcase, skeleton, or bone of this whale has ever
been discovered. For seventeen hours a ship, in which Mr. Gosse was
travelling to Jamaica, was surrounded by a species of whale never
before noticed—30 feet long, black above and white beneath, with
swimming paws white on the upper surface. Here, he says, was “a whale
of large size, occurring in great numbers in the North Atlantic, which
on no other occasion has fallen under scientific observation. The
toothless whale of Havre, a species actually inhabiting the British
Channel, is only known from a single specimen accidentally stranded on
the French coast; and another whale, also British, is known only from
a single specimen cast ashore on the Elgin roast, and there seen and
described by the naturalist Sowerby.
Dr. Andrew Wilson, in an interesting paper, in which he maintains that
sea-serpent tales are not to be treated with derision, but are worthy
of serious consideration, “supported as they are by zoological science,
and in the actual details of the case by evidence as trustworthy in
many cases as that received in our courts of law,” expresses the
opinion that plesiosauri and ichthyosauri have been unnecessarily
disinterred to do duty for the sea-serpents. But he offers as an
alternative only the ribbon-fish; and though some of these may attain
enormous dimensions, yet we have seen that some of the accounts of
the supposed sea-serpent, and especially the latest narrative by the
captain and crew of the _Pauline_, cannot possibly be explained by any
creature so flat and relatively so feeble as the ribbon-fish.
On the whole, it appears to me that a very strong case has been made
out for the enaliosaurian, or serpent-turtle, theory of the so-called
sea-serpent.
One of the ribbon-fish mentioned by Dr. Wilson, which was captured,
and measured more than 60 feet in length, might however fairly take
its place among strange sea creatures. I scarcely know whether to add
to the number a monstrous animal like a tadpole, or even more perhaps
like a gigantic skate, 200 feet in length, said to have been seen in
the Malacca Straits by Captain Webster and Surgeon Anderson, of the
ship _Nestor_. Perhaps, indeed, this monster, mistaken in the first
instance for a shoal, but presently found to be travelling along at
the rate of about ten knots an hour, better deserves to be called
a strange sea creature even than any of those which have been dealt
with in the preceding pages. But the only account I have yet seen
of Captain Webster’s statement, and Mr. Anderson’s corroboration,
appeared in an American newspaper; and though the story is exceedingly
well authenticated if the newspaper account of the matter is true, it
would not be at all a new feature in American journalism if not only
the story itself, but all the alleged circumstances of its narration,
should in the long run prove to be pure invention.
_ON SOME MARVELS IN TELEGRAPHY._
Within the last few years Electric Telegraphy has received some
developments which seem wonderful even by comparison with those other
wonders which had before been achieved by this method of communication.
In reality, all the marvels of electric telegraphy are involved, so
to speak, in the great marvel of electricity itself, a phenomenon
as yet utterly beyond the interpretation of physicists, though not
more so than its fellow marvels, light and heat. We may, indeed,
draw a comparison between some of the most wonderful results which
have recently been achieved by the study of heat and light and those
effected in the application of electricity to telegraphy. It is as
startling to those unfamiliar with the characteristics of light, or
rather with certain peculiarities resulting from these characteristics,
to be told that an astronomer can tell whether there is water in the
air of Mars or Venus, or iron vapour in the atmosphere of Aldebaran
or Betelgeux, as it is to those unfamiliar with the characteristics
of electricity, or with the results obtained in consequence of these
characteristics, to be told that a written message can be copied by
telegraph, a map or diagram reproduced, or, most wonderful of all,
a musical air correctly repeated, or a verbal message made verbally
audible. Telegraphic marvels such as these bear to the original marvel
of mere telegraphic communication, somewhat the same relation which
the marvels of spectroscopic analysis as applied to the celestial orbs
bear to that older marvel, the telescopic scrutiny of those bodies. In
each case, also, there lies at the back of all these marvels a greater
marvel yet—electricity in the one case, light in the other.
I propose in this essay to sketch the principles on which some of the
more recent wonders of telegraphic communication depend. I do not
intend to describe at any length the actual details or construction
of the various instruments employed. Precisely as the principles of
spectroscopic analysis can be made clear to the general reader without
the examination of the peculiarities of spectroscopic instruments,
so can the methods and principles of telegraphic communication be
understood without examining instrumental details. In fact, it may
be questioned whether general explanations are not in such cases
more useful than more detailed ones, seeing that these must of
necessity be insufficient for a student who requires to know the
subject practically in all its details, while they deter the general
reader by technicalities in which he cannot be expected to take any
interest. If it be asked, whether I myself, who undertake to explain
the principles of certain methods of telegraphic communication, have
examined _practically_ the actual instrumental working of these
methods, I answer frankly that I have not done so. As some sort
of proof, however, that without such practical familiarity with
working details the principles of the construction of instruments
may be thoroughly understood, I may remind the reader (see p. 96)
that the first spectroscopic battery I ever looked through—one in
which the dispersive power before obtained in such instruments had
been practically doubled—was of my own invention, constructed (with
a slight mechanical modification) by Mr. Browning, and applied at
once successfully to the study of the sun by Mr. Huggins, in whose
observatory I saw through this instrument the solar spectrum extended
to a length which, could it all have been seen at once, would have
equalled many feet.[27] On the other hand, it is possible to have a
considerable practical experience of scientific instruments without
sound knowledge of the principles of their construction; insomuch that
instances have been known in which men who have effected important
discoveries by the use of some scientific instrument, have afterwards
obtained their first clear conception of the principles of its
construction from a popular description.
It may be well to consider, though briefly, some of the methods of
communication which were employed before the electric telegraph was
invented. Some of the methods of electric telegraphy have their
antitypes, so to speak, in methods of telegraphy used ages before the
application of electricity. The earliest employment of telegraphy
was probably in signalling the approach of invading armies by beacon
fires. The use of this method must have been well known in the time
of Jeremiah, since he warns the Benjamites “to set up a sign of fire
in Beth-haccerem,” because “evil appeareth out of the north and great
destruction.” Later, instead of the simple beacon fire, combinations
were used. Thus, by an Act of the Scottish Parliament in 1455, the
blazing of one bale indicated the probable approach of the English, two
bales that they were coming indeed, and four bales blazing beside each
other that they were in great force. The smoke of beacon fires served
as signals by day, but not so effectively, except under very favourable
atmospheric conditions.
Torches held in the hand, waved, depressed, and so forth, were
anciently used in military signalling at night; while in the day-time
boards of various figures in different positions indicated either
different messages or different letters, as might be pre-arranged.
Hooke communicated to the Royal Society in 1684 a paper describing a
method of “communicating one’s mind at great distances.” The letters
were represented by various combinations of straight lines, which might
be agreed upon previously if secrecy were desired, otherwise the same
forms might represent constantly the same letters. With four straight
planks any letter of this alphabet could be formed as wanted, and being
then run out on a framework (resembling a gallows in Hooke’s picture),
could be seen from a distant station. Two curved beams, combined in
various ways, served for arbitrary signals.
Chappe, in 1793, devised an improvement on this in what was called
the T telegraph. An upright post supported a cross-bar (the top of
the T), at each end of which were the short dependent beams, making
the figure a complete Roman capital T. The horizontal bar as first
used could be worked by ropes within the telegraph-house, so as to be
inclined either to right or left. It thus had three positions. Each
dependent beam could be worked (also from within the house) so as to
turn upwards, horizontally, or downwards (regarding the top bar of
the T as horizontal), thus having also three positions. It is easily
seen that, since each position of one short beam could be combined
with each position of the other, the two together would present
three times three arrangements, or nine in all; and as these nine
could be given with the cross-bar in any one of its three positions,
there were in all twenty-seven possible positions. M. Chappe used an
alphabet of only sixteen letters, so that all messages could readily
be communicated by this telegraph. For shorter distances, indeed, and
in all later uses of Chappe’s telegraph, the short beams could be
used in intermediate positions, by which 256 different signals could
be formed. Such telegraphs were employed on a line beginning at the
Louvre and proceeding by Montmartre to Lisle, by which communications
were conveyed from the Committee of Public Welfare to the armies in the
Low Countries. Telescopes were used at each station. Barrère stated,
in an address to the Convention on August 17, 1794, that the news of
the recapture of Lisle had been sent by this line of communication to
Paris in one hour after the French troops had entered that city. Thus
the message was conveyed at the rate of more than 120 miles per hour.
Various other devices were suggested and employed during the first half
of the present century. The semaphores still used in railway signalling
illustrate the general form which most of these methods assumed. An
upright, with two arms, each capable of assuming six distinct positions
(excluding the upright position), would give forty-eight different
signals; thus each would give six signals alone, or twelve for the
pair, and each of the six signals of one combined with each of the six
signals of the other, would give thirty-six signals, making forty-eight
in all. This number suffices to express the letters of the alphabet
(twenty-five only are needed), the Arabic numerals, and thirteen
arbitrary signals.
The progress of improvement in such methods of signalling promised to
be rapid, before the invention of the electric telegraph, or rather,
before it was shown how the principle of the electric telegraph could
be put practically into operation. We have seen that they were capable
of transmitting messages with considerable rapidity, more than twice
as fast as we could now send a written message by express train. But
they were rough and imperfect. They were all, also, exposed to one
serious defect. In thick weather they became useless. Sometimes, at the
very time when it was most important that messages should be quickly
transmitted, fog interrupted the signalling. Sir J. Barrow relates that
during the Peninsular War grave anxiety was occasioned for several
hours by the interruption of a message from Plymouth, really intended
to convey news of a victory. The words transmitted were, “Wellington
defeated;” the message of which these words formed the beginning was:
“Wellington defeated the French at,” etc. As Barrow remarks, if the
message had run, “French defeated at,” etc., the interruption of the
message would have been of less consequence.
Although the employment of electricity as a means of communicating
at a distance was suggested before the end of the last century, in
fact, so far back as 1774, the idea has only been worked out during
the last forty-two years. It is curious indeed to note that until
the middle of the present century the word “telegraph,” which is now
always understood as equivalent to electric telegraph, unless the
contrary is expressed, was commonly understood to refer to semaphore
signalling,[28] unless the word “electric” were added.
The general principle underlying all systems of telegraphic
communication by electricity is very commonly misunderstood. The idea
seems to prevail that electricity can be sent out along a wire to any
place where some suitable arrangement has been made to receive it. In
one sense this is correct. But the fact that the electricity has to
make a circuit, returning to the place from which it is transmitted,
seems not generally understood. Yet, unless this is understood, the
principle, even the possibility, of electric communication is not
recognized.
Let us, at the outset, clearly understand the nature of electric
communication.
In a variety of ways, a certain property called electricity can be
excited in all bodies, but more readily in some than in others. This
property presents itself in two forms, which are called positive
and negative electricity, words which we may conveniently use, but
which must not be regarded as representing any real knowledge of
the distinction between these two kinds of electricity. In fact,
let it be remembered throughout, that we do not in the least know
what electricity is; we only know certain of the phenomena which
it produces. Any body which has become charged with electricity,
either positive or negative, will part with its charge to bodies in a
neutral condition, or charged with the opposite electricity (negative
or positive). But the transference is made much more readily to
some substances than to others—so slowly, indeed, to some, that in
ordinary experiments the transference may be regarded as not taking
place at all. Substances of the former kind are called good conductors
of electricity; those which receive the transfer of electricity less
readily are said to be bad conductors; and those which scarcely receive
it at all are called insulating substances. The reader must not
confound the quality I am here speaking of with readiness to become
charged with electricity. On the contrary, the bodies which most
freely receive and transmit electricity are least readily charged with
electricity, while insulating substances are readily electrified. Glass
is an insulator, but if glass is briskly rubbed with silk it becomes
charged (or rather, the part rubbed becomes charged) with positive
electricity, formerly called _vitreous_ electricity for this reason;
and again, if wax or resin, which are both good insulators, be rubbed
with cloth or flannel, the part rubbed becomes charged with negative,
formerly called _resinous_, electricity.
Electricity, then, positive or negative, however generated, passes
freely along conducting substances, but is stopped by an insulating
body, just as light passes through transparent substances, but is
stopped by an opaque body. Moreover, electricity may be made to pass
to any distance along conducting bodies suitably insulated. Thus, it
might seem that we have here the problem of distant communication
solved. In fact, the first suggestion of the use of electricity in
telegraphy was based on this property. When a charge of electricity has
been obtained by the use of an ordinary electrical machine, this charge
can be drawn off at a distant point, if a conducting channel properly
insulated connects that point with the bodies (of whatever nature)
which have been charged with electricity. In 1747, Dr. Watson exhibited
electrical effects from the discharges of Leyden jars (vessels
suitably constructed to receive and retain electricity) at a distance
of two miles from the electrical machine. In 1774, Le Sage proposed
that by means of wires the electricity developed by an electrical
machine should be transmitted by insulated wires to a point where an
electroscope, or instrument for indicating the presence of electricity,
should, by its movements, mark the letters of the alphabet, one wire
being provided for each letter. In 1798 Béthencourt repeated Watson’s
experiment, increasing the distance to twenty-seven miles, the
extremities of his line of communication being at Madrid and Aranjuez.
(Guillemin, by the way, in his “Applications of the Physical Forces,”
passes over Watson’s experiment; in fact, throughout his chapters on
the electric telegraph, the steam-engine, and other subjects, he seems
desirous of conveying as far as possible the impression that all the
great advances of modern science had their origin in Paris and its
neighbourhood.)
From Watson’s time until 1823 attempts were made in this country
and on the Continent to make the electrical machine serve as the
means of telegraphic communication. All the familiar phenomena of
the lecture-room have been suggested as signals. The motion of pith
balls, the electric spark, the perforation of paper by the spark, the
discharge of sparks on a fulminating pane (a glass sheet on which
pieces of tinfoil are suitably arranged, so that sparks passing from
one to another form various figures or devices), and other phenomena,
were proposed and employed experimentally. But practically these
methods were not effectual. The familiar phenomenon of the electric
spark explains the cause of failure. The spark indicates the passage of
electricity across an insulating medium—dry air—when a good conductor
approaches within a certain distance of the charged body. The greater
the charge of electricity, the greater is the distance over which the
electricity will thus make its escape. Insulation, then, for many miles
of wire, and still more for a complete system of communication such
as we now have, was hopeless, so long as frictional electricity was
employed, or considerable electrical intensity required.
We have now to consider how galvanic electricity, discovered in 1790,
was rendered available for telegraphic communication. In the first
place, let us consider what galvanic or voltaic electricity is.
I have said that electricity can be generated in many ways. It may
be said, indeed, that every change in the condition of a substance,
whether from mechanical causes, as, for instance, a blow, a series of
small blows, friction, and so forth, or from change of temperature,
moisture, and the like, or from the action of light, or from chemical
processes, results in the development of more or less electricity.
When a plate of metal is placed in a vessel containing some acid
(diluted) which acts chemically on the metal, this action generates
negative electricity, which passes away as it is generated. But if a
plate of a different metal, either not chemically affected by the acid
or less affected than the former, be placed in the dilute acid, the two
plates being only partially immersed and not in contact, then, when a
wire is carried from one plate to the other, the excess of positive
electricity in the plate least affected by the acid is conveyed to
the other, or, in effect, discharged; the chemical action, however,
continues, or rather is markedly increased, fresh electricity is
generated, and the excess of positive electricity in the plate least
affected is constantly discharged. Thus, along the wire connecting
the two metals a current of electricity passes from the metal least
affected to the metal most affected; a current of negative electricity
passes in a contrary direction in the dilute acid.
I have spoken here of currents passing along the wire and in the acid,
and shall have occasion hereafter to speak of the plate of metal least
affected as the positive pole, this plate being regarded, in this
case, as a source whence a current of positive electricity flows along
the wire connection to the other plate, which is called the negative
pole. But I must remind the reader that this is only a convenient
way of expressing the fact that the wire assumes a certain condition
when it connects two such plates, and is capable of producing certain
effects. Whether in reality any process is taking place which can be
justly compared to the flow of a current one way or the other, or
whether a negative current flows along the circuit one way, while the
positive current flows the other way, are questions still unanswered.
We need not here enter into them, however. In fact, very little is
known about these points. Nor need we consider here the various ways in
which many pairs of plates such as I have described can be combined in
many vessels of dilute acid to strengthen the current. Let it simply
be noted that such a combination is called a battery; that when the
extreme plates of opposite kinds are connected by a wire, a current
of electricity passes along the wire from the extreme plate of that
metal which is least affected, forming the positive pole, to the other
extreme plate of that metal which is most affected and forms the
negative pole. The metals commonly employed are zinc and copper, the
former being the one most affected by the action of the dilute acid,
usually sulphuric acid. But it must here be mentioned that the chemical
process, affecting both metals, but one chiefly, would soon render a
battery of the kind described useless; wherefore arrangements are made
in various ways for maintaining the efficiency of the dilute acid and
of the metallic plates, especially the copper: for the action of the
acid on the zinc tends, otherwise, to form on the copper a deposit of
zinc. I need not describe the various arrangements for forming what are
called constant batteries, as Daniell’s, Grove’s, Bunsen’s, and others.
Let it be understood that, instead of a current which would rapidly
grow weaker and weaker, these batteries give a steady current for a
considerable time. Without this, as will presently be seen, telegraphic
communication would be impossible.
We have, then, in a galvanic battery a steady source of electricity.
This electricity is of low intensity, incompetent to produce the more
striking phenomena of frictional electricity. Let us, however, consider
how it would operate at a distance.
The current will pass along any length of conducting substance properly
insulated. Suppose, then, an insulated wire passes from the positive
pole of a battery at a station A to a station B, and thence back to the
negative pole at the station A. Then the current passes along it, and
this can be indicated at B by some action such as electricity of low
intensity can produce. If now the continuity of the wire be interrupted
close by the positive pole at A, the current ceases and the action is
no longer produced. The observer at B knows then that the continuity of
the wire has been interrupted; he has been, in fact, signalled to that
effect.
But, as I have said, the electrical phenomena which can be produced by
the current along a wire connecting the positive and negative poles
of a galvanic battery are not striking. They do not afford effective
signals when the distance traversed is very great and the battery not
exceptionally strong. Thus, at first, galvanic electricity was not more
successful in practice than frictional electricity.
It was not until the effect of the galvanic current on the magnetic
needle had been discovered that electricity became practically
available in telegraphy.
Oersted discovered in 1820 that a magnetic needle poised horizontally
is deflected when the galvanic current passes above it (parallel to
the needle’s length) or below it. If the current passes above it, the
north end of the needle turns towards the east when the current travels
from north to south, but towards the west when the current travels from
south to north; on the other hand, if the current passes below the
needle, the north end turns towards the west when the current travels
from south to north, and towards the east when the current travels from
north to south. The deflection will be greater or less according to the
power of the current. It would be very slight indeed in the case of a
needle, however delicately poised, above or below which passed a wire
conveying a galvanic current from a distant station. But the effect can
be intensified, as follows:—
[Illustration: FIG. 1.]
Suppose _a b c d e f_ to be a part of the wire from A to B, passing
above a delicately poised magnetic needle N S, along _a b_ and then
below the needle along _c d_, and then above again along _e f_ and so
to the station B. Let a current traverse the wire in the direction
shown by the arrows. Then N, the north end of the needle, is deflected
towards the east by the current passing along _a b_. But it is also
deflected to the east by the current passing along _c d_; for this
produces a deflection the reverse of that which would be produced by a
current in the same direction above the needle—that is, in direction
_b a_, and therefore the same as that produced by the current along
_a b_. The current along _e f_ also, of course, produces a deflection
of the end N towards the east. All three parts, then, _a b_, _c d_,
_e f_, conspire to increase the deflection of the end N towards the
east. If the wire were twisted once again round N S, the deflection
would be further increased; and finally, if the wire be coiled in the
way shown in Fig. 1, but with a great number of coils, the deflection
of the north end towards the east, almost imperceptible without such
coils, will become sufficiently obvious. If the direction of the
current be changed, the end N will be correspondingly deflected towards
the west.
The needle need not be suspended horizontally. If it hang vertically,
that is, turn freely on a horizontal axis, and the coil be carried
round it as above described, the deflection of the upper end will be to
the right or to the left, according to the direction of the current.
The needle actually seen, moreover, is not the one acted upon by the
current. This needle is inside the coil; the needle seen turns on the
same axis, which projects through the coil.
If, then, the observer at the station B have a magnetic needle suitably
suspended, round which the wire from the battery at A has been coiled,
he can tell by the movement of the needle whether a current is passing
along the wire in one direction or in the other; while if the needle is
at rest he knows that no current is passing.
[Illustration: FIG. 2.]
[Illustration: FIG. 3.]
Now suppose that P and N, Fig. 2, are the positive and negative poles
of a galvanic battery at A, and that a wire passes from P to the
station B, where it is coiled round a needle suspended vertically
at _n_, and thence passes to the negative pole N. Let the wire be
interrupted at _a b_ and also at _c d_. Then no current passes along
the wire, and the needle _n_ remains at rest in a vertical position.
Now suppose the points _a b_ connected by the wire _a b_, and at the
same moment the points _c d_ connected by the wire _c d_, then a
current flows along P _a b_ to B, as shown in Fig. 2, circuiting the
coil round the needle _n_ and returning by _d c_ to N. The upper end
of the needle is deflected to the right while this current continues
to flow; returning to rest when the connection is broken at _a b_
and _c d_. Next, let _c b_ and _a d_ be simultaneously connected as
shown by the cross-lines in Fig. 3. (It will be understood that _a d_
and _b c_ do not touch each other where they cross.) The current will
now flow from P along _a d_ to B, circuiting round the needle _n_ in
a contrary direction to that in which it flowed in the former case,
returning by _b c_ to N. The upper end of the needle is deflected then
to the left while the current continues to flow along this course.
I need not here describe the mechanical devices by which the connection
at _a b_ and _c d_ can be instantly changed so that the current may
flow either along _a b_ and _d c_, as in Fig. 2, circuiting the needle
in one direction, or along _a d_ and _b c_, as in Fig. 3, circuiting
the needle in the other direction. As I said at the outset, this paper
is not intended to deal with details of construction, only to describe
the general principles of telegraphic communication, and especially
those points which have to be explained in order that recent inventions
may be understood. The reader will see that nothing can be easier than
so to arrange matters that, by turning a handle, either (1), _a b_ and
_c d_ may be connected, or, (2), _a d_ and _c b_, or, (3), both lines
of communication interrupted. The mechanism for effecting this is
called a _commutator_.
Two points remain, however, to be explained: First, A must be a
receiving station as well as a transmitting station; secondly, the
wire connecting B with N, in Figs. 2 and 3, can be dispensed with, for
it is found that if at B the wire is carried down to a large metal
plate placed some depth underground, while the wire at _c_ is carried
down to another plate similarly buried underground, the circuit is
completed even better than along such a return wire as is shown in the
figures. The earth either acts the part of a return wire, or else,
by continually carrying off the electricity, allows the current to
flow continuously along the single wire. We may compare the current
carried along the complete wire circuit, to water circulating in a pipe
extending continuously from a reservoir to a distance and back again to
the reservoir. Water sucked up continuously at one end could be carried
through the pipe so long as it was continuously returned to the
reservoir at the other; but it could equally be carried through a pipe
extending from that reservoir to some place where it could communicate
with the open sea—the reservoir itself communicating with the open
sea—an arrangement corresponding to that by which the return wire is
dispensed with, and the current from the wire received into the earth.
The discovery that the return wire may be dispensed with was made by
Steinheil in 1837.
The actual arrangement, then, is in essentials that represented in Fig.
4.
[Illustration: FIG. 4.]
A and B are the two stations; P N is the battery at A, P´ N´ the
battery at B; P´ P´ are the positive poles, N´ N´, the negative poles.
At _n_ is the needle of station A, at _n´_ the needle of station B.
When the handle of the commutator is in its mean position—which is
supposed to be the case at station B—the points _b´ d´_ are connected
with each other, but neither with _a´_ nor _c´_; no current, then,
passes from B to A, but station B is in a condition to receive
messages. (If _b´_ and _d´_ were not connected, of course no messages
could be received, since the current from A would be stopped at
_b´_—which does not mean that it would pass round _n´_ to _b´_, but
that, the passage being stopped at _b´_, the current would not flow at
all.) When (the commutator at B being in its mean position, or _d´ b´_
connected, and communication with _c´_ and _a´_ interrupted) the handle
of the commutator at A is turned from its mean position in _one_
direction, _a_ and _b_ are connected, as are _c_ and _d_—as shown in
the figure—while the connection between _b_ and _d_ is broken. Thus
the current passes from P by _a_ and _b_, round the needle _n_; thence
to station B, round needle _n´_, and by _b´_ and _d´_, to the earth
plate G´; and so along the earth to G, and by _d c_, to the negative
pole N. The upper end of the needle of both stations is deflected to
the right by the passage of the current in this direction. When the
handle of the commutator at A is turned in the other direction, _b_ and
_c_ are connected, as also _a_ and _d_; the current from P passes along
_a d_ to the ground plate G, thence to G´, along _d´ b´_, round the
needle _n´_, back by the wire to the station A, where, after circuiting
the needle _n_ in the same direction as the needle _n´_, it travels by
_b_ and _c_ to the negative pole N. The upper end of the needle, at
both stations, is deflected to the left by the passage of the current
in this direction.
It is easily seen that, with two wires and one battery, two needles
can be worked at both stations, either one moving alone, or the other
alone, or both together; but for the two to move differently, two
batteries must be used. The systems by which either the movements of
a single needle, or of a pair of needles, may be made to indicate the
various letters of the alphabet, numerals, and so on, need not here be
described. They are of course altogether arbitrary, except only that
the more frequent occurrence of certain letters, as _e_, _t_, _a_,
renders it desirable that these should be represented by the simplest
symbols (as by a single deflection to right or left), while letters
which occur seldom may require several deflections.
One of the inventions to which the title of this paper relates can now
be understood.
[Illustration: FIG. 5.]
In the arrangement described, when a message is transmitted, the
needle of the sender vibrates synchronously with the needle at the
station to which the message is sent. Therefore, till that message is
finished, none can be received at the transmitting station. In what
is called duplex telegraphy, this state of things is altered, the
needle at the sending station being left unaffected by the transmitted
current, so as to be able to receive messages, and in self-recording
systems to record them. This is done by dividing the current from the
battery into two parts of equal efficiency, acting on the needle at
the transmitting station in contrary directions, so that this needle
remains unaffected, and ready to indicate signals from the distant
station. The principle of this arrangement is indicated in Fig. 5. Here
_a b n_ represents the main wire of communication with the distant
station, coiled round the needle of the transmitting station in one
direction; the dotted lines indicate a finer short wire, coiled round
the needle in a contrary direction. When a message is transmitted,
the current along the main wire tends to deflect the needle at _n_ in
one direction, while the current along the auxiliary wire tends to
deflect it in the other direction. If the thickness and length of the
short wire are such as to make these two tendencies equal, the needle
remains at rest, while a message is transmitted to the distant station
along the main wire. In this state of things, if a current is sent
from the distant station along the wire in the direction indicated by
the dotted arrow, this current also circuits the auxiliary wire, but
in the direction indicated by the arrows on the dotted curve, which
is the same direction in which it circuits the main wire. Thus the
needle is deflected, and a signal received. When the direction of the
chief current at the transmitting station is reversed, so also is
the direction of the artificial current, so that again the needle is
balanced. Similarly, if the direction of the current from the distant
station is reversed, so also is the direction in which this current
traverses the auxiliary wire, so that again both effects conspire to
deflect the needle.
There is, however, another way in which an auxiliary wire may be made
to work. It may be so arranged that, when a message is transmitted,
the divided current flowing equally in opposite directions, the
instrument at the sending station is not affected; but that when the
operator at the distant station sends a current along the main wire,
this neutralizes the current coming towards him, which current had
before balanced the artificial current. The latter, being no longer
counterbalanced, deflects the needle; so that, in point of fact, by
this arrangement, the signal received at a station is produced by the
artificial current at that station, though of course the real cause of
the signal is the transmission of the neutralizing current from the
distant station.
The great value of duplex telegraphy is manifest. Not only can
messages be sent simultaneously in both directions along the wire—a
circumstance which of itself would double the work which the wire is
capable of doing—but all loss of time in arranging about the order
of outward and homeward messages is prevented. The saving of time is
especially important on long lines, and in submarine telegraphy. It is
also here that the chief difficulties of duplex telegraphy have been
encountered. The chief current and the artificial current must exactly
balance each other. For this purpose the flow along each must be
equal. In passing through the long wire, the current has to encounter
a greater resistance than in traversing the short wire; to compensate
for this difference, the short wire must be much finer than the long
one. The longer the main wire, the more delicate is the task of
effecting an exact balance. But in the case of submarine wires, another
and a much more serious difficulty has to be overcome. A land wire
is well insulated. A submarine wire is separated by but a relatively
moderate thickness of gutta-percha from water, an excellent conductor,
communicating directly with the earth, and is, moreover, surrounded by
a protecting sheathing of iron wires, laid spirally round the core,
within which lies the copper conductor. Such a cable, as Faraday long
since showed, acts precisely as an enormous Leyden jar; or rather,
Faraday showed that such a cable, without the wire sheathing, would
act when submerged as a Leyden jar, the conducting wire acting as
the interior metallic coating of such a jar, the gutta-percha as the
glass of the jar (the insulating medium), and the water acting as the
exterior metallic coating. Wheatstone showed further that such a cable,
with a wire sheathing, would act as a Leyden jar, even though not
submerged, the metal sheathing taking the part of the exterior coating
of the jar. Now, regarding the cable thus as a condenser, we see that
the transmission of a current along it may in effect be compared with
the passage of a fluid along a pipe of considerable capacity, into
which and from which it is conveyed by pipes of small capacity. There
will be a retardation of the flow of water corresponding to the time
necessary to fill up the large part of the pipe; the water may indeed
begin to flow through as quickly as though there were no enlargement of
the bore of the pipe, but the full flow from the further end will be
delayed. Just so it is with a current transmitted through a submarine
cable. The current travels instantly (or with the velocity of freest
electrical transmission) along the entire line; but it does not attain
a sufficient intensity to be recognized for some time, nor its full
intensity till a still longer interval has elapsed. The more delicate
the means of recognizing its flow, the more quickly is the signal
received. The time intervals in question are not, indeed, very great.
With Thomson’s mirror galvanometer, in which the slightest motion of
the needle is indicated by a beam of light (reflected from a small
mirror moving with the needle), the Atlantic cable conveys its signal
from Valentia to Newfoundland in about one second, while with the less
sensitive galvanometer before used the time would be rather more than
two seconds.
Now, in duplex telegraphy the artificial current must be equal to the
chief current in intensity all the time; so that, since in submarine
telegraphy the current rises gradually to its full strength and as
gradually subsides, the artificial current must do the same. Reverting
to the illustration derived from the flow of water, if we had a small
pipe the rapid flow through which was to carry as much water one way as
the slow flow through a large pipe was to carry water the other way,
then if the large pipe had a widening along one part of its long course
the short pipe would require to have a similar widening along the
corresponding part of its short course. And to make the illustration
perfect, the widenings along the large pipe should be unequal in
different parts of the pipe’s length; for the capacity of a submarine
cable, regarded as a condenser, is different along different parts of
its length. What is wanted, then, for a satisfactory system of duplex
telegraphy in the case of submarine cables, is an artificial circuit
which shall not only correspond as a whole to the long circuit, but
shall reproduce at the corresponding parts of its own length all the
varieties of capacity existing along various parts of the length of the
submarine cable.
Several attempts have been made by electricians to accomplish this
result. Let it be noticed that two points have to be considered: the
intensity of the current’s action, which depends on the resistance
it has to overcome in traversing the circuit; and the velocity of
transmission, depending on the capacity of various parts of the circuit
to condense or collect electricity. Varley, Stearn, and others have
endeavoured by various combinations of condensers with resistance coils
to meet these two requisites. But the action of artificial circuits
thus arranged was not sufficiently uniform. Recently Mr. J. Muirhead,
jun., has met the difficulty in the following way (I follow partially
the account given in the _Times_ of February 3, 1877, which the reader
will now have no difficulty in understanding):—He has formed his
second circuit by sheets of paper prepared with paraffin, and having
upon one side a strip of tinfoil, wound to and fro to represent
resistance. Through this the artificial current is conducted. On the
other side is a sheet of tinfoil to represent the sheathing,[29] and
to correspond to the capacity of the wire. Each sheet of paper thus
prepared may be made to represent precisely a given length of cable,
having enough tinfoil on one side to furnish the resistance, and on the
other to furnish the capacity. A sufficient number of such sheets would
exactly represent the cable, and thus the artificial or non-signalling
part of the current would be precisely equivalent to the signalling
part, so far as its action on the needle at the transmitting station
was concerned. “The new plan was first tried on a working scale,” says
the _Times_, “on the line between Marseilles and Bona; but it has
since been brought into operation from Marseilles to Malta, from Suez
to Aden, and lastly, from Aden to Bombay. On a recent occasion when
there was a break-down upon the Indo-European line, the duplex system
rendered essential service, and maintained telegraphic communication
which would otherwise have been most seriously interfered with.” The
invention, we may well believe, “cannot fail to be highly profitable to
the proprietors of submarine cables,” or to bring about “before long a
material reduction in the cost of messages from places beyond the seas.”
* * * * *
The next marvel of telegraphy to be described is the transmission
of actual facsimiles of writings or drawings. So far as strict
sequence of subject-matter is concerned, I ought, perhaps, at this
point, to show how duplex telegraphy has been surpassed by a recent
invention, enabling three or four or more messages to be simultaneously
transmitted telegraphically. But it will be more convenient to consider
this wonderful advance after I have described the methods by which
facsimiles of handwriting, etc., are transmitted.
Hitherto we have considered the action of the electric current
in deflecting a magnetic needle to right or left, a method of
communication leaving no trace of its transmission. We have now to
consider a method at once simpler in principle and affording means
whereby a permanent record can be left of each message transmitted.
[Illustration: FIG. 6.]
If the insulated wire is twisted in the form of a helix or coil round
a bar of soft iron, the bar becomes magnetized while the current is
passing. If the bar be bent into the horse-shoe form, as in Fig. 6,
where A C B represents the bar, _a b c d e f_ the coil of insulated
wire, the bar acts as a magnet while the current is passing along the
coil, but ceases to do so as soon as the current is interrupted.[30]
If, then, we have a telegraphic wire from a distant station in electric
connection with the wire _a b c_, the part _e f_ descending to an
earth-plate, then, according as the operator at that distant station
transmits or stops the current, the iron A C B is magnetized or
demagnetized. The part C is commonly replaced by a flat piece of iron,
as is supposed to be the case with the temporary magnets shown in Fig.
7, where this flat piece is below the coils.
So far back as 1838 this property was applied by Morse in America
in the recording instrument which bears his name, and is now (with
slight modifications) in general use not only in America but on the
Continent. The principle of this instrument is exceedingly simple. Its
essential parts are shown in Fig. 7; H is the handle, H _b_ the lever
of the manipulator at the station A. The manipulator is shown in the
position for receiving a message from the station B along the wire W.
The handle H´ of the manipulator at the station B is shown depressed,
making connection at _a´_ with the wire from the battery N´ P´. Thus a
current passes through the handle to _c´_, along the wire to _c_ and
through _b_ to the coil of the temporary magnet M, after circling which
it passes to the earth at _e_ and so by E´ to the negative pole N´. The
passage of this current magnetizes M, which draws down the armature
_m_. Thus the lever _l_, pulled down on this side, presses upwards the
pointed style _s_ against a strip of paper _p_ which is steadily rolled
off from the wheel W so long as a message is being received. (The
mechanism for this purpose is not indicated in Fig. 7.) Thus, so long
as the operator at B holds down the handle H´, the style _s_ marks the
moving strip of paper, the spring _r_, under the lever _s l_, drawing
the style away so soon as the current ceases to flow and the magnet to
act. If he simply depresses the handle for an instant, a dot is marked;
if longer, a dash; and by various combinations of dots and dashes all
the letters, numerals, etc., are indicated. When the operator at B has
completed his message, the handle H´ being raised by the spring under
it (to the position in which H is shown), a message can be received at
B.
[Illustration: FIG. 7.]
I have in the figure and description assumed that the current from
either station acts directly on the magnet which works the recording
style. Usually, in long-distance telegraphy, the current is too weak
for this, and the magnet on which it acts is used only to complete the
circuit of a local battery, the current from which does the real work
of magnetizing M at A or M´ at B, as the case may be. A local battery
thus employed is called a _relay_.
The Morse instrument will serve to illustrate the _principle_ of the
methods by which facsimiles are obtained. The details of construction
are altogether different from those of the Morse instrument; they
also vary greatly in different instruments, and are too complex to be
conveniently described here. But the principle, which is the essential
point, can be readily understood.
In working the Morse instrument, the operator at B depresses the handle
H´. Suppose that this handle is kept depressed by a spring, and that
a long strip of paper passing uniformly between the two points at _a_
prevents contact. Then no current can pass. But if there is a hole in
this paper, then when the hole reaches _a_ the two metal points at _a_
meet and the current passes. We have here the principle of the Bain
telegraph. A long strip of paper is punched with round and long holes,
corresponding to the dots and marks of a message by the Morse alphabet.
As it passes between a metal wheel and a spring, both forming part of
the circuit, it breaks the circuit until a hole allows the spring to
touch the wheel, either for a short or longer time-interval, during
which the current passes to the other station, where it sets a relay
at work. In Bain’s system the message is received on a chemically
prepared strip of paper, moving uniformly at the receiving station, and
connected with the negative pole of the relay battery. When contact is
made, the face of the paper is touched by a steel pointer connected
with the positive pole, and the current which passes from the end of
the pointer through the paper to the negative pole produces a blue
mark on the chemically prepared paper.[31]
We see that by Bain’s arrangement a paper is marked with dots and
lines, corresponding to round and elongated holes, in a ribbon of
paper. It is only a step from this to the production of facsimiles of
writings or drawings.
Suppose a sheet of paper so prepared as to be a conductor of
electricity, and that a message is written on the paper with some
non-conducting substance for ink. If that sheet were passed between
the knobs at _a_ (the handle H being pressed down by a spring),
whilst simultaneously a sheet of Bain’s chemically prepared paper
were passed athwart the steel pointer at the receiving station,
there would be traced across the last-named paper a blue line, which
would be broken at parts corresponding to those on the other paper
where the non-conducting ink interrupted the current. Suppose the
process repeated, each paper being slightly shifted so that the line
traced across either would be parallel and very close to the former,
but precisely corresponding as respects the position of its length.
Then this line, also, on the recording paper will be broken at parts
corresponding to those in which the line across the transmitting paper
meets the writing. If line after line be drawn in this way till the
entire breadth of the transmitting paper has been crossed by close
parallel lines, the entire breadth of the receiving paper will be
covered by closely marked blue lines except where the writing has
broken the contact. Thus a negative facsimile of the writing will
be found in the manner indicated in Figs. 8 and 9.[32] In reality,
in processes of this kind, the papers (unlike the ribbons on Bain’s
telegraph) are not carried across in the way I have imagined, but are
swept by successive strokes of a movable pointer, along which the
current flows; but the principle is the same.
[Illustration: FIG. 8. FIG. 9.]
It is essential, in such a process as I have described, first, that the
recording sheet should be carried athwart the pointer which conveys
the marking current (or the pointer carried across the recording
sheet) in precise accordance with the motion of the transmitting sheet
athwart the wire or style which conveys the current to the long wire
between the stations (or of this style across the transmitting sheet).
The recording sheet and the transmitting sheet must also be shifted
between each stroke by an equal amount. The latter point, is easily
secured; the former is secured by causing the mechanism which gives the
transmitting style its successive strokes to make and break circuit,
by which a temporary magnet at the receiving station is magnetized and
demagnetized; by the action of this magnet the recording pointer is
caused to start on its motion athwart the receiving sheet, and moving
uniformly it completes its thwart stroke at the same instant as the
transmitting style.
Caselli’s pantelegraph admirably effects the transmission of
facsimiles. The transmitting style is carried by the motion of a
heavy pendulum in an arc of constant range over a cylindrical surface
on which the paper containing the message, writing, or picture, is
spread. As the swing of the pendulum begins, a similar pendulum at the
receiving station begins its swing; the same break of circuit which
(by demagnetizing a temporary magnet) releases one, releases the other
also. The latter swings in an arc of precisely the same range, and
carries a precisely similar style over a similar cylindrical surface
on which is placed the prepared receiving paper. In fact, the same
pendulum at either station is used for transmitting and for receiving
facsimiles. Nay, not only so, but each pendulum, as it swings, serves
in the work both of transmitting and recording facsimiles. As it
swings one way, it travels along a line over each of two messages or
drawings, while the other pendulum in its synchronous swing traces a
corresponding line over each of two receiving sheets; and as it swings
the other way, it traces a line on each of two receiving sheets,
corresponding to the lines along which the transmitting style of the
other is passing along two messages or drawings. Such, at least, is the
way in which the instrument works in busy times. It can, of course,
send a message, or two messages, without receiving any.[33]
In Caselli’s pantelegraph matters are so arranged that instead of a
negative facsimile, like Fig. 9, a true facsimile is obtained in all
respects except that the letters and figures are made by closely set
dark lines instead of being dark throughout as in the message. The
transmitting paper is conducting and the ink non-conducting, as in
Bakewell’s original arrangement; but instead of the conducting paper
completing the circuit for the distant station, it completes a short
home circuit (so to speak) along which the current travels without
entering on the distant circuit When the non-conducting ink breaks the
short circuit, the current travels in the long circuit through the
recording pointer at the receiving station; and a mark is thus made
corresponding to the inked part of the transmitting sheet instead of
the blank part, as in the older plan.
The following passage from Guillemin’s “Application of the Physical
Forces” indicates the effectiveness of Caselli’s pantelegraph not
only as respects the character of the message it conveys, but as
to rapidity of transmission. (I alter the measures from the metric
to our usual system of notation.[34]) “Nothing is simpler than the
writing of the pantelegraph. The message when written is placed on
the surface of the transmitting cylinder. The clerk makes the warning
signals, and then sets the pendulum going. The transmission of the
message is accomplished automatically, without the clerk having any
work to do, and consequently without [his] being obliged to acquire
any special knowledge. Since two despatches may be sent at the same
time—and since shorthand may be used—the rapidity of transmission
may be considerable.” “The long pendulum of Caselli’s telegraph,” says
M. Quet, “generally performs about forty oscillations a minute, and
the styles trace forty broken lines, separated from each other by less
than the hundredth part of an inch. In one minute the lines described
by the style have ranged over a breadth of more than half an inch,
and in twenty minutes of nearly 10½ inches. As we can give the lines
a length of 4¼ inches, it follows that in twenty minutes Caselli’s
apparatus furnishes the facsimile of the writing or drawing traced on a
metallized plate 4¼ inches broad by 10½ inches long. For clearness of
reproduction, the original writing must be very legible and in large
characters.” “Since 1865 the line from Paris to Lyons and Marseilles
has been open to the public for the transmission of messages by this
truly marvellous system.”
It will easily be seen that Caselli’s method is capable of many
important uses besides the transmission of facsimiles of handwriting.
For instance, by means of it a portrait of some person who is to be
identified—whether fraudulent absconder, or escaped prisoner or
lunatic, or wife who has eloped from her husband, or husband who has
deserted his wife, or missing child, and so on—can be sent in a few
minutes to a distant city where the missing person is likely to be. All
that is necessary is that from a photograph or other portrait an artist
employed for the purpose at the transmitting station should, in bold
and heavy lines, sketch the lineaments of the missing person on one
of the prepared sheets, as in Fig. 10. The portrait at the receiving
station will appear as in Fig. 11, and if necessary an artist at this
station can darken the lines or in other ways improve the picture
without altering the likeness.
[Illustration: FIG. 10. FIG. 11.]
But now we must turn to the greatest marvel of all—the transmission of
tones, tunes, and words by the electric wire.
The transmission of the rhythm of an air is of course a very simple
matter. I have seen the following passage from “Lardner’s Museum of
Science and Art,” 1859, quoted as describing an anticipation of the
telephone, though in reality it only shows what every one who has
heard a telegraphic indicator at work must have noticed, that the
click of the instrument may be made to keep time with an air. “We
were in the Hanover Street Office, when there was a pause in the
business operations. Mr. M. Porter, of the office at Boston—the
writer being at New York—asked what tune we would have? We replied,
‘Yankee Doodle,’ and to our surprise he immediately complied with our
request. The instrument, a Morse one, commenced drumming the notes of
the tune as perfectly and distinctly as a skilful drummer could have
made them at the head of a regiment, and many will be astonished to
hear that ‘Yankee Doodle’ can travel by lightning.... So perfectly
and distinctly were the sounds of the tunes transmitted, that good
instrumental performers could have no difficulty in keeping time with
the instruments at this end of the wires.... That a pianist in London
should execute a fantasia at Paris, Brussels, Berlin, and Vienna, at
the same moment, and with the same spirit, expression, and precision as
if the instruments at these distant places were under his fingers, is
not only within the limits of practicability, but really presents no
other difficulty than may arise from the expense of the performances.
From what has just been stated, it is clear that the time of music
has been already transmitted, and the production of the sounds does
not offer any more difficulty than the printing of the letters of a
despatch.” Unfortunately, Lardner omitted to describe how this easy
task was to be achieved.
Reuss first in 1861 showed how a sound can be transmitted. At the
sending station, according to his method, there is a box, into which,
through a pipe in the side, the note to be transmitted is sounded. The
box is open at the top, and across it, near the top, is stretched
a membrane which vibrates synchronously with the aerial vibrations
corresponding to the note. At the middle of the membrane, on its upper
surface, is a small disc of metal, connected by a thin strip of copper
with the positive pole of the battery at the transmitting station. The
disc also, when the machine is about to be put in use, lightly touches
a point on a metallic arm, along which (while this contact continues)
the electric current passes to the wire communicating with the distant
station. At that station the wire is carried in a coil round a straight
rod of soft iron suspended horizontally in such a way as to be free
to vibrate between two sounding-boards. After forming this coil, the
wire which conveys the current passes to the earth-plate and so home.
As already explained, while the current passes, the rod of iron is
magnetized, but the rod loses its magnetization when the current ceases.
Now, when a note is sounded in the box at the transmitting station, the
membrane vibrates, and at each vibration the metal disc is separated
from the point which it lightly touches when at rest. Thus contact is
broken at regular intervals, corresponding to the rate of vibration
due to the note. Suppose, for instance, the note _C_ is sounded; then
there are 256 complete vibrations in a second, the electric current is
therefore interrupted and renewed, and the bar of soft iron magnetized
and demagnetized, 256 times in a second. Now, it had been discovered
by Page and Henry that when a bar of iron is rapidly magnetized
and demagnetized, it is put into vibrations synchronizing with the
interruptions of the current, and therefore emits a note of the same
tone as that which has been sounded into the transmitting box.
Professor Heisler, in his “Lehrbuch der technischen Physik,” 1866,
wrote of Reuss’s telephone: “The instrument is still in its infancy;
however, by the use of batteries of proper strength, it already
transmits not only single musical tones, but even the most intricate
melodies, sung at one end of the line, to the other, situated at a
great distance, and makes them perceptible there with all desirable
distinctness.” Dr. Van der Weyde, of New York, states that, after
reading an account of Reuss’s telephone, he had two such instruments
constructed, and exhibited them at the meeting of the Polytechnic
Club of the American Institute. “The original sounds were produced at
the furthest extremity of the large building (the Cooper Institute),
totally out of hearing of the Association; and the receiving
instrument, standing on the table in the lecture-room, produced, with
a peculiar and rather nasal twang, the different tunes sung into the
box at the other end of the line; not powerfully, it is true, but very
distinctly and correctly. In the succeeding summer I improved the form
of the box, so as to produce a more powerful vibration of the membrane.
I also improved the receiving instrument by introducing several iron
wires into the coil, so as to produce a stronger vibration. I submitted
these, with some other improvements, to the meeting of the American
Association for the Advancement of Science, and on that occasion (now
seven years ago) expressed the opinion that the instrument contained
the germ of a new method of working the electric telegraph, and would
undoubtedly lead to further improvements in this branch of science.”
The telephonic successes recently achieved by Mr. Gray were in
part anticipated by La Cour, of Copenhagen, whose method may be
thus described: At the transmitting station a tuning-fork is set
in vibration. At each vibration one of the prongs touches a fine
strip of metal completing a circuit. At the receiving station the
wire conveying the electric current is coiled round the prongs of
another tuning-fork of the same tone, but without touching them.
The intermittent current, corresponding as it does with the rate of
vibration proper to the receiving fork, sets this fork in vibration;
and in La Cour’s instrument the vibrations of the receiving fork
were used to complete the circuit of a local battery. His object was
not so much the production of tones as the use of the vibrations
corresponding to different tones, to act on different receiving
instruments. For only a fork corresponding to the sending fork could
be set in vibration by the intermittent current resulting from the
latter’s vibrations. So that, if there were several transmitting forks,
each could send its own message at the same time, each receiving fork
responding only to the vibrations of the corresponding transmitting
fork. La Cour proposed, in fact, that his instrument should be used
in combination with other methods of telegraphic communication. Thus,
since the transmitting fork, whenever put in vibration, sets the local
battery of the receiving station at work, it can be used to work a
Morse instrument, or it could work an ordinary Wheatstone and Cook
instrument, or it could be used for a pantelegraph. The same wire, when
different forks are used, could work simultaneously several instruments
at the receiving station. One special use indicated by La Cour was the
adaptation of his system to the Caselli pantelegraph, whereby, instead
of one style, a comb of styles might be carried over the transmitting
and recording plates. It would be necessary, in all such applications
of his method (though, strangely enough, La Cour’s description makes
no mention of the point), that the vibrations of the transmitting fork
should admit of being instantly stopped or “damped.”
Mr. Gray’s system is more directly telephonic, as aiming rather at the
development of sound itself than at the transmission of messages by
the vibrations corresponding to sound. A series of tuning-forks are
used, which are set in separate vibration by fingering the notes of a
key-board. The vibrations are transmitted to a receiving instrument
consisting of a series of reeds, corresponding in note to the series of
transmitting forks, each reed being enclosed in a sounding-box. These
boxes vary in length from two feet to six inches, and are connected
by two wooden bars, one of which carries an electro-magnet, round the
coils of which pass the currents from the transmitting instrument. When
a tuning-fork is set in vibration by the performer at the transmitting
key-board, the electro-magnet is magnetized and demagnetized
synchronously with the vibrations of the fork. Not only are vibrations
thus imparted to the reed of corresponding note, but these are
synchronously strengthened by thuds resulting from the lengthening of
the iron when magnetized.
So far as its musical capabilities are concerned, Gray’s telephone can
hardly be regarded as fulfilling all the hopes that have been expressed
concerning telephonic music. “Dreaming enthusiasts of a prophetic turn
of mind foretold,” we learn, “that a time would come when future Pattis
would sing on a London stage to audiences in New York, Berlin, St.
Petersburg, Shanghai, San Francisco, and Constantinople all at once.”
But the account of the first concert given at a distance scarcely
realizes these fond expectations. When “Home, Sweet Home,” played at
Philadelphia, came floating through the air at the Steinway Hall, New
York, “the sound was like that of a distant organ, rather faint, for a
hard storm was in progress, and there was consequently a great leakage
of the electric current, but quite clear and musical. The lower notes
were the best, the higher being sometimes almost inaudible. ‘The Last
Rose of Summer,’ ‘Com’ è gentil,’ and other melodies, followed, with
more or less success. There was no attempt to play chords,” though
three or four notes can be sounded together. It must be confessed that
the rosy predictions of M. Strakosch (the _impresario_) “as to the
future of this instrument seem rather exalted, and we are not likely as
yet to lay on our music from a central reservoir as we lay on gas and
water, though the experiment was certainly a very curious one.”
The importance of Mr. Gray’s, as of La Cour’s inventions, depends,
however, far more on the way in which they increase the message-bearing
capacity of telegraphy than on their power of conveying airs to a
distance. At the Philadelphia Exhibition, Sir W. Thomson heard four
messages sounded simultaneously by the Gray telephone. The Morse
alphabet was used. I have mentioned that in that alphabet various
combinations of dots and dashes are used to represent different
letters; it is only necessary to substitute the short and long duration
of a note for dots and dashes to have a similar sound alphabet.
Suppose, now, four tuning-forks at the transmitting station, whose
notes are _Do_ [Illustration], _Mi_, _Sol_, and _Do_ [Illustration],
or say _C_, _E_, _G_, and _C_´, then by each of these forks a
separate message may be transmitted, all the messages being carried
simultaneously by the same line to separate sounding reeds (or forks,
if preferred), and received by different clerks. With a suitable
key-board, a single clerk could send the four messages simultaneously,
striking chords instead of single notes, though considerable practice
would be necessary to transform four verbal messages at once into the
proper telephonic music, and some skill in fingering to give the proper
duration to each note.
Lastly, we come to the greatest achievement of all, Professor Graham
Bell’s vocal telephone. In the autumn of 1875 I had the pleasure
of hearing from Professor Bell in the course of a ride—all too
short—from Boston to Salem, Mass., an account of his instrument as
then devised, and of his hopes as to future developments. These hopes
have since been in great part fulfilled, but I venture to predict that
we do not yet know all, or nearly all, that the vocal telephone, in
Bell’s hands, is to achieve.
It ought to be mentioned at the outset that Bell claims to have
demonstrated in 1873 (a year before La Cour) the possibility of
transmitting several messages simultaneously by means of the Morse
alphabet.
Bell’s original arrangement for vocal telephony was as follows:—At one
station a drumhead of goldbeaters’ skin, about 2¾ inches in diameter,
was placed in front of an electro-magnet. To the middle of the
drumhead, on the side towards the magnet, was glued a circular piece
of clockspring. A similar electro-magnet, drumhead, etc., were placed
at the other station. When notes were sung or words spoken before one
drumhead, the vibrations of the goldbeaters’ skin carried the small
piece of clockspring vibratingly towards and from the electro-magnet,
without producing actual contact. Now, the current which was passing
along the coil round the electro-magnet changed in strength with each
change of position of this small piece of metal. The more rapid the
vibrations, and the greater their amplitude, the more rapid and the
more intense were the changes in the power of the electric current.
Thus, the electro-magnet at the other station underwent changes of
power which were synchronous with, and proportionate to, those changes
of power in the current which were produced by the changes of position
of the vibrating piece of clockspring. Accordingly, the piece of
clockspring at the receiving station, and with it the drumhead there,
was caused by the electro-magnet to vibrate with the same rapidity and
energy as the piece at the transmitting station. Therefore, as the
drumhead at one station varied its vibrations in response to the sounds
uttered in its neighbourhood, so the drumhead at the other station,
varying its vibrations, emitted similar sounds. Later, the receiving
drumhead was made unlike the transmitting one. Instead of a membrane
carrying a small piece of metal, a thin and very flexible disc of
sheet-iron, held in position by a screw, was used. This disc, set in
vibration by the varying action of an electro-magnet, as in the older
arrangement, uttered articulate sounds corresponding to those which,
setting in motion the membrane at the transmitting station, caused the
changes in the power of the electric current and in the action of the
electro-magnet.
At the meeting of the British Association in 1876 Sir W. Thomson gave
the following account of the performance of this instrument at the
Philadelphia Exhibition:—“In the Canadian department” (for Professor
Bell was not at the time an American citizen) “I heard ‘To be or not
to be—there’s the rub,’ through the electric wire; but, scorning
monosyllables, the electric articulation rose to higher flights, and
gave me passages taken at random from the New York newspapers:—‘S. S.
Cox has arrived’ (I failed to make out the ‘S. S. Cox’), ‘the City
of New York,’ ‘Senator Morton,’ ‘the Senate has resolved to print a
thousand extra copies,’ ‘the Americans in London have resolved to
celebrate the coming Fourth of July.’ All this my own ears heard
spoken to me with unmistakable distinctness by the thin circular disc
armature of just such another little electro-magnet as this which I
hold in my hand. The words were shouted with a clear and loud voice
by my colleague judge, Professor Watson, at the far end of the line,
holding his mouth close to a stretched membrane, carrying a piece of
soft iron, which was thus made to perform in the neighbourhood of an
electro-magnet, in circuit with the line, motions proportional to the
sonorific motions of the air. This, the greatest by far of all the
marvels of the electric telegraph, is due to a young countryman of
our own, Mr. Graham Bell, of Edinburgh, and Montreal, and Boston, now
about to become a naturalized citizen of the United States. Who can
but admire the hardihood of invention which devised such very slight
means to realize the mathematical conception that, if electricity is
to convey all the delicacies of quality which distinguish articulate
speech, the strength of its current must vary continuously, and as
nearly as may be in simple proportion to the velocity of a particle of
air engaged in constituting the sound?”
Since these words were spoken by one of the highest authorities in
matters telegraphic, Professor Bell has introduced some important
modifications in his apparatus. He now employs, not an electro-magnet,
but a permanent magnet. That is to say, instead of using at each
station such a bar of soft iron as is shown in Fig. 6, which becomes
a magnet while the electric current is passing through the coil
surrounding it, he uses at each station a bar of iron permanently
magnetized (or preferably a powerful magnet made of several horse-shoe
bars—that is, a compound magnet), surrounded similarly by coils of
wire. No battery is needed. Instead of a current through the coils
magnetizing the iron, the iron already magnetized causes a current
to traverse the coils whenever it acts, or rather whenever its action
changes. If an armature were placed across its ends or poles, at
the moment when it drew that armature to the poles by virtue of its
magnetic power, a current would traverse the coils; but afterwards,
so long as the armature remained there, there would be no current. If
an armature placed near the poles were shifted rapidly in front of
the poles, currents would traverse the coils, or be induced, their
intensity depending on the strength of the magnet, the length of the
coil, and the rapidity and range of the motions. In front of the
poles of the magnet is a diaphragm of very flexible iron (or else
some other flexible material bearing a small piece of iron on the
surface nearest the poles). A mouthpiece to converge the sound upon
this diaphragm substantially completes the apparatus at each station.
Professor Bell thus describes the operation of the instrument:—“The
motion of steel or iron in front of the poles of a magnet creates a
current of electricity in coils surrounding the poles of the magnet,
and the duration of this current of electricity coincides with the
duration of the motion of the steel or iron moved or vibrated in the
proximity of the magnet. When the human voice causes the diaphragm to
vibrate, electrical undulations are induced in the coils around the
magnets precisely similar to the undulations of the air produced by the
voice. The coils are connected with the line wire, and the undulations
induced in them travel through the wire, and, passing through the coils
of another instrument of similar construction at the other end of the
line, are again resolved into air undulations by the diaphragm of this
(other) instrument.”
So perfectly are the sound undulations repeated—though the instrument
has not yet assumed its final form—that not only has the lightest
whisper uttered at one end of a line of 140 miles been distinctly heard
at the other, but the speaker can be distinguished by his voice when he
is known to the listener. So far as can be seen, there is every room
to believe that before long Professor Bell’s grand invention will be
perfected to such a degree that words uttered on the American side of
the Atlantic will be heard distinctly after traversing 2000 miles under
the Atlantic, at the European end of the submarine cable—so that Sir
W. Thomson at Valentia could tell by the voice whether Graham Bell,
or Cyrus Field, or his late colleague Professor Watson, were speaking
to him from Newfoundland. Yet a single wave of those which toss in
millions on the Atlantic, rolling in on the Irish strand, would utterly
drown the voices thus made audible after passing beneath two thousand
miles of ocean.
Here surely is the greatest of telegraphic achievements. Of all the
marvels of telegraphy—and they are many—none are equal to, none
seem even comparable with, this one. Strange truly is the history of
the progress of research which has culminated in this noble triumph,
wonderful the thought that from the study of the convulsive twitchings
of a dead frog by Galvani, and of the quivering of delicately poised
magnetic needles by Ampère, should gradually have arisen through
successive developments a system of communication so perfect and so
wonderful as telegraphy has already become, and promising yet greater
marvels in the future.
The last paragraph had barely been written when news arrived of another
form of telephone, surpassing Gray’s and La Cour’s in some respects as
a conveyor of musical tones, but as yet unable to speak like Bell’s. It
is the invention of Mr. Edison, an American electrician. He calls it
the motograph. He discovered about six years ago the curious property
on which the construction of the instrument depends. If a piece of
paper moistened with certain chemical solutions is laid upon a metallic
plate connected with the positive pole of a galvanic battery, and a
platinum wire connected with the negative pole is dragged over the
moistened paper, the wire slides over the paper like smooth iron over
ice—the usual friction disappearing so long as the current is passing
from the wire to the plate through the paper. At the receiving station
of Mr. Edison’s motograph there is a resonating box, from one face
of which extends a spring bearing a platinum point, which is pressed
by the spring upon a tape of chemically prepared paper. This tape is
steadily unwound, drawing by its friction the platinum point, and
with it the face of the resonator, outwards. This slight strain on
the face of the resonator continues so long as no current passes from
the platinum point to the metallic drum over which the moistened tape
is rolling. But so soon as a current passes, the friction immediately
ceases, and the face of the resonator resumes its normal position. If
then at the transmitting station there is a membrane or a very fine
diaphragm (as in Reuss’s or Bell’s arrangement) which is set vibrating
by a note of any given tone, the current, as in those arrangements, is
transmitted and stopped at intervals corresponding to the tone, and the
face of the resonating box is freed and pulled at the same intervals.
Hence, it speaks the corresponding tone. The instrument appears to have
the advantage over Gray’s in range. In telegraphic communication Gray’s
telephone is limited to about one octave. Edison’s extends from the
deepest bass notes to the highest notes of the human voice, which, when
magnets are employed, are almost inaudible. But Edison’s motograph has
yet to learn to speak.
Other telegraphic marvels might well find a place here. I might speak
of the wonders of submarine telegraphy, and of the marvellous delicacy
of the arrangements by which messages by the Atlantic Cable are read,
and not only read, but made to record themselves. I might dwell, again,
on the ingenious printing telegraph of Mr. Hughes, which sets up its
own types, inks them, and prints them, or on the still more elaborate
plan of the Chevalier Bonelli “for converting the telegraph stations
into so many type-setting workshops.” But space would altogether
fail me to deal properly with these and kindred marvels. There is,
however, one application of telegraphy, especially interesting to the
astronomer, about which I must say a few words: I mean, the employment
of electricity as a regulator of time. Here again it is the principle
of the system, rather than details of construction, which I propose to
describe. Suppose we have a clock not only of excellent construction,
but under astronomical surveillance, so that when it is a second or so
in error it is set right again by the stars. Let the pendulum of this
clock beat seconds; and at each beat let a galvanic current be made and
broken. This may be done in many ways—thus the pendulum may at each
swing tilt up a very light metallic hammer, which forms part of the
circuit when down; or the end of the pendulum may be covered with some
non-conducting substance which comes at each swing between two metallic
springs in very light contact, separating them and so breaking circuit;
or in many other ways the circuit may be broken. When the circuit
is made, let the current travel along a wire which passes through a
number of stations near or remote, traversing at each the coils of a
temporary magnet. Then, at each swing of the pendulum of the regulating
clock, each magnet is magnetized and demagnetized. Thus each, once in
a second, draws to itself, and then releases its armature, which is
thereupon pulled back by a spring. Let the armature, when drawn to the
magnet, move a lever by which one tooth of a wheel is carried forward.
Then the wheel is turned at the rate of one tooth per second. This
wheel communicates motion to others in the usual way. In fact, we have
at each station a clock driven, _not_ by a weight or spring and with a
pendulum which allows one tooth of an escapement wheel to pass at each
swing, but by the distant regulating clock which turns a driving wheel
at the rate of one tooth per second, that is, one tooth for each swing
of the regulating clock’s pendulum. Each clock, then, keeps perfect
time with the regulating clock. In astronomy, where it is often of the
utmost importance to secure perfect synchronism of observation, or the
power of noting the exact difference of time between observations made
at distant stations, not only can the same clock thus keep time for
two observers hundreds of miles apart, but each observer can record by
the same arrangement the moment of the occurrence of some phenomenon.
For if a tape be unwound automatically, as in the Morse instrument,
it is easy so to arrange matters that every second’s beat of the
pendulum records itself by a dot or short line on the tape, and that
the observer can with a touch make (or break) contact at the instant of
observation, and so a mark be made properly placed between two seconds’
marks—thus giving the precise time when the observation was made. Such
applications, however, though exceedingly interesting to astronomers,
are not among those in which the general public take chief interest.
There was one occasion, however, when astronomical time-relations were
connected in the most interesting manner with one of the greatest of
all the marvels of telegraphy: I mean, when the _Great Eastern_ in
mid-ocean was supplied regularly with Greenwich time, and this so
perfectly (and therefore with such perfect indication of her place in
the Atlantic), that when it was calculated from the time-signals that
the buoy left in open ocean to mark the place of the cut cable had been
reached, and the captain was coming on deck with several officers to
look for it, the buoy announced its presence by thumping the side of
the great ship.
_THE PHONOGRAPH, OR VOICE-RECORDER._
In the preceding essay I have described the wonderful instrument called
the telephone, which has recently become as widely known in this
country as in America, the country of its first development. I propose
now briefly to describe another instrument—the phonograph—which,
though not a telegraphic instrument, is related in some degree to the
telephone. In passing, I may remark that some, who as telegraphic
specialists might be expected to know better, have described the
phonograph as a telegraphic invention. A writer in the _Telegraphic
Journal_, for instance, who had mistaken for mine a paper on the
phonograph in one of our daily newspapers, denounced me (as the
supposed author of that paper) for speaking of the possibility of
crystallizing sound by means of this instrument; and then went on to
speak of the mistake I (that is, said author) had made in leaving my
own proper subject of study to speak of telegraphic instruments and
to expatiate on the powers of electricity. In reality the phonograph
has no relation to telegraphy whatever, and its powers do not in the
slightest degree depend on electricity. If the case had been otherwise,
it may be questioned whether the student of astronomy, or of any other
department of science, should be considered incompetent of necessity
to describe a telegraphic instrument, or to discuss the principles
of telegraphic or electrical science. What should unquestionably be
left to the specialist, is the description of the practical effect of
details of instrumental construction, and the like—for only he who is
in the habit of using special instruments or classes of instrument can
be expected to be competent adequately to discuss such matters.
Although, however, the phonograph is not an instrument depending, like
the telephone, on the action of electricity (in some form or other),
yet it is related closely enough to the telephone to make the mistake
of the _Telegraphic_ journalist a natural one. At least, the mistake
would be natural enough for any one but a telegraphic specialist; the
more so that Mr. Edison is a telegraphist, and that he has effected
several important and interesting inventions in telegraphic and
electrical science. For instance, in the previous article, pp. 270,
271, I had occasion to describe at some length the principles of his
“Motograph.” I spoke of it as “another form of telephone, surpassing
Gray’s and La Cour’s in some respects as a conveyer of musical
tones, but as yet unable to speak like Bell’s ... in telegraphic
communication.” I proceeded: “Gray’s telephone is limited to about one
octave. Edison’s extends from the deepest bass notes to the highest
notes of the human voice, which, when magnets are employed, are almost
inaudible; but it has yet to learn to speak.”
The phonograph is an instrument which _has_ learned to speak, though
it does not speak at a distance like the telephone or the motograph.
Yet there seems no special reason why it should not combine both
qualities—the power of repeating messages at considerable intervals of
time after they were originally spoken, and the power of transmitting
them to great distances.
I have said that the phonograph is an instrument closely related to the
telephone. If we consider this feature of the instrument attentively,
we shall be led to the clearer recognition of the acoustical principles
on which its properties depend, and also of the nature of some of the
interesting acoustical problems on which light seems likely to be
thrown by means of experiments with this instrument.
In the telephone a stretched membrane, or a diaphragm of very flexible
iron, vibrates when words are uttered in its neighbourhood. When
a stretched membrane is used, with a small piece of iron at the
centre, this small piece of iron, as swayed by the vibrations of the
membrane, causes electrical undulations to be induced in the coils
round the poles of a magnet placed in front of the membrane. These
undulations travel along the wire and pass through the coils of another
instrument of similar construction at the other end of the wire, where,
accordingly, a stretched membrane vibrates precisely as the first had
done. The vibrations of this membrane excite atmospheric vibrations
identical in character with those which fell upon the first membrane
when the words were uttered in its neighbourhood; and therefore the
same words appear to be uttered in the neighbourhood of the second
membrane, however far it may be from the transmitting membrane, so only
that the electrical undulations are effectually transmitted from the
sending to the receiving instrument.
I have here described what happened in the case of that earlier form
of the telephone in which a stretched membrane of some such substance
as goldbeater’s skin was employed, at the centre of which only was
placed a small piece of iron. For in its bearing on the subject of
the phonograph, this particular form of telephonic diaphragm is
more suggestive than the later form in which very flexible iron was
employed. We see that the vibrations of a small piece of iron at the
centre of a membrane are competent to reproduce all the peculiarities
of the atmospheric waves which fall upon the membrane when words are
uttered in its neighbourhood. This must be regarded, I conceive, as a
remarkable acoustical discovery. Most students of acoustics would have
surmised that to reproduce the motions merely of the central parts
of a stretched diaphragm would be altogether insufficient for the
reproduction of the complicated series of sound-waves corresponding to
the utterance of words. I apprehend that if the problem had originally
been suggested simply as an acoustical one, the idea entertained
would have been this—that though the motions of a diaphragm receiving
vocal sound-waves _might_ be generated artificially in such sort as to
produce the same vocal sounds, yet this could only be done by first
determining what particular points of the diaphragm were centres of
motion, so to speak, and then adopting some mechanical arrangements for
giving to small portions of the membrane at these points the necessary
oscillating motions. It would not, I think, have been supposed that
motions communicated to the centre of the diaphragm would suffice to
make the whole diaphragm vibrate properly in all its different parts.
Let us briefly consider what was before known about the vibrations
of plates, discs, and diaphragms, when particular tones were sounded
in their neighbourhood; and also what was known respecting the
requirements for vocal sounds and speech as distinguished from simple
tones. I need hardly say that I propose only to consider these points
in a general, not in a special, manner.
We must first carefully draw a distinction between the vibrations of a
plate or disc which is itself the source of sound, and those vibrations
which are excited in a plate or disc by sound-waves otherwise
originated. If a disc or plate of given size be set in vibration by a
blow or other impulse it will give forth a special sound, according to
the place where it is struck, or it will give forth combinations of
the several tones which it is capable of emitting. On the other hand,
experiment shows that a diaphragm like that used in the telephone—not
only the electric telephone, but such common telephones as have been
sold of late in large quantities in toy shops, etc.—will respond
to any sounds which are properly directed towards it, not merely
reproducing sounds of different tones, but all the peculiarities which
characterize vocal sounds. In the former case, the size of a disc and
the conditions under which it is struck determine the nature of its
vibrations, and the air responds to the vibrations thus excited; in the
latter, the air is set moving in vibrations of a special kind by the
sounds or words uttered, and the disc or diaphragm responds to these
vibrations. Nevertheless, though it is important that this distinction
be recognized, we can still learn, from the behaviour of discs and
plates set in vibration by a blow or other impulse, the laws according
to which the actual motions of the various parts of a vibrating disc
or plate take place. We owe to Chladni the invention of a method for
rendering visible the nature of such motions.
Certain electrical experiments of Lichtenberg suggested to Chladni
the idea of scattering fine sand over the plate or disc whose motions
he wished to examine. If a horizontal plate covered with fine sand is
set in vibration, those parts which move upwards and downwards scatter
the sand from their neighbourhood, while on those points which undergo
no change of position the sand will remain. Such points are called
_nodes_; and rows of such points are called _nodal lines_, which may be
either straight or curved, according to circumstances.
If a square plate of glass is held by a suitable clamp at its centre,
and the middle point of a side is touched while a bow is drawn across
the edge near a corner, the sand is seen to gather in the form of a
cross dividing the square into four equal squares—like a cross of St
George. If the finger touches a corner, and the bow is drawn across the
middle of a side, the sand forms a cross dividing the square along its
diagonals—like a cross of St Andrew. Touching two points equidistant
from two corners, and drawing the bow along the middle of the opposite
edge, we get the diagonal cross and also certain curved lines of
sand systematically placed in each of the four quarters into which
the diagonals divide the square. We also have, in this case, a far
shriller note from the vibrating plate. And so, by various changes in
the position of the points clamped by the finger and of the part of the
edge along which the bow is drawn, we can obtain innumerable varieties
of nodal lines and curves along which the sand gathers upon the surface
of the vibrating plate.
When we take a circular plate of glass, clamped at the middle, and
touching one part of its edge with the finger, draw the bow across a
point of the edge half a quadrant from the finger, we see the sand
arrange itself along two diameters intersecting at right angles. If the
bow is drawn at a point one-third a quadrant from the finger-clamped
point, we get a six-pointed star. If the bow is drawn at a point
a fourth of a quadrant from the finger-clamped point, we get an
eight-pointed star. And so we can get the sand to arrange itself into a
star of any even number of points; that is, we can get a star of four,
six, eight, ten, twelve, etc., points, but not of three, five, seven,
etc.
In these cases the centre of the plate or disc has been fixed. If,
instead, the plate or disc be fixed by a clip at the edge, or clamped
elsewhere than at the centre, we find the sand arranging itself into
other forms, in which the centre may or may not appear; that is, the
centre may or may not be nodal, according to circumstances.
A curious effect is produced if very fine powder be strewn along
with the sand over the plate. For it is found that the dust gathers,
not where the nodes or places of no vibration lie, but where the
motion is greatest. Faraday assigns as the cause of this peculiarity
the circumstance that “the light powder is entangled by the little
whirlwinds of air produced by the vibrations of the plate; it cannot
escape from the little cyclones, though the heavier sand particles are
readily driven through them; when, therefore, the motion ceases, the
light powder settles down in heaps at the places where the vibration
was a maximum.” In proof of this theory we have the fact that “in vacuo
no such effect is produced; all powders light and heavy move to the
nodal lines.” (Tyndall on “Sound.”)
Now if we consider the meaning of such results as these, we shall begin
to recognize the perplexing but also instructive character of the
evidence derived from the telephone, and applied to the construction
of the phonograph. It appears that when a disc is vibrating under such
special conditions as to give forth a particular series of tones (the
so-called fundamental tone of the disc and other tones combined with it
which belong to its series of overtones), the various parts of the disc
are vibrating to and fro in a direction square to the face of the disc,
except certain points at which there is no vibration, these points
together forming curves of special forms along the substance of the
disc.
When, on the other hand, tones of various kinds are sounded in the
neighbourhood of a disc or of a stretched circular membrane, we may
assume that the different parts of the disc are set in vibration after
a manner at least equally complicated. If the tones belong to the
series which could be emitted by the diaphragm when struck, we can
understand that the vibrations of the diaphragm would resemble those
which would result from a blow struck under special conditions. When
other tones are sounded, it may be assumed that the sound-waves which
reach the diaphragm cause it to vibrate as though not the circumference
(only) but a circle in the substance of the diaphragm—concentric,
of course, with the circumference, and corresponding in dimensions
with the tone of the sounds—were fixed. If a drum of given size is
struck, we hear a note of particular tone. If we heard, as the result
of a blow on the same drum, a much higher tone, we should know that
in some way or other the effective dimensions of the drum-skin had
been reduced—as for instance, by a ring firmly pressed against the
inside of the skin. So when a diaphragm is responding to tones other
than those corresponding to its size, tension, etc., we infer that the
sound-waves reaching it cause it to behave, so far as its effective
vibrating portion is concerned, as though its conformation had altered.
When several tones are responded to by such a diaphragm, we may infer
that the vibrations of the diaphragm are remarkably complicated.
Now the varieties of vibratory motion to which the diaphragm of the
telephone has been made to respond have been multitudinous. Not only
have all orders of sound singly and together been responded to, but
vocal sounds which in many respects differ widely from ordinary tones
are repeated, and the peculiarities of intonation which distinguish one
voice from another have been faithfully reproduced.
Let us consider in what respects vocal sounds, and especially the
sounds employed in speech, differ from mere combinations of ordinary
tones.
It has been said, and with some justice, that the organ of voice
is of the nature of a reed instrument. A reed instrument, as most
persons know, is one in which musical sounds are produced by the
action of a vibrating reed in breaking up a current of air into a
series of short puffs. The harmonium, accordion, concertina, etc.,
are reed instruments, the reed for each note being a fine strip of
metal vibrating in a slit. The vocal organ of man is at the top of
the windpipe, along which a continuous current of air can be forced
by the lungs. Certain elastic bands are attached to the head of the
windpipe, almost closing the aperture. These vocal chords are thrown
into vibration by the current of air from the lungs; and as the rate
of their vibration is made to vary by varying their tension, the sound
changes in tone. So far, we have what corresponds to a reed instrument
admitting of being altered in pitch so as to emit different notes.
The mouth, however, affects the character of the sound uttered from
the throat. The character of a _tone_ emitted by the throat cannot be
altered by any change in the configuration of the mouth; so that if a
single tone were in reality produced by the vocal chords, the resonance
of the mouth would only strengthen that tone more or less according to
the figure given to the cavity of the mouth at the will of the singer
or speaker. But in reality, besides the fundamental tone uttered by
the vocal chords, a series of overtones are produced. Overtones are
tones corresponding to vibration at twice, three times, four times,
etc., the rate of the vibration producing the fundamental tone. Now the
cavity of the mouth can be so modified in shape as to strengthen either
the fundamental tone or any one of these overtones. And according as
special tones are strengthened in this way various vocal sounds are
produced, without changing the pitch or intensity of the sound actually
uttered. Calling the fundamental tone the first tone, the overtones
just mentioned the second, third, fourth, etc., tones respectively
(after Tyndall), we find that the following relations exist between the
combinations of these tones and the various vowel sounds:—
If the lips are pushed forward so as to make the cavity of the mouth
deep and the orifice of the mouth small, we get the deepest resonance
of which the mouth is capable, the fundamental tone is reinforced,
while the higher tones are as far as possible thrown into the shade.
The resulting vowel sound is that of deep U (“oo” in “hoop”).
If the mouth is so far opened that the fundamental tone is accompanied
by a strong second tone (the next higher octave to the fundamental
tone), we get the vowel sound O (as in “hole”). The third and fourth
tones feebly accompanying the first and second make the sound more
perfect, but are not necessary.
If the orifice of the mouth is so widened, and the volume of the cavity
so reduced, that the fundamental tone is lost, the second somewhat
weakened, and the third given as the chief tone, with very weak fourth
and fifth tones, we have the vowel sound A.
To produce the vowel sound E, the resonant cavity of the mouth must be
considerably reduced. The fourth tone is the characteristic of this
vowel. Yet the second tone also must be given with moderate strength.
The first and third tones must be weak, and the fifth tone should be
added with moderate strength.
To produce the vowel sound A, as in “far,” the higher overtones are
chiefly used, the second is wanting altogether, the third feeble, the
higher tones—especially the fifth and seventh—strong.
The vowel sound I, as in “fine,” it should be added, is not a simple
sound, but diphthongal. The two sounds whose succession gives the sound
we represent (erroneously) by a single letter I (long), are not very
different from “a” as in “far,” and “ee” (or “i” as in “ravine”);
they, lie, however, in reality, respectively between “a” in “far” and
“fat,” and “i” in “ravine” and “pin.” Thus the tones and overtones
necessary for sounding “I” long, do not require a separate description,
any more than those necessary for sounding other diphthongs, as “oi,”
“oe,” and so forth.
We see, then, that the sound-waves necessary to reproduce accurately
the various vowel sounds, are more complicated than those which would
correspond to the fundamental tones simply in which any sound may be
uttered. There must not only be in each case certain overtones, but
each overtone must be sounded with its due degree of strength.
But this is not all, even as regards the vowel sounds, the most
readily reproducible peculiarities of ordinary speech. Spoken sounds
differ from musical sounds properly so called, in varying in pitch
throughout their continuance. So far as tone is concerned, apart from
vowel quality, the speech note may be imitated by sliding a finger up
the finger-board of a violin while the bow is being drawn. A familiar
illustration of the varying pitch of a speech note is found in the
utterance of Hamlet’s question, “Pale, or red?” with intense anxiety of
inquiry, if one may so speak. “The speech note on the word ‘pale’ will
consist of an upward movement of the voice, while that on ‘red’ will
be a downward movement, and in both words the voice will traverse an
interval of pitch so wide as to be conspicuous to ordinary ears; while
the cultivated perception of the musician will detect the voice moving
through a less interval of pitch while he is uttering the word ‘or’
of the same sentence. And he who can record in musical notation the
sounds which he hears, will perceive the musical interval traversed in
these vocal movements, and the place also of these speech notes on the
musical staff.” Variations of this kind, only not so great in amount,
occur in ordinary speech; and no telephonic or phonographic instrument
could be regarded as perfect, or even satisfactory, which did not
reproduce them.
But the vowel sounds are, after all, combinations and modifications
of musical tones. It is otherwise with consonantal sounds, which, in
reality, result from various ways in which vowel sounds are commenced,
interrupted (wholly or partially), and resumed. In one respect this
statement requires, perhaps, some modification—a point which has not
been much noticed by writers on vocal sounds. In the case of liquids,
vowel sounds are not partially interrupted only, as is commonly stated.
They cease entirely as vowel sounds, though the utterance of a vocal
sound is continued when a liquid consonant is uttered. Let the reader
utter any word in which a liquid occurs, and he will find that while
the liquid itself is sounded the vowel sounds preceding or following
the liquid cease entirely. Repeating slowly, for example, the word
“remain,” dwelling on all the liquids, we find that while the “r” is
being sounded the “ē” sound cannot be given, and this sound ceases so
soon as the “m” is sounded; similarly the long “a” sound can only be
uttered when the “m” sound ceases, and cannot be carried on into the
sound of the final liquid “n.” The liquids are, in fact, improperly
called semi-vowels, since no vowel sound can accompany their utterance.
The tone, however, with which they are sounded can be modified during
their utterance. In sounding labials the emission of air is not stopped
completely at any moment. The same is true of the sibilants s, z, sh,
zh, and of the consonants g, j, f, v, th (hard and soft). These are
called, on this account, _continuous_ consonants. The only consonants
in pronouncing which the emission of air is for a moment entirely
stopped, are the true mutes, sometimes called the six _explosive_
consonants, b, p, t, d, k, and g.
To reproduce artificially sounds resembling those of the consonants
in speech, we must for a moment interrupt, wholly for explosive and
partially for continuous consonant sounds, the passage of air through a
reed pipe. Tyndall thus describes an experiment of this kind in which
an imperfect imitation of the sound of the letter “m” was obtained—an
imitation only requiring, to render it perfect, as I have myself
experimentally verified, attention to the consideration respecting
liquids pointed out in the preceding paragraph. “Here,” says Tyndall,
describing the experiment as conducted during a lecture, “is a free
reed fixed in a frame, but without any pipe associated with it, mounted
on the acoustic bellows. When air is urged through the orifice, it
speaks in this forcible manner. I now fix upon the frame of the reed
a pyramidal pipe; you notice a change in the clang, and, by pushing
my flat hand over the open end of the pipe, the similarity between
the sounds produced and those of the human voice is unmistakable.
Holding the palm of my hand over the end of the pipe, so as to close
it altogether, and then raising my hand twice in quick succession, the
word ‘mamma’ is heard as plainly as if it were uttered by an infant.
For this pyramidal tube I now substitute a shorter one, and with it
make the same experiment. The ‘mamma’ now heard is exactly such as
would be uttered by a child with a stopped nose. Thus, by associating
with a vibrating reed a suitable pipe, we can impart to the sound of
the reed the qualities of the human voice.” The “m” obtained in these
experiments was, however, imperfect. To produce an “m” sound such as an
adult would utter without a “stopped nose,” all that is necessary is
to make a small opening (experiment readily determines the proper size
and position) in the side of the pyramidal pipe, so that, as in the
natural utterance of this liquid, the emission of air is not altogether
interrupted.
I witnessed in 1874 some curious illustrations of the artificial
production of vocal sounds, at the Stevens Institute, Hoboken,
N.J., where the ingenious Professor Mayer (who will have, I trust,
a good deal to say about the scientific significance of telephonic
and phonographic experiments before long) has acoustic apparatus,
including several talking-pipes. By suitably moving his hand on the top
of some of these pipes, he could make them speak certain words with
tolerable distinctness, and even utter short sentences. I remember
the performance closed with the remarkably distinct utterance, by one
profane pipe, of the words euphemistically rendered by Mark Twain (in
his story of the Seven Sleepers, I think), “Go thou to Hades!”
Now, the speaking diaphragm in the telephone, as in the phonograph,
presently to be described, must reproduce not only all the varieties
of sound-wave corresponding to vowel sounds, with their intermixtures
of the fundamental tone and its overtones and their inflexions or
sliding changes of pitch, but also all the effects produced on the
receiving diaphragm by those interruptions, complete or partial, of
aerial emission which correspond to the pronunciation of the various
consonant sounds. It might certainly have seemed hopeless, from all
that had been before known or surmised respecting the effects of aerial
vibrations on flexible diaphragms, to attempt to make a diaphragm speak
artificially—in other words, to make the movements of all parts of
it correspond with those of a diaphragm set in vibration by spoken
words—by movements affecting only its central part. It is in the
recognition of the possibility of this, or rather in the discovery
of the fact that the movements of a minute portion of the middle of
a diaphragm regulate the vibratory and other movements of the entire
diaphragm, that the great scientific interest of Professor Graham
Bell’s researches appears to me to reside.
It may be well, in illustration of the difficulties with which formerly
the subject appeared to be surrounded, to describe the results of
experiments which preceded, though they can scarcely be said to have
led up to, the invention of artificial ways of reproducing speech.
I do not now refer to experiments like those of Kratzenstein of
St. Petersburg, and Von Kempelen of Vienna, in 1779, and the more
successful experiments by Willis in later years, but to attempts
which have been made to obtain material records of the aerial motions
accompanying the utterance of spoken words. The most successful of
these attempts was that made by Mr. W. H. Barlow. His purpose was “to
construct an instrument which should record the pneumatic actions”
accompanying the utterance of articulated sounds “by diagrams, in
a manner analogous to that in which the indicator-diagram of a
steam-engine records the action of the engine.” He perceived that the
actual aerial pressures involved being very small and very variable,
and the succession of impulses and changes of pressure being very
rapid, it was necessary that the moving parts should be very light,
and that the movement and marking should be accomplished with as
little friction as possible. The instrument he constructed consisted
of a small speaking-trumpet about four inches long, having an ordinary
mouthpiece connected to a tube half an inch in diameter, the thin end
of which widened out so as to form an aperture of 2¼ inches diameter.
This aperture was covered with a membrane of goldbeater’s skin, or thin
gutta-percha. A spring carrying a marker was made to press against the
membrane with a slight initial pressure, to prevent as far as possible
the effects of jarring and consequent vibratory action. A light arm
of aluminium was connected with the spring, and held the marker; and
a continuous strip of paper was made to pass under the marker in the
manner employed in telegraphy. The marker consisted of a small, fine
sable brush, placed in a light tube of glass one-tenth of an inch in
diameter, the tube being rounded at the lower end, and pierced with a
hole about one-twentieth of an inch in diameter. Through this hole the
tip of the brush projected, and was fed by colour put into the glass
tube by which it was held. It should be added that, to provide for the
escape of air passing through the speaking-trumpet, a small opening
was made in the side, so that the pressure exerted upon the membrane
was that due to the excess of air forced into the trumpet over that
expelled through the orifice. The strength of the spring which carried
the marker was so adjusted to the size of the orifice that, while the
lightest pressures arising under articulation could be recorded, the
greatest pressures should not produce a movement exceeding the width of
the paper.
“It will be seen,” says Mr. Barlow, “that in this construction of the
instrument the sudden application of pressure is as suddenly recorded,
subject only to the modifications occasioned by the inertia, momentum,
and friction of the parts moved. But the record of the sudden cessation
of pressure is further affected by the time required to discharge the
air through the escape-orifice. Inasmuch, however, as these several
effects are similar under similar circumstances, the same diagram
should always be obtained from the same pneumatic action when the
instrument is in proper adjustment; and this result is fairly borne out
by the experiments.”
The defect of the instrument consisted in the fact that it recorded
changes of pressure only; and in point of fact it seems to result,
from the experiments made with it, that it could only indicate the
order in which explosive, continuant, and liquid consonants succeeded
each other in spoken words, the vowels being all expressed in the
same way, and only one letter—the rough R, or R with a burr—being
always unmistakably indicated. The explosives were represented by a
sudden sharp rise and fall in the recorded curve; the height of the
rise depending on the strength with which the explosive is uttered,
not on the nature of the consonant itself. Thus the word “tick” is
represented by a higher elevation for the “t” than for the “k,” but the
word “kite” by a higher elevation for the “k” than for the “t.” It is
noteworthy that there is always a second smaller rise and fall after
the first chief one, in the case of each of the explosives. This shows
that the membrane, having first been forcibly distended by the small
aerial explosion accompanying the utterance of such a consonant, sways
back beyond the position where the pressure and the elasticity of the
membrane would (for the moment) exactly balance, and then oscillates
back again over that position before returning to its undistended
condition. Sometimes a third small elevation can be recognized,
and when an explosive is followed by a rolling “r” several small
elevations are seen. The continuous consonants produce elevations less
steep and less high; aspirates and sibilants give rounded hills. But
the results vary greatly according to the position of a consonant; and,
so far as I can make out from a careful study of the very interesting
diagrams accompanying Mr. Barlow’s paper, it would be quite impossible
to define precisely the characteristic records even of each order of
consonantal sounds, far less of each separate sound.
We could readily understand that the movement of the central part of
the diaphragm in the telephone should give much more characteristic
differences for the various sounds than Barlow’s logograph. For if
we imagine a small pointer attached to the centre of the face of the
receiving diaphragm while words are uttered in its neighbourhood, the
end of that pointer would not only move to and fro in a direction
square to the face of the diaphragm, as was the case with Barlow’s
marker, but it would also sway round its mean position in various small
circles or ovals, varying in size, shape, and position, according to
the various sounds uttered. We might expect, then, that if in any way
a record of the actual motions of the extremity of that small pointer
could be obtained, in such sort that its displacement in directions
square to the face of the diaphragm, as well as its swayings around
its mean position, would be indicated in some pictorial manner, the
study of such records would indicate the exact words spoken near the
diaphragm, and even, perhaps, the precise tones in which they were
uttered. For Barlow’s logograph, dealing with one only of the orders
of motion (really triple in character), gives diagrams in which the
general character of the sounds uttered is clearly indicated, and the
supposed records would show much more.
But although this might, from _à priori_ considerations, have been
reasonably looked for, it by no means follows that the actual results
of Bell’s telephonic experiments could have been anticipated. That the
movement of the central part of the diaphragm should suffice to show
that such and such words had been uttered, is one thing; but that these
movements should of themselves suffice, if artificially reproduced, to
cause the diaphragm to reproduce these words, is another and a very
different one. I venture to express my conviction that at the beginning
of his researches Professor Bell can have had very little hope that
any such result would be obtained, notwithstanding some remarkable
experiments respecting the transmission of sound which we can _now_
very clearly perceive to point in that direction.
When, however, he had invented the telephone, this point was in effect
demonstrated; for in that instrument, as we have seen, the movements
of the minute piece of metal attached (at least in the earlier forms
of the instrument) to the centre of the receiving membrane, suffice,
when precisely copied by the similar central piece of metal in the
transmitting membrane, to cause the words which produced the motions of
the receiving or hearing membrane to be uttered (or seem to be uttered)
by the transmitting or speaking membrane.
It was reserved, however, for Edison (of New Jersey, U.S.A., Electrical
Adviser to the Western Union Telegraph Company) to show how advantage
might be taken of this discovery to make a diaphragm speak, not
directly through the action of the movements of a diaphragm affected by
spoken words or other sounds, and therefore either simultaneously with
these or in such quick succession after them as corresponds with the
transmission of their effects along some line of electrical or other
communication, but by the mechanical reproduction of similar movements
at any subsequent time (within certain limits at present, but probably
hereafter with practically unlimited extension as to time).
The following is slightly modified from Edison’s own description of the
phonograph:—
The instrument is composed of three parts mainly; namely, a receiving,
a recording, and a transmitting apparatus. The receiving apparatus
consists of a curved tube, one end of which is fitted with a
mouthpiece. The other end is about two inches in diameter, and is
closed with a disc or diaphragm of exceedingly thin metal, capable of
being thrust slightly outwards or vibrated upon gentle pressure being
applied to it from within the tube. To the centre of this diaphragm
(which is vertical) is fixed a small blunt steel pin, which shares the
vibratory motion of the diaphragm. This arrangement is set on a table,
and can be adjusted suitably with respect to the second part of the
instrument—the recorder. This is a brass cylinder, about four inches
in length and four in diameter, cut with a continuous V-groove from
one end to the other, so that in effect it represents a large screw.
There are forty of these grooves in the entire length of the cylinder.
The cylinder turns steadily, when the instrument is in operation,
upon a vertical axis, its face being presented to the steel point of
the receiving apparatus. The shaft on which it turns is provided with
a screw-thread and works in a screwed bearing, so that as the shaft
is turned (by a handle) it not only turns the cylinder, but steadily
carries it upwards. The rate of this vertical motion is such that the
cylinder behaves precisely as if its groove worked in a screw-bearing.
Thus, if the pointer be set opposite the middle of the uppermost part
of the continuous groove at the beginning of this turning motion, it
will traverse the groove continuously to its lowest part, which it will
reach after forty turnings of the handle. (More correctly, perhaps, we
might say that the groove continuously traverses past the pointer.)
Now, suppose that a piece of some such substance as tinfoil is wrapped
round the cylinder. Then the pointer, when at rest, just touches the
tinfoil. But when the diaphragm is vibrating under the action of aerial
waves resulting from various sounds, the pointer vibrates in such a way
as to indent the tinfoil—not only to a greater or less depth according
to the play of the pointer to and fro in a direction square to the face
of the diaphragm, but also over a range all round its mean position,
corresponding to the play of the end of the pointer around _its_ mean
position. The groove allows the pressure of the pointer against the
tinfoil free action. If the cylinder had no groove the dead resistance
of the tinfoil, thus backed up by an unyielding surface, would stop
the play of the pointer. Under the actual conditions, the tinfoil
is only kept taut enough to receive the impressions, while yielding
sufficiently to let the play of the pointer continue unrestrained.
If now a person speaks into the receiving tube, and the handle of
the cylinder be turned, the vibrations of the pointer are impressed
upon the portion of the tinfoil lying over the hollow groove, and are
retained by it. They will be more or less deeply marked according to
the quality of the sounds emitted, and according also, of course, to
the strength with which the speaker utters the sounds, and to the
nature of the modulations and inflexions of his voice. The result is
a message verbally imprinted upon a strip of metal. It differs from
the result in the case of Barlow’s logograph, in being virtually a
record in three dimensions instead of one only. The varying depth of
the impressions corresponds to the varying height of the curve in
Barlow’s diagrams; but there the resemblance ceases; for that was
the single feature which Barlow’s logographs could present. Edison’s
imprinted words show, besides varying depth of impression, a varying
range on either side of the mean track of the pointer, and also—though
the eye is not able to detect this effect—there is a varying rate of
progression according as the end of the pointer has been swayed towards
or from the direction in which, owing to the motion of the cylinder,
the pointer is virtually travelling.
We may say of the record thus obtained that it is sound presented
in a visible form. A journalist who has written on the phonograph
has spoken of this record as corresponding to the crystallization of
sound. And another who, like the former, has been (erroneously, but
that is a detail) identified with myself, has said, in like fanciful
vein, that the story of Baron Münchausen hearing words which had been
frozen during severe cold melting into speech again, so that all the
babble of a past day came floating about his ears, has been realized
by Edison’s invention. Although such expressions may not be, and in
point of fact are not, strictly scientific, I am not disposed, for my
own part, to cavil with them. If they could by any possibility be taken
_au pied de la lettre_ (and, by the way, we find quite a new meaning
for this expression in the light of what is now known about vowels
and consonants), there would be valid objection to their use. But, as
no one supposes that Edison’s phonograph really crystallizes words or
freezes sounds, it seems hypercritical to denounce such expressions as
the critic of the _Telegraphic Journal_ has denounced them.
To return to Edison’s instrument.
Having obtained a material record of sounds, vocal or otherwise,
it remains that a contrivance should be adopted for making this
record reproduce the sounds by which it was itself formed. This is
effected by a third portion of the apparatus, the transmitter. This
is a conical drum, or rather a drum shaped like a frustum of a cone,
having its larger end open, the smaller—which is about two inches in
diameter—being covered with paper stretched tight like the parchment
of a drumhead. In front of this diaphragm is a light flat steel spring,
held vertically, and ending in a blunt steel point, which projects
from it and corresponds precisely with that on the diaphragm of the
receiver. The spring is connected with the paper diaphragm by a silken
thread, just sufficiently in tension to cause the outer face of the
diaphragm to be slightly convex. Having removed the receiving apparatus
from the cylinder and set the cylinder back to its original position,
the transmitting apparatus is brought up to the cylinder until the
steel point just rests, without pressure, in the first indentation
made in the tinfoil by the point of the receiver. If now the handle is
turned at the same speed as when the message was being recorded, the
steel point will follow the line of impression, and will vibrate in
periods corresponding to the impressions which were produced by the
point of the receiving apparatus. The paper diaphragm being thus set
into vibrations of the requisite kind in number, depth, and side-range,
there are produced precisely the same sounds that set the diaphragm of
the receiver into vibration originally. Thus the words of the speaker
are heard issuing from the conical drum in his own voice, tinged
with a slightly metallic or mechanical tone. If the cylinder be more
slowly turned when transmitting than it had been when receiving the
message, the voice assumes a base tone; if more quickly, the message
is given with a more treble voice. “In the present machine,” says the
account, “when a long message is to be recorded, so soon as one strip
of tinfoil is filled, it is removed and replaced by others, until the
communication has been completed. In using the machine for the purpose
of correspondence, the metal strips are removed from the cylinder
and sent to the person with whom the speaker desires to correspond,
who must possess a machine similar to that used by the sender. The
person receiving the strips places them in turn on the cylinder of
his apparatus, applies the transmitter, and puts the cylinder in
motion, when he hears his friend’s voice speaking to him from the
indented metal. And he can repeat the contents of the missive as often
as he pleases, until he has worn the metal through. The sender can
make an infinite number of copies of his communication by taking a
plaster-of-Paris cast of the original, and rubbing off impressions from
it on a clean sheet of foil.”
I forbear from dwelling further on the interest and value of this
noble invention, or of considering some of the developments which it
will probably receive before long, for already I have occupied more
space than I had intended. I have no doubt that in these days it will
bring its inventor less credit, and far less material gain, than would
be acquired from the invention of some ingenious contrivance for
destroying many lives at a blow, bursting a hole as large as a church
door in the bottom of an ironclad, or in some other way helping men to
carry out those destructive instincts which they inherit from savage
and brutal ancestors. But hereafter, when the representatives of the
brutality and savagery of our nature are held in proper disesteem, and
those who have added new enjoyments to life are justly valued, a high
place in the esteem of men will be accorded to him who has answered
one-half of the poet’s aspiration,
“Oh for the touch of a vanished hand,
And the sound of a voice that is still!”
* * * * *
NOTE.—Since the present paper was written, M. Aurel de Ratti has
made some experiments which he regards as tending to show that there
is no mechanical vibration. Thus, “when the cavities above and below
the iron disc of an ordinary telephone are filled with wadding, the
instrument will transmit and speak with undiminished clearness. On
placing a finger on the iron disc opposite the magnet, the instrument
will transmit and speak distinctly, only ceasing to act when sufficient
pressure is applied to bring plate and magnet into contact. Connecting
the centre of the disc by means of a short thread with an extremely
sensitive membrane, no sound is given out by the latter when a message
is transmitted. Bringing the iron cores of the double telephone in
contact with the disc, and pressing with the fingers against the
plate on the other side, a weak current from a Daniell cell produced
a distinct click in the plate, and on drawing a wire from the cell
over a file which formed part of the circuit, a rattling noise was
produced in the instrument.” If these experiments had been made
before the phonograph was invented, they would have suggested the
impracticability of constructing any instrument which would do what the
phonograph actually does, viz., cause sounds to be repeated by exciting
a merely mechanical vibration of the central part of a thin metallic
disc. But as the phonograph proves that this can actually be done,
we must conclude that M. Aurel de Ratti’s experiments will not bear
the interpretation he places upon them. They show, nevertheless, that
exceedingly minute vibrations of probably a very small portion of the
telephonic disc suffice for the distinct transmission of vocal sounds.
This might indeed be inferred from the experiments of M. Demozet, of
Nantes, who finds that the vibrations of the transmitting telephone
are in amplitude little more than 1-2000th those of the receiving
telephone.
_THE GORILLA AND OTHER APES._
About twenty-five centuries ago, a voyager called Hanno is said to
have sailed from Carthage, between the Pillars of Hercules—that is,
through the Straits of Gibraltar—along the shores of Africa. “Passing
the Streams of Fire,” says the narrator, “we came to a bay called the
Horn of the South. In the recess there was an island, like the first,
having a lake, and in this there was another island full of wild men.
But much the greater part of them were women, with hairy bodies, whom
the interpreters called ‘Gorillas.’ Pursuing them, we were not able to
take the men; they all escaped, being able to climb the precipices;
and defended themselves with pieces of rock. But three women, who bit
and scratched those who led them, were not willing to follow. However,
having killed them, we flayed them, and conveyed the skins to Carthage;
for we did not sail any further, as provisions began to fail.”[35]
In the opinion of many naturalists, the wild men of this story
were the anthropoid or manlike apes which are now called gorillas,
rediscovered recently by Du Chaillu. The region inhabited by the
gorillas is a well-wooded country, “extending about a thousand miles
from the Gulf of Guinea southward,” says Gosse; “and as the gorilla
is not found beyond these limits, so we may pretty conclusively infer
that the extreme point of Hanno was somewhere in this region.” I must
confess these inferences seem to me somewhat open to question, and
the account of Hanno’s voyage only interesting in its relation to the
gorilla, as having suggested the name now given to this race of apes.
It is not probable that Hanno sailed much further than Sierra Leone;
according to Rennell, the island where the “wild men” were seen, was
the small island lying close to Sherbro, some seventy miles south of
Sierra Leone. To have reached the gorilla district after doubling Cape
Verd—which is itself a point considerably south of the most southerly
city founded by Hanno—he would have had to voyage a distance exceeding
that of Cape Verd from Carthage. Nothing in the account suggests that
the portion of the voyage, after the colonizing was completed, had
so great a range. The behaviour of the “wild men,” again, does not
correspond with the known habits of the gorilla. The idea suggested
is that of a species of anthropoid ape far inferior to the gorilla in
strength, courage, and ferocity.
The next accounts which have been regarded as relating to the gorilla
are those given by Portuguese voyagers. These narratives have been
received with considerable doubt, because in some parts they seem
manifestly fabulous. Thus the pictures representing apes show also
huge flying dragons with a crocodile’s head; and we have no reason for
believing that batlike creatures like the pterodactyls of the greensand
existed in Africa or elsewhere so late as the time of the Portuguese
voyages of discovery. Purchas, in his history of Andrew Battell,
speaks of “a kinde of great apes, if they might so bee termed, of the
height of a man, but twice as bigge in feature of their limmes, with
strength proportionable, hairie all over, otherwise altogether like
men and women in their whole bodily shape, except that their legges
had no calves.” This description accords well with the peculiarities
of gorillas, and may be regarded as the first genuine account of these
animals. Battell’s contemporaries called the apes so described Pongoes.
It is probable that in selecting the name Pongo for the young gorilla
lately at the Westminster Aquarium, the proprietors of this interesting
creature showed a more accurate judgment of the meaning of Purchas’s
narrative than Du Chaillu showed of Hanno’s account, in calling the
great anthropoid ape of the Gulf of Guinea a gorilla.
I propose here briefly to sketch the peculiarities of the four apes
which approach nearest in form to man—the gorilla, the chimpanzee, the
orang-outang, and the gibbon; and then, though not dealing generally
with the question of our relationship to these non-speaking (and, in
some respects, perhaps, “unspeakable”) animals, to touch on some points
connected with this question, and to point out some errors which are
very commonly entertained on the subject.
It may be well, in the first place, to point out that the terms “ape,”
“baboon,” and “monkey” are no longer used as they were by the older
naturalists. Formerly the term “ape” was limited to tailless simians
having no cheek-pouches, and the same number of teeth as man; the
term “baboon” to short-tailed simians with dog-shaped heads; and the
term “monkey,” unless used generically, to the long-tailed species.
This was the usage suggested by Ray, and adopted systematically
thirty or forty years ago. But it is no longer followed, though no
uniform classification has been substituted for the old arrangement.
Thus Mivart divides the apes into two classes—calling the first the
_Simiadæ_, or Old World apes; and the second the _Cebidæ_, or New World
apes. He subdivides the _Simiadæ_ into (1) the _Siminæ_, including the
gorilla, chimpanzee, orang, and gibbon; (2) the _Semnopithecinæ_; and
(3) the _Cynopithecinæ_; neither of which subdivisions will occupy much
of our attention here, save as respects the third subdivision of the
_Cynopithecinæ_, viz., the _Cynocephali_, which includes the baboons.
The other great division, the _Cebidæ_, or New World apes, are for the
most part very unlike the Old World apes. None of them approach the
gorilla or orang-outang in size; most of them are long-tailed; and the
number and arrangement of the teeth is different. The feature, however,
which most naturalists have selected as the characteristic distinction
between the apes of the Old World and of the New World is the position
of the nostrils. The former are called Catarhine, a word signifying
that the nostrils are directed downwards; the latter are called
Platyrhine, or broad-nosed. The nostrils of all the Old World apes are
separated by a narrow cartilaginous plate or septum, whereas the septum
of the New World apes is broad. After the apes come, according to
Mivart’s classification, the half-apes or lemuroids.
I ought, perhaps, to have mentioned that Mivart, in describing the
lemuroids as the second sub-order of a great order of animals, the
Primates, speaks of a man as (zoologically speaking) belonging to the
first sub-order. So that, in point of fact, the two sub-orders are the
Anthropoids, including the Anthropos (man) and the Lemuroids, including
the lemur.
The classification here indicated will serve our present purpose
very well. But the reader is reminded that, as already mentioned,
naturalists do not adopt at present any uniform system of
classification. Moreover, the term _Simiadæ_ is usually employed—and
will be employed here—to represent the entire simian race, _i.e._,
both the Simiadæ and the Cebidæ of Mivart’s classification.
And now, turning to the Anthropoid apes, we find ourselves at the
outset confronted by the question, Which of the four apes, the gorilla,
the orang-outang, the chimpanzee, or the gibbon, is to be regarded
as nearest to man in intelligence? So far as bodily configuration is
concerned, our opinion would vary according to the particular feature
which we selected for consideration. But it will probably be admitted
that intelligence should be the characteristic by which our opinions
should be guided.
The gibbon may be dismissed at once, though, as will presently appear,
there are some features in which this ape resembles man more closely
than either the gorilla, the orang-outang, or the chimpanzee.
The gorilla must, I fear, be summarily ejected from the position of
honour to which he has been raised by many naturalists. Though the
gorilla is a much larger animal than the chimpanzee, his brain barely
equals the chimpanzee’s in mass. It is also less fully developed in
front. In fact Gratiolet asserts that of all the broad-chested apes,
the gorilla is—so far as brain character is concerned—the lowest
and most degraded. He regards the gorilla’s brain as only a more
advanced form of that of the brutal baboons, while the orang’s brain
is the culminating form of the gibbon type, and the chimpanzee’s the
culminating form of the macaque type. This does not dispose of the
difficulty very satisfactorily, however, because it remains to be shown
whether the gibbon type and the macaque type are superior as types to
the baboon types. But it may suffice to remark that the baboons are
all brutal and ferocious, whereas the gibbons are comparatively gentle
animals, and the macaques docile and even playful. It may be questioned
whether brutality and ferocity should be regarded as necessarily
removing the gorilla further from man; because it is certain that the
races of man which approach nearest to the anthropoid apes, with which
races the comparison should assuredly be made, are characterized by
these very qualities, brutality and ferocity. Intelligence must be
otherwise gauged. Probably the average proportion of the brain’s weight
to that of the entire body, and the complexity of the structure of
the brain, would afford the best means of deciding the question. But,
unfortunately, we have very unsatisfactory evidence on these points.
The naturalists who have based opinions on such evidence as has been
obtained, seem to overlook the poverty of the evidence. Knowing as we
do how greatly the human brain varies in size and complexity, not only
in different races, but in different individuals of the same race, it
appears unsatisfactory in the extreme to regard the average of the
brains of each simian species hitherto examined as presenting the true
average cerebral capacity for each species.
Still it seems tolerably clear that the choice as to the race of apes
which must be regarded as first in intelligence, and therefore as on
the whole the most manlike, rests between the orang-outang and the
chimpanzee. “In the world of science, as in that of politics,” said
Professor Rolleston in 1862, “France and England have occasionally
differed as to their choice between rival candidates for royalty. If
either hereditary claims or personal merits affect at all the right
of succession, beyond a question the gorilla is but a pretender, and
one or other of the two (other) candidates the true prince. There is
a graceful as well as an ungraceful way of withdrawing from a false
position, and the British public will adopt the graceful course
by accepting forthwith and henceforth the French candidate”—the
orang-outang. If this were intended as prophecy, it has not been
fulfilled by the event, for the gorilla is still regarded by most
British naturalists as the ape which comes on the whole nearest to man;
but probably, in saying “the British public will adopt the graceful
course” in accepting the orang-outang as “the king of the Simiadæ,”
Professor Rolleston meant only that that course would be graceful if
adopted.
Before the discovery of the gorilla, the chimpanzee was usually
regarded as next to man in the scale of the animal creation. It was
Cuvier who first maintained the claim of the orang-outang to this
position. Cuvier’s opinion was based on the greater development
of the orang-outang’s brain, and the height of its forehead. But
these marks of superiority belong to the orang only when young. The
adult orang seems to be inferior, or at least not superior, to the
chimpanzee as respects cerebral formation, and in other respects seems
less to resemble man. The proportions of his body, his long arms,
high shoulders, deformed neck, and imperfect ears are opposed to its
claims to be regarded as manlike. In all these respects, save one, the
chimpanzee seems to be greatly its superior. (The ear of the chimpanzee
is large, and not placed as with us: that of the gorilla is much more
like man’s.)
As to the intelligence exhibited in the conduct of the chimpanzee and
orang-outang, various opinions may be formed according to the various
circumstances under which the animals are observed. The following
has been quoted in evidence of the superiority of the chimpanzee in
this respect:—“About fifty years ago, a young chimpanzee and an
orang-outang of about the same age were exhibited together at the
Egyptian Hall. The chimpanzee, though in a declining state of health,
and rendered peevish and irritable by bodily suffering, exhibited
much superior marks of intelligence to his companion; he was active,
quick, and observant of everything that passed around him; no new
visitor entered the apartment in which he was kept, and no one left it,
without attracting his attention. The orang-outang, on the contrary,
exhibited a melancholy and a disregard of passing occurrences almost
amounting to apathy; and though in the enjoyment of better health, was
evidently much inferior to his companion in quickness and observation.
On one occasion, when the animals were dining on potatoes and boiled
chicken, and surrounded as usual with a large party of visitors, the
orang-outang allowed her plate to be taken without exhibiting the least
apparent concern. Not so, however, the chimpanzee. We took advantage
of an opportunity when his head was turned (to observe a person coming
in) to secrete his plate also. For a few seconds he looked round to
see what had become of it, but, not finding it, began to pout and fret
exactly like a spoiled child, and perceiving a young lady, who happened
to be standing near him, laughing, perhaps suspecting her to be the
delinquent, he flew at her in the greatest rage, and would probably
have bitten her had she not got beyond his reach. Upon having his plate
restored, he took care to prevent the repetition of the joke by holding
it firmly with one hand, while he fed himself with the other.”
This story can hardly be regarded as deciding the question in favour
of the chimpanzee. Many animals, admittedly far inferior to the lowest
order of monkeys in intelligence, show watchfulness over their food,
and as much ill-temper when deprived of it, and as much anxiety to
recover it, as this chimpanzee did. A hundred cases in point might
readily be cited.[36]
Perhaps the soundest opinion respecting the relative position of
the gorilla, chimpanzee, and orang-outang with reference to man, is
that which places the gorilla nearest to the lower tribes of man now
inhabiting Africa, the chimpanzee approximating, but not so closely,
to higher African tribes, and the orang-outang approximating, but
still less closely, to Asiatic tribes. It appears to me that, whatever
weight naturalists may attach to those details in which the gorilla
and the chimpanzee are more removed from man than the orang, no one
who takes a _general_ view of these three races of anthropoid apes can
hesitate to regard the gorilla as that which, on the whole, approaches
nearest to man; but it is to a much lower race of man that the gorilla
approximates, so that the chimpanzee and the orang-outang may fairly be
regarded as higher in the scale of animal life.
If we consider young specimens of the three animals, which is, on
the whole, the safest way of forming an opinion, we are unmistakably
led, in my judgment, to such a conclusion. I have seen three or four
young chimpanzees, two young orangs, and the young gorilla lately
exhibited at the Aquarium (where he could be directly compared with
the chimpanzee), and I cannot hesitate to pronounce Pongo altogether
the most human of the three. A young chimpanzee reminds one rather of
an old man than of a child, and the same may be said of young orangs;
but the young gorilla unmistakably reminds one of the young negro.
Repeatedly, while watching Pongo, I was reminded of the looks and
behaviour of young negroes whom I had seen in America, though not able
in every case to fix definitely on the feature of resemblance which
recalled the negro to my mind. (The reader is, doubtless, familiar with
half-remembered traits such as those I refer to—traits, for instance,
such as assure you that a person belongs to some county or district,
though you may be unable to say what feature, expression, or gesture
suggests the idea.) One circumstance may be specially noted, not only
as frequently recurring, but as illustrating the traits on which the
resemblance of the gorilla (when young, at any rate) to the negro
depends. A negro turns his eyes where a Caucasian would turn his head.
The peculiarity is probably a relic of savage life; for the savage,
whether engaged in war or in the chase, avoids, as far as possible,
every movement of body or limb. Pongo looked in this way. When he thus
cast his black eyes sideways at an object I found myself reminded
irresistibly of the ways of the watchful negro waiters at an American
hotel. Certainly there is little in the movements of the chimpanzee to
remind one of any kind of human child. He is impish; but not the most
impish child of any race or tribe ever had ways, I should suppose,
resembling his.
The four anthropoid apes, full grown and in their native wilds, differ
greatly from each other in character. It may be well to consider their
various traits, endeavouring to ascertain how far diversities existing
among them may be traced to the conditions under which the four orders
subsist.
The gorilla occupies a well-wooded country extending along the coast
of Africa from the Gulf of Guinea southwards across the equator. When
full grown he is equal to a man in height, but much more powerfully
built. “Of specimens shot by Du Chaillu,” says Rymer Jones, “the
largest male seems to have been at least six feet two in height;
so that, making allowance for the shortness of the lower limbs, the
dimensions of a full-grown male may be said to equal those of a man of
eight or nine feet high, and it is only in their length that the lower
limbs are disproportionate to the gigantic trunk. In the thickness and
solidity of their bones, and in the strength of their muscles, these
limbs are quite in keeping with the rest of the body. When upright,
the gorilla’s arms reach to his knees; the hind hands are wide, and of
amazing size and power; the great toe or thumb measures six inches in
circumference; the palms and soles, and the naked part of the face, are
of an intense black colour, as is also the breast. The other parts are
thickly clothed with hair of an iron grey, except the head, on which it
is reddish brown, and the arms, where it is long and nearly black. The
female is wholly tinged with red.”
Du Chaillu gives the following account of the aspect of the gorilla
in his native woods:—“Suddenly, as we were yet creeping along in a
silence which made even a heavy breath seem loud and distinct, the
woods were at once filled with a tremendous barking roar; then the
underbrush swayed rapidly just ahead, and presently stood before us an
immense gorilla. He had gone through the jungle on all-fours; but when
he saw our party he erected himself and looked us boldly in the face.
He stood about a dozen yards from us, and was a sight I think I shall
never forget. Nearly six feet high (he proved four inches shorter),
with immense body, huge chest, and great muscular arms, with fiercely
glaring, large, deep-grey eyes, and a hellish expression of face, which
seemed to me some night-mare vision; thus stood before us the king of
the African forest. He was not afraid of us; he stood there and beat
his breasts with his large fists till it resounded like an immense bass
drum (which is their mode of bidding defiance), meantime giving vent to
roar after roar.”
The gorilla is a fruit-eater, but as fierce as the most carnivorous
animals. He is said to show an enraged enmity against men, probably
because he has found them not only hostile to himself, but successful
in securing the fruits which the gorilla loves, for he shows a similar
hatred to the elephant, which also seeks these fruits. We are told
that when the gorilla “sees the elephant busy with his trunk among
the twigs, he instantly regards this as an infraction of the laws
of property, and, dropping silently down to the bough, he suddenly
brings his club smartly down on the sensitive finger of the elephant’s
proboscis, and drives off the alarmed animal trumpeting shrilly with
rage and pain.” His enmity to man is more terribly manifested. “The
young athletic negroes in their ivory-haunts,” says Gosse, “well know
the prowess of the gorilla. He does not, like the lion, sullenly
retreat on seeing them, but swings himself rapidly down to the lower
branches, courting the conflict, and clutches the nearest of his
enemies. The hideous aspect of his visage (his green eyes flashing
with rage) is heightened by the thick and prominent brows being drawn
spasmodically up and down, with the hair erect, causing a horrible
and fiendish scowl. Weapons are torn from their possessor’s grasp,
gun-barrels bent and crushed in by the powerful hands and vice-like
teeth of the enraged brute. More horrid still, however, is the sudden
and unexpected fate which is often inflicted by him. Two negroes will
be walking through one of the woodland paths unsuspicious of evil, when
in an instant one misses his companion, or turns to see him drawn up
in the air with a convulsed choking cry, and in a few minutes dropped
to the ground, a strangled corpse. The terrified survivor gazes up,
and meets the grin and glare of the fiendish giant, who, watching his
opportunity, had suddenly put down his immense hind hand, caught the
wretch by the neck with resistless power, and dropped him only when he
ceased to struggle.”
The chimpanzee inhabits the region from Sierra Leone to the southern
confines of Angola, possibly as far as Cape Negro, so that his domain
includes within it that of the gorilla. He attains almost the same
height as the gorilla when full grown, but is far less powerfully
built. In fact, in general proportions the chimpanzee approaches man
more nearly than does any other animal. His body is covered with long
black coarse hair, thickest on the head, shoulders, and back, and
rather thin on the breast and belly. The face is dark brown and naked,
as are the ears, except that long black whiskers adorn the animal’s
cheeks. The hair on the forearms is directed towards the elbows,
as is the case with all the anthropoid apes, and with man himself.
This hair forms, where it meets the hair from the upper arm, a small
ruff about the elbow joint. The chimpanzees live in society in the
woods, constructing huts from the branches and foliage of trees to
protect themselves against the sun and heavy rains. It is said by some
travellers that the chimpanzee walks upright in its native woods, but
this is doubtful; though certainly the formation of the toes better
fits them to stand upright than either the gorilla or the orang. They
arm themselves with clubs, and unite to defend themselves against the
attacks of wild beasts, “compelling,” it is said, “even the elephant
himself to abandon the districts in which they reside.” We learn that
“it is dangerous for men to enter their forests, unless in companies
and well armed; women in particular are often said to be carried away
by these animals, and one negress is reported to have lived among them
for the space of three years, during which time they treated her with
uniform kindness, but always prevented any attempt on her part to
escape. When the negroes leave a fire in the woods, it is said that
the chimpanzees will gather round and warm themselves at the blaze,
but they have not sufficient intelligence to keep it alive by fresh
supplies of fuel.”
The orang-outang inhabits Borneo, Java, Sumatra, and other islands
of the Indian coast. He attains a greater height than the gorilla,
but, though very powerful and active, would probably not be a match
for the gorilla in a single combat. His arms are by comparison as
well as actually much longer. Whereas the gorilla’s reach only to the
knees, the arms of the orang-outang almost reach the ground when the
animal is standing upright. The orang does not often assume an upright
attitude, however. “It seldom attempts to walk on the hind feet alone,
and when it does the hands are invariably employed for the purpose of
steadying its tottering equilibrium, touching the ground lightly on
each side as it proceeds, and by this means recovering the lost balance
of the body.” The gorilla uses his hands differently. He can scarcely
be said to walk on all-fours, because he does not place the inside of
the hand on the ground, but walks on the knuckles, evidently trying
to keep the fore part of the body as high as possible. “The muzzle is
somewhat long, the mouth ill-shaped, the lips thin and protuberant; the
ears are very small, the chin scarcely recognizable, and the nose only
to be recognized by the nostrils. The face, ears, and inside of the
hands of the orang are naked and of a brick-red colour; the fore parts
are also but thinly covered with hair; but the head, shoulders, back,
and extremities are thickly clothed with long hair of dark wine-red
colour, directed forwards on the crown of the head and upwards towards
the elbows on the forearms.”
The orang-outang changes remarkably in character and appearance as he
approaches full growth. “Though exhibiting in early youth a rotundity
of the cranium and a height of forehead altogether peculiar, and
accompanied at the same time with a gentleness of disposition and
a gravity of manners which contrast strongly with the petulant and
irascible temper of the lower orders of quadrumanous mammals, the
orang-outang in its adult state is even remarkable for the flatness
of its retiring forehead, the great development of the superorbital
and occipital crests, the prominence of its jaws, the remarkable
size of its canine teeth, and the whole form of the skull, which
from the globular shape of the human head, as in the young specimen,
assumes all the forms and characters belonging to that of a large
carnivorous animal. The extraordinary contrasts thus presented in the
form of the skull at different epochs of the same animal’s life were
long considered as the characters of distinct species; nor was it
till intermediate forms were obtained, exhibiting in some degree the
peculiarities of both extremes, that they were finally recognized as
distinguishing different periods of growth only.”
Unlike the gorilla, which attacks man with peculiar malignity, and the
chimpanzee, which when in large troops assails those who approach its
retreats, the orang, even in its adult state, seems not to be dangerous
unless attacked. Even then he does not always show great ferocity.
The two following anecdotes illustrate well its character. The first
is from the pen of Dr. Abel Clarke (fifth volume of the “Asiatic
Researches”); the other is from Wallace’s interesting work, “The Malay
Archipelago.” An orang-outang fully seven feet high was discovered
by the company of a merchant ship, at a place called Ramboon, on the
north-west coast of Sumatra, on a spot where there were few trees
and little cultivated ground. “It was evident that he had come from
a distance, for his legs were covered with mud up to the knees, and
the natives were unacquainted with him. On the approach of the boat’s
crew he came down from the tree in which he was discovered, and made
for a clump at some distance; exhibiting, as he moved, the appearance
of a tall man-like figure, covered with shining brown hair, walking
erect, with a waddling gait, but sometimes accelerating his motion
with his hands, and occasionally impelling himself forward with the
bough of a tree. His motion on the ground was evidently not his natural
mode of progression, for, even when assisted by his hands and the
bough, it was slow and vacillating; it was necessary to see him among
the trees to estimate his strength and agility. On being driven to a
small clump, he gained by one spring a very lofty branch and bounded
from one branch to another with the swiftness of a common monkey, his
progress being as rapid as that of a swift horse. After receiving
five balls his exertions relaxed, and, reclining exhausted against a
branch, he vomited a quantity of blood. The ammunition of the hunters
being by this time exhausted, they were obliged to fell the tree
in order to obtain him; but what was their surprise to see him, as
the tree was falling, effect his retreat to another, with seemingly
undiminished vigour! In fact, they were obliged to cut down all the
trees before they could force him to combat his enemies on the ground,
and when finally overpowered by numbers, and nearly in a dying state,
he seized a spear made of supple wood, which would have withstood the
strength of the stoutest man, and broke it like a reed. It was stated,
by those who aided in his death, that the human-like expression of
his countenance and his piteous manner of placing his hands over his
wounds, distressed their feelings so as almost to make them question
the nature of the act they were committing. He was seven feet high,
with a broad expanded chest and narrow waist. His chin was fringed
with a beard that curled neatly on each side, and formed an ornamental
rather than a frightful appendage to his visage. His arms were long
even in proportion to his height, but his legs were much shorter. Upon
the whole, he was a wonderful beast to behold, and there was more about
him to excite amazement than fear. His hair was smooth and glossy, and
his whole appearance showed him to be in the full vigour of his youth
and strength.” On the whole, the narrative seems to suggest a remark
similar to one applied by Washington Irving to the followers of Ojeda
and their treatment of the (so-called) Indians of South America, “we
confess we feel a momentary doubt whether the arbitrary appellation of
‘brute’ is always applied to the right party.”
The other story also presents man as at least as brutal as the orang
concerned in the event. “A few miles down the river,” says Wallace,
“there is a Dyak house, and the inhabitants saw a large orang feeding
on the young shoots of a palm by the river-side. On being alarmed he
retreated towards the jungle which was close by, and a number of the
men, armed with spears and choppers, ran out to intercept him. The man
who was in front tried to run his spear through the animal’s body; but
the orang seized it in his hands, and in an instant got hold of the
man’s arm, which he seized in his mouth, making his teeth meet in
the flesh above the elbow, which he tore and lacerated in a dreadful
manner. Had not the others been close behind, the man would have been
more seriously injured, if not killed, as he was quite powerless; but
they soon destroyed the creature with their spears and choppers. The
man remained ill for a long time, and never fully recovered the use of
his arm.”
The term gibbon includes several varieties of tail-less, long-armed,
catarhine apes. The largest variety, called the siamang, need alone be
described here.
The siamang inhabits Sumatra. It presents several points of resemblance
to the orang-outang, but is also in several respects strongly
distinguished from that animal. The arms are longer even than the
orang’s, and the peculiar use which the orang makes of his long arms
is more strikingly shown in the progression of the long-armed siamang,
for the body inclining slightly forward, when the animal is on level
ground the long arms are used somewhat like crutches, and they advance
by jerks resembling the hobbling of a lame man whom fear compels
to make an extraordinary effort. The skull is small, and much more
depressed than that of the orang or chimpanzee. The face is naked and
black, straggling red hairs marking the eyebrows. The eyes are deeply
sunk, a peculiarity which, by the way, seems characteristic of arboreal
creatures generally;[37] the nose broad and flat, with wide-open
nostrils; the cheeks sunk under high cheekbones; the chin almost
rudimentary. “The hair over the whole body is thick, long, and of a
glossy black colour, much closer on the shoulders, back, and limbs than
on the belly, which, particularly in the females, is nearly naked. The
ears are entirely concealed by the hair of the head; they are naked,
and, like all the other naked parts, of a deep black colour. Beneath
the chin there is a large, bare sac, of a lax and oily appearance,
which is distended with air when the animal cries, and in that state
resembles an enormous goitre. It is similar to that possessed by
the orang-outang, and undoubtedly assists in swelling the volume of
the voice, and producing those astounding cries which, according to
Duvancelle’s account, may be heard at the distance of several miles.”
This, however, may be doubted, for M. Duvancelle himself remarks of the
wouwou, that, “though deprived of the guttural sac so remarkable in the
siamang, its cry is very nearly the same; so that it would appear that
this organ does not produce the effect of increasing the sound usually
attributed to it, or else that it must be replaced in the wouwou by
some analogous formation.”
The habits of the siamang are interesting, especially in their bearing
on the relationship between the various orders of anthropoid apes
and man; for, though the gibbon is unquestionably the lowest of the
four orders of the anthropoid apes in intelligence, it possesses
some characteristics which bring it nearer to man (so far as they
are concerned) than any of its congeners. The chief authorities
respecting the ways of the siamang are the French naturalists Diard and
Duvancelle, and the late Sir Stamford Raffles.
The siamangs generally assemble in large troops, “conducted, it is
said, by a chief, whom the Malays believe to be invulnerable, probably
because he is more agile, powerful, and difficult to capture than the
rest.” “Thus united,” proceeds M. Duvancelle (in a letter addressed
to Cuvier), “the siamangs salute the rising and the setting sun with
the most terrific cries” (like sun-worshippers), “which may be heard
at the distance of many miles, and which, when near, stun when they
do not frighten. This is the morning call of the mountain Malays; but
to the inhabitants of the town, who are unaccustomed to it, it is an
unsupportable annoyance. By way of compensation, the siamangs keep
a profound silence during the day, unless when interrupted in their
repose or their sleep. They are slow and heavy in their gait, wanting
confidence when they climb and agility when they leap, so that they may
be easily caught when they can be surprised. But nature, in depriving
them of the means of readily escaping danger, has endowed them with a
vigilance which rarely fails them; and if they hear a noise which is
unusual to them, even at the distance of a mile, fright seizes them and
they immediately take flight. When surprised on the ground, however,
they may be captured without resistance, either overwhelmed with fear
or conscious of their weakness and the impossibility of escaping. At
first, indeed, they endeavour to avoid their pursuers by flight, and
it is then that their want of skill in this exercise becomes most
apparent.”
“However numerous the troop may be, if one is wounded it is immediately
abandoned by the rest, unless, indeed, it happen to be a young one.
Then the mother, who either carries it or follows close behind, stops,
falls with it, and, uttering the most frightful cries, precipitates
herself upon the common enemy with open mouth and arms extended. But it
is manifest that these animals are not made for combat; they neither
know how to deal nor to shun a blow. Nor is their maternal affection
displayed only in moments of danger. The care which the females bestow
upon their offspring is so tender and even refined, that one would be
almost tempted to attribute the sentiment to a rational rather than
an instinctive process. It is a curious and interesting spectacle,
which a little precaution has sometimes enabled me to witness, to see
these females carry their young to the river, wash their faces in
spite of their outcries, wipe and dry them, and altogether bestow
upon their cleanliness a time and attention that in many cases the
children of our own species might well envy. The Malays related a
fact to me, which I doubted at first, but which I consider to be in
a great measure confirmed by my own subsequent observations. It is
that the young siamangs, whilst yet too weak to go alone, are always
carried by individuals of their own sex, by their fathers if they are
males, and by their mothers if females. I have also been assured that
these animals frequently become the prey of the tiger, from the same
species of fascination which serpents are said to exercise over birds,
squirrels, and other small animals. Servitude, however long, seems
to have no effect in modifying the characteristic defects of this
ape—his stupidity, sluggishness, and awkwardness. It is true that a
few days suffice to make him as gentle and contented as he was before
wild and distrustful; but, constitutionally timid, he never acquires
the familiarity of other apes, and even his submission appears to be
rather the result of extreme apathy than of any degree of confidence or
affection. He is almost equally insensible to good or bad treatment;
gratitude and revenge are equally strange to him.”
We have next to consider certain points connected with the theory of
the relationship between man and the anthropoid apes. It is hardly
necessary for me to say, perhaps, that in thus dealing with a subject
requiring for its independent investigation the life-long study of
departments of science which are outside those in which I have taken
special interest, I am not pretending to advance my opinion as of
weight in matters as yet undetermined by zoologists. But it has always
seemed to me, that when those who have made special study of a subject
collect and publish the result of their researches, and a body of
evidence is thus made available for the general body scientific, the
facts can be advantageously considered by students of other branches
of science, so only that, in leaving for a while their own subject,
they do not depart from the true scientific method, and that they are
specially careful to distinguish what has been really ascertained from
what is only surmised with a greater or less degree of probability.
In the first place, then, I would call attention to some very common
mistakes respecting the Darwinian theory of the Descent of Man. I
do not refer here to ordinary misconceptions respecting the theory
of natural selection. To say the truth, those who have not passed
beyond _this_ stage of error,—those who still confound the theory of
natural selection with the Lamarckian and other theories (or rather
hypotheses[38]) of evolution,—are not as yet in a position to deal
with our present subject, and may be left out of consideration.
The errors to which I refer are in the main included in the following
statement. It is supposed by many, perhaps by most, that according to
Darwin man is descended from one or other of the races of anthropoid
apes; and that the various orders and sub-orders of apes and monkeys
at present existing can be arranged in a series gradually approaching
more and more nearly to man, and indicating the various steps (or some
of them, for gaps exist in the series) by which man was developed.
Nothing can be plainer, however, than Darwin’s contradiction of this
genealogy for the human races. Not only does he not for a moment
countenance the belief that the present races of monkeys and apes can
be arranged in a series gradually approximating more and more nearly to
man, not only does he reject the belief that man is descended from any
present existing anthropoid ape, but he even denies that the progenitor
of man resembled any known ape. “We must not fall into the error of
supposing,” he says, “that the early progenitor of the whole simian
stock, including man, was identical with, or even closely resembled,
any existing ape or monkey.”
It appears to me, though it may seem somewhat bold to express this
opinion of the views of a naturalist so deservedly eminent as Mr.
Mivart, that in his interesting little treatise, “Man and Apes,”—a
treatise which may be described as opposed to Darwin’s special views
but not generally opposed to the theory of evolution,—he misapprehends
Darwin’s position in this respect. For he arrives at the conclusion
that if the Darwinian theory is sound, then “low down” (_i.e._, far
remote) “in the scale of Primates” (tri-syllabic) “was an ancestral
form so like man that it might well be called an _homunculus_; and we
have the virtual pre-existence of man’s body supposed, in order to
account for the actual first appearance of that body as we know it—a
supposition manifestly absurd if put forward as an explanation.”[39]
How, then, according to the Darwinian theory, is man related to the
monkey? The answer to this question is simply that the relationship
is the same in kind, though not the same in degree, as that by which
the most perfect Caucasian race is related to the lowest race of
Australian, or Papuan, or Bosjesman savages. No one supposes that one
of these races of savages could by any process of evolution, however
long-continued, be developed into a race resembling the Caucasian
in bodily and mental attributes. Nor does any one suppose that the
savage progenitor of the Caucasian races was identical with, or even
closely resembled, any existing race of savages. Yet we recognize in
the lowest forms of savage man our blood relations. In other words, it
is generally believed that if our genealogy, and that of any existing
race of savages, could be traced back through all its reticulations,
we should at length reach a race whose blood we share with that race.
It is also generally believed (though for my own part I think the
logical consequences of the principle underlying all theories of
evolution is in reality opposed to the belief) that, by tracing the
genealogical reticulations still further back, we should at length
arrive at a single race from which all the present races of man and no
other animals have descended. The Darwinian faith with respect to men
and monkeys is precisely analogous. It is believed that the genealogy
of every existent race of monkeys, if traced back, would lead us to
a race whose blood we share with that race of monkeys; and—which is
at once a wider and a more precise proposition—that, as Darwin puts
it, “the two main divisions of the Simiadæ, namely, the catarhine
and platyrhine monkeys, with their sub-groups, have all proceeded
from some one extremely ancient progenitor.” This proposition is
manifestly wider. I call it also more precise, because it implies, and
is evidently intended by Darwin to signify, that from that extremely
ancient progenitor no race outside the two great orders of Simiadæ have
even partially _descended_, though other races share with the Simiadæ
descent from some still more remote race of progenitors.
This latter point, however, is not related specially to the common
errors respecting the Darwinian theory which I have indicated above,
except in so far as it is a detail of the actual Darwinian theory.
I would, in passing, point out that, like the detail referred to in
connection with the relationship of the various races of man, this
one is not logically deducible from the theory of evolution. In fact,
I have sometimes thought that the principal difficulties of that
theory arise from this unnecessary and not logically sound doctrine.
I pointed out, rather more than three years ago, in an article “On
some of our Blood Relations,” in a weekly scientific journal, that the
analogy between the descent of races and the descent of individual
members of any race, requires us rather to believe that the remote
progenitor of the human race and the Simiadæ has had its share—though
a less share—in the generation of other races related to these in more
or less remote degrees. I may perhaps most conveniently present the
considerations on which I based this conclusion, by means of a somewhat
familiar illustration:—
Let us take two persons, brother and sister (whom let us call the
pair A), as analogues of the human race. Then these two have four
great-grandparents on the father’s side, and four on the mother’s side.
All these may be regarded as equally related to the pair A. Now, let us
suppose that the descendants of the four families of great-grandparents
intermarry, no marriages being in any case made outside these families,
and that the descendants in the same generation as the pair A are
regarded as corresponding to the entire order of the Simiadæ, the
pair A representing, as already agreed, the race of man, and all
families outside the descendants of the four great-grandparental
families corresponding to orders of animals more distantly related
than the Simiadæ to man. Then we have what corresponds (so far as
our illustration is concerned) to Darwin’s views respecting man
and the Simiadæ, and animals lower in the scale of life. The first
cousins of the pair A may be taken as representing the anthropoid
apes; the second cousins as representing the lemurs or half-apes; the
third cousins as representing the platyrhine or American apes. The
entire family—including the pair A, representing man—is descended
also, in accordance with the Darwinian view, from a single family of
progenitors, no outside families sharing _descent_, though all share
_blood_, with that family.
But manifestly, this is an entirely artificial and improbable
arrangement in the case of families. The eight grandparents _might_
be so removed in circumstances from surrounding families—so much
superior to them, let us say—that neither they nor any of their
descendants would intermarry with these inferior families: and thus
none of their great-grandchildren would share descent from some other
stock contemporary with the great-grandparents; or—which is the same
thing, but seen in another light—none of the contemporaries of the
great-grandchildren would share descent from the eight grandparents.
But so complete a separation of the family from surrounding families
would be altogether exceptional and unlikely. For, even assuming the
eight families to be originally very markedly distinguished from all
surrounding families, yet families rise and fall, marry unequally, and
within the range of a few generations a wide disparity of blood and
condition appears among the descendants of any group of families. So
that, in point of fact, the relations assumed to subsist between man,
the Simiadæ, and lower animal forms, corresponds to an unusual and
improbable set of relations among families of several persons. Either,
then, the relations of families must be regarded as not truly analogous
to the relations of races, which no evolutionist would assert, or else
we must adopt a somewhat different view of the relationship between
man, the Simiadæ, and inferior animals.
One other illustration may serve not only to make my argument clearer,
but also, by presenting an actual case, to enforce the conclusion to
which it points.
We know that the various races of man are related together more or
less closely, that some are purer than others, and that one or two
claim almost absolute purity. Now, if we take one of these last, as,
for instance, the Jewish race, and trace the race backwards to its
origin, we find it, according to tradition, carried back to twelve
families, the twelve sons of Jacob and their respective wives. (We
cannot go further back because the wives of Jacob’s sons must be taken
into account, and they were not descended from Abraham or Isaac and
their wives only,—in fact, could not have been.) If the descendants
of those twelve families had never intermarried with outside families
in such sort that the descendants of such mixed families came to
be regarded as true Hebrews, we should have in the Hebrews a race
corresponding to the Simiadæ as regarded by Darwin, _i.e._, a race
entirely descended from one set of families, and so constituting,
in fact, a single family. But we know that, despite the objections
entertained by the Hebrews against the intermixture of their race with
other races, this did not happen. Not only did many of those regarded
as true Hebrews share descent from nations outside their own, but many
of those regarded as truly belonging to nations outside the Jewish race
shared descent from the twelve sons of Jacob.
The case corresponding, then, to that of the purest of all human
races, and the case therefore most favourable to the view presented
by Darwin (though very far from essential to the Darwinian theory),
is simply this, that, in the first place, many animals regarded as
truly Simiadæ share descent from animals outside that family which
Darwin regards as the ape progenitor of man; and, in the second place,
many animals regarded as outside the Simiadæ share descent from that
ape-like progenitor. This involves the important inference that the
ape-like progenitor of man was not so markedly differentiated from
other families of animals then existing, that fertile intercourse
was impossible. A little consideration will show that this inference
accords well with, if it might not almost have been directly deduced
from, the Darwinian doctrine that all orders of mammals were, in
turn, descended from a still more remote progenitor race. The same
considerations may manifestly be applied also to that more remote
race, to the still more remote race from which all the vertebrates
have descended, and so on to the source itself from which all forms of
living creatures are supposed to have descended. A difficulty meets
us at that remotest end of the chain analogous to the difficulty of
understanding how life began at all; but we should profit little by
extending the inquiry to these difficulties, which remain, and are
likely long to remain, insuperable.
So far, however, are the considerations above urged from introducing
any new or insuperable objection to the Darwinian theory, that, rightly
understood, they indicate the true answer to an objection which has
been urged by Mivart and others against the belief that man has
descended from some ape-like progenitor.
Mivart shows that no existing ape or monkey approaches man more nearly
in all respects than other races, but that one resembles man more
closely in some respects, another in others, a third in yet others,
and so forth. “The ear lobule of the gorilla makes him our cousin,”
he says, “but his tongue is eloquent in his own dispraise.” If the
“bridging convolutions of the orang[’s brain] go to sustain his claim
to supremacy, they also go far to sustain a similar claim on the
part of the long-tailed thumbless spider-monkeys. If the obliquely
ridged teeth of _Simia_ and _Troglodytes_ (the chimpanzee) point to
community of origin, how can we deny a similar community of origin, as
thus estimated, to the howling monkeys and galagos? The liver of the
gibbons proclaims them almost human; that of the gorilla declares him
comparatively brutal. The lower American apes meet us with what seems
the ‘front of Jove himself,’ compared with the gigantic but low-browed
denizens of tropical Western Africa.”
He concludes that the existence of these wide-spread signs of affinity
and the associated signs of divergence, disprove the theory that the
structural characters existing in the human frame have had their origin
in the influence of inheritance and “natural selection.” “In the words
of the illustrious Dutch naturalists, Messrs. Schroeder, Van der Kolk
and Vrolik,” he says, “the lines of affinity existing between different
Primates construct rather a network than a ladder. It is indeed a
tangled web, the meshes of which no naturalist has as yet unravelled
by the aid of natural selection. Nay, more, these complex affinities
form such a net for the use of the teleological _retiarius_ as it
will be difficult for his Lucretian antagonist to evade, even with the
countless turns and doublings of Darwinian evolutions.”
It appears to me that when we observe the analogy between the
relationships of individuals, families, and races of man, and the
relationships of the various species of animals, the difficulty
indicated by Mr. Mivart disappears. Take, for instance, the case
of the eight allied families above considered. Suppose, instead of
the continual intermarriages before imagined—an exceptional order
of events, be it remembered—that the more usual order of things
prevails, viz., that alliances take place with other families. For
simplicity, however, imagine that each married pair has two children,
male and female, and that each person marries once and only once. Then
it will be found that the pair A have ten families of cousins, two
first-cousin families, and eight second-cousin families; these are all
the families which share descent from the eight great-grandparents of
the pair. (To have third-cousin families we should have to go back to
the fourth generation.) Thus there are eleven families in all. Now,
in the case first imagined of constant intermarrying, there would
still have been eleven families, but they would all have descended
from eight great-grandparents, and we should then expect to find
among the eleven families various combinations, so to speak, of the
special characteristics of the eight families from which they had
descended. On the other hand, eleven families, in _no_ way connected,
have descended from eighty-eight great-grandparents, and would
present a corresponding variety of characteristics. But in the case
actually supposed, in which the eleven families are so related that
each one (for what applies to the pair A applies to the others) has
two first-cousin families, and eight second-cousin families, it will
be found that instead of 88 they have only 56 great-grandparents,
or ancestors, in the third generation above them. The two families
related as first cousins to the pair A have, like these, eight
great-grandparents, four out of these eight for one family, being the
four grandparents of the father of the pair A, the other four being
outsiders; while four of the eight great-grandparents of the other
family of first cousins are the four grandparents of the mother of the
pair A, the other four being outsiders. The other eight families each
have eight great-grandparents; two of the families having among their
great-grandparents the parents of one of the grandfathers of the pair
A, but no other great-grandparent in common with the pair A; other two
of the eight families having among their great-grandparents the parents
of the other grandfather of the pair A; other two having among their
great-grandparents the parents of one of the grandmothers of the pair
A; the remaining two families having among their great-grandparents the
parents of the other grandmother of the pair A; while in all cases the
six remaining great-grandparents of each family are outsiders, in no
way related, on our assumption, either to the eight great-grandparents
of the pair A or to each other, except as connected in pairs by
marriage.
Now manifestly in such a case, which, save for the symmetry introduced
to simplify its details, represents fairly the usual relationships
between any family, its first cousins, and its second cousins, we
should not expect to find any one of the ten other families resembling
the pair A more closely in _all_ respects than would any other of
the ten. The two first-cousin families would _on the whole_ resemble
the pair A more nearly than would any of the other eight, but we
should expect to find _some_ features or circumstances in which one
or other or all of the second-cousin families would show a closer
resemblance to one or other or both of the pair A. This is found often,
perhaps generally, to be the case, even as respects the ordinary
characteristics in which resemblance is looked for, as complexion,
height, features, manner, disposition, and so forth. Much more would
it be recognized, if such close investigation could be made among the
various families as the naturalist can make into the characteristics
of men and animals. The fact, then, that features of resemblance to
man are found, not all in one order of the Simiadæ, but scattered among
the various orders, is perfectly analogous with the laws of resemblance
recognized among the various members of more or less closely related
families.
The same result follows if we consider the analogy between various
different species of animals on the one hand and between various races
of the human family on the other. No one thinks of urging against the
ordinary theory that men form only a single species, the objection that
none of the other families of the human race can be regarded as the
progenitor of the Caucasian family, seeing that though the Mongolian
type is nearer in some respects, the Ethiopian is nearer in others,
the American in others, the Malay in yet others. We find in this the
perfect analogue of what is recognized in the relationships between
families all belonging to one nation, or even to one small branch of
a nation. Is it not reasonable, then, to find in the corresponding
features of scattered resemblance observed among the various branches
of the great Simian family, not the objection which Mivart finds
against the theory of relationship, but rather what should be expected
if that theory is sound, and therefore, _pro tanto_, a confirmation of
the theory?
But now, in conclusion, let us briefly consider the great difficulty
of the theory that man is descended from some ape-like, arboreal,
speechless animal,—the difficulty of bridging over the wide gap which
confessedly separates the lowest race of savages from the highest
existing race of apes. After all that has been done to diminish the
difficulty, it remains a very great one. It is quite true that what
is going on at this present time shows how the gap has been widened,
and therefore indicates how it may once have been comparatively small.
The more savage races of man are gradually disappearing on the one
hand, the most man-like apes are being destroyed on the other,—so
that on both sides of the great gap a widening process is at work. Ten
thousand years hence the least civilized human race will probably be
little inferior to the average Caucasian races of the present day,
the most civilized being far in advance of the most advanced European
races of our time. On the other hand, the gorilla, the chimpanzee, the
orang-outang, and the gibbon will probably be extinct or nearly so.
True, the men of those days will probably have very exact records of
the characteristics not only of the present savage races of man, but of
the present races of apes. Nay, they will probably know of intermediate
races, long since extinct even now, whose fossil remains geologists
hope to discover before long as they have already discovered the
remains of an ape as large as man (the _Dryopithecus_) which existed
in Europe during the Miocene period;[40] and more recently the remains
of a race of monkeys akin to Macacus, which once inhabited Attica. But
although our remote descendants will thus possess means which we do not
possess of bridging the gap between the highest races of apes and the
lowest races of man, the gap will nevertheless be wider in their time.
And tracing backwards the process, which, thus traced forward, shows a
widened gap, we see that once the gap must have been much narrower than
it is. Lower races of man than any now known once existed on the earth,
and also races of apes nearer akin to man than any now existing, even
if the present races of apes are not the degraded descendants of races
which, living under more favourable conditions, were better developed
after their kind than the gorilla, chimpanzee, orang, and gibbon of the
present time.
It may be, indeed, that in the consideration last suggested we may find
some assistance in dealing with our difficult problem. It is commonly
assumed that the man-like apes are the most advanced members of the
Simian family save man alone, and so far as their present condition is
concerned this may be true. But it is not necessarily the case that
the anthropoid apes have advanced to their present condition. Judging
from the appearance of the young of these races, we may infer with some
degree of probability that these apes are the degraded representatives
of more intelligent and less savage creatures. Whereas the young of
man is decidedly more savage in character than the well-nurtured and
carefully trained adult, the young of apes are decidedly less savage
than the adult. The same reasoning which leads us to regard the
wildness, the natural cruelty, the destructiveness, the love of noise,
and many other little ways of young children, as reminders of a more or
less remote savage ancestry, should lead us to regard the comparative
tameness and quiet of the young gorilla, for example, as evidence that
in remote times the progenitors of the race were not so wild and fierce
as the present race of gorillas.
But even when all such considerations, whether based on the known or
the possible, have been taken into account, the gap between the lowest
savage and the highest ape is not easily bridged. It is easier to see
how man _may_ have developed from an arboreal, unspeaking animal to his
present state, than to ascertain how any part of the development was
actually effected; in other words, it is easier to suggest a general
hypothesis than to establish an even partial theory.
That the progenitor of man was arboreal in his habits seems altogether
probable. Darwin recognizes in the arrangement of the hair on the human
forearm the strongest evidence on this point, so far as the actual
body of man is concerned; the remaining and perhaps stronger evidence
being derived from appearances recognized in the unborn child. He,
who usually seems as though he could overlook nothing, seems to me to
have overlooked a peculiarity which is even more strikingly suggestive
of original arboreal habits. There is one set of muscles, and, so far
as I know, one only, which the infant uses freely, while the adult
scarcely uses them at all. I mean the muscles which separate the toes,
and those, especially, which work the big toe. Very young children
not only move the toes apart, so that the great toe and the little toe
will be inclined to each other (in the plane of the sole) nearly ninety
degrees, but also distinctly clutch with the toes. The habit has no
relation to the child’s actual means of satisfying its wants. I have
often thought that the child’s manner of clutching with its fingers is
indicative of the former arboreal habits of the race, but it is not
difficult to explain the action otherwise. The clutching movement of
the toes, however, cannot be so explained. The child can neither bring
food to its mouth in this way nor save itself from falling; and as the
adult does not use the toes in this way the habit cannot be regarded
as the first imperfect effort towards movements subsequently useful.
In fact, the very circumstance that the movement is gradually disused
shows that it is useless to the human child in the present condition
of the race. In the very young gorilla the clutching motion of the
toes is scarcely more marked than it is in a very young child; only in
the gorilla the movement, being of use, is continued by the young, and
is developed into that effective clutch with the feet which has been
already described. Here we have another illustration of that divergency
which, rather than either simple descent or ascent, characterizes the
relationship between man and the anthropoid ape. In the growing gorilla
a habit is more and more freely used, which is more and more completely
given up by the child as he progresses towards maturity.
Probably the arboreal progenitor of man was originally compelled to
abandon his arboreal habits by some slow change in the flora of his
habitat, resulting in the diminution and eventual disappearance of
trees suited for his movements. He would thus be compelled to adopt, at
first, some such course as the chimpanzee—making huts of such branches
and foliage as he could conveniently use for the purpose. The habit
of living in large companies would (as in the case of the chimpanzee)
become before long necessary, especially if the race or races thus
driven from their former abode in the trees were, like the gibbons,
unapt when alone both in attack and in defence. One can imagine how
the use of vocal signals of various kinds would be of service to the
members of these troops, not only in their excursions, but during the
work of erecting huts or defences against their enemies. If in two
generations the silent wild dog acquires, when brought into the company
of domestic dogs, no less than five distinct barking signals, we can
well believe that a race much superior in intelligence, and forced
by necessity to associate in large bodies, would—in many hundreds
of generations, perhaps—acquire a great number of vocal symbols.
These at first would express various emotions, as of affection, fear,
anxiety, sympathy, and so forth. Other signals would be used to
indicate the approach of enemies, or as battle-cries. I can see no
reason why gradually the use of particular vocal signs to indicate
various objects, animate or inanimate, and various actions, should
not follow after a while. And though the possession and use of many,
even of many hundreds, of such signs would be very far from even the
most imperfect of the languages now employed by savage races, one can
perceive the possibility—which is all that at present we can expect
to recognize—that out of such systems of vocal signalling a form of
language might arise, which, undergoing slow and gradual development,
should, in the course of many generations, approach in character
the language of the lowest savage races. That from such a beginning
language should attain its higher and highest developments is not more
wonderful in kind, though much more wonderful, perhaps, in degree,
than that from the first imperfect methods of printing should have
arisen the highest known developments of the typographic art. The
real difficulty lies in conceiving how mere vocal signalling became
developed into what can properly be regarded as spoken language.
Of the difficulties related to the origin of, or rather the development
of, man’s moral consciousness, space will not permit me to speak, even
though there were much to be said beyond the admission that these
difficulties have not as yet been overcome. It must be remembered,
however, that races of men still exist whose moral consciousness can
hardly be regarded as very fully developed. Not only so, but, through
a form of reversion to savage types, the highest and most cultivated
races of man bring forth from time to time (as our police reports too
plainly testify) beings utterly savage, brutal, and even (“which is
else”) bestial. Nay, the man is fortunate who has never had occasion
to control innate tendencies to evil which are at least strongly
significant of the origin of our race. To most minds it must be
pleasanter as certainly it seems more reasonable, to believe that the
evil tendencies of our race are manifestations of qualities undergoing
gradual extinction, than to regard them as the consequences of one
past offence, and so to have no reason for trusting in their gradual
eradication hereafter. But, as Darwin says, in the true scientific
spirit, “We are not here concerned with hopes or fears, only with
the truth as far as our reason allows us to discover it. We must
acknowledge that man, with all his noble qualities, with sympathy which
feels for the most debased, with benevolence which extends not only
to other men but to the humblest living creature, with his God-like
intellect which has penetrated into the movements and constitution of
the solar system,—with all these exalted powers, man still bears in
his bodily frame the indelible stamp of his lowly origin.” As it seems
to me, man’s moral nature teaches the same lesson with equal, if not
greater, significance.
_THE USE AND ABUSE OF FOOD._
Francis Bacon has laid it down as an axiom that experiment is the
foundation of all real progress in knowledge. “Man,” he said, “as the
minister and interpreter of nature, does and understands as much as
his observations on the order of nature permit him, and neither knows
nor is capable of more.”[41] It would seem, then, as if there could be
no subject on which man should be better informed than on the value
of various articles of food, and the quantity in which each should
be used. On most branches of experimental inquiry, a few men in each
age—perhaps but for a few ages in succession—have pursued for a
longer or shorter portion of their life, a system of experiment and
observation. But on the subject of food or diet all men in all ages
have been practical experimenters, and not for a few years only, but
during their entire life. One would expect, then, that no questions
could be more decisively settled than those which relate to the use or
the abuse of food. Every one ought to know, it might be supposed, what
kinds of food are good for the health, in what quantity each should
be taken, what changes of diet tend to correct this or that kind of
ill-health, and how long each change should be continued.
Unfortunately, as we know, this is far from being the case. We all
eat many things which are bad for us, and omit to eat many things
which would be good for us. We change our diet, too often, without
any consideration, or from false considerations, of the wants of the
body. When we have derived benefit from some change of diet, we are apt
to continue the new diet after the necessity for it has passed away.
As to quantity, also, we seldom follow well-judged rules. Some take
less nutriment (or less of some particular form of nutriment) than
is needed to supply the absolute requirements of the system; others
persistently overload the system, despite all the warnings which their
own experience and that of others should afford of the mischief likely
to follow that course.
It is only of late years that systematic efforts have been made to
throw light on the subject of the proper use of food, to distinguish
between its various forms, and to analyze the special office of each
form. I propose to exhibit, in a popular manner, some of the more
important practical conclusions to which men of science have been led
by their investigations into these questions.
The human body has been compared to a lamp in which a flame is burning.
In some respects the comparison is a most apt one, as we shall see
presently. But man does more than _live_; he _works_,—with his
brain or with his muscles. And therefore the human frame may be more
justly compared to a steam-engine than to the flame of a lamp. Of
mere life, the latter illustration is sufficiently apt, but it leaves
unillustrated man’s capacity for work; and since food is taken with
two principal objects—the maintenance of life and the renewal of
material used up in brain work and muscular work—we shall find that
the comparison of man to a machine affords a far better illustration
of our subject than the more common comparisons of the life of man
to a burning flame, and of food to the fuel which serves to maintain
combustion.
There is, however, one class of food, and, perhaps, on the whole, the
most important, the operation of which is equally well illustrated by
either comparison. The sort of food to which I refer may be termed
_heat-maintaining_ food. I distinguish it thus from food which serves
other ends, but of course it is not to be understood that any article
of diet serves _solely_ the end of maintaining heat. Accordingly, we
find that heat-maintaining substance exists in nearly all the ordinary
articles of food. Of these there are two—sugar and fat—which may be
looked on as special “heat-givers.” Starch, also, which appears in all
vegetables, and thus comes to form a large proportion of our daily
food, is a heat-giver. In fact, this substance only enters the system
in the form of sugar, the saliva having the power of converting starch
(which is insoluble in water) into sugar, and thus rendering it soluble
and digestible.
Starch, as I have said, appears in all vegetables. But it is found
more freely in some than in others. It constitutes nearly the whole
substance of arrowroot, sago, and tapioca, and appears more or less
freely in potatoes, rice, wheat, barley, and oats. In the process
of vegetation it is converted into sugar; and thus it happens that
vegetable diet—whether presenting starch in its natural form to
be converted into sugar by the consumer, or containing sugar which
has resulted from a process of change undergone by starch—is in
general heat-maintaining. Sugar is used as a convenient means of
maintaining the heat-supply; for in eating sugar we are saved the
trouble of converting starch into sugar. A love for sweet things is
the instinctive expression of the necessity for heat-maintaining
food. We see this liking strongly developed in children, whose rapid
growth is continually drawing upon their heat-supply. So far as adults
are concerned, the taste for sweet food is found to prevail more in
temperate than in tropical climes, as might be expected; but, contrary
to what we might at first expect, we do not find any increase in
the liking for sweet food in very cold climates. Another and a more
effective way of securing the required heat-supply prevails in such
countries.
As starch is converted into sugar, so by a further process sugar is
converted into fat. It is by the conversion of sugar into fat that
its heat-supplying power is made available. This conversion takes
place in the vegetable as well as in the animal system, and thus fat
appears in a variety of forms—as butter, suet, oil, and so forth. Now,
precisely as sugar is a more convenient heat-supplier than starch,
so fat exceeds sugar in its power of maintaining animal heat. It has
been calculated that one pound of fat—whether in the form of suet,
butter, or oil—will go as far towards the maintenance of animal heat
as two pounds of sugar, or as two pounds and a half of starch. Thus
it happens that in very cold countries there is developed a taste for
such articles of food as contain most fat, or even for pure fat and its
analogues—oil, butter, tallow, dripping, and other forms of _grease_.
I have spoken of starch, sugar, and fat as heat-forming articles of
food; but I must note their influence in the development of muscles and
nerves. Without a certain proportion of fat in the food a wasting of
the tissues will always take place; for muscles and nerves cannot form
without fat. And conversely, the best remedy for wasting diseases is to
be found in the supply of some easily digestible form of fatty food.
Well-fatted meat, and especially meat in which the fat is to be seen
distributed through the flesh, may be taken under such circumstances.
Butter and salad oil are then also proper articles of food. Cream is
still better, and cream cheeses may be used with advantage. It is on
account of its heat-supplying and fat-forming qualities that cod-liver
oil has taken its place as one of the most valuable remedies for
scrofulous and consumptive patients.
But it must be noted that the formation of fat is not the object with
which heat-supplying food is taken. It is an indication of derangement
of the system when heat-giving food is too readily converted into
fat. And in so far as this process of conversion takes place beyond
what is required for the formation of muscles and nerves, the body
suffers in the loss of its just proportion of heat-supply. Of course,
if too large an amount of heat-giving food is taken into the system,
we may expect that the surplus will be deposited in the form of
adipose tissue. The deposition of fat in such a case will be far less
injurious to the system than an excessive heat-supply would be. But
when only a just amount of heat-giving food is taken, and in place
of fulfilling its just office this food is converted into adipose
tissue, it becomes necessary to inquire into the cause of the mischief.
Technically, the evil may be described as resulting from the deficient
oxygenation of the heat-supplying food. This generally arises from
defective circulation, and may often be cured by a very moderate but
_systematic_ increase in the amount of daily exercise, or by the use
of the sponge-bath, or, lastly, by such changes in the dress—and
especially in the articles of attire worn next to the skin—as tend to
encourage a freer circulation of the blood. The tendency to accumulate
fat may sometimes be traced to the use of over-warm coverings at night,
and especially to the use of woollen night-clothes. By attending to
considerations of this sort, more readily and safely than by an undue
diminution of the amount of heat-supplying food, the tendency to
obesity may frequently be corrected.
In warm weather we should diminish the supply of heat-giving food. In
such weather the system does not require the same daily addition to its
animal heat, and the excess is converted into fat. Experiments have
shown that despite the increased rate at which perspiration proceeds
during the summer months, men uniformly fed throughout the year
increase in weight in summer and lose weight in winter.
So far as mere existence is concerned, heat-forming food may be looked
upon as the real fuel on which the lamp of life is sustained. But man,
considered as a working being, cannot exist without _energy-forming_
food. All work, whether of the brain or of the limbs, involves the
exhaustion of nervous and muscular matter; and unless the exhausted
matter be renewed, the work must come to an end. The supply of
heat-giving food may be compared to the supply of fuel for the fire
of a steam-engine. By means of this supply the _fire_ is kept alive;
but if the fire have nothing to work upon, its energies are wasted or
used to the injury of the machine itself. The supply of water, and its
continual use (in the form of steam) in the propulsion of the engine,
are the processes corresponding to the continual exhaustion and renewal
of the muscles and nerves of the human frame. And the comparison may be
carried yet further. We see that in the case of the engine the amount
of smoke, or rather of carbonic acid, thrown out by the blast-pipe is
a measure of the vital energy (so to speak) within the engine; but the
amount of work done by the engine is measured rather by the quantity of
steam which is thrown out, because the elastic force of every particle
of steam has been exerted in the propulsion of the engine before being
thrown out through the blast-pipe. In a manner precisely corresponding
to this, the amount of carbonic acid gas exhaled by a man is a measure
of the rate at which mere existence is proceeding; but the amount of
work, mental or muscular, which the man achieves, is measured by the
amount of used-up brain-material and muscle-material which is daily
thrown off by the body. I shall presently show in what way this amount
is estimated.
In the composition of the muscles there is a material called _fibrine_,
and in the composition of the nerves there is a material called
_albumen_. These are the substances[42] which are exhausted during
mental and bodily labour, and which have to be renewed if we are to
continue working with our head or with our hands. Nay more, life itself
involves work; the heart, the lungs, the liver, each internal organ of
the body, performs its share of work, just as a certain proportion of
the power of a steam-engine is expended in merely moving the machinery
which sets it in action. If the waste of material involved in this form
of work is not compensated by a continual and sufficient supply of
fibrine and albumen the result will be a gradual lowering of all the
powers of the system, until some one or other gives way,—the heart
ceases to beat, or the stomach to digest, or the liver to secrete
bile,—and so death ensues.
The fibrine and albumen in the animal frame are derived exclusively
from vegetables. For although we seem to derive a portion of the
supply from animal food, yet the fibrine and albumen thus supplied
have been derived in the beginning from the vegetable kingdom. “It is
the peculiar property of the plant,” says Dr. Lankester, “to be able,
in the minute cells of which it is composed, to convert the carbonic
acid and ammonia which it gets from the atmosphere into fibrine
and albumen, and by easy chemical processes we can separate these
substances from our vegetable food. Wheat, barley, oats, rye, rice, all
contain fibrine, and some of them also albumen. Potatoes, cabbage, and
asparagus contain albumen. It is a well-ascertained fact that those
substances which contain most of these ‘nutritious secretions,’ as they
have been called, support life the longest.” They change little during
the process of digestion, entering the blood in a pure state, and being
directly employed to renew the nervous and muscular matter which has
been used up during work, either mental or muscular. Thus the supply
of these substances is continually being drawn upon. The carbon, which
forms their principal constituent, is converted into carbonic acid;
and the nitrogen, which forms about a sixth part of their substance,
re-appears in the nitrogen of urea, a substance which forms the
principal solid constituent of the matter daily thrown from the system
through the action of the kidneys. Thus the amount of urea which daily
passes from the body affords a measure of the work done during the day.
“This is not,” says Dr. Lankester, “the mere dream of the theorist;
it has been practically demonstrated that increased stress upon the
nervous system, viz., brain work, emotion, or excitement from disease,
increases the quantity of urea and the demand for nitrogenous food. In
the same manner the amount of urea is the representative of the amount
of muscular work done.”
It has been calculated that the average amount of urea daily formed
in the body of a healthy man is about 470 grains. To supply this
daily consumption of nitrogenous matter, it is necessary that about
four ounces of flesh-forming substance should be consumed daily.
It is important, therefore, to inquire how this substance may be
obtained. The requisite quantity of albuminous and fibrinous matter
“is contained,” says Dr. Lankester, “in a pound of beef; in two pounds
of eggs; in two quarts of milk; in a pound of peas; in five pounds of
rice; in sixteen pounds of potatoes; in two pounds of Indian meal;
in a pound and a half of oatmeal; and in a pound and three-quarters
of flour.” A consideration of this list will show the importance of
attending to the quality as well as the quantity of our food. A man
of ordinary appetite might satisfy his hunger on potatoes or on rice,
without by any means supplying his system with a sufficient amount of
flesh-forming food. On the other hand, if a man were to live on bread
and beef alone, he would load his system with an amount of nitrogenous
food, although not taking what could be considered an excessive amount
of daily nourishment. We see, also, how it is possible to continually
vary the form in which we take the required supply of nitrogenous food,
without varying the amount of that supply from day to day.
The supply itself should of course also vary from day to day as the
amount of daily work may vary. What would be ample for a person
performing a moderate amount of work would be insufficient for one
who underwent daily great bodily or mental exertions, and would be
too much for one who was taking holiday. It would appear, from the
researches of Dr. Haughton, that the amount of urea daily formed in
the body of a healthy man of average weight varies from 400 to 630
grains. Of this weight it appears that 300 grains results from the
action of the internal organs. It would seem, therefore, that the
amount of flesh-forming food indicated in the preceding paragraph may
be diminished in the proportion of 47 to 40 in the case of a person
taking the minimum of exercise—that is, avoiding all movements save
those absolutely necessary for comfort or convenience. On the other
hand, that amount must be increased in the proportion of 74 to 63 in
the case of a person (of average weight) working up to his full powers.
It will be seen at once, therefore, that a hardworking man, whether
labourer or thinker, must make good flesh-forming food constitute a
considerable portion of his diet; otherwise he would require to take an
amount of food which would seriously interfere with his comfort and the
due action of his digestive organs. For instance, if he lived on rice
alone, he would require to ingest nearly seven pounds of food daily; if
on potatoes, he would require upwards of twenty-one pounds; whereas one
pound and a third of meat would suffice to supply the same amount of
flesh-forming food.
Men who have to work, quickly find out what they require in the way of
food. The Irishman who, while doing little work, will live contentedly
on potatoes, asks for better flesh-forming food when engaged in heavy
labour. In fact, the employer of the working man, so far from feeling
aggrieved when his men require an improvement in their diet, either as
respects quality or quantity, ought to look on the want as evidence
that they are really working hard in his service, and also that they
have a capacity for continuous work. The man who lives on less than
the average share of flesh-forming food is doing less than an average
amount of work; the man who is unable to eat an average quantity of
flesh-forming food, is _unable_ to do an average amount of work. “‘On
what principle do you discharge your men?’ I once said,” relates Dr.
Lankester, “to a railway contractor. ‘Oh,’ he said, ‘it’s according to
their appetites.’ ‘But,’ I said, ‘how do you judge of that?’ ‘Why,’
he said, ‘I send a clerk round when they are getting their dinners,
and those who can’t eat he marks with a bit of chalk, and we send them
about their business.’”
At a lecture delivered at the Royal Museum of Physics and Natural
History at Florence, by Professor Mantegazza, a few years since, the
Professor dwelt on the insufficient food which Italians are in the
habit of taking, as among the most important causes of the weakness of
the nation. “Italians,” he said, “you should follow as closely as you
can the example of the English in your eating and in your drinking,
in the choice of flesh-meat (in tossing off bumpers of your rich
wines),[43] in the quality of your coffee, your tea, and your tobacco.
I give you this advice, dear countrymen, not only as a medical man, but
also as a patriot. It is quite evident, from the way millions of you
perform the process which you call eating and drinking, that you have
not the most elementary notions of the laws of physiology. You imagine
that you are living. You are barely prolonging existence on maccaroni
and water-melons. You neither know how to eat nor how to drink. You
have no muscular energy; and, therefore, you have no continuous mental
energy. The weakness of the individual, multiplied many millions of
times, results in the collective weakness of the nation. Hence results
insufficient work, and thence insufficient production. Thus the returns
of the tax-collector and the custom-house officer are scanty, and the
national exchequer suffers accordingly.” Nor is all this, strange as it
may sound, the mere gossip of the lecture-room. “The question of good
feeding,” says Dr. Lankester, “is one of national importance. It is
vain to expect either brain or muscles to do efficient work when they
are not provided with the proper material. Neither intellectual nor
physical work can be done without good food.”
We have now considered the two principal forms of food, the
heat-forming—sometimes called the _amylaceous_—constituents, and
the flesh-forming or _nitrogenous_ constituents. But there are other
substances which, although forming a smaller proportion of the daily
food, are yet scarcely less important. Returning to our comparison of
the human system to a steam-engine—we have seen how the heat-forming
and flesh-forming constituents of food correspond to the supply of
fuel and water; but an engine would quickly fall into a useless state
if the wear and tear of the material of which it is constructed were
not attended to and repaired. Now, in the human frame there are
materials which are continually being used up, and which require to be
continually restored, if the system is to continue free from disease.
These materials are the mineral constituents of the system. Amongst
them we must include _water_, which composes a much larger portion of
our bodies than might be supposed. Seven-ninths of our weight consists
simply of water. Every day there is a loss of about one-thirtieth
part of this constituent of our system. The daily repair of this
important waste of material is not effected by imbibing a corresponding
supply of water. A large proportion of the weight of water daily lost
is renewed in the solid food. Many vegetables consist principally
of water. This is notably the case with potatoes. Where the water
supplied to a district is bad, so that little water is consumed by the
inhabitants—at least, without the addition of some other substance—it
becomes important to notice the varying proportion of water present
in different articles of food. As an instance of this, I may call
attention to a remarkable circumstance observed during the failure of
the potato crops in Ireland. Notwithstanding the great losses which
the people sustained at that time, it was noticed that the amount of
tea imported into Ireland exhibited a remarkable increase. This seemed
at first sight a somewhat perplexing phenomenon. The explanation was
recognized in the circumstance that the potato—a watery vegetable, as
we have said—no longer formed the chief portion of the people’s diet.
Thus the deficiency in the supply of water had to be made up by the
use of a larger quantity of fluid food; and as simple water was not
palatable to the people, they drank tea in much larger quantities than
they had been in the habit of taking before the famine.
But we have to consider the other mineral constituents of the system.
If I were to run through the list of all the minerals which exist
within the body, I should weary the patience of the reader, and
perhaps not add very much to the clearness of his ideas respecting the
constitution of the human frame. Let it suffice to state generally
that, according to the calculations of physiologists, a human body
weighing 154 pounds contains about 17½ pounds of mineral matter; and
that the most important mineral compounds existing within the body are
those which contain lime, soda, and potash. Without pretending to any
strictly scientific accuracy in the classification, we may say that
the lime is principally found in the bones, the soda in the blood, the
potash in the muscles; and according as one or other of these important
constituents is wanting in our food, so will the corresponding portions
of the frame be found to suffer.
We have a familiar illustration of the effects of unduly diminishing
the supply of the mineral constituents of the body in the ravages
which scurvy has worked amongst the crews of ships which have remained
for a long period ill-supplied with fresh vegetables. Here it is
chiefly the want of potash in the food which causes the mischief.
An interesting instance of the rapid—almost startling—effects of
food containing potash, in the cure of men stricken by scurvy, is
related by Dana. The crew of a ship which had been several months at
sea, but was now nearing the land, were prostrated by the ravages of
scurvy. Nearly all seemed hopelessly ill. One young lad was apparently
dying, the livid spots which were spreading over his limbs seeming to
betoken his rapidly approaching end. At this moment a ship appeared
in view which had but lately left the land, and was laden with fresh
vegetables. Before long large quantities of the life-bearing food had
been transferred to the decks of the other ship. The instincts of life
taught the poor scurvy-stricken wretches to choose the vegetable which
of all others was best suited to supply the want under which their
frames were wasting. They also were led by the same truthful instincts
to prefer the raw to cooked vegetables. Thus the sick were to be seen
eating raw onions with a greater relish than the gourmand shows for
the most appetising viands. But the poor lad who was the worse of the
sufferers had already lost the power of eating; and it was without
a hope of saving his life that some of his companions squeezed the
juice of onions between his lips, already quivering with the tremor of
approaching death. He swallowed a few drops, and presently asked for
more. Shortly he began to revive, and to the amazement of all those
who had seen the state of prostration to which he had been reduced, he
regained in a few days his usual health and strength.
The elements which we require in order to supply the daily waste of
the mineral constituents of the body are contained in greater or less
quantities in nearly all the articles which man uses for food. But it
may readily happen that, by adopting an ill-regulated diet, a man may
not take a sufficient quantity of these important elements. It must
also be noticed that articles of food, both animal and vegetable, may
be deprived of a large proportion of their mineral elements by boiling;
and if, as often happens, the water in which the food has been boiled
is thrown away, injurious effects can scarcely fail to result from
the free use of food which has lost so important a portion of its
constituent elements. Accordingly, when persons partake much of boiled
meat, they should either consume the broth with the meat, or use it
as soup on the alternate days. Vegetables steamed in small quantities
of water (this water being taken with them), also afford a valuable
addition to boiled meat. In fact, experience seems to have suggested
the advantage of mixing carrots, parsnips, turnips, and greens with
boiled meat; but unfortunately the addition is not always made in
a proper manner. If the vegetables are boiled separately in large
quantities of water, and served up after this water has been thrown
away, more harm than good is done by the addition; since the appetite
is satisfied with comparatively useless food, instead of being left
free to choose, as it might otherwise do, such forms of food as would
best supply the requirements of the system. Salads and uncooked fruits,
for instance, contain saline ingredients in large proportion, and
could be used advantageously after a meal of boiled meat. Potatoes are
likewise a valuable article of food on account of the mineral elements
contained in them. And there can be no doubt that the value of potatoes
as an article of food is largely increased when they are cooked in
their skins, after the Irish fashion.
Lastly, we must consider those articles of food which promote the
natural vital changes, but do not themselves come to form part of the
frame, or, at least, not in any large proportion of their bulk. Such
are tea, coffee, and cocoa: alchoholic drinks; narcotics; and lastly,
spices and condiments. We may compare the use of these articles of food
to that of oil in lubricating various parts of a steam-engine. For, as
the oil neither forms part of the heat-supply nor of the force-supply
of the steam-engine, nor is used to replace the worn material of its
structure, yet serves to render the movements of the machine more
equable and effective, so the forms of food we are considering are
neither heat-producing nor flesh-forming, nor do they serve to replace,
to any great extent, the mineral constituents of the body, yet they
produce a sense of refreshment accompanied with renewed vigour. It is
difficult to determine in what precise way these effects are produced,
but no doubt can exist as to the fact that they are really attributable
to the forms of food to which we have assigned them.
Tea, coffee, and cocoa owe their influence on the nervous system to
the presence of a substance which has received the various names of
_theine_, _caffeine_, and _theobromine_. It is identical in composition
with _piperine_, the most important ingredient in pepper. It may be
separated in the form of delicate white, silky crystals, which have a
bitter taste. In its concentrated form this substance is poisonous, and
to this circumstance must be ascribed the ill effects which follow
from the too free use of strong tea or coffee. However, the instances
of bad effects resulting from the use of “the cup which cheers but not
inebriates” are few and far between, while the benefits derived from
it are recognized by all. It has, indeed, been stated that no nation
which has begun to make use of tea, coffee, or cocoa, has ever given up
the practice; and no stronger evidence can be required of the value of
those articles of food.
Of alcoholic liquors it is impossible to speak so favourably. They
are made use of, indeed, almost as extensively as tea or coffee; they
have been made the theme of the poet, and hailed as the emblems of
all that is genial and convivial. Yet there can be little doubt that,
when a balance is struck between the good and evil which have resulted
to man from their use, the latter is found largely to preponderate.
The consideration of these evils belongs, however, rather to the
moralist than to the physiologist. I have here simply to consider
alcoholic liquors as articles of food. There can be little doubt that,
when used with caution and judgment, they afford in certain cases an
important adjunct to those articles which are directly applied to
the reparation of bodily waste. Without absolutely nourishing the
frame, they ultimately lead to this end by encouraging the digestive
processes which result in the assimilation of nutritive articles of
food. But the quantity of alcohol necessary to effect this is far less
than is usually taken even by persons who are termed temperate. It is
also certain that hundreds make use of alcoholic liquors who have no
necessity for them, and who would be better without them. Those who
require them most are men who lead a studious sedentary life; and it
is such men, also, who suffer most from excess in the use of alcoholic
liquors.
It remains that I should make a few remarks on mistakes respecting the
quantity of food.
Some persons fall into the habit of taking an excessive quantity of
food, not from greediness, but from the idea that a large amount of
food is necessary for the maintenance of their strength. They thus
overtax the digestive organs, and not only fail of their purpose, but
weaken instead of strengthening the system. Especially serious is the
mistake often made by persons in delicate health of swallowing—no
other word can be used, for the digestive organs altogether refuse
to respond to the action of the mouth—large quantities of some
concentrated form of food, such as even the strongest stomach could
not deal with in that form. I knew a person who, though suffering
from weakness such as should have suggested the blandest and simplest
forms of food, adopted as a suitable breakfast mutton-chops and
bottled stout, arguing, when remonstrated with, that he required more
support than persons in stronger health. He was simply requiring his
weak digestive organs to accomplish work which would have taxed the
digestive energies of the most stalwart labourer working daily in the
open air for many hours.
On the other hand, a too abstemious diet is as erroneous in principle
as a diet in excess of the natural requirements of the system. A
diet which is simply too abstemious is perhaps less dangerous than
persistent abstinence from the use of certain necessary forms of food.
Nature generally prevents us from injuring ourselves by unwisely
diminishing the quantity of food we take; but unfortunately she is not
always equally decided in her admonitions respecting the quality of
our food. A man may be injuring his health through a deficiency in the
amount either of the heat-forming or of the flesh-forming food which he
consumes, and yet know nothing of the origin of the mischief. It may
also be noted that systematic abstinence, either as respects quantity
or quality of food, is much more dangerous than an occasional fast.
Indeed, it is not generally injurious either to abstain for several
days from particular articles or forms of food, or to remain, for
several hours beyond the usual interval between meals, without food of
any sort. On the contrary, benefit often arises from each practice. The
Emperor Aurelian used to attribute the good health he enjoyed to his
habit of abstaining for a whole day, once a month, from food of all
sorts; and many have found the Lenten rules of abstinence beneficial.
As a rule, however, change of diet is a safer measure than periodical
fasting or abstinence from either heat-producing or flesh-forming
food. It must be noticed, in conclusion, that young persons ought not,
without medical advice, to fast or abstain for any length of time from
the more important forms of food, as serious mischief to the digestive
organs frequently follows from either course.
_OZONE._
The singular gas termed ozone has attracted a large amount of attention
from chemists and meteorologists. The vague ideas which were formed as
to its nature when as yet it had been but newly discovered, have given
place gradually to more definite views; and though we cannot be said
to have thoroughly mastered all the difficulties which this strange
element presents, yet we know already much that is interesting and
instructive.
Let us briefly consider the history of ozone.
Nine years after Priestley had discovered oxygen, Van Marum, the
electrician, noticed that when electric sparks are taken through that
gas, a peculiar odour is evolved. Most people know this odour, since
it is always to be recognized in the neighbourhood of an electrical
machine in action. In reality, it indicates the presence of ozone in
the air. But for more than half a century after Van Marum had noticed
it, it was supposed to be the “smell of electricity.”
In 1840, Schönbein began to inquire into the cause of this peculiar
odour. He presently found that it is due to some change in the oxygen;
and that it can be produced in many ways. Of these, the simplest, and,
in some respects, the most interesting, is the following:—“Take sticks
of common phosphorus, scrape them until they have a metallic lustre,
place them in this condition under a large bell-jar, and half-cover
them with water. The air in the bell-jar is soon charged with ozone,
and a large room can readily be supplied with ozonized air by this
process.”
Schönbein set himself to inquire into the properties of this new gas,
and very interesting results rewarded his researches. It became quite
clear, to begin with, that whatever ozone may be, its properties are
perfectly distinct from those of oxygen. Its power of oxidizing or
rusting metals, for example, is much greater than that which oxygen
possesses. Many metals which oxygen will not oxidize at all, even
when they are at a high temperature, submit at once to the influence
of ozone. But the power of ozone on other substances than metals is
equally remarkable. Dr. Richardson states that, when air is so ozonized
as to be only respirable for a short time, its destructive power is
such that gutta-percha and india-rubber tubings are destroyed by merely
conveying it.
The bleaching and disinfecting powers of ozone are very striking.
Schönbein was at first led to associate them with the qualities of
chlorine gas; but he soon found that they are perfectly distinct.
It had not yet been shown whether ozone was a simple or a compound
gas. If simple, of course it could be but another form of oxygen. At
first, however, the chances seemed against this view; and there were
not wanting skilful chemists who asserted that ozone was a compound of
the oxygen of the air with the hydrogen which forms an element of the
aqueous vapour nearly always present in the atmosphere.
It was important to set this question at rest. This was accomplished by
the labours of De la Rive and Marignac, who proved that ozone is simply
another form of oxygen.
Here we touch on a difficult branch of modern chemical research. The
chemical elements being recognized as the simplest forms of matter,
it might be supposed that each element would be unchangeable in its
nature. That a compound should admit of change, is of course a thing to
be expected. If we decompose water, for instance, into its component
elements, oxygen and hydrogen, we may look on these gases as exhibiting
water to us in another form. And a hundred instances of the sort might
be adduced, in which, either by separating the elements of a compound,
or by re-arranging them, we obtain new forms of matter without any real
change of substance. But with an element, the case, one would suppose,
should be different.
However, the physicist must take facts as he finds them; and amongst
the most thoroughly recognized chemical facts we have this one, that
elementary substances may assume different forms. Chemists call the
phenomenon allotropy. A well-known instance of allotropy is seen in
red phosphorus. Phosphorus is one of the chemical elements; and, as
every one knows, the form in which it is usually obtained is that of a
soft, yellow, semi-transparent solid, somewhat resembling bees’ wax in
consistence, poisonous, and readily taking fire. Red phosphorus is the
same element, yet differs wholly in its properties. It is a powder, it
does not readily take fire, and it is not poisonous.
Ozone, then, is another form of oxygen. It is the only instance yet
discovered of gaseous allotropy.
And now we have to deal with the difficult and still-vexed questions
of the way in which the change from oxygen is brought about, and the
actual distinction between the two forms of the same gas. Schönbein
held that common oxygen is produced by the combination of two special
forms of oxygen—the positive and the negative, or, as he called them,
ozone and antozone. He showed that, in certain conditions of the air,
the atmospheric oxygen exhibits qualities which are the direct reverse
of those which ozone exhibits, and are distinct from those of ordinary
oxygen. In oxygen thus negatived or antozonized, animals cannot live
any more than they can in nitrogen. The products of decomposition are
not only not destroyed as by ozone, but seem subject to preservative
influences, and speedily become singularly offensive; dead animal
matter rapidly putrefies, and wounds show a tendency to mortification.
But the theory of positive and negative forms of oxygen, though still
held by a few physicists, has gradually given way before the advance
of new and sounder modes of inquiry. It has been proved, in the first
place, that ozone is denser than ordinary oxygen. The production of
ozone is always followed by a contraction of the gas’s volume, the
contraction being greater or less according to the amount of oxygen
which has been ozonized. Regularly as the observers—Messrs. Andrews
and Tait—converted a definite proportion of oxygen into ozone, the
corresponding contraction followed, and as regularly was the original
volume of the gas restored when, by the action of heat, the ozone was
reconverted into oxygen.
And now a very singular experiment was made by the observers, with
results which proved utterly perplexing to them. Mercury has the power
of absorbing ozone; and the experimenters thought that if, after
producing a definite contraction by the formation of ozone, they could
absorb the ozone by means of mercury, the quantity of oxygen which
remained would serve to show them how much ozone had been formed, and
thence, of course, they could determine the density of ozone.
Suppose, for instance, that we have one hundred cubic inches of oxygen,
and that by any process we reduce it to a combination of oxygen and
ozone occupying ninety-five cubic inches. Now, if the mercury absorbed
the ozone, and we found, say, that there only remained eighty-five
cubic inches of oxygen, we could reason in this way:—Ten cubic inches
were occupied by the ozone before the mercury absorbed it; but these
correspond to fifteen cubic inches of oxygen; hence, ozone must be
denser than oxygen in the proportion of fifteen to ten, or three to
two. And whatever result might have followed, a real absorption of the
ozone by the mercury would have satisfactorily solved the problem.
But the result actually obtained did not admit of interpretation in
this way. The apparent absorption of the ozone by the mercury, that
is, the disappearance of the ozone from the mixture, was accompanied
by _no diminution of volume at all_. In other words, returning to
our illustrative case, after the absorption of the ozone from the
ninety-five cubic inches occupied by the mixture, there still remained
ninety-five cubic inches of oxygen; so that it seemed as though an
evanescent volume of ozone corresponded in weight to five cubic inches
of oxygen. This solution, of course, could not be admitted, since it
made the density of ozone _infinite_.
The explanation of this perplexing experiment is full of interest and
instruction. The following is the account given by Mr. C. W. Heaton
(Professor of Chemistry at Charing Cross Hospital), slightly modified,
however, so that it may be more readily understood.
Modern chemists adopt, as a convenient mode of representing the
phenomena which gases exhibit, the theory that every gas, whether
elementary or compound, consists of minute molecules. They suppose
that these molecules are of equal size, and are separated by equal
intervals so long as the gas remains unchanged in heat and density.
This view serves to account for the features of resemblance presented
by all gases. The features in which gases vary are accounted for by the
theory that the molecules are differently constituted. The molecules
are supposed to be clusters of atoms, and the qualities of a gas are
assumed to depend on the nature and arrangement of these ultimate
atoms. The molecules of some elements consist but of a single atom;
the molecules of others are formed by pairs of atoms; those of others
by triplets; and so on. Again, the molecules of compound gases are
supposed to consist of combinations of different _kinds_ of atoms.
Now, Dr. Odling, to whom we owe the solution of the perplexing problem
described above, thus interpreted the observed phenomena. A molecule
of oxygen contains two atoms, one of ozone contains three, _and the
oxidizing power of ozone depends on the ease with which it parts with
its third atom of oxygen_. Thus, in the experiment which perplexed
Messrs. Andrews and Tait, the mercury only _seemed_ to absorb the
ozone; in reality it converted the ozone into oxygen by removing
its third atom. And now we see how to interpret such a result as we
considered in our illustrative case. Five cubic inches of oxygen
gave up their atoms, each atom combining with one of the remaining
oxygen doublets, so as to form a set of ozone triplets. Clearly, then,
fifteen cubic inches of oxygen were transformed into ozone. They now
occupied but ten cubic inches; so that the mixture, or ozonized oxygen,
contained eighty-five cubic inches of oxygen and ten of ozone. When the
mercury was introduced, it simply transformed all the ozone triplets
into oxygen doublets, by taking away the odd atom from each. It thus
left ten cubic inches of oxygen, which, with the remaining eighty-five,
constituted the ninety-five cubic inches observed to remain after the
supposed absorption of the ozone.
It follows, of course, that ozone is half as heavy again as oxygen.
But, as Mr. Heaton remarked, “this beautiful hypothesis, although
accounting perfectly for all known facts, was yet but a probability.
One link was lacking in the chain of evidence, and that link M. Soret
has supplied by a happily devised experiment.” Although mercury and
most substances are only capable of converting ozone into oxygen, oil
of turpentine has the power of absorbing ozone in its entirety. Thus,
when the experiment was repeated, with oil of turpentine in place of
the mercury, the ozone was absorbed, and the remaining oxygen, instead
of occupying ninety-five inches, occupied but eighty-five. After
this, no doubt could remain that Dr. Odling’s ingeniously conceived
hypothesis was the correct explanation of Messrs. Andrews and Tait’s
experiment.
We recognize, then, in ozone a sort of concentrated oxygen, with this
peculiar property, that it possesses an extraordinary readiness to
part with its characteristic third atom, and so disappear _as ozone_,
two-thirds of its weight remaining as oxygen.
It is to this peculiarity that ozone owes the properties which render
it so important to our welfare. We are indeed, as yet, in no position
to theorize respecting this element, our knowledge of its very
existence being so recent, and our information respecting its presence
in our atmosphere being of still more recent acquisition.
Indeed, it is well remarked by Mr. Heaton, that we had, until quite
lately, no reason for confidently adopting Schönbein’s view that ozone
exists in our atmosphere. The test-papers which Schönbein made use of
turned blue under the influence of ozone, it is true, but they were
similarly influenced by other elements which are known to exist in our
atmosphere, and even the sun’s rays turned them blue. However, Dr.
Andrews has shown how the character of the air producing the change
can be further tested, so as to render it certain that ozone only has
been at work. If air which colours the test-papers be found to lose
the property after being heated, the change can only be due to ozone,
because nitrous and nitric acids (which have the power of colouring the
test-papers) would not be removed by the heat, whereas ozone is changed
by heat into oxygen.
Once we are certain that ozone exists in the air, we must recognize
the fact that its presence cannot fail to have an important bearing on
our health and comfort; for ozone is an exceedingly active agent, and
cannot exist anywhere without setting busily to its own proper work.
What that work is, and whether it is beneficial or deleterious to
ourselves, remains to be considered.
In the first place, ozone has immense power as a disinfectant.
It decomposes the products emanating from putrefying matter more
effectually than any other known element. Perhaps the most striking
proof ever given of its qualities in this respect is that afforded by
an experiment conducted by Dr. Richardson a few years ago.
He placed a pint of blood taken from an ox in a large wide-mouthed
bottle. The blood had then coagulated, and it was left exposed to
the air until it had become entirely redissolved by the effects of
decomposition. At the end of a year the blood was put into a stoppered
bottle, and set aside for seven years. “The bottle was then taken from
its hiding-place,” says Dr. Richardson, “and an ounce of the blood was
withdrawn. The fluid was so offensive as to produce nausea when the
gases evolved from it were inhaled. It was subjected by Dr. Wood and
myself to a current of ozone. For a few minutes the odour of ozone
was destroyed by the odour of the gases from the blood; gradually the
offensive smell passed away; then the fluid mass became quite sweet,
and at last a faint odour of ozone was detected, whereupon the current
was stopped. The blood was thus entirely deodorized; but another and
most singular phenomenon was observed. The dead blood coagulated as the
products of decomposition were removed, and this so perfectly, that
from the new clot that was formed serum exuded. Before the experiment
commenced, I had predicted on theoretical grounds that secondary
coagulation would follow on purification; and this experiment, as well
as several others afterwards performed, verified the truth of the
prediction.”
It will of course be understood that ozone, in thus acting as a
disinfectant, is transformed into oxygen. It parts with its third atom
as in the mercury experiment, and so loses its distinctive peculiarity.
Thus we might be led to anticipate the results which come next to be
considered.
Ozone has certain work to do, and in doing that work is transmuted into
oxygen. It follows, then, that where there has been much work for ozone
to do, there we shall find little ozone left in the air. Hence, in
open spaces where there is little decomposing matter, we should expect
to find more ozone than in towns or cities. This accords with what is
actually observed. And not only is it found that country air contains
more ozone than town air, but it is found that air which has come from
the sea has more ozone than even the country air, while air in the
crowded parts of large cities has no ozone at all, nor has the air of
inhabited rooms.
So far as we have gone, we might be disposed to speak unhesitatingly in
favour of the effects produced by ozone. We see it purifying the air
which would otherwise be loaded by the products of decomposing matter,
we find it present in the sea air and the country air which we know
to be so bracing and health-restoring after a long residence in town,
and we find it absent just in those places which we look upon as most
unhealthy.
Again, we find further evidence of the good effects of ozone in
the fact that cholera and other epidemics never make their dreaded
appearance in the land when the air is well supplied with ozone—or
in what the meteorologists call “the ozone-periods.” And though we
cannot yet explain the circumstance quite satisfactorily, we yet seem
justified in ascribing to the purifying and disinfecting qualities of
ozone our freedom at those times from epidemics to which cleanliness
and good sanitary regulations are notedly inimical.
But there is a reverse side to the picture. And as we described an
experiment illustrating the disinfecting qualities of ozone before
describing the good effects of the element, we shall describe an
experiment illustrating certain less pleasing qualities of ozone,
before discussing the deleterious influences which it seems capable of
exerting.
Dr. Richardson found that when the air of a room was so loaded with
ozone as to be only respirable with difficulty, animals placed in the
room were affected in a very singular manner. “In the first place,”
he says, “all the symptoms of nasal catarrh and of irritation of the
mucous membranes of the nose, the mouth, and the throat were rapidly
induced. Then followed free secretion of saliva and profuse action of
the skin—perspiration. The breathing was greatly quickened, and the
action of the heart increased in proportion.” When the animals were
suffered to remain yet longer within the room, congestion of the lungs
followed, and the disease called by physicians “congestive bronchitis”
was set up.
A very singular circumstance was noticed also as to the effects of
ozone on the different orders of animals. The above-mentioned effects,
and others which accompanied them, the description of which would be
out of place in these pages, were developed more freely in carnivorous
than in herbivorous animals. Rats, for example, were much more easily
influenced by ozone than rabbits were.
The results of Dr. Richardson’s experiments prepare us to hear that
ozone-periods, though characterized by the absence of certain diseases,
bring with them their own forms of disease. Apoplexy, epilepsy,
and other similar diseases seem peculiarly associated with the
ozone-periods, insomuch that eighty per cent. of the deaths occurring
from them take place on days when ozone is present in the air in larger
quantities than usual. Catarrh, influenza, and affections of the
bronchial tubes, also affect the ozone-periods.
We see, then, that we have much yet to learn respecting ozone before
we can pronounce definitively whether it is more to be welcomed or
dreaded. We must wait until the researches which are in progress have
been carried out to their conclusion, and perhaps even then further
modes of inquiry will have to be pursued before we can form a definite
opinion.
_DEW._
There are few phenomena of common occurrence which have proved more
perplexing to philosophers than those which attend the deposition of
dew. Every one is familiar with these phenomena, and in very early
times observant men had noticed them; yet it is but quite recently
that the true theory of dew has been put forward and established.
This theory affords a striking evidence of the value of careful and
systematic observation applied even to the simplest phenomena of nature.
It was observed, in very early times, that dew is only formed on
clear nights, when, therefore, the stars are shining. It was natural,
perhaps, though hardly philosophical, to conclude that dew is directly
shed down upon the earth from the stars; accordingly, we find the
reference of dew to stellar influences among the earliest theories
propounded in explanation of the phenomenon.
A theory somewhat less fanciful, but still depending on supposed
stellar influences, was shortly put forward. It was observed that
dew is only formed when the atmosphere is at a low temperature; or,
more correctly, when the air is at a much lower temperature than has
prevailed during the daytime. Combining this peculiarity with the
former ancient philosophers reasoned in the following manner: Cold
generates dew, and dew appears only when the skies are clear—that is,
when the stars are shining; hence it follows that the stars generate
cold, and thus lead indirectly to the formation of dew. Hence arose
the singular theory, that as the sun pours down heat upon the earth, so
the stars (and also the moon and planets) pour down cold.
Nothing is more common—we may note in passing—than this method of
philosophizing, especially in all that concerns weather-changes; and
perhaps it would be impossible to find a more signal instance of the
mistakes into which men are likely to fall when they adopt this false
method of reasoning; for, so far is it from being true that the stars
shed cold upon the earth, that the exact reverse is the case. It has
been established by astronomers and physicists that an important
portion of the earth’s heat-supply is derived from the stars.
Following on these fanciful speculations came Aristotle’s theory
of dew—celebrated as one of the most remarkable instances of the
approximation which may sometimes be made to the truth by clever
reasoning on insufficient observations. For we must not fall into
the mistake of supposing, as many have done, that Aristotle framed
hypotheses without making observations; indeed, there has seldom lived
a philosopher who has made more observations than he did. His mistake
was that he extended his observations too widely, not making enough on
each subject. He imagined that, by a string of syllogisms, he could
make a few supply the place of many observations.
Aristotle added two important facts to our knowledge respecting
dew—namely, first, that dew is only formed in serene weather; and
secondly, that it is not formed on the summits of mountains. Modern
observations show the more correct statement of the case to be that dew
is _seldom_ formed either in windy weather or on the tops of mountains.
Now, Aristotle reasoned in a subtle and able manner on these two
observations. He saw that dew must be the result of processes which
are interfered with when the air is agitated, and which do not extend
high above the earth’s surface; he conjectured, therefore, that dew is
simply caused by the discharge of vapour from the air. “Vapour is a
mixture,” he said, “of water and heat, and as long as water can get a
supply of heat, vapour rises. But vapour cannot rise high, or the heat
would get detached from it; and vapour cannot exist in windy weather,
but becomes dissipated. Hence, in high places, and in windy weather,
dew cannot be formed for want of vapour.” He derided the notion that
the stars and moon cause the precipitation of dew. “On the contrary,
the sun,” he said, “is the cause; since its heat raises the vapour,
from which the dew is formed when that heat is no longer present to
keep up the vapour.”
Amidst much that is false, there is here a good deal that is sound.
The notion that heat is some substance which floats up the vapour,
and may become detached from it in high or windy places, is of course
incorrect. So also is the supposition that the dew is produced by
the _fall_ of condensed vapour as the heat passes away. Nor is it
correct to say that the absence of the sun causes the condensation of
vapour, since, as we shall presently see, the cold which causes the
deposition of dew results from more than the mere absence of the sun.
But, in pointing out that the discharge of vapour from the air, owing
to loss of heat, is the true cause of the deposition of dew, Aristotle
expressed an important truth. It was when he attempted to account for
the discharge that he failed. It will be observed, also, that his
explanation does not account for the observed fact that dew is only
formed in clear weather.
Aristotle’s views did not find acceptance among the Greeks or Romans;
they preferred to look on the moon, stars, and planets as the agents
which cause the deposition of dew. “This notion,” says a modern author,
“was too beautiful for a Greek to give up, and the Romans could not do
better than follow the example of their masters.”
In the middle ages, despite the credit attached to Aristotle’s name,
those who cultivated the physical sciences were unwilling to accept his
views; for the alchemists (who alone may be said to have been students
of nature) founded their hopes of success in the search for the
philosopher’s stone, the _elixir vitæ_, and the other objects of their
pursuit, on occult influences supposed to be exercised by the celestial
bodies. It was unlikely, therefore, that they would willingly reject
the ancient theory which ascribed dew to lunar and stellar radiations.
But at length Baptista Porta adduced evidence which justified him in
denying positively that the moon or stars exercise any influence on the
formation of dew. He discovered that dew is sometimes deposited on the
inside of glass panes; and again, that a bell-glass placed over a plant
in cold weather is more copiously covered with dew within than without;
nay, he observed that even some opaque substances show dew on their
_under_ surface when none appears on the upper. Yet, singularly enough,
Baptista Porta rejected that part of Aristotle’s theory which was alone
correct. He thought his observations justified him in looking on dew
as condensed—not from vapour, as Aristotle thought—but from the air
itself.
But now a new theory of dew began to be supported. We have seen that
not only the believers in stellar influence, but Aristotle also, looked
on dew as falling from above. Porta’s experiments were opposed to this
view. It seemed rather as if dew rose from the earth. Observation also
showed that the amount of dew obtained at different heights from the
ground diminishes with the height. Hence, the new theorists looked upon
dew as an exhalation from the ground and from plants—a fine steam, as
it were, rising upwards, and settling principally on the under surfaces
of objects.
But this view, like the others, was destined to be overthrown.
Muschenbroek, when engaged in a series of observations intended to
establish the new view, made a discovery which has a very important
bearing on the theory of dew: he found that, instead of being deposited
with tolerable uniformity upon different substances,—as falling rain
is, for instance, and as the rising rain imagined by the new theorists
ought to be,—dew forms very much more freely on some substances than
on others.
Here was a difficulty which long perplexed physicists. It appeared that
dew neither fell from the sky nor arose from the earth. The object
itself on which the dew was formed seemed to play an important part in
determining the amount of deposition.
At length it was suggested that Aristotle’s long-neglected explanation
might, with a slight change, account for the observed phenomena. The
formation of dew was now looked upon as a discharge of vapour from the
air, this discharge not taking place necessarily upwards or downwards,
but always from the air next to the object. But it was easy to test
this view. It was understood that the coldness of the object, as
compared with the air, was a necessary element in the phenomenon. It
followed, that if a cold object is suddenly brought into warm air,
there ought to be a deposition of moisture upon the object. This was
found to be the case. Any one can readily repeat the experiment. If a
decanter of ice-cold water is brought into a warm room, in which the
air is not dry—a crowded room, for example—the deposition of moisture
is immediately detected by the clouding of the glass. But there is, in
fact, a much simpler experiment. When we breathe, the moisture in the
breath generally continues in the form of vapour. But if we breathe
upon a window-pane, the vapour is immediately condensed, because the
glass is considerably colder than the exhaled air.
But although this is the correct view, and though physicists had made
a noteworthy advance in getting rid of erroneous notions, yet a theory
of dew still remained to be formed; for it was not yet shown how the
cold, which causes the deposition of dew, is itself occasioned. The
remarkable effects of a clear sky and serene weather in encouraging the
formation of dew, were also still unaccounted for. On the explanation
of these and similar points, the chief interest of the subject depends.
Science owes the elucidation of these difficulties to Dr. Wells, a
London physician, who studied the subject of dew in the commencement
of the present century. His observations were made in a garden three
miles from Blackfriars Bridge.
Wells exposed little bundles of wool, weighing, when dry, ten grains
each, and determined by their increase in weight the amount of moisture
which had been deposited upon them. At first, he confined himself to
comparing the amount of moisture collected on different nights. He
found that although it was an invariable rule that cloudy nights were
unfavourable to the deposition of dew, yet that on some of the very
clearest and most serene nights, less dew was collected than on other
occasions. Hence it became evident that mere clearness was not the only
circumstance which favoured the deposition of dew. In making these
experiments, he was struck by results which appeared to be anomalous.
He soon found that these anomalies were caused by any obstructions
which hid the heavens from his wool-packs: such obstructions hindered
the deposition of dew. He tried a crucial experiment. Having placed
a board on four props, he laid a piece of wool _on_ the board,
and another _under_ it. During a clear night, he found that the
difference in the amount of dew deposited on the two pieces of wool
was remarkable: the upper one gained fourteen grains in weight, the
lower one gained only four grains. He made a little roof over one piece
of wool, with a sheet of pasteboard; and the increase of weight was
reduced to two grains, while a piece of wool outside the roof gained no
less than sixteen grains in weight.
Leaving these singular results unexplained for a while, Dr. Wells
next proceeded to test the temperature near his wool-packs. He found
that where dew is most copiously produced, there the temperature is
lowest. Now, since it is quite clear that the deposition of dew was not
the cause of the increased cold—for the condensation of vapour is a
process _producing heat_—it became quite clear that the formation of
dew is dependent on and proportional to the loss of heat.
And now Wells was approaching the solution of the problem he had set
himself; for it followed from his observations, that such obstructions
as the propped board and the pasteboard roof _kept in the heat_. It
followed also, from the observed effects of clear skies, that clouds
_keep in the heat_. Now, what sort of heat is that which is prevented
from escaping by the interference of screens, whether material or
vaporous? There are three processes by which heat is transmitted from
one body to another,—these are, conduction, convection, and radiation.
The first is the process by which objects in contact communicate
their heat to each other, or by which the heat in one part of a body
is gradually transmitted to another part. The second is the process
by which heat is carried from one place to another by the absolute
transmission of heated matter. The third is that process by which heat
is spread out in all directions, in the same manner as light. A little
consideration will show that the last process is that with which we
are alone concerned; and this important result flows from Dr. Wells’
experiments, that _the rate of the deposition of dew depends on the
rate at which bodies part with their heat by radiation_. If the process
of radiation is checked, dew is less copiously deposited, and _vice
versâ_.
When we consider the case of heat accompanied by light, we understand
readily enough that a screen may interfere with the emission of
radiant heat. We use a fire-screen, for instance, with the object of
producing just such an interference. But we are apt to forget that
what is true of luminous heat is true also of that heat which every
substance possesses. In fact, we do not meet with many instances in
which the effect of screens in preventing the loss of obscure heat is
very noteworthy. There are some, as the warmth of a green-house at
night, and so on; but they pass unnoticed, or are misunderstood. It
was in this way that the explanation of dew-phenomena had been so long
delayed. The very law on which it is founded had been _practically_
applied, while its meaning had not been recognized. “I had often
in the pride of half-knowledge,” says Wells, “smiled at the means
frequently employed by gardeners to protect tender plants from cold,
as it appeared to me impossible that a thin mat, or any such flimsy
substance, could prevent them from attaining the temperature of the
atmosphere, by which alone I thought them liable to be injured. But
when I had seen that bodies on the surface of the earth become, during
a still and serene night, colder than the atmosphere, by radiating
their heat to the heavens, I perceived immediately a just reason for
the practice which I had before deemed useless.”
And now all the facts which had before seemed obscure were accounted
for. It had been noticed that metallic plates were often dry when
grass or wood was copiously moistened. Now, we know that metals part
unwillingly with their heat by radiation, and therefore the temperature
of a metal plate exposed in the open air is considerably higher than
that of a neighbouring piece of wood. For a similar reason, dew is
more freely deposited on grass than on gravel. Glass, again, is a
good radiator, so that dew is freely deposited on glass objects,—a
circumstance which is very annoying to the telescopist. The remedy
employed is founded on Wells’ observations—a cylinder of tin or card,
called a dew-cap, is made to project beyond the glass, and thus to act
as a screen, and prevent radiation.
We can now also interpret the effects of a clear sky. Clouds act the
part of screens, and check the emission of radiant heat from the earth.
This fact has been noticed before, but misinterpreted, by Gilbert White
of Selborne. “I have often observed,” he says, “that cold seems to
descend from above; for when a thermometer hangs abroad on a frosty
night, the intervention of a cloud shall immediately raise the mercury
ten degrees, and a clear sky shall again compel it to descend to its
former gauge.” Another singular mistake had been made with reference
to the power which clouds possess of checking the emission of radiant
heat. It had been observed that on moonlit nights the eyes are apt to
suffer in a peculiar way, which has occasionally brought on temporary
blindness. This had been ascribed to the moon’s influence, and the term
moon-blindness had therefore been given to the affection. In reality,
the moon has no more to do with this form of blindness than the stars
have to do with the formation of dew. The absence of clouds from the
air is the true cause of the mischief. There is no sufficient check
to the radiation of heat from the eyeballs, and the consequent chill
results in temporary loss of sight, and sometimes even in permanent
injury.
Since clouds possess this important power, it is clear that while they
are present in the air there can never be a copious formation of dew,
which requires, as we have seen, a considerable fall in the temperature
of the air around the place of deposition. When the air is clear,
however, radiation proceeds rapidly, and therefore dew is freely formed.
But it might seem that since objects in the upper regions of the air
part with their radiant heat more freely than objects on the ground,
the former should be more copiously moistened with dew than the latter.
That the fact is exactly the reverse is thus explained. The cold
which is produced by the radiation of heat from objects high in the
air is communicated to the surrounding air, which, growing heavier,
descends towards the ground, its place being supplied by warmer air.
Thus the object is prevented from reducing the air in its immediate
neighbourhood to so low a temperature as would be attained if this
process of circulation were checked. Hence, a concave vessel placed
below an object high in air, would serve to increase the deposition
of dew by preventing the transfer of the refrigerated air. We are not
aware that the experiment has ever been tried, but undoubtedly it would
have the effect we have described. An object on the ground grows cold
more rapidly, because the neighbouring air cannot descend after being
chilled, but continues in contact with the object; also cold air is
continually descending from the neighbourhood of objects higher in
air which are parting with their radiant heat, and the cold air thus
descending takes the place of warmer air, whose neighbourhood might
otherwise tend to check the loss of heat in objects on the ground.
Here, also, we recognize the cause of the second peculiarity detected
by Aristotle—namely, that dew is only formed copiously in serene
weather. When there is wind, it is impossible that the refrigerated air
around an object which is parting with its radiant heat, can remain
long in contact with the object. Fresh air is continually supplying the
place of the refrigerated air, and thus the object is prevented from
growing so cold as it otherwise would.
In conclusion, we should wish to point out the important preservative
influence exercised during the formation of dew. If the heat which is
radiated from the earth, or from objects upon it, during a clear night,
were not repaired in any way, the most serious injury would result to
vegetation. For instance, if the sun raised no vapour during the day,
so that when night came on the air was perfectly dry, and thus the
radiant heat passed away into celestial space without compensation, not
a single form of vegetation could retain its life during the bitter
cold which would result. But consider what happens. The sun’s heat,
which has been partly used up during the day in supplying the air
with aqueous vapour, is gradually given out as this vapour returns to
the form of water. Thus the process of refrigeration is effectually
checked, and vegetation is saved from destruction. There is something
very beautiful in this. During the day, the sun seems to pour forth his
heat with reckless profusion, yet all the while it is being silently
stored up; during the night, again, the earth seems to be radiating
her heat too rapidly into space, yet all the while a process is going
on by which the loss of heat is adequately compensated. Every particle
of dew which we brush from the blades of grass, as we take our morning
rambles, is an evidence of the preservative action of nature.
_THE LEVELLING POWER OF RAIN._
It has been recognized, ever since geology has become truly a science,
that the two chief powers at work in remodelling the earth’s surface,
are fire and water. Of these powers one is in the main destructive, and
the other preservative. Were it not for the earth’s vulcanian energies,
there can be no question that this world would long since have been
rendered unfit for life,—at least of higher types than we recognize
among sea creatures. For at all times igneous causes are at work,
levelling the land, however slowly; and this not only by the action
of sea-waves at the border-line between land and water, but by the
action of rain and flood over inland regions. Measuring the destructive
action of water by what goes on in the lifetime of a man, or even
during many successive generations, we might consider its effects very
slight, even as on the other hand we might underrate the effects of the
earth’s internal fires, were we to limit our attention to the effects
of upheaval and of depression (not less preservative in the long run)
during a few hundreds or thousands of years. As Lyell has remarked in
his “Principles of Geology,” “our position as observers is essentially
unfavourable when we endeavour to estimate the nature and magnitude of
the changes now in progress. As dwellers on the land, we inhabit about
a fourth part of the surface; and that portion is almost exclusively
a theatre of decay, and not of reproduction. We know, indeed, that
new deposits are annually formed in seas and lakes, and that every
year some new igneous rocks are produced in the bowels of the earth,
but we cannot watch the progress of their formation; and as they are
only present to our minds by the aid of reflection, it requires an
effort both of the reason and the imagination to appreciate duly their
importance.” But that they are actually of extreme importance, that in
fact all the most characteristic features of our earth at present are
due to the steady action of these two causes, no geologist now doubts.
I propose now to consider one form in which the earth’s aqueous
energies effect the disintegration and destruction of the land. The sea
destroys the land slowly but surely, by beating upon its shores and by
washing away the fragments shaken down from cliffs and rocks, or the
more finely divided matter abstracted from softer strata. In this work
the sea is sometimes assisted by the other form of aqueous energy—the
action of rain. But in the main, the sea is the destructive agent by
which shore-lines are changed. The other way in which water works the
destruction of the land affects the interior of land regions, or only
affects the shore-line by removing earthy matter from the interior of
continents to the mouths of great rivers, whence perhaps the action of
the sea may carry it away to form shoals and sandbanks. I refer to the
direct and indirect effects of the downfall of rain. All these effects,
without a single exception, tend to level the surface of the earth. The
mountain torrent whose colour betrays the admixture of earthy fragments
is carrying those fragments from a higher to a lower level. The river
owes its colour in like manner to earth which it is carrying down to
the sea level. The flood deposits in valleys matter which has been
withdrawn from hill slopes. Rainfall, acts, however, in other ways, and
sometimes still more effectively. The soaked slopes of great hills give
way, and great landslips occur. In winter the water which has drenched
the land freezes, in freezing expands, and then the earth crumbles and
is ready to be carried away by fresh rains; or when dry, by the action
even of the wind alone. Landslips, too, are brought about frequently in
the way, which are even more remarkable than those which are caused by
the unaided action of heavy rainfalls.
The most energetic action of aqueous destructive forces is seen when
water which has accumulated in the higher regions of some mountain
district breaks its way through barriers which have long restrained it,
and rushes through such channels as it can find or make for itself into
valleys and plains at lower levels. Such catastrophes are fortunately
not often witnessed in this country, nor when seen do they attain the
same magnitude as in more mountainous countries. It would seem, indeed,
as though they could attain very great proportions only in regions
where a large extent of mountain surface lies above the snow-line.
The reason why in such regions floods are much more destructive than
elsewhere will readily be perceived if we consider the phenomena of one
of these terrible catastrophes.
Take, for instance, the floods which inundated the plains of Martigny
in 1818. Early in that year it was found that the entire valley of the
Bagnes, one of the largest side-valleys of the great valley of the
Rhône, above Geneva, had been converted into a lake through the damming
up of a narrow outlet by avalanches of snow and ice from a loftier
glacier overhanging the bed of the river Dranse. The temporary lake
thus formed was no less than half a league in length, and more than
200 yards wide, its greatest depth exceeding 200 feet. The inhabitants
perceived the terrible effects which must follow when the barrier
burst, which it could not fail to do in the spring. They, therefore,
cut a gallery 700 feet long through the ice, while as yet the water
was at a moderate height. When the waters began to flow through this
channel, their action widened and deepened it considerably. At length
nearly half the contents of the lake were poured off. Unfortunately,
as the heat of the weather increased, the middle of the barrier slowly
melted away, until it became too weak to withstand the pressure of
the vast mass of water. Suddenly it gave way; and so completely that
all the water in the lake rushed out in half an hour. The effects of
this tremendous outrush of the imprisoned water were fearful. “In
the course of their descent,” says one account of the catastrophe,
“the waters encountered several narrow gorges, and at each of these
they rose to a great height, and then burst with new violence into the
next basin, sweeping along forests, houses, bridges, and cultivated
land.” It is said by those who witnessed the passage of the flood at
various parts of its course, that it resembled rather a moving mass
of rock and mud than a stream of water. “Enormous masses of granite
were torn out of the sides of the valleys, and whirled for hundreds
of yards along the course of the flood.” M. Escher the engineer tells
us that a fragment thus whirled along was afterwards found to have a
circumference of no less than sixty yards. “At first the water rushed
on at a rate of more than a mile in three minutes, and the whole
distance (forty-five miles) which separates the Valley of Bagnes from
the Lake of Geneva was traversed in little more than six hours. The
bodies of persons who had been drowned in Martigny were found floating
on the further side of the Lake of Geneva, near Vevey. Thousands of
trees were torn up by the roots, and the ruins of buildings which had
been overthrown by the flood were carried down beyond Martigny. In
fact, the flood at this point was so high, that some of the houses in
Martigny were filled with mud up to the second story.”
It is to be noted respecting this remarkable flood, that its effects
were greatly reduced in consequence of the efforts made by the
inhabitants of the lower valleys to make an outlet for the imprisoned
waters. It was calculated by M. Escher that the flood carried down
300,000 cubic feet of water every second, an outflow five times as
great as that of the Rhine below Basle. But for the drawing off of the
temporary lake, the flood, as Lyell remarks, would have approached in
volume some of the largest rivers in Europe. “For several months after
the _débâcle_ of 1818,” says Lyell, “the Dranse, having no settled
channel, shifted its position continually from one side to the other of
the valley, carrying away newly erected bridges, undermining houses,
and continuing to be charged with as large a quantity of earthy
matter as the fluid could hold in suspension. I visited this valley
four months after the flood, and was witness to the sweeping away of
a bridge and the undermining of part of a house. The greater part of
the ice-barrier was then standing, presenting vertical cliffs 150 feet
high, like ravines in the lava-currents of Etna, or Auvergne, where
they are intersected by rivers.” It is worthy of special notice that
inundations of similar or even greater destructiveness have occurred in
the same region at former periods.
It is not, however, necessary for the destructive action of floods
in mountain districts that ice and snow should assist, as in the
Martigny flood. In October, 1868, the cantons of Tessin, Grisons, Uri,
Valois, and St. Gall, suffered terribly from the direct effects of
heavy rainfall. The St. Gothard, Splugen, and St. Bernhardin routes
were rendered impassable. In the former pass twenty-seven lives were
lost, besides many horses and waggons of merchandise. On the three
routes more than eighty persons in all perished. In the small village
of Loderio alone, no less than fifty deaths occurred. The damage in
Tessin was estimated at £40,000. In Uri and Valois large bridges were
destroyed and carried away. Everything attested the levelling power
of rain; a power which, when the rain is falling steadily on regions
whence it as steadily flows away, we are apt to overlook.
It is not, however, necessary to go beyond our own country for
evidence of the destructive action of water. We have had during the
past few years very striking evidence in this respect, which need
scarcely be referred to more particularly here, because it will be
in the recollection of all our readers. Looking over the annals of
the last half-century only, we find several cases in which the power
of running water in carrying away heavy masses of matter has been
strikingly shown. Consider, for instance, the effects of the flood in
Aberdeenshire and the neighbouring counties, early in August, 1829. In
the course of two days a great flood extended itself over “that part of
the north-east of Scotland which would be cut off by two lines drawn
from the head of Loch Rannoch, one towards Inverness and the other to
Stonehaven.” The total length of various rivers in this region which
were flooded amounted to between 500 and 600 miles. Their courses were
marked everywhere by destroyed bridges, roads, buildings, and crops.
Sir T. D. Lauder records “the destruction of thirty-eight bridges, and
the entire obliteration of a great number of farms and hamlets. On the
Nairn, a fragment of sandstone fourteen feet long by three feet wide
and one foot thick, was carried about 200 yards down the river. Some
new ravines were formed on the sides of mountains where no streams had
previously flowed, and ancient river channels, which had never been
filled from time immemorial, gave passage to a copious flood.” But
perhaps the most remarkable effect of these inundations was the entire
destruction of the bridge over the Dee at Ballater. It consisted of
five arches, spanning a waterway of 260 feet. The bridge was built of
granite, the pier, resting on rolled pieces of granite and gneiss.
We read that the different parts of this bridge were swept away in
succession by the flood, the whole mass of masonry disappearing in the
bed of the river. Mr. Farquharson states that on his own premises the
river Don forced a mass of 400 or 500 tons of stones, many of them of
200 or 300 pounds’ weight, up an inclined plane, rising six feet in
eight or ten yards, and left them in a rectangular heap about three
feet deep on a flat ground, the heap ending abruptly at its lower
extremity.” At first sight this looks like an action the reverse of
that levelling action which we have here attributed to water. But in
reality it indicates the intense energy of this action; which drawing
heavy masses down along with swiftly flowing water, communicates to
them so great a momentum, that on encountering in their course a rising
slope, they are carried up its face and there left by the retreating
flood. The rising of these masses no more indicates an inherent
uplifting power in running water, than the ascent of a gently rising
slope by a mass which has rolled headlong down the steep side of a
hill indicates an upward action exerted by the force of gravity.
Even small rivers, when greatly swollen by rain, exhibit great energy
in removing heavy masses. Thus Lyell mentions that in August, 1827, the
College, a small river which flows down a slight declivity from the
eastern watershed of the Cheviot Hills, carried down several thousand
tons’ weight of gravel and sand to the plain of the Till. This little
river also carried away a bridge then in process of building, “some of
the arch stones of which, weighing from half to three-quarters of a ton
each, were propelled two miles down the rivulet.” “On the same occasion
the current tore away from the abutment of a mill-dam a large block
of greenstone porphyry, weighing nearly two tons, and transported it
to a distance of nearly a quarter of a mile. Instances are related as
occurring repeatedly, in which from 1000 to 3000 tons of gravel are in
like manner removed by this streamlet to still greater distances in one
day.”
It may appear, however, to the reader that we have in such instances
as these the illustration of destructive agencies which are of their
very nature limited within very narrow areas. The torrent, or even
the river, may wear out its bed or widen it, but nevertheless can
hardly be regarded as modifying the aspect of the region through which
it flows. Even in this respect, however, the destructive action of
water is not nearly so limited as it might appear to be. Taking a few
centuries or a few thousand years, no doubt, we can attribute to the
action of rivers, whether in ordinary flow or in flood, little power
of modifying the region which they drain. But taking that wider survey
(in time) of fluviatile work which modern science requires, dealing
with this form of aqueous energy as we deal with the earth’s vulcanian
energies, we perceive that the effects of river action in the course of
long periods of time are not limited to the course which at any given
time a river may pursue. In carrying down material along its course
to the sea, a river is not merely wearing down its own bed, but is so
changing it that in the course of time it will become unfit to drain
the region through which it flows. Its bottom must of necessity become
less inclined. Now although it will then be lower than at present,
and therefore be then even more than now the place to which the water
falling upon the region traversed by the river will naturally tend,
it will no longer carry off that water with sufficient velocity.
Three consequences will follow from this state of things. In the
first place there will be great destruction in the surrounding region
through floods because of inadequate outflow; in the second place, the
overflowing waters will in the course of time find new channels, or in
other words new rivers will be formed in this region; thirdly, owing to
the constant presence of large quantities of water in the depressed bed
of the old river, the banks on either side will suffer, great landslips
occurring and choking up its now useless channel. Several rivers are
undergoing these changes at the present time, and others, which are
manifestly unfit for the work of draining the region through which they
flow (a circumstance attested by the occurrence of floods in every wet
season), must before long be modified in a similar way.
We are thus led to the consideration of the second form in which
the destructive action of inland waters, or we may truly say, the
destructive action of _rain_, is manifested,—viz., in landslips.
These, of course, are also caused not unfrequently by vulcanian action,
but equally of course landslips so caused do not belong to our present
subject. Landslips caused directly or indirectly by rain, are often
quite as extensive as those occasioned by vulcanian energy, and they
are a great deal more common. We may cite as a remarkable instance
a landslip of nearly half a mile in breadth, now in progress, in a
district of the city of Bath called Hedgmead, which forms a portion
of the slope of Beacon Hill. It is attributed to the action of a
subterranean stream on a bed of gravel, the continued washing away of
which causes the shifting; but the heavy rains of 1876–77 caused the
landslip to become much more marked.
Besides slow landslips, however, rain not unfrequently causes great
masses of earth to be precipitated suddenly, and where such masses fall
into the bed of a river, local deluges of great extent and of the most
destructive character often follow. The following instances, cited in
an abridged form from the pages of Lyell’s “Principles of Geology,”
attest the terrible nature of catastrophes such as these.
Two dry seasons in the White Mountains of New Hampshire were followed
by heavy rains on August 28, 1826. From the steep and lofty slopes
of the River Saco great masses of rock and stone were detached, and
descending carried along with them “in one promiscuous and frightful
ruin, forests, shrubs, and the earth which sustained them.” “Although
there are numerous indications on the steep sides of these hills of
former slides of the same kind, yet no tradition had been handed down
of any similar catastrophe within the memory of man, and the growth of
the forest on the very spots now devastated clearly showed that for a
long interval nothing similar had occurred. One of these moving masses
was afterwards found to have slid three miles, with an average breadth
of a quarter of a mile.” At the base of the vast chasms formed by these
natural excavations, a confused mass of ruins was seen, consisting of
transported earth, gravel, rocks, and trees. Forests were prostrated
with as much ease as if they had been mere fields of grain; if they
resisted for a while, “the torrent of mud and rock accumulated behind
till it gathered sufficient force to burst the temporary barrier.”
“The valleys of the Amonoosuck and Saco presented, for many miles, an
uninterrupted scene of desolation, all the bridges being carried away,
as well as those over the tributary streams. In some places the road
was excavated to the depth of from fifteen to twenty feet; in others
it was covered with earth, rocks, and trees to as great a height.
The water flowed for many weeks after the flood, as densely charged
with earth as it could be without being changed into mud, and marks
were seen in various localities of its having risen on either side of
the valley to more than twenty-five feet above the ordinary level.”
But perhaps the most remarkable evidence of the tremendous nature
of this cataclysm is to be found in Lyell’s statements respecting
the condition of the region nineteen years later. “I found the signs
of devastation still very striking,” he says; “I also particularly
remarked that the surface of the bare granite rocks had been smoothed
by the passage over them of so much mud and stone.” Professor Hubbard
mentions in _Silliman’s Journal_ that “in 1838 the deep channels worn
by the avalanches of mud and stone, and the immense heaps of boulders
and blocks of granite in the river channel, still formed a picturesque
feature in the scenery.”
It will readily be understood that when destruction such as this
follows from landslips along the borders of insignificant rivers,
those occurring on the banks of the mighty rivers which drain whole
continents are still more terrible. The following account from the pen
of Mr. Bates the naturalist, indicates the nature of the landslips
which occur on the banks of the Amazon. “I was awoke before sunrise,
one morning,” he says, “by an unusual sound resembling the roar of
artillery; the noise came from a considerable distance, one crash
succeeding another. I supposed it to be an earthquake, for, although
the night was breathlessly calm, the broad river was much agitated,
and the vessel rolled heavily. Soon afterwards another loud explosion
took place, followed by others which lasted for an hour till the day
dawned, and we then saw the work of destruction going forward on the
other side of the river, about three miles off. Large masses of forest,
including trees of colossal size, probably 200 feet in height, were
rocking to and fro, and falling headlong one after another into the
water. After each avalanche the wave which it caused returned on the
crumbly bank with tremendous force, and caused the fall of other masses
by undermining. The line of coast over which the landslip extended was
a mile or two in length; the end of it, however, was hid from our view
by an intervening island. It was a grand sight; each downfall created
a cloud of spray; the concussion in one place causing other masses
to give way a long distance from it, and thus the crashes continued,
swaying to and fro, with little prospect of termination. When we glided
out of sight two hours after sunrise the destruction was still going
on.”
We might consider here the action of glaciers in gradually grinding
down the mountain slopes, the destructive action of avalanches, and a
number of other forms in which snow and ice break down by slow degrees
the upraised portions of the earth. For in reality all these forms of
destructive action take their origin in the same process whence running
waters and heavy rainfalls derive their power. All these destructive
agencies are derived from the vapour of water in the air. But it seems
better to limit the reader’s attention in this place to the action of
water in the liquid form; and therefore we proceed to consider the
other ways in which rain wears down the land.
Hitherto we have considered effects which are produced chiefly along
the courses of rivers, or in their neighbourhood. But heavy rainfall
acts, and perhaps in the long run as effectively (when we remember the
far wider region affected) over wide tracts of nearly level ground, as
along the banks of torrents and rivers.
The rain which falls on plains or gently undulating surfaces, although
after a while it dries up, yet to some degree aids in levelling the
land, partly by washing down particles of earth, however slowly, to
lower levels, partly by soaking the earth and preparing a thin stratum
of its upper surface to be converted into dust, and blown away by the
wind. But it is when very heavy storms occur that the levelling action
of rain over widely extending regions can be most readily recognized.
Of this fact observant travellers cannot fail to have had occasional
evidence. Sir Charles Lyell mentions one instance observed by him,
which is specially interesting. “During a tour in Spain,” he says,
“I was surprised to see a district of gently undulating ground in
Catalonia, consisting of red and grey sandstone, and in some parts
of red marl, almost entirely denuded of herbage, while the roots of
the pines, holm oaks, and some other trees, were half exposed, as if
the soil had been washed away by a flood. Such is the state of the
forests, for example, between Oristo and Vich, and near San Lorenzo.
But being overtaken by a violent thunderstorm, in the month of August,
I saw the whole surface, even the highest levels of some flat-topped
hills, streaming with mud, while on every declivity the devastation
of torrents was terrific. The peculiarities in the physiognomy of the
district were at once explained, and I was taught that, in speculating
on the greater effects which the direct action of rain may once have
produced on the surface of certain parts of England, we need not revert
to periods when the heat of the climate was tropical.” He might have
cited instances of such storms occurring in England. For example,
White, in his delightful “Natural History of Selborne,” describes
thus the effects of a storm which occurred on June 5, 1784: “At about
a quarter after two the storm began in the parish of Harpley, moving
slowly from north to south, and from thence it came over Norton Farm
and so to Grange Farm, both in this parish. Had it been as extensive
as it was violent (for it was very short) it must have ravaged all the
neighbourhood. The extent of the storm was about two miles in length
and one in breadth. There fell prodigious torrents of rain on the farms
above mentioned, which occasioned a flood as violent as it was sudden,
doing great damage to the meadows and fallows by deluging the one and
washing away the soil of the other. The hollow lane towards Alton was
so torn and disordered as not to be passable till mended, rocks being
removed which weighed two hundredweight.”
We have mentioned the formation of dust, and the action of wind upon
it, as a cause tending to level the surface of the land. It may appear
to many that this cause is too insignificant to be noticed among those
which modify the earth’s surface. In reality, however, owing to its
continuous action, and to its always acting (in the main) in one
direction, this cause is much more important than might be supposed.
We overlook its action as actually going on around us, because in a
few years, or in a few generations, it produces no change that can be
readily noticed. But in long periods of time it changes very markedly
the level of lower lands, and that too even in cities, where means
exist for removing the accumulations of dust which are continually
collecting on the surface of the earth. We know that the remains of
old Roman roads, walls, houses, and so forth, in this country, are
found, not at the present level of the surface, but several feet—in
some cases many yards—below this level. The same holds elsewhere,
under the same conditions—that is, where we know quite certainly
that the substances thus found underground were originally on the
surface, and that there has been neither any disturbance causing them
to be engulfed, nor any deposition of scoriæ, volcanic dust, or other
products of subterranean disturbance. We cannot hesitate to regard this
burying of old buildings as due to the continual deposition of dust,
which eventually becomes compacted into solid earth. We know, moreover,
that the formation of dust is in the main due to rain converting the
surface layers of the earth into mud, which on drying requires but the
frictional action of heavy winds to rise in clouds of dust. In some
soils this process goes on more rapidly than in others, as every one
who has travelled much afoot is aware. There are parts of England, for
instance, where, even in the driest summer, the daily deposition of
dust on dry and breezy days is but slight, others where in such weather
a dust layer at least a quarter of an inch in thickness is deposited
in the course of a day. If we assumed, which would scarcely seem an
exaggerated estimate, that in the course of a single year a layer of
dust averaging an inch in thickness is deposited over the lower levels
of the surface of the land, we should find that the average depth of
the layer formed in the last thousand years would amount to no less
than eighty-three feet. Of course in inhabited places the deposition
of dust is checked, though not so much as most persons imagine. There
is not probably in this country a single building five hundred years
old, originally built at a moderately low level, the position of whose
foundation does not attest the constant gathering of matter upon the
surface. The actual amount by which the lower levels are raised and
the higher levels diminished in the course of a thousand years may be
very much less, but that it must amount to many feet can scarcely be
questioned.
And as in considering the action of rain falling over a wide range of
country, we have to distinguish between the slow but steady action
of ordinary rains and the occasional violent action of great storms
of rain, so in considering the effects of drought following after
rain which has well saturated the land we have to distinguish between
ordinarily dusty times and occasions when in a very short time, owing
to the intensity of the heat and the violence of the wind large
quantities of dust are spread over a wide area. Darwin thus describes
the effect of such exceptional drought, as experienced in the years
1827–1832 in Buenos Ayres:—“So little rain fell that the vegetation,
even to the thistles, failed; the brooks were dried up, and the
whole country assumed the appearance of a dusty high road. This was
especially the case in the northern part of the province of Buenos
Ayres, and the southern part of Santa Fé.” He describes the loss of
life caused by the want of water, and many remarkable circumstances of
the drought which do not here specially concern us. He then goes on to
speak of the dust which gathered over the open country. “Sir Woodbine
Parish,” he says, “informed me of a very curious source of dispute.
The ground being so long dry, such quantities of dust were blown about
that in this open country the landmarks became obliterated, and people
could not tell the limits of their estates.” The dust thus scattered
over the land, whether left or removed, necessarily formed part of the
solid material brought from higher to lower levels, indirectly (in
this case) through the action of rain; for a drought can only convert
into friable matter earth which has before been thoroughly soaked. But
the action of rain, which had originally led to the formation of these
enormous masses of dust, presently took part in carrying the dust in
the form of mud to yet lower levels. “Subsequently to the drought of
1827 to 1832,” proceeds Darwin, “a very rainy season followed, which
caused great floods. Hence it is almost certain that some thousands
of the skeletons” (of creatures whose deaths he had described before)
“were buried by the deposits of the very next year. What could be the
opinion of a geologist, viewing such an enormous collection of bones,
of all kinds of animals and of all ages, thus embedded in one thick
earthy mass? Would he not attribute it to a flood having swept over the
surface of the land, rather than to the common order of things?” In
fact, a single great drought, followed by a very rainy season, must in
this instance, which was however altogether exceptional, have produced
a layer or stratum such as geologists would ordinarily regard as the
work of a much longer time and much more potent disturbing causes.
It may be well to consider in this place the question whether in
reality the quantity of rain which falls now during our winter months
does not greatly exceed that which formerly fell in that part of
the year. The idea is very prevalent that our winters have changed
entirely in character in recent times, and the fear (or the hope?) is
entertained that the change may continue in the same direction until
wet and mild winters replace altogether the cold which prevailed in
former years. There is no sufficient reason, however, for supposing
that any such change is taking place. It is, indeed, not difficult to
find in the meteorological annals of the first half of the present
century, instances of the occurrence of several successive winters very
unlike the greater number of those which we have experienced during
the last ten or twelve years. But if we take any considerable series
of years in the last century we find the alternations of the weather
very similar to those we at present recognize. Consider, for instance,
Gilbert White’s brief summary of the weather from 1768 onwards:—
For the winter of 1768–69 we have October and the first part of
November rainy; thence to the end of 1768 alternate rains and frosts;
January and February frosty and rainy, with gleams of fine weather; to
the middle of March, wind and rain.
For the winter of 1769–70 we have October frosty, the next fortnight
rainy, the next dry and frosty. December windy, with rain and intervals
of frost (the first fortnight very foggy); the first half of January
frosty, thence to the end of February mild hazy weather. March frosty
and brighter.
For 1770–71, from the middle of October to the end of the year, almost
incessant rains; January severe frosts till the last week, the next
fortnight rain and snow, and spring weather to the end of February.
March frosty.
For 1771–72, October rainy, November frost with intervals of fog and
rain, December bright mild weather with hoar frosts; then six weeks of
frost and snow, followed by six of frost, sleet, hail, and snow.
For 1772–73, October, November, and to December 22, rain, with mild
weather; to the end of 1772, cold foggy weather; then a week of frost,
followed by three of dark rainy weather. First fortnight of February
frost; thence to the end of March misty showery weather.
Passing over the winter of 1773–74, which was half rainy, half frosty,
what could more closely resemble the winter weather we have had so much
of during the last few years, than that experienced in the winter of
1774–75? From August 24 to the third week of November, there was rain,
with frequent intervals of sunny weather; to the end of December, dark
dripping fogs; to the end of the first fortnight in March, rain almost
every day.
And so on, with no remarkable changes, until the year 1792, the last of
Gilbert White’s records.
If we limit our attention to any given month of winter, we find the
same mixture of cold and dry with wet and open weather as we are
familiar with at present. Take, for instance, the month usually the
most wintry of all, viz., January. Passing over the years already
considered, we have January, 1776, dark and frosty with much snow
till the 26th (at this time the Thames was frozen over), then foggy
with hoar frost; January, 1777, frosty till the 10th, then foggy and
showery; 1778, frosty till the 13th, then rainy to the 24th, then
hard frost; 1779, frost and showers throughout January; 1780, frost
throughout; 1781, frost and snow to the 25th, then rain and snow;
1782, open and mild; 1783, rainy with heavy winds; 1784, hard frost;
1785, a thaw on the 2nd, then rainy weather to the 28th, the rest of
the month frosty; 1786, frost and snow till January 7, then a week
mild with much rain, the next week heavy snow, and the rest mild with
frequent rain; 1787, first twenty-four days dark moist mild weather,
then four days frost, the rest mild and showery; 1788, thirteen days
mild and wet, five days of frost, and from January 18 to the end of the
month dry windy weather; 1789, thirteen days hard frost, the rest of
the month mild with showers; 1790, sixteen days of mild foggy weather
with occasional rain, to the 21st frost, to the 28th dark with driving
rains, and the rest mild dry weather; 1791, the whole of January mild
with heavy rains; and lastly 1792, “some hard frost in January, but
mostly wet and mild.”
There is nothing certainly in this record to suggest that any material
change has taken place in our January weather during the last eight
years. And if we had given the record of the entire winter for each of
the years above dealt with the result would have been the same.
We have, in fact, very striking evidence in Gilbert White’s account
of the cold weather of December, 1784, which he specially describes
as “very extraordinary,” to show that neither our severe nor our
average winter weather can differ materially from that which people
experienced in the eighteenth century. “In the evening of December 9,”
he says, “the air began to be so very sharp that we thought it would be
curious to attend to the motions of a thermometer; we therefore hung
out two, one made by Martin and one by Dolland” (_sic_, presumably
Dollond), “which soon began to show us what we were to expect; for by
ten o’clock they fell to twenty-one, and at eleven to four, when we
went to bed. On the 10th, in the morning the quicksilver in Dolland’s
glass was down to half a degree below zero, and that of Martin’s, which
was absurdly graduated only to four degrees above zero, sank quite
into the brass guard of the ball, so that when the weather became most
interesting this was useless. On the 10th, at eleven at night, though
the air was perfectly still, Dolland’s glass went down to one degree
below zero!” The note of exclamation is White’s. He goes on to speak
of “this strange severity of the weather,” which was not exceeded
that winter, or at any time during the twenty-four years of White’s
observations. Within the last quarter of a century, the thermometer,
on more than one occasion, has shown two or three degrees below zero.
Certainly the winters cannot be supposed to have been ordinarily
severer than ours in the latter half of the last century, when we find
that thermometers, by well-known instrument makers, were so constructed
as to indicate no lower temperature than four degrees above zero.
Let us return, after this somewhat long digression, to the levelling
action of rain and rivers.
If we consider this action alone, we cannot but recognize in it a cause
sufficient to effect the removal of all the higher parts of the land
to low levels, and eventually of all the low-lying land to the sea, in
the course of such periods as geology makes us acquainted with. The
mud-banks at the mouths of rivers show only a part of what rain and
river action is doing, yet consider how enormous is the mass which is
thus carried into the sea. It has been calculated that in a single week
the Ganges alone carries away from the soil of India and delivers
into the sea twice as much solid substance as is contained in the
great pyramid of Egypt. “The Irrawaddy,” says Sir J. Herschel, “sweeps
off from Burmah 62 cubit feet of earth in every second of time on an
average, and there are 86,400 seconds in every day, and 365 days in
every year; and so on for other rivers. Nor is there any reason to fear
or hope that the rains will cease, and this destructive process come to
an end. For though the quantity of water on the surface of the earth
is probably undergoing a slow process of diminution, small portions of
it year by year taking their place as waters under the earth,[44] yet
these processes are far too slow to appreciably affect the supply of
water till a far longer period has elapsed than that during which (in
all probability) life can continue upon the earth.
When we consider the force really represented by the downfall of rain,
we need not greatly wonder that the levelling power of rain is so
effective. The sun’s heat is the true agent in thus levelling the
earth, and if we regard, as we justly may, the action of water, whether
in the form of rain or river, or of sea-wave raised by wind or tide, as
the chief levelling and therefore destructive force at work upon the
earth, and the action of the earth’s vulcanian energies as the chief
restorative agent, then we may fairly consider the contest as lying
between the sun’s heat and the earth’s internal heat. There can be
little question as to what would be the ultimate issue of the contest
if land and sea and air all endured or were only so far modified as
they were affected by these causes. Sun-heat would inevitably prevail
in the long run over earth-heat. But we see from the condition of
our moon how the withdrawal of water and air from the scene must
diminish the sun’s power of levelling the irregularities of the earth’s
surface. We say advisedly _diminish_, not _destroy_; for there can be
no question that the solar heat alternating with the cold of the long
lunar night is still at work levelling, however slowly, the moon’s
surface; and the same will be the case with our earth when her oceans
and atmosphere have disappeared by slow processes of absorption.
The power actually at work at present in producing rain, and so,
indirectly, in levelling the earth’s surface, is enormous. I have shown
that the amount of heat required to evaporate a quantity of water which
would cover an area of 100 square miles to a depth of one inch would
be equal to the heat which would be produced by the combustion of half
a million tons of coals, and that the amount of force of which this
consumption of heat would be the equivalent corresponds to that which
would be required to raise a weight of upwards of one thousand millions
of tons to a height of one mile.[45] When we remember that the land
surface of the earth amounts to about fifty millions of square miles,
we perceive how enormous must be the force-equivalent of the annual
rainfall of our earth. We are apt to overlook when contemplating the
silent and seemingly quiet processes of nature—such as the formation
of the rain-cloud or the precipitation of rain—the tremendous energy
of the forces really causing these processes. “I have seen,” says
Professor Tyndall, “the wild stone-avalanches of the Alps, which smoke
and thunder down the declivities with a vehemence almost sufficient to
stun the observer. I have also seen snow-flakes descending so softly
as not to hurt the fragile spangles of which they were composed; yet
to produce from aqueous vapour a quantity which a child could carry of
that tender material demands an exertion of energy competent to gather
up the shattered blocks of the largest stone-avalanche I have ever
seen, and pitch them to twice the height from which they fell.”
_ANCIENT BABYLONIAN ASTROGONY._
It is singular to consider how short a time elapsed, after writings
in the arrow-headed or cuneiform letters (the Keilschriften of the
Germans) were discovered, before, first, the power of interpreting them
was obtained, and, secondly, the range of the cuneiform literature
(so to speak) was recognized. Not more than ninety years have passed
since the first specimens of arrow-headed inscriptions reached Europe.
They had been known for a considerable time before this. Indeed, it
has been supposed that the Assyrian letters referred to by Herodotus,
Thucydides, and Pliny, were in this character. Della Valle and
Figueroa, early in the seventeenth century, described inscriptions in
arrow-headed letters, and hazarded the idea that they are to be read
from left to right. But no very satisfactory evidence was advanced to
show whether the inscriptions were to be so read, or from right to
left, or, as Chardin suggested, in vertical lines. The celebrated Olaus
Gerhard Tychsen, of Rostock, and other German philologists, endeavoured
to decipher the specimens which reached Europe towards the end of the
last century; but their efforts, though ingenious and zealous, were not
rewarded with success. In 1801 Dr. Hager advanced the suggestion that
the combinations formed by the arrow-heads did not represent letters
but words, if not entire sentences. Lichtenstein, on the other hand,
maintained that the letters belonged to an old form of the Arabic
or Coptic character; and he succeeded to his own satisfaction in
finding various passages from the Koran in the cuneiform inscriptions.
Dr. Grotefend was the first to achieve any real success in this line
of research. It is said that he was led to take up the subject by a
slight dispute with one of his friends, which led to a wager that he
would decipher one of the cuneiform inscriptions. The results of his
investigations were that cuneiform inscriptions are alphabetical, not
hieroglyphical; that the language employed is the basis of most of the
Eastern languages; and that it is written from right to left. Since
his time, through the labours of Rich, Botta, Rawlinson, Hincks, De
Saulcy, Layard, Sayce, George Smith, and others, the collection and
interpretation of the arrow-headed inscriptions have been carried
out with great success. We find reason to believe that, though the
original literature of Babylon was lost, the tablet libraries of
Assyria contained copies of most of the writings of the more ancient
nation. Amongst these have been found the now celebrated descriptions
of the Creation, the Fall of Man, the Deluge, the Tower of Babel, and
other matters found in an abridged and expurgated form in the book of
Genesis. It is to that portion of the Babylonian account which relates
to the creation of the sun and moon and stars that I wish here to call
attention. It is not only curious in itself, but throws light, in my
opinion, on questions of considerable interest connected with the views
of ancient Eastern nations respecting the heavenly bodies.
It may be well, before considering the passage in question, to consider
briefly—though we may not be able definitely to determine—the real
antiquity of the Babylonian account.
In Smith’s interesting work on the Chaldæan account of Genesis, the
question whether the Babylonian account preceded the writing of the
book of Genesis, or _vice versâ_, is not definitely dealt with.
Probably this part of his subject was included among the “important
comparisons and conclusions with respect to Genesis” which he preferred
to avoid, as his “desire was first to obtain the recognition of the
evidence without prejudice.” It might certainly have interfered to
some degree with the unprejudiced recognition of the evidence of the
tablets if it had been maintained by him, and still more if he had
demonstrated, that the Babylonian is the earlier version. For the
account in the book of Genesis, coming thus to be regarded as merely an
expurgated version of a narrative originally containing much fabulous
matter, and not a little that is monstrous and preposterous, would
certainly not have been presented to us in quite that aspect in which
it had long been regarded by theologians.
But although Mr. Smith states that he placed the various dates as low
as he fairly could, considering the evidence,—nay, that he “aimed to
do this rather than to establish any system of chronology,”—there can
be no mistake about the relative antiquity which he in reality assigns
to the Babylonian inscriptions. He states, indeed, that every copy of
the Genesis legends belongs to the reign of Assurbanipal, who reigned
over Assyria B.C. 670. But it is “acknowledged on all hands that the
tablets are not the originals, but are only copies from earlier texts.”
The Assyrians acknowledge themselves that this literature was borrowed
from Babylonian sources, and of course it is to Babylonia we have to
look to ascertain the approximate dates of the original documents.
“The difficulty,” he proceeds, “is increased by the following
considerations: it appears that at an early period in Babylonian
history a great literary development took place, and numerous works
were produced which embodied the prevailing myths, religion, and
science of that day. Written, many of them, in a noble style of poetry
on one side, or registering the highest efforts of their science on
the other, these texts became the standards for Babylonian literature,
and later generations were content to copy these writings instead of
making new works for themselves. Clay, the material on which they were
written, was everywhere abundant, copies were multiplied, and by the
veneration in which they were held these texts fixed and stereotyped
the style of Babylonian literature, and the language in which they
were written remained the classical style in the country down to the
Persian conquest. Thus it happens that texts of Rim-agu, Sargon, and
Hammurabi, who were 1000 years before Nebuchadnezzar and Nabonidus,
show the same language as the texts of these later kings, there being
no sensible difference in style to match the long interval between
them,”—precisely as a certain devotional style of writing of our own
day closely resembles the style of the sixteenth century.
We cannot, then, from the style, determine the age of the original
writings from which the Assyrian tablets were copied. But there are
certain facts which enable us to form an opinion on this point.
Babylonia was conquered about B.C. 1300, by Tugultininip, king of
Assyria. For 250 years before that date a foreign race (called by
Berosus, Arabs) had ruled in Babylonia. There is no evidence of any of
the original Babylonian Genesis tablets being written after the date of
Hammurabi, under whom it is supposed that this race obtained dominion
in Babylonia. Many scholars, indeed, regard Hammurabi as much more
ancient; but none set him later than 1550 B.C.
Now, before the time of Hammurabi several races of kings reigned,
their reigns ranging over a period of 500 years. They were called
chiefly Kings of Sumir and Akkad—that is, Kings of Upper and Lower
Babylonia. It is believed that before this period,—ranging, say, from
about 2000 B.C. to 1550 B.C. (at least not later, though possibly,
and according to many scholars, probably, far earlier),—the two
divisions of Babylonia were separate monarchies. Thus, evidence
whether any literature was written before or after B.C. 2000, may
be found in the presence or absence of mention, or traces, of this
division of the Babylonian kingdom. Mr. Smith considers, for example,
that two works,—the great Chaldæan work on astrology, and a legend
which he calls “The Exploits of Lubara,”—certainly belong to the
period preceding B.C. 2000. In the former work, the subject of which
specially connects it, as will presently be seen, with the tablet
relating to the creation of the heavenly bodies, Akkad is always
referred to as a separate state.
Now Mr. Smith finds that the story of the Creation and Fall belongs
to the upper or Akkad division of the country. The Izdubar legends,
containing the story of the Flood, and what Mr. Smith regards as
probably the history of Nimrod, seem to belong to Sumir, the southern
division of Babylonia. He considers the Izdubar legends to have been
written at least as early as B.C. 2000. The story of the Creation
“may not have been committed to writing so early;” but it also is
of great antiquity. And these legends “were traditions before they
were committed to writing, and were common, in some form, to all the
country.” Remembering Mr. Smith’s expressed intention of setting all
dates as late as possible, his endeavour to do this rather than to
establish any system of chronology, we cannot misunderstand the real
drift of his arguments, or the real significance of his conclusion that
the period when the Genesis tablets were originally written extended
from B.C. 2000 to B.C. 1550, or roughly synchronized with the period
from Abraham to Moses, according to the ordinary chronology of our
Bibles. “During this period it appears that traditions of the creation
of the universe, and human history down to the time of Nimrod, existed
parallel to, and in some points identical with, those given in the book
of Genesis.”
Thus viewing the matter, we recognize the interest of that passage in
the Babylonian Genesis tablets which corresponds with the account in
the book of Genesis respecting the creation of the heavenly bodies. We
find in it the earliest existent record of the origin of astrological
superstitions. It does not express merely the vague belief, which
might be variously interpreted, that the sun and moon and stars were
specially created (after light had been created, after the firmament
had been formed separating the waters above from the waters below, and
after the land had been separated from the water) to be for signs and
for seasons for the inhabitants of the world—that is, of our earth.
It definitely states that those other suns, the stars, were set into
constellation figures for man’s benefit; the planets and the moon next
formed for his use; and the sun set thereafter in the heavens as the
chief among the celestial bodies.
It runs thus, so far as the fragments have yet been gathered together:—
FIFTH TABLET OF CREATION LEGEND.
1. It was delightful all that was fixed by the great gods.
2. Stars, their appearance [in figures] of animals he arranged,
3. To fix the year through the observation of their
constellations,
4. Twelve months (or signs) of stars in three rows he arranged,
5. From the day when the year commences unto the close.
6. He marked the positions of the wandering stars (planets) to
shine in their courses,
7. That they may not do injury, and may not trouble any one.
8. The positions of the gods Bel and Hea he fixed with him.
9. And he opened the great gates in the darkness shrouded,
10. The fastenings were strong on the left and right.
11. In its mass (_i.e._ the lower chaos) he made a boiling.
12. The god Uru (the moon) he caused to rise out, the night he
over shadowed,
13. To fix it also for the light of the night until the shining
of the day,
14. That the month might not be broken, and in its amount be
regular.
15. At the beginning of the month, at the rising of the night,
16. His horns are breaking through to shine on the heaven.
17. On the seventh day to a circle he begins to swell,
18. And stretches towards the dawn further.
19. When the god Shamas (the sun) in the horizon of heaven, in
the east,
20. . . . formed beautifully and . . .
21. . . . . . . to the orbit Shamas was perfected
22. . . . . . . . . . the dawn Shamas should change
23. . . . . . . . . . . . . going on its path
24. . . . . . . . . . . . . . . . giving judgment
25. . . . . . . . . . . . . . . . . . . to tame
26. . . . . . . . . . . . . . . . . . . . . . a second time
27. . . .
Of this tablet Smith remarks that it is a typical specimen of the
style of the series, and shows a marked stage in the Creation, the
appointment of the heavenly orbs running parallel to the biblical
account of the fourth day of Creation. It is important to notice
its significance in this respect. We can understand now the meaning
underlying the words, “God said, Let there be lights in the firmament
of the heavens, to divide the day from the night; and let them be for
signs and for seasons, and for days and years.” The order, indeed,
in which the bodies are formed according to the biblical account is
inverted. The greater light—the sun—is made first, to rule the day:
then the lesser light—the moon—to rule the night. These are the
heavenly bodies which in this description rule the day of 24 hours.
The sun may be regarded also as ruling (according to the ancient view,
as according to nature) the seasons and the year. The stars remain as
set in the heaven for signs. “He made the stars also.” “And God set
them”—that is, the sun, moon, and stars—“in the firmament of the
heaven to give light upon the earth, and to rule over the day and over
the night,” and so forth.
No one can doubt, I conceive, that the biblical account is superior
to the other, both in a scientific and in a literary sense. It states
much less as actually known, and what it does state accords better with
the facts known in the writer’s day. Then, the Babylonian narrative,
though impressive in certain passages, is overloaded with detail.
In both accounts we find the heavenly bodies set in the firmament
by a special creative act, and specially designed for the benefit
of man. And in passing I would observe that the discovery of these
Babylonian inscriptions, however they may be interpreted, and whether
they be regarded as somewhat earlier or somewhat later than the Bible
narrative, appears to dispose finally of the fantastic interpretation
assigned by Hugh Miller and others to the biblical cosmogony, as
corresponding to a series of visions in which the varying aspects
of the world were presented. It has long seemed to me an utterly
untenable proposition that a narrative seemingly intended to describe
definitely a certain series of events should, after being for ages
so interpreted, require now for its correct interpretation to be
regarded as an account of a series of visions. If the explanation were
reconcilable in any way with the words of Genesis, there yet seems
something of profanity in imagining that men’s minds had thus been
played with by a narrative purporting to be of one sort yet in reality
of quite a different character. But whatever possibility there may be
(and it can be but the barest possibility) that the Genesis narrative
admits of the vision interpretation, no one can reasonably attempt to
extend that interpretation to the Babylonian account. So that either
a narrative from which the Genesis account was presumably derived was
certainly intended to describe a series of events, or else a narrative
very nearly as early as the Genesis account, and presumably derived
from it at a time when its true meaning must have been known, presents
the sun, moon, and stars as objects expressly created and set in the
sky after the earth had been formed, and for the special benefit of man
as yet uncreated.
I am not concerned, however, either to dwell upon this point, or to
insist on any of its consequences. Let us return to the consideration
of the Babylonian narrative as it stands.
We find twelve constellations or signs of the zodiac are mentioned
as set to fix the year. I am inclined to consider that the preceding
words, “stars, their appearance in figures of animals he arranged,”
relate specially to the stars of the zodiac. The inventor of this
astrogony probably regarded the stars as originally scattered in an
irregular manner over the heavens,—rather as chaotic material from
which constellations might be formed, than as objects separately and
expressly created. Then they were taken and formed into figures of
animals, set in such a way as to fix the year through the observation
of these constellations. It is hardly necessary, perhaps, to remind the
reader that the word zodiac is derived from a Greek word signifying
an animal, the original name of the zone being the zodiacal way,
or the pathway of the animals. Our older navigators called it the
Bestiary.[46] “Twelve months or signs in three rows.” Smith takes the
three rows to mean (i.) the zodiacal signs, (ii.) the constellations
north of the zodiac, and (iii.) the constellations south of the zodiac.
But this does not agree with the words “twelve signs in three rows.”
Possibly the reference is to three circles, two bounding the zodiac
on the north and south respectively, the third central, the ecliptic,
or track of the sun; or the two tropics and the equator may have
been signified. Instead of “twelve signs in three rows,” we should,
probably, read “twelve signs along a triple band.” The description was
written long after astronomical temples were first erected, and as
the designer of a zodiacal dome like that (far more recently) erected
at Denderah would set the twelve zodiacal signs along a band formed
by three parallel circles, marking its central line and its northern
and southern limits, so we can understand the writer of the tablet
presenting the celestial architect as working in the same lines, on a
grander scale; setting the twelve zodiacal signs on the corresponding
triple band in the heavens themselves.
The next point to be noticed in the Babylonian astrology is the
reference to “wandering stars.” Mr. Smith remarks that the word
_nibir_, thus translated, “is not the usual word for planet, and
there is a star called _Nibir_ near the place where the sun crossed
the boundary between the old and new years, and this star was one of
twelve supposed to be favourable to Babylonia.” “It is evident,” he
proceeds, “from the opening of the inscription on the first tablet of
the Chaldæan astrology and astronomy, that the functions of the stars
were, according to the Babylonians, to act not only as regulators of
the seasons and the year, but also to be used as signs, as in Genesis
i. 14; for in those ages it was generally believed that the heavenly
bodies gave, by their appearance and positions, signs of events which
were coming on the earth.” The two verses relating to Nibir seem to
correspond to no other celestial bodies but planets (unless, perhaps,
to comets). If we regard Nibir as signifying any fixed star, we can
find no significance in the marking of the course of the star Nibir,
that it may do no injury and may not trouble any one. Moreover, as the
fixed stars, the sun, and the moon, are separately described, it seems
unlikely that the planets would be left unnoticed. In the biblical
narrative the reference to the celestial bodies is so short that we
can understand the planets being included in the words, “He made the
stars also.” But in an account so full of detail as that presented
in the Babylonian tablet, the omission of the planets would be very
remarkable. It is also worthy of notice that in Polyhistor’s Babylonian
traditions, recorded by Berosus, we read that “Belus formed the stars,
the sun, the moon, and the five planets.”
In the tablet narrative the creator of the heavenly bodies is supposed
to be Anu, god of the heavens. This is inferred by Mr. Smith from the
fact “that the God who created the stars, fixed places or habitations
for Bel and Hea with himself in the heavens.” For according to the
Babylonian theogony, the three gods Anu, Bel, and Hea share between
them the divisions of the face of the sky.
The account of the creation of the moon is perhaps the most
interesting part of the narrative. We see that, according to the
Babylonian philosophy, the earth is regarded as formed from the waters
and resting after its creation above a vast abyss of chaotic water.
We find traces of this old hypothesis in several biblical passages,
as, for instance, in the words of the Third Commandment, “the heaven
above, the earth beneath, and the waters under the earth;” and again
in Proverbs xxx. 4, “Who hath bound the waters in a garment? who
hath established all the ends of the earth?” “The great gates in the
darkness shrouded, the fastenings strong on the left and right,” in the
Babylonian account, refer to the enclosure of the great infernal lake,
so that the waters under the earth might not overwhelm the world. It
is from out the dark ocean beneath the earth that the god Anu calls
the moon into being. He opens the mighty gates shrouded in the nether
darkness, and creates a vast whirlpool in the gloomy ocean; then “at
his bidding, from the turmoil arose the moon like a giant bubble, and
passing through the open gates mounted on its destined way across the
vaults of heaven.” It is strange to reflect that in quite recent times,
at least 4000 years after the Babylonian tablet was written, and who
shall tell how many years after the tradition was first invented?—a
theory of the moon’s origin not unlike the Babylonian hypothesis has
been advanced, despite overwhelming dynamical objections; and a modern
paradoxist has even pointed to the spot beneath the ocean where a
sudden increase of depth indicates that matter was suddenly extruded
long ago, and driven forcibly away from the earth to the orbit along
which that expelled mass—our moon—is now travelling.
It would have been interesting to have known how the Babylonian tablet
described the creation of Shamas, the sun; though, so far as can be
judged from the fragments above quoted, there was not the same fulness
of detail in this part of the description as in that relating to the
moon. Mr. Smith infers that the Babylonians considered the moon the
more important body, unlike the writer or compiler of the book of
Genesis, who describes the sun as the greater light. It does not seem
to follow very clearly, however, from the tablet record, that the
sun was considered inferior to the moon in importance, and certainly
we cannot imagine that the Babylonians considered the moon a greater
light. The creation of the stars precedes that of the moon, though
manifestly the moon was judged to be more important than the stars. Not
improbably, therefore, the sun, though following the moon in order of
creation, was regarded as the more important orb of the two. In fact,
in the Babylonian as in the (so-called) Mosaic legend of Creation,
the more important members of a series of created bodies are, in some
cases, created last—man last of all orders of animated beings, for
instance.
If we turn now from the consideration of the Babylonian tradition of
the creation of the heavenly bodies to note how the biblical account
differs from it, not only or chiefly in details, but in general
character, we seem to recognize in the latter a determination to
detach from the celestial orbs the individuality, so to speak, which
the older tradition had given to them. The account in Genesis is not
only simpler, and, in a literary sense, more effective, but it is in
another sense purified. The celestial bodies do not appear in it as
celestial beings. The Babylonian legend is followed only so far as it
can be followed consistently with the avoidance of all that might tempt
to the worship of the sun, moon, and stars. The writer of the book of
Genesis, whether Moses or not, seems certainly to have shared the views
of Moses as to the Sabæanism of the nation from which the children
of Abraham had separated. Moses warned the Israelite,—“Take good
heed unto thyself, lest thou lift up thine eyes unto heaven; and when
thou seest the sun, and the moon, and the stars, even all the host of
heaven, shouldest be driven to worship them, and serve them, which the
Lord thy God hath divided unto all nations under the whole heaven.” So
the writer of Genesis is careful to remove from the tradition which he
follows all that might suggest the individual power and influence of
the heavenly bodies. The stars are to be for signs, but we read nothing
of the power of the wandering stars “to do injury or trouble any one.”
(That is, not in the book of Genesis. In the song of Deborah we find,
though perhaps only in a poetic fashion, the old influences assigned
to the planets, when the singer says that the “stars in their courses
fought against Sisera.” Deborah, however, was a woman, and women have
always been loth and late to give up ancient superstitions.) Again, the
sun and the moon in Genesis are the greater and the lesser lights, not,
as in the Babylonian narrative, the god Shamas and the god Uru.
We may find a parallel to this treatment of the Babylonian myth in the
treatment by Moses of the observance of the Sabbath, a day of rest
which the Babylonian tablets show to have had, as for other reasons
had been before suspected, an astrological significance. The Jewish
lawgiver does not do away with the observance; in fact, he was probably
powerless to do away with it. At any rate, he suffers the observance
to remain, precisely as the writer of the book of Genesis retains the
Babylonian tradition of the creation of the celestial bodies. But he
is careful to expurgate the Chaldæan observance, just as the writer
of Genesis is careful to expurgate the Babylonian tradition. The week
as a period is no longer associated with astrological superstitions,
nor the Sabbath rest enjoined as a fetish. Both ideas are directly
associated with the monotheistic principle which primarily led to the
separation of the family of Abraham from the rest of the Chaldæan race.
In Babylonia, the method of associating the names of the sun, moon,
and stars with the days, doubtless had its origin. Saturn was the
Sabbath star, as it is still called (Sabbatai) in the Talmud. But, as
Professor Tischendorf told Humboldt, in answer to a question specially
addressed to him on the subject, “there is an entire absence in both
the Old and New Testaments, of any traces of names of week-days taken
from the planets.” The lunar festivals, again, though unquestionably
Sabaistic in their origin, were apparently too thoroughly established
to be discarded by Moses; nay, he was even obliged to permit the
continuance of many observances which suspiciously resembled the old
offerings of sacrifice to the moon as a deity. He had also to continue
the sacrifice of the passover, the origin of which was unmistakably
astronomical,—corresponding in time to the sun’s passage across the
equator, or rather to the first lunar month following and including
that event. But he carefully dissociates both the lunar and the
lunisolar sacrifices from their primary Sabaistic significance. In
fact, the history of early Hebrew legislation, so far as it related to
religion, is the history of a struggle on the part of the lawgivers and
the leaders of opinion against the tendency of the people to revert to
the idolatrous worship of their ancestors and of races closely akin to
them—especially against the tendency to the worship of the sun and
moon and all the host of heaven.
In the very fact, however, that this contest was maintained, while yet
the Hebrew cosmogony, and in particular the Hebrew astrogony, contains
indubitable evidence of its origin in the poetical myths of older
Babylonia, we find one of the strongest proofs of the influence which
the literature of Babylon, when at the fulness of its development,
exerted upon surrounding nations. This influence is not more clearly
shown even by the fact that nearly 2000 years after the decay of
Babylonian literature, science, and art, a nation like the Assyrians,
engaged in establishing empire rather than in literary and scientific
pursuits, should have been at the pains to obtain copies of many
thousands of the tablet records which formed the libraries of older
Babylonia. In both circumstances we find good reason for hoping that
careful search among Assyrian and Babylonian ruins may not only be
rewarded by the discovery of many other portions of the later Assyrian
library (which was also in some sense a museum), but that other and
earlier copies of the original Babylonian records may be obtained.
For it seems unlikely that works so valuable as to be thought worth
recopying after 1500 or 2000 years, in Assyria, had not been more than
once copied during the interval in Babylonia. “Search in Babylonia,”
says Mr. Smith, “would no doubt yield earlier copies of all these
works, but that search has not yet been instituted, and for the present
we have to be contented with our Assyrian copies. Looking, however, at
the world-wide interest of the subjects, and at the important evidence
which perfect copies of these works would undoubtedly give, there can
be no doubt,” Mr. Smith adds, “that the subject of further search and
discovery will not slumber, and that all as yet known will one day be
superseded by newer texts and fuller and more perfect light.”
Printed by BALLANTYNE, HANSON & CO.
Edinburgh & London
FOOTNOTES
[1] More strictly, it plays the same part as a glass screen before a
glowing fire. When the heat of the fire falls on such a screen (through
which light passes readily enough), it is received by the glass,
warming the glass up to a certain point, and the warmed glass emits in
all directions the heat so received; thus scattering over a large space
the rays which, but for the glass, would have fallen directly upon the
objects which the screen is intended to protect.
[2] The case here imagined is not entirely hypothetical. We examine
Mercury and Venus very nearly under the conditions here imagined; for
we can obtain only spectroscopic evidence respecting the existence
of water on either planet. In the case of Mars we have telescopic
evidence, and no one now doubts that the greenish parts of the planet
are seas and oceans. But Venus and Mercury are never seen under
conditions enabling the observer to determine the colour of various
parts of their discs.
I may add that a mistake, somewhat analogous to that which I have
described in the cases of an imagined observer of our earth, has
been made by some spectroscopists in the case of the planets Jupiter
and Saturn. In considering the spectroscopic evidence respecting
the condition of these planets’ atmospheres, they have overlooked
the circumstance that we can judge only of the condition of the
outermost and coolest layers, for the lower layers are concealed
from view by the enormous cloud masses, floating, as the telescope
shows, in the atmospheric envelopes of the giant planets. Thus the
German spectroscopist Vögel argues that because in the spectrum
of Jupiter dark lines are seen which are known to belong to the
absorption-spectrum of aqueous vapour, the planet’s surface cannot be
intensely hot. But Jupiter’s absorption-spectrum belongs to layers of
his atmosphere lying far above his surface. We can no more infer the
actual temperature of Jupiter’s surface from the temperature of the
layers which produce his absorption-spectrum, than a visitor who should
view our earth from outer space, observing the low temperature of the
air ten or twelve miles above the sea-level, could infer thence the
actual temperature of the earth’s surface.
[3] In “Other Worlds than Ours,” I wrote as follows:—“The lines of
hydrogen, which are so well marked in the solar spectrum, are not seen
in the spectrum of Betelgeux. We are not to conclude from this that
hydrogen does not exist in the composition of the star. We know that
certain parts of the solar disc, when examined with the spectroscope,
do not at all times exhibit the hydrogen lines, or may even present
them as bright instead of dark lines. It may well be that in Betelgeux
hydrogen exists under such conditions that the amount of light it sends
forth is nearly equivalent to the amount it absorbs, in which case its
characteristic lines would not be easily discernible. In fact, it is
important to notice generally, that while there can be no mistaking
the positive evidence afforded by the spectroscope as to the existence
of any element in sun or star, the negative evidence supplied by the
absence of particular lines is not to be certainly relied upon.”
[4] Dr. Draper remarks here in passing, “I do not think that, in
comparisons of the spectra of the elements and sun, enough stress has
been laid on the general appearance of lines apart from their mere
position; in photographic representations this point is very prominent.”
[5] The word “ignited” may mislead, and indeed is not correctly used
here. The oxygen in the solar atmosphere, like the hydrogen, is simply
glowing with intensity of heat. No process of combustion is taking
place. Ignition, strictly speaking, means the initiation of the process
of combustion, and a substance can only be said to be ignited when it
has been set burning. The word _glowing_ is preferable; or if reference
is made to heat and light combined, then “glowing with intensity of
heat” seems the description most likely to be correctly understood.
[6] It would be an interesting experiment, which I would specially
recommend to those who, like Dr. Draper, possess instrumental means
specially adapted to the inquiry, to ascertain what variations, if any,
occur in the solar spectrum when (i.) the central part of the disc
alone, and (ii.) the outer part alone, is allowed to transmit light to
the spectroscope. The inquiry seems specially suited to the methods
of spectral photography pursued by Dr. Draper, and by Dr. Huggins, in
this country. Still, I believe interesting results can be obtained even
without these special appliances; and I hope before long to employ my
own telescope in this department of research.
[7] In 1860, a year of maximum sun-spot frequency, Cambridge won the
University boat-race; the year 1865, of minimum sun-spot frequency,
marked the middle of a long array of Oxford victories; 1872, the next
maximum, marked the middle of a Cambridge series of victories. May we
not anticipate that in 1878, the year of minimum spot frequency, Oxford
will win? [This prediction made in autumn, 1877, was fulfilled.] I
doubt not similar evidence might be obtained about cricket.
[8] It must be understood that this remark relates only to the theory
that by close scrutiny of the sun a power of predicting weather
peculiarities can be obtained, not to the theory that there may be
a cyclic association between sun-spots and the weather. If this
association exists, yet no scrutiny of the sun can tell us more than
we already know, and it will scarcely be pretended that new solar
observatories could give us any better general idea of the progress of
the great sun-spot period than we obtain from observatories already in
existence, or, indeed, might obtain from the observations of a single
amateur telescopist.
I think it quite possible that, from the systematic study of
terrestrial relations, the existence of a cyclic association between
the great spot period and terrestrial phenomena may be demonstrated,
instead of being merely surmised, as at present. By the way, it may be
worth noting that a prediction relative to the coming winter [that of
1877–78] has been made on the faith of such association by Professor
Piazzi Smyth. It runs as follows:—
“Having recently computed the remaining observations of our
earth-thermometers here, and prepared a new projection of all the
observations from their beginning in 1837 to their calamitous close
last year [1876]—results generally confirmatory of those arrived at in
1870 have been obtained, but with more pointed and immediate bearing on
the weather now before us.
“The chief features undoubtedly deducible for the past thirty-nine
years, after eliminating the more seasonal effects of ordinary summer
and winter, are:—
“1. Between 1837 and 1876 three great heat-waves, from without,
struck this part of the earth, viz., the first in 1846·5, the second
in 1858·0, and the third in 1868·7. And unless some very complete
alteration in the weather is to take place, the next such visitation
may be looked for in 1879·5, within limits of half a year each way.
“2. The next feature in magnitude and certainty is that the periods
of minimum temperature, or cold, are not either in, or anywhere near,
the middle time between the crests of those three chronologically
identified heat-waves, but are comparatively close up to them _on
either side_, at a distance of about a year and a half, so that the
next such cold-wave is due at the end of the present year [1877].
“This is, perhaps, not an agreeable prospect, especially if political
agitators are at this time moving amongst the colliers, striving to
persuade them to decrease the out-put of coal at every pit’s mouth.
Being, therefore, quite willing, for the general good, to suppose
myself mistaken, I beg to send you a first impression of plate 17 of
the forthcoming volume of observations of this Royal Observatory, and
shall be very happy if you can bring out from the measures recorded
there any more comfortable view for the public at large.
“PIAZZI SMYTH,
“Astronomer-Royal for Scotland.”
If this prediction shall be confirmed [this was written in autumn,
1877], it will afford an argument in favour of the existence of the
cyclic relation suggested, but no argument for the endowment of solar
research. Professor Smyth’s observations were not solar but terrestrial.
[The prediction was not confirmed, the winter of 1877–78 being, on the
contrary, exceptionally mild.]
[9] The reader unfamiliar with the principles of the telescope may
require to be told that in the ordinary telescope each part of the
object-glass forms a complete image of the object examined. If, when
using an opera-glass (one barrel), a portion of the large glass be
covered, a portion of what had before been visible is concealed. But
this is not the case with a telescope of the ordinary construction. All
that happens when a portion of the object-glass is covered is that the
object appears in some degree less fully illuminated.
[10] It may be briefly sketched, perhaps, in a note. The force
necessary to draw the earth inwards in such sort as to make her follow
her actual course is proportional to (i) the square of her velocity
directly, and (ii) her distance from the sun inversely. If we increase
our estimate of the earth’s distance from the sun, we, in the same
degree, increase our estimate of her orbital velocity. The square of
this velocity then increases as the square of the estimated distance;
and therefore, the estimated force sunwards is increased as the square
of the distance on account of (i), and diminished as the distance on
account of (ii), and is, therefore, on the whole, increased as the
distance. That is, we now regard the sun’s action as greater at this
greater distance, and in the same degree that the distance is greater;
whereas, if it had been what we before supposed it, it would be less
at the greater distance as the square of the distance (attraction
varying inversely as the square of the distance). Being greater as the
distance, instead of less as the square of the distance, it follows
that our estimate of the sun’s absolute force is now greater as the
cube of the distance. Similarly, if we had diminished our estimate
of the sun’s distance, we should have diminished our estimate of his
absolute power (or mass) as the cube of the distance. But our estimate
of the sun’s volume is also proportional to the cube of his estimated
distance. Hence our estimate of his mass varies as our estimate of his
volume; or, our estimate of his mean density is constant.
[11] Only very recently an asteroid, Hilda (153rd in order of
detection), has been discovered which travels very much nearer to the
path of Jupiter than to that of Mars—a solitary instance in that
respect. Its distance (the earth’s distance being represented by
unity), is 3·95, Jupiter’s being 5·20, and Mars’s 1·52; its period
falls short of 8 years by only two months, the average period of the
asteroidal family being only about 4½ years. Five others, Cybele,
Freia, Sylvia, Camilla, and Hermione, travel rather nearer to Jupiter
than to Mars; but the remaining 166 travel nearer to Mars, and most of
them much nearer.
[12] Even this statement is not mathematically exact. If the rails are
straight and parallel, the ratio of approach and recession of an engine
on one line, towards or from an engine on the other, is never quite
equal to the engines’ velocities added together; but the difference
amounts practically to nothing, except when the engines are near each
other.
[13] I have omitted all reference to details; but in reality the
double battery was automatic, the motion of the observing telescope,
as different colours of the spectrum were brought into view, setting
all the prisms of the double battery into that precise position which
causes them to show best each particular part of the spectrum thus
brought into view. It is rather singular that the first view I ever had
of the solar prominences, was obtained (at Dr. Huggins’s observatory)
with this instrument of my own invention, which also was the first
powerful spectroscope I had ever used or even seen.
[14] It varies more in some months than in others, as the moon’s orbit
changes in shape under the various perturbing influences to which she
is subject.
[15] It may seem strange to say that one hundred and twenty years after
the passage of a comet which last passed in 1862, and was then first
discovered, August meteors have been seen. But in reality, as we know
the period of that comet to be about one hundred and thirty years, we
know that the displays of the years 1840, 1841, etc., to 1850, must
have followed the preceding passage by about that interval of time.
[16] The D line, properly speaking, as originally named by Fraunhofer,
belongs to sodium. The line spoken of above as the sierra D line is
one close by the sodium line, and mistaken for it when first seen in
the spectrum of the coloured prominences as a bright line. It does not
appear as a dark line in the solar spectrum.
[17] Since this was written, I have learned that Mr. Backhouse, of
Sunderland, announced similar results to those obtained at Dunecht, as
seen a fortnight or so earlier.
[18] Here no account is taken of the motions of the stars within the
system; such motions must ordinarily be minute compared with the common
motion of the system.
[19] Eight pictures of nebulæ were exhibited in illustration of this
peculiarity.
[20] Sir John Herschel long since pointed to the variation of our sun
as a possible cause of such changes of terrestrial climate.
[21] During these journeys the Atlantic was sounded, and Scoresby’s
estimate of the enormous depth of the Atlantic to the north-west of
Spitzbergen was fully confirmed, the line indicating a depth of more
than two miles. It was found also that Spitzbergen is connected with
Norway by a submarine bank.
[22] It is far from improbable that a change has taken place in the
climate of the part of the Arctic regions traversed by Koldewey; for
the Dutch seem readily to have found their way much further north two
centuries ago. Indeed, among Captain Koldewey’s results is one which
seems to indicate the occurrence of such a change. The country he
explored was found to have been inhabited. “Numerous huts of Esquimaux
were seen, and various instruments and utensils of primitive form;
but for some reason or other the region seems to have been finally
deserted. The Polar bear reigns supreme on the glaciers, as the walrus
does among the icebergs.” Not improbably the former inhabitants were
forced to leave this region by the gradually increasing cold.
[23] Dr. Emile Bessels was tried at New York in 1872, on the charge of
having poisoned Captain Hall, but was acquitted.
[24] The phenomena here described are well worth observing on their
own account, as affording a very instructive and at the same time very
beautiful illustration of wave motions. They can be well seen at many
of our watering-places. The same laws of wave motion can be readily
illustrated also by throwing two stones into a large smooth pool, at
points a few yards apart. The crossing of the two sets of circular
waves produces a wave-net, the meshes of which vary in shape according
to their position.
[25] It is a pity that men of science so often forget, when addressing
those who are not men of science, or who study other departments than
theirs, that technical terms are out of place. Most people, I take it
are more familiar, on the whole, with eyelids than with _palpebræ_.
[26] This nautical expression is new to me. Top-gallants—fore,
main, and mizen—I know, and forecastle I know, but the top-gallant
forecastle I do not know.
[27] The instrument was lent to Mr. Huggins by Mr. W. Spottiswoode. It
has been recently employed successfully at Greenwich.
[28] Thus in _Christie Johnstone_, written in 1853, when Flucker
Johnstone tells Christie the story of the widow’s sorrows, giving
it word for word, and even throwing in what dramatists call “the
business,” he says, “‘Here ye’ll play your hand like a geraffe.’
‘Geraffe?’ she says; ‘that’s a beast, I’m thinking.’ ‘Na; it’s the
thing on the hill that makes signals.’ ‘Telegraph, ye fulish goloshen!’
‘Oo, ay, telegraph! geraffe’s sunnest said for a’.’” “Playing the hand
like a telegraph” would now be as unmeaning as Flucker Johnstone’s
original description.
[29] Not “to represent the gutta-percha,” as stated in the _Times_
account of Mr. Muirhead’s invention. The gutta-percha corresponds
to the insulating material of the artificial circuit; viz., the
prepared paper through which the current along the tinfoil strips acts
inductively on the coating of tinfoil.
[30] I must caution the reader against Fig. 348 in Guillemin’s
_Application of the Physical Forces_, in which the part _c d_ of the
wire is not shown. The two coils are in reality part of a single coil,
divided into two to permit of the bar being bent; and to remove the
part _c d_ is to divide the wire, and, of course, break the current. It
will be seen that _c d_ passes from the remote side of coil _b c_, Fig.
6, to the near side of coil _d e_. If it were taken round the remote
side of the latter coil, the current along this would neutralize the
effect of the current along the other.
[31] The paper is soaked in dilute ferrocyanide of potassium, and the
passage of the current forms a Prussian blue.
[32] Sir W. Thomson states, in his altogether excellent article on the
electric telegraph, in Nichol’s _Cyclopædia_, that the invention of
this process is due to Mr. Bakewell.
[33] It is to be noticed, however, that the recording pointer must
always mark its lines in the same direction, so that, unless a message
is being transmitted at the same time that one is being received (in
which case the oscillations both ways are utilized), the instrument
works only during one-half of each complete double oscillation.
[34] It seems to me a pity that in the English edition of this work
the usual measures have not been substituted throughout. The book is
not intended or indeed suitable for scientific readers, who alone are
accustomed to the metric system. Other readers do not care to have a
little sum in reduction to go through at each numerical statement.
[35] Hanno’s _Periplus_—the voyage of Hanno, chief of the
Carthaginians, round the parts of Libya, beyond the Pillars of
Hercules, the narrative of which he posted up in the Temple of Kronos.
[36] I may mention one which occurred within my own experience. A
mastiff of mine, some years ago, was eating from a plate full of broken
meat. It was his custom to bury the large pieces when there was more
than he could get through. While he was burying a large piece, a cat
ran off with a small fragment. The moment he returned to the plate he
missed this, and, seeing no one else near the plate, he, in his own
way, accused a little daughter of mine (some two or three years old)
of the theft. Looking fiercely at her, he growled his suspicions, and
would not suffer her to escape from the corner where his plate stood
until I dragged him away by his chain. Nor did he for some time forget
the wrong which he supposed she had done him, but always growled when
she came near his house.
[37] It may be suggested, in passing, that the association which
has been commonly noticed between prominent eyeballs and command
of language (phrenologists place the organ of language, in their
unscientific phraseology, behind the eyeballs) may be related in
some degree to the circumstance that in gradually emerging from the
condition of an arboreal creature the anthropoid ape would not only
cease to derive advantage from sunken eyes, but would be benefited by
the possession of more prominent eyeballs. The increasing prominence
of the eyeballs would thus be a change directly associated with the
gradual advance of the animal to a condition in which, associating
into larger and larger companies and becoming more and more dependent
on mutual assistance and discipline, they would require the use of a
gradually extending series of vocal signs to indicate their wants and
wishes to each other.
[38] The word hypothesis is too often used as though it were synonymous
with theory, so that Newton’s famous saying, “Hypotheses non fingo”
has come to be regarded by many as though it expressed an objection on
Newton’s part against the formation of theories. This would have been
strange indeed in the author of the noblest theory yet propounded by
man in matters scientific. Newton indicates his meaning plainly enough,
in the very paragraph in which the above expression occurs, defining an
hypothesis as an opinion not based on phenomena.
[39] I find it somewhat difficult to understand clearly Mr. Mivart’s
own position with reference to the general theory of evolution. He
certainly is an evolutionist, and as certainly he considers natural
selection combined with the tendency to variation (as ordinarily
understood) insufficient to account for the existence of the various
forms of animal and vegetable existence. He supplies the missing factor
in “an innate law imposed on nature, by which new and definite species,
under definite conditions, emerged from a latent and potential being
into actual and manifest existence;” and, so far as can be judged,
he considers that the origin of man himself is an instance of the
operation of this law.
[40] The Middle Tertiary period—the Tertiary, which includes the
Eocene, Miocene, and Pliocene periods, being the latest of the three
great periods recognized by geologists as preceding the present
era, which includes the entire history of man as at present known
geologically.
[41] Closely following in this respect his illustrious namesake
Roger, who writes, in the sixth chapter of his _Opus Majus_, “_Sine
experientia nihil sufficienter sciri potest._”
[42] Fibrine and albumen are identical in composition. _Caseine_, which
is the coagulable portion of milk, is composed in the same manner. The
chief distinction between the three substances consists in their mode
of coagulation; fibrine coagulating spontaneously, albumen under the
action of heat, and caseine by the action of acetic acid.
[43] To this article of the Professor’s faith decided objection must be
taken, however.
[44] Those whose custom it is to regard all theorizing respecting
the circumstances revealed by observation as unscientific, may read
with profit an extremely speculative passage in Newton’s _Principia_
relating to the probable drying up of the earth in future ages. “As the
seas,” he says, “are absolutely necessary to the constitution of our
earth, that from them the sun, by its heat, may exhale a sufficient
quantity of vapours, which, being gathered together into clouds, may
drop down in rain, for watering of the earth, and for the production
and nourishment of vegetables; or being condensed with cold on the tops
of mountains (as some philosophers with reason judge), may run down in
springs and rivers; so for the conservation of the seas and fluids of
the planets, comets seem to be required, that, from their exhalations
and vapours condensed, the wastes of the planetary fluids spent upon
vegetation and putrefaction, and converted into dry earth, may be
ultimately supplied and made up; for all vegetables entirely derive
their growths from fluids, and afterwards, in great measure, are turned
into dry earth by putrefaction; and a sort of slime is always found
to settle at the bottom of putrefied fluids; and hence it is that the
bulk of the solid earth is continually increased; and the fluids, if
they are not supplied from without, must be in a continual decrease,
and quite fail at last. I suspect, moreover, that it is chiefly from
the comets that spirit comes which is indeed the smallest but the most
subtle and useful part of our air, and so much required to sustain the
life of all things with us.”
[45] See my “Science Byways,” pp. 244, 245.
[46] The following passage from Admiral Smyth’s Bedford Catalogue is
worth noticing in this connection:—“We find that both the Chinese and
the Japanese had a zodiac consisting of animals, as _zodiacs_ needs
must, among which they placed a tiger, a peacock, a cat, an alligator,
a duck, an ape, a hog, a rat, and what not. Animals also formed the
_Via Solis_ of the Kirghis, the Mongols, the Persians, the Mantshus,
and the ancient Turks; and the Spanish monks in the army of Cortes
found that the Mexicans had a zodiac with strange creatures in the
departments. Such a striking similitude is assuredly indicative of a
common origin, since the coincidences are too exact in most instances
to be the effect of chance; but where this origin is to be fixed has
been the subject of interminable discussions, and learning, ignorance,
sagacity, and prejudice have long been in battle array against each
other. Diodorus Siculus considers it to be Babylonian, but Bishop
Warburton, somewhat dogmatically tells us, ‘Brute worship gave rise to
the Egyptian asterisms prior to the time of Moses.’” There is now, of
course, very little reason for questioning that Egyptian astronomy was
borrowed from Babylon.
Transcriber’s Notes
Cover created by Transcriber and placed in the Public Domain.
Punctuation, hyphenation, and spelling were made consistent when a
predominant preference was found in this book; otherwise they were not
changed.
Simple typographical errors were corrected; occasional unbalanced
quotation marks retained.
Ambiguous hyphens at the ends of lines were retained.
Some ditto marks have been replaced by the actual text.
Page 83: In the illustration, “O” should be “C”.
Page 171: There is no obvious closing quotation mark to match the
opening mark at “of most unusual age and thickness”.
Page 192: “Divided even between the ocean” may be a misprint for
“evenly”.
Page 197: No matching closing quotation mark for the opening mark at
“the small bright spot”.
Page 222: Transcriber added an opening quotation mark at “Down his
back” to match the closing mark after “He was seen by every one on
board.”
Page 230: No matching closing quotation mark for the opening mark at “a
whale of large size”.
Page 302: Transcriber added an opening quotation mark at “About fifty
years ago” to match the closing mark after “fed himself with the other.”
Page 372: No matching opening quotation mark for the closing mark after
“its lower extremity.”
Page 385: No matching closing quotation mark for the opening mark at
“sweeps off from”.
*** End of this LibraryBlog Digital Book "Pleasant Ways in Science" ***
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