| By Author | [ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | Other Symbols ] |
| By Title | [ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | Other Symbols ] |
| By Language |
|
Download this book: [ ASCII | HTML | PDF ] Look for this book on Amazon Tweet |
Title: Mars and its Canals
Author: Lowell, Percival
Language: English
As this book started as an ASCII text book there are no pictures available.
*** Start of this LibraryBlog Digital Book "Mars and its Canals" ***
Transcriber's Notes
When italics were used in the original book, the corresponding text has
been surrounded by _underscores_. The oe ligature has been replaced by
the letters oe. The Greek letter lambda has been represented as
[lambda]. Some presumed printer's errors have been corrected. These
have been listed in a second transcriber's note at the end of the text.
MARS AND ITS CANALS
------------------------------------------------------------------------
[Illustration: _Mars’ Hill_]
------------------------------------------------------------------------
MARS
AND ITS CANALS
BY
PERCIVAL LOWELL
DIRECTOR OF THE OBSERVATORY AT FLAGSTAFF, ARIZONA; NON-RESIDENT
PROFESSOR OF ASTRONOMY AT THE MASSACHUSETTS INSTITUTE OF
TECHNOLOGY; FELLOW OF THE AMERICAN ACADEMY OF ARTS AND
SCIENCES; MEMBRE DE LA SOCIÉTÉ ASTRONOMIQUE DE FRANCE;
MEMBER OF THE ASTRONOMICAL AND ASTROPHYSICAL SOCIETY
OF AMERICA; MITGLIED DER ASTRONOMISCHEN GESELLSCHAFT;
MEMBRE DE LA SOCIÉTÉ BELGE D’ASTRONOMIE; HONORARY
MEMBER OF THE SOCIEDAD ASTRONOMICA DE MEXICO;
JANSSEN MEDALIST OF THE SOCIÉTÉ ASTRONOMIQUE
DE FRANCE, 1904, FOR RESEARCHES ON MARS;
ETC., ETC.
_ILLUSTRATED_
New York
THE MACMILLAN COMPANY
LONDON: MACMILLAN & CO., LTD.
1906
_All rights reserved_
COPYRIGHT, 1906,
BY THE MACMILLAN COMPANY.
-------
Set up and electrotyped. Published December, 1906.
Norwood Press
J. S. Cushing & Co.—Berwick & Smith Co.
Norwood, Mass., U.S.A.
------------------------------------------------------------------------
To
G. V. SCHIAPARELLI
THE COLUMBUS OF A NEW PLANETARY WORLD
THIS INVESTIGATION UPON IT
IS APPRECIATIVELY
INSCRIBED
PREFACE
Eleven years have elapsed since the writer’s first work on Mars was
published in which were recorded the facts gleaned in his research up
to that time and in which was set forth a theory of their explanation.
Continued work in the interval has confirmed the conclusions there
stated; sometimes in quite unexpected ways. Five times during that
period Mars has approached the earth within suitable scanning distance
and been subjected to careful and prolonged scrutiny. Familiarity with
the subject, improved telescopic means, and long-continued training
have all combined to increased efficiency in the procuring of data and
to results which have been proportionate. A mass of new material has
thus been collected,—some of it along old lines, some of it in lines
that are themselves new,—and both have led to the same outcome. In
addition to thus pushing inquiry into advanced portions of the subject,
study has been spent in investigation of the reality of the phenomena
upon which so much is based, and in testing every theory which has been
suggested to account for them. From diplopia to optical interference,
each of these has been examined and found incompatible with the
observations. The phenomena are all they have been stated to be, and
more. Each step forward in observation has confirmed the genuineness of
those that went before.
To set forth science in a popular, that is, in a generally
understandable, form is as obligatory as to present it in a more
technical manner. If men are to benefit by it, it must be expressed to
their comprehension. To do this should be feasible for him who is
master of his subject and is both the best test of, and the best
training to, that post. Especially vital is it that the exposition
should be done at first hand; for to describe what a man has himself
discovered comes as near as possible to making a reader the
co-discoverer of it. Not only are thus escaped the mistaken glosses of
second-hand knowledge, but an aroma of actuality, which cannot be
filtered through another mind without sensible evaporation, clings to
the account of the pioneer. Nor is it so hard to make any well-grasped
matter comprehensible to a man of good general intelligence as is
commonly supposed. The whole object of science is to synthesize, and so
simplify; and did we but know the uttermost of a subject we could make
it singularly clear. Meanwhile technical phraseology, useful as
shorthand to the cult, becomes meaningless jargon to the uninitiate and
is paraded most by the least profound. But worse still for their employ
symbols tend to fictitious understanding. Formulæ are the anæsthetics
of thought, not its stimulants; and to make any one think is far better
worth while than cramming him with ill-considered, and therefore
indigestible, learning.
Even to the technical student, a popular book, if well done, may yield
most valuable results. For nothing in any branch of science is so
little known as its articulation,—how the skeleton of it is put
together, and what may be the mode of attachment of its muscles.
CONTENTS
PAGE
PREFACE vii
PART I
NATURAL FEATURES
CHAPTER
I. ON EXPLORATION 3
II. A DEPARTURE-POINT 12
III. A BIRD’S-EYE VIEW OF PAST MARTIAN DISCOVERY 20
IV. THE POLAR CAPS 32
V. BEHAVIOR OF THE POLAR CAPS 41
VI. MARTIAN POLAR EXPEDITIONS 54
VII. WHITE SPOTS 73
VIII. CLIMATE AND WEATHER 82
IX. MOUNTAINS AND CLOUD 96
X. THE BLUE-GREEN AREAS 108
XI. VEGETATION 119
XII. TERRAQUEOUSNESS AND TERRESTRIALITY 128
XIII. THE REDDISH-OCHRE TRACTS 148
XIV. SUMMARY 159
PART II
NON-NATURAL FEATURES
XV. THE CANALS 173
XVI. THEIR SYSTEM 184
XVII. GEMINATION OF THE CANALS 192
I. THE DIPLOPIC THEORY 196
II. THE INTERFERENCE THEORY 201
III. THE ILLUSION THEORY 202
XVIII. THE DOUBLE CANALS 204
XIX. CANALS IN THE DARK REGIONS 243
XX. OASES 249
XXI. CARETS ON THE BORDERS OF THE GREAT DIAPHRAGM 265
XXII. THE CANALS PHOTOGRAPHED 271
PART III
THE CANALS IN ACTION
XXIII. CANALS: KINEMATIC 281
XXIV. CANAL DEVELOPMENT INDIVIDUALLY INSTANCED 304
XXV. HIBERNATION OF THE CANALS 313
XXVI. ARCTIC CANALS AND POLAR RIFTS 325
XXVII. OASES: KINEMATIC 330
PART IV
EXPLANATION
XXVIII. CONSTITUTION OF THE CANALS AND OASES 337
XXIX. LIFE 348
XXX. EVIDENCE 360
XXXI. THE HUSBANDING OF WATER 366
XXXII. CONCLUSION 376
INDEX 385
LIST OF ILLUSTRATIONS
PLATES
MARS’ HILL _Frontispiece_
PAGE
THE HERMITAGE 8
THE SAN FRANCISCO PEAKS 18
MARTIAN MAPS BY:
I. BEER AND MAEDLER. 1840 26
II. KAISER. 1864 26
III. FLAMMARION (RÉSUMÉ). 1876 27
IV. GREEN. 1877 27
V. SCHIAPARELLI. 1877 28
VI. SCHIAPARELLI. 1879 28
VII. SCHIAPARELLI. 1881 29
VIII. SCHIAPARELLI. 1884 29
IX. LOWELL. 1894 30
X. LOWELL. 1896 30
XI. LOWELL. 1901 31
XII. LOWELL. 1905 31
SOUTH POLAR CAP. 1905 42
NORTH POLAR CAP. 1905 44
MARE ERYTHRAEUM, MARTIAN DATE, DECEMBER 30 120
MARE ERYTHRAEUM, MARTIAN DATE, JANUARY 16 122
MARE ERYTHRAEUM, MARTIAN DATE, FEBRUARY 1 124
MARE ERYTHRAEUM, MARTIAN DATE, FEBRUARY 21 126
MARS, ON MERCATOR’S PROJECTION 384
CUTS APPEARING IN TEXT
SOUTH POLAR CAP IN WINTER 56
HELLAS IN WINTER 59
WHITE SOUTH OF NECTAR AND SOLIS LACUS 59
NORTHERN CAP HOODED WITH VAPOR 64
NORTHERN CAP UNMASKED 65
DEPOSITION OF FROST 70
FIRST NORTHERN SNOW 72
WHITE IN ELYSIUM 75
WHITE IN THE PONS HECTORIS 78
PROJECTION ON TERMINATOR 101
LINES IN DARK AREA 117
MAP OF NORTH AMERICA AT THE CLOSE OF ARCHÆAN TIME 132
NORTH AMERICA AT OPENING OF UPPER SILURIAN PERIOD 134
MAP OF NORTH AMERICA AFTER THE APPALACHIAN REVOLUTION 135
NORTH AMERICA IN THE CRETACEOUS PERIOD 136
NORTH AMERICA, SHOWING THE PARTS UNDER WATER IN THE
TERTIARY ERA 137
EARTH’S DESERT AREAS, WESTERN HEMISPHERE 156
EARTH’S DESERT AREAS, EASTERN HEMISPHERE 157
SHOWING THE EUMENIDES-ORCUS 183
MARTIAN DOUBLES 206
MARTIAN DOUBLES 207
MOUTHS OF EUPHRATES AND PHISON. JUNE, 1903 219
PECULIAR DEVELOPMENT OF THE GANGES 228
DJIHOUN, THE NARROWEST DOUBLE 229
THE SABAEUS SINUS, EMBOUCHURE FOR THE DOUBLE HIDDEKEL
AND GIHON 232
THE PROPONTIS, 1905 247
FONS IMMORTALIS, JUNE 19 254
UTOPIA REGIO. 1903 256
ASCRAEUS LUCUS AND GIGAS. MARCH 2, 1903 258
PECULIAR ASSOCIATION OF THE LUCI ISMENII WITH DOUBLE
CANALS 260
LUCUS ISMENIUS. MARCH, 1903 262
SHOWING SEASONAL CHANGE. I 285
SHOWING SEASONAL CHANGE. II 285
MEAN CANAL CARTOUCHES 298
SHOWING DEVELOPMENT OF THE BRONTES:
I. FEBRUARY 25 306
II. MARCH 30 307
III. APRIL 3 307
IV. MAY 4 308
V. MAY 7 308
VI. JULY 18 309
CARTOUCHES OF THE BRONTES 311
AMENTHES ALONE IN FEBRUARY 319
AMENTHES FEEBLER AND STILL ALONE IN MARCH 319
APPEARANCE OF THOTH WITH TRITON AND CURVED NEPENTHES.
AMENTHES VANISHED, APRIL 20 320
ADVENT OF THE LUCUS MOERIS. MAY 29 321
AMENTHES WITH THOTH-NEPENTHES. JULY 322
CARTOUCHES OF AMENTHES, THOTH, AND THEIR COMBINATION 323
PHENOLOGY CURVES—EARTH 342
PHENOLOGY CURVES—MARS 343
PART I
NATURAL FEATURES
MARS AND ITS CANALS
CHAPTER I
ON EXPLORATION
From time immemorial travel and discovery have called with strange
insistence to him who, wondering on the world, felt adventure in his
veins. The leaving familiar sights and faces to push forth into the
unknown has with magnetic force drawn the bold to great endeavor and
fired the thought of those who stayed at home. Spur to enterprise since
man first was, this spirit has urged him over the habitable globe.
Linked in part to mere matter of support it led the more daring of the
Aryans to quit the shade of their beech trees, reposeful as that
umbrage may have been, and wander into Central Asia, so to perplex
philologists into believing them to have originated there; it lured
Columbus across the waste of waters and caused his son to have carved
upon his tomb that ringing couplet of which the simple grandeur still
stirs the blood:—
Á CASTILLA Y Á LEON
NUEVO MONDO DIÓ COLON;
(To Castile and Leon beyond the wave
Another world Columbus gave;)
it drove the early voyagers into the heart of the vast wilderness,
there to endure all hardship so that they might come where their kind
had never stood before; and now it points man to the pole.
Something of the selfsame spirit finds a farther field today outside
the confines of our traversable earth. Science which has caused the
world to shrink and dwindle has been no less busy bringing near what in
the past seemed inaccessibly remote. Beyond our earth man’s penetration
has found it possible to pierce, and in its widening circle of research
has latterly been made aware of another world of strange enticement
across the depths of space. Planetary distances, not mundane ones, are
here concerned, and the globe to be explored, though akin to, is yet
very different from, our own. This other world is the planet Mars.
Sundered from us by the ocean of ether, a fellow-member of our own
community of matter there makes its circuit of the sun upon whose face
features show which stamp it as cognate to that on which we live. In
spite of the millions of miles of intervening matterless void, upon it
markings can be made out that distantly resemble our earth’s topography
and grow increasingly suggestive as vision shapes them better; and yet
among the seemingly familiar reveal aspects which are completely
strange. But more than this: over the face of it sweep changes that
show it to be not a dead but a living world, like ours in this, and
luring curiosity by details unknown here to further exploration of its
unfamiliar ground.
To observe Mars is to embark upon this enterprise; not in body but in
mind. Though parted by a gulf more impassable than any sea, the
telescope lets us traverse what otherwise had been barred and lands us
at last above the shores we went forth to seek. Real the journey is,
though incorporeal in kind. Since the seeing strange sights is the
essence of all far wanderings, it is as truly travel so the eye arrive
as if the body kept it company. Indeed, sight is our only far viatic
sense. Touch and taste both hang on contact, smell stands indebted to
the near and even hearing waits on ponderable matter where sound soon
dissipates away; only sight soars untrammeled of the grosser adjunct of
the flesh to penetrate what were otherwise unfathomable space.
What the voyager thus finds himself envisaging shares by that very fact
in the expansion of the sense that brought him there. No longer tied by
means of transport to seas his sails may compass or lands his feet may
tread, the traveler reaches a goal removed in kind from his own
habitat. He proves to have adventured, not into unknown parts of a
known world, but into one new to him in its entirety. In extent alone
he surveys what dwarfs the explorer’s conquests on Earth. But size is
the least of the surprises there in store for him. What confronts his
gaze finds commonly no counterpart on Earth. His previous knowledge
stands him in scant stead. For he faces what is so removed from every
day experience that analogy no longer offers itself with safety as a
guide. He must build up new conceptions from fresh data and slowly
proceed to deduce the meaning they may contain. Science alone can help
him to interpretation of what he finds, and above all must he wean
himself from human prejudice and earthbound limitation. For he deals
here with ultramundane things. With just enough of cosmogony in common
to make decipherment not despairable this world is yet so different
from the one he personally knows as to whet curiosity at every turn. He
is permitted to perceive what piques inquiry and by patient adding of
point to point promises at last a rational result.
Like mundane exploration, it is arduous too; _ad astra per aspera_ is
here literally true. For it is a journey not devoid of hardship and
discomfort by the way. Its starting-point preludes as much. To get
conditions proper for his work the explorer must forego the haunts of
men and even those terrestrial spots found by them most habitable.
Astronomy now demands bodily abstraction of its devotee. Its deities
are gods that veil themselves amid man-crowded marts and impose
withdrawal and seclusion for the prosecution of their cult as much as
any worshiped for other reason in more primeval times. To see into the
beyond requires purity; in the medium now as formerly in the man. As
little air as may be and that only of the best is obligatory to his
enterprise, and the securing it makes him perforce a hermit from his
kind. He must abandon cities and forego plains. Only in places raised
above and aloof from men can he profitably pursue his search, places
where nature never meant him to dwell and admonishes him of the fact by
sundry hints of a more or less distressing character. To stand a mile
and a half nearer the stars is not to stand immune.
Thus it comes about that today besides its temples erected in cities,
monasteries in the wilds are being dedicated to astronomy as in the
past to faith; monasteries made to commune with its spirit, as temples
are to communicate the letter of its law. Pioneers in such profession,
those already in existence are but the precursors of many yet to come
as science shall more and more recognize their need. Advance in
knowledge demands what they alone can give. Primitive, too, they must
be as befits the still austere sincerity of a cult, in which the
simplest structures are found to be the best.
Still the very wildness of the life their devotee is forced to lead has
in it a certain fittingness for his post in its primeval detachment
from the too earthbound, in concept as in circumstance. Withdrawn from
contact with his kind, he is by that much raised above human prejudice
and limitation. To sally forth into the untrod wilderness in the cold
and dark of a winter’s small hours of the morning, with the snow feet
deep upon the ground and the frosty stars for mute companionship, is
almost to forget one’s self a man for the solemn awe of one’s
surroundings. Fitting portal to communion with another world, it is
through such avenue one enters on his quest where the common and
familiar no longer jostle the unknown and the strange. Nor is the
stillness of the stars invaded when some long unearthly howl, like the
wail of a lost soul, breaks the slumber of the mesa forest, marking the
prowling presence of a stray coyote. Gone as it came, it dies in the
distance on the air that gave it birth; and the gloom of the pines
swallows up one’s vain peering after something palpable, their tops
alone decipherable in dark silhouette against the sky. From amid
surroundings that for their height and their intenancy fringe the
absolute silence of space the observer must set forth who purposes to
cross it to another planetary world.
[Illustration: _The Hermitage_]
But the isolation of his journey is not always so forbidding. His
coming back is no less girt with grandeur of a different though equally
detached a kind. Even before the stars begin to dim in warning to him
to return, a faint suffusion as of half-suspected light creeps into the
border of the eastern sky. Against it, along the far pine-clad horizon,
mesa after mesa in shaggy lines of sentineling earth, stands forth dark
marshaled in the gloom, informed with prescience of what is soon to
come. Imperceptibly the pallor grows, blanching the face of night and
one by one extinguishing the stars. Slowly then it takes on color,
tingeing ever so faintly to a flush that swells and deepens as the
minutes pass. One had said the sky lay dreaming of the sun in pale
imagery at first that gathers force and feeling till the dreamer turns
thus rosy red in slumbering supposition of reality. Then the blush dies
out. The crimson fades to pink, the pink to ashes. The stars have
disappeared and yet it is not day. It is the supreme moment of the
dawn, the hush with which the Earth awaits its full awakening. For now
again the color gathers in the east, not with the impalpable suffusion
it had before but nearer and more vivid. No longer reflectively remote,
rays imminent of the sun strike the upper air, the most adventurously
refrangible turning the underside of a few stray clouds into flame-hued
bars of glowing metal. They burn thus in the silent east first red,
then orange, and then gold, each spectral tint in prismatic revelation
coming to join the next till in a sudden blinding burst of splendor the
solar disk tops the horizon’s rim.
Not less impressive is the journey when the afternoon watch has
replaced the morning vigil by the drawing of the planet nearer to the
sun. Lost in the brilliance of the dazzling sky, the planet lies hid
from the senses’ search. The quest were hopeless did not the mind guide
the telescope to its goal. To theory alone is it visible still, and so
to its predicted place the observer sets his circles, and punctual to
the prophecy the planet swings into the field of view. One must be
dulled by long routine to such mastery of mind not to have the act
itself clothe with a sense of charmed withdrawal the object of his
quest.
So much and more there are of traveler’s glimpses by the way,
compensation that offsets the frequent discomfort, and even balking of
his purpose by inopportune cloud. For the best of places is not
perfect, and a storm will sometimes rob him of a region he wished to
see. He must learn to wait upon his opportunities and then no less to
wait for mankind’s acceptance of his results; for in common with most
explorers he will encounter on his return that final penalty of
penetration, the certainty at first of being disbelieved.
In such respect he will be even worse off than were the other world
discoverers of the fifteenth and sixteenth centuries. For they at least
could offer material proof of things that they had seen. Dumb Indians
and gold spoke more convincingly than the lips of the great navigators.
To astronomy, too, that other world was due. Without a knowledge of the
earth’s shape and size got from Francisco of Pisa, Columbus had never
adventured himself upon the deep. But more than this, an astronomer it
was, in the person of Americus Vespucius, who first discovered the new
world, by recognizing it as such; Columbus never dreaming he had
lighted upon a world that was new. Nor does it impair one jot or tittle
of his glory that he knew it not. Nothing can deprive him of the
imperishable fame of launching forth into the void in hope of a beyond,
though he found not what he sought but something stranger still.
So, curiously, has it been with the trans-etherian. To Schiaparelli the
republic of science owes a new and vast domain. His genius first
detected those strange new markings on the Martian disk which have
proved the portal to all that has since been seen, and his courage in
the face of universal condemnation led to exploration of them. He made
there voyage after voyage, much as Columbus did on Earth, with even
less of recognition from home. As with Columbus, too, the full import
of his great discovery lay hid even to him and only by discoveries
since is gradually resulting in recognition of another sentient world.
CHAPTER II
A DEPARTURE-POINT
As the character of the travel is distinctive, so the outcome of the
voyage is unique. If he choose his departure-point aright, the observer
will be vouchsafed an experience without parallel on Earth. To select
this setting-out station is the first step in the journey upon which
everything depends. For it is essential to visual arrival that a
departure-point be taken where definition is at its best. Now, so far
as our present knowledge goes, the conditions most conducive to good
seeing turn out to lie in one or other of the two great desert belts
that girdle the globe. Many of us are unaware of the existence of such
belts and yet they are among the most striking features of physical
geography. Could we get off our globe and view it from without we
should mark two sash-like bands of country, to the poleward side of
either tropic, where the surface itself lay patently exposed. Unclothed
of verdure themselves they would stand forth doubly clear by contrast.
For elsewhere cloud would hide to a greater or less extent the actual
configuration of the Earth’s topography to an observer scanning it from
space.
One of these sash-like belts of desert runs through southern
California, Arizona, New Mexico, the Sahara, Arabia Petræa and the
Desert of Gobi; the other traverses Peru, the South African veldt, and
Western Australia. They are desert because in them rain is rare; and
even clouds seldom form. In a twofold way they conduce to astronomic
ends. Absence of rain makes primarily for clear skies and secondarily
for steady air; and the one of these conditions is no less vital to
sight than the other. Water vapor is a great upsetter of atmospheric
equilibrium and commotion in the air the spoiler of definition. Thus
from the cloudlessness of their skies man finds in them most chance of
uninterrupted communion with the stars, while by suitably choosing his
spot he here obtains as well that prime desideratum for planetary work,
as near a heavenly equanimity in the air currents over his head as is
practically possible.
From the fact that these regions are desert they are less frequented of
man, and the observer is thus perforce isolated by the nature of the
case, the regions best adapted to mankind being the least suited to
astronomic observations. In addition to what nature has thus done in
the matter, humanity has further differentiated the two classes of
sights by processes of its own contriving. Not only is civilized man
actively engaged in defacing such part of the Earth’s surface as he
comes in contact with, he is equally busy blotting out his sky. In the
latter uncommendable pursuit he has in the last quarter of a century
made surprising progress. With a success only too undesirable his
habitat has gradually become canopied by a welkin of his own
fashioning, which has rendered it largely unfit for the more delicate
kinds of astronomic work. Smoke from multiplying factories by rising
into the air and forming the nucleus about which cloud collects has
joined with electric lighting to help put out the stars. These
concomitants of advancing civilization have succeeded above the dreams
of the most earth-centred in shutting off sight of the beyond so that
today few city-bred children have any conception of the glories of the
heavens which made of the Chaldean shepherds astronomers in spite of
themselves.
The old world and the new are alike affected by such obliteration. Long
ago London took the lead with fogs proverbial wholly due to smoke, fine
particles of solid matter in suspension making these points of
condensation about which water vapor gathers to form cloud. With the
increase of smoke-emitting chimneys over the world other centres of
population have followed suit till today Europe and eastern North
America vie with each other as to which sky shall be the most
obliterate. Even when the obscuration is not patent to the layman it is
evident to the meteorologist or astronomer. By a certain dimming of the
blue, smoke or dust reveals its presence high up aloft as telltalely as
if the thing itself were visible. Some time since the writer had
occasion to traverse Germany in summer from Göttingen to Cologne and in
so doing was impressed by a cloudiness of the sky he felt sure had not
existed when he knew it as a boy. For the change was too startling and
extensive to be wholly laid to the score of the brighter remembrances
of youth. On reaching Cologne he mentioned his suspicion to Klein, only
to find his own inference corroborated; observations made twenty years
ago being impracticable today. Two years later in Milan Celoria told
the same story, the study of Mars having ceased to be possible there
for like cause. Factory smoke and electric lights had combined to veil
the planet at about the time Schiaparelli gave up his observations
because of failing sight. With a certain poetic fitness the sky had
itself been blotted just at the time the master’s eye had dimmed.
America is not behind in this race for sky extinction. In the
neighborhood of its great cities and spreading into the country round
about the heavens have ceased to be favorable to research. Not till we
pass beyond the Missouri do the stars shine out as they shone before
the white man came.
Few astronomers even fully appreciate how much this means, so used does
man get to slowly changing conditions. It amounts, indeed, between
Washington and Arizona to a whole magnitude in the stars which may be
seen. At the Naval Observatory of the former sixty-four stars were
mapped in a region where with a slightly smaller glass one hundred and
seventy-two were charted at Flagstaff.
Besides their immediate use as observing stations these desert belts
possess mediate interest on their own account in a branch of the very
study their cloudlessness helps to promote, the branch here considered,
the study of the planet Mars. They help explain what they permit to be
visible. For in the physical history of the Earth’s development they
are among the latest phenomena and mark the beginning of that stage of
world evolution into which Mars is already well advanced. They are
symptomatic of the passing of a terraqueous globe into a purely
terrestrial one. Desertism, the state into which every planetary body
must eventually come and for which, therefore, it becomes necessary to
coin a word, has there made its first appearance upon the Earth.
Standing as it does for the approach of age in planetary existence, it
may be likened to the first gray hairs in man. Or better still it
corresponds to early autumnal frost in the passage of the seasons. For
the beginning to age in a planet means not decrepitude in its
inhabitants but the very maturing of this its fruit. Evolution of mind
in its denizens continues long after desolation in their habitat has
set in. Indeed, advance in brain-power seriously develops only when
material conditions cease to be bodily propitious and the loss of
corporeal facilities renders its acquisition necessary to life.
The resemblance, distant but distinctive, of the climatic conditions
necessary on earth for the best scanning of Mars with those which prove
to be actually existent on that other world has a bearing on the
subject worth considerable attention. It helps directly to an
understanding and interpretation of the Martian state of things. Though
partial only, the features and traits of our arid zones are
sufficiently like what prevails on Mars to make them in some sort
exponent of physical conditions and action there. Much that is hard of
appreciation in a low, humid land shows itself an everyday possibility
in a high and dry one. The terrible necessity of water to all forms of
life, animal or vegetal, so that in the simple thought of the
aborigines rain is the only god worth great propitiation upon the due
observance of which everything depends, brings to one a deeper
realization of what is really vital and what but accessory at best. One
begins to conceive what must be the controlling principle of a world
where water is only with difficulty to be had, and rain unknown.
But in addition to the fundamental importance of water, the relative
irrelevancy of some other conditions usually deemed indispensable to
organic existence there find illustration too. On the high plateau of
northern Arizona and on the still higher volcanic cones that rise from
them as a base into now disintegrating peaks, the thin cold air proves
no bar to life. To the fauna there air is a very secondary
consideration to water, and because the latter is scarce in the
lowlands and more abundant higher up, animals ascend after it, making
their home at unusual elevations with no discomfort to themselves. Deer
range to heights where the barometric pressure is but three fifths that
of their generic habitat. Bear do the like, the brown bear of northern
American sea-level being here met with two miles above it. Nor is
either animal a depauperate form. Man himself contrives to live in
comfort and propagate his kind where at first he finds it hard to
breathe. Nor are these valiant exceptions; as Merriam has ably shown in
his account of the San Francisco peak region for the Smithsonian
Institution—a most interesting report, by the way—the other animals
are equally adaptive to the zones of more northern latitudes on the
American continent, zones paralleled in their flora and fauna by the
zones of altitude up this peak. All which shows that paucity of air is
nothing like the barrier to life we ordinarily suppose and is not for
an instant to be compared with dearth of water. If in a comparatively
short time an animal or plant accustomed to thirty inches of barometric
pressure can contrive to subsist sensibly unchanged at eighteen, it
would be rash to set limits to what time may not do. And this the more
for another instructive fact discovered in this region by Merriam: that
the existence of a species was determined not by the mean temperature
of its habitat but by the maximum temperature during the time of
procreation. A short warm season in summer alone decides whether the
species shall survive and flourish; that it has afterward to hibernate
for six months at a time does not in the least negative the result.
[Illustration: _The San Francisco Peaks_]
That the point of departure should thus prove of twofold importance,
speeding the observer on his journey and furnishing him with a _vade
mecum_ on arrival, is as curious as opportune. Without such
furtherance, to the bodily eye on the one hand and the mind’s eye on
the other, the voyage were less conclusive in advent and less
satisfactory in attent.
CHAPTER III
A BIRD’S-EYE VIEW OF PAST MARTIAN DISCOVERY
With Mars discovery has from the start waited on apparent disk. To this
end every optical advance has contributed from the time of Galileo’s
opera-glass to the present day. For apparent distance stands determined
by the size of the eye. But although it is the telescopic eye that has
increased, not the distance that has diminished, the effect has been
kin to being carried nearer the planet and so to a scanning of its disk
with constantly increasing particularity. Mankind has to all intents
and purposes been journeying Marsward through the years. Any historic
account of the planet, therefore, becomes a chronicle of seeming bodily
approach.
Perhaps no vivider way of making this evident and at the same time no
better preface to the present work could be devised than by putting
before the eye in orderly succession the maps made of Mars by the
leading areographers of their day, since the planet first began to be
charted sixty-five years ago. The procedure is as much as possible like
standing at the telescope and seeing the phenomena steadily disclose.
Seen thus in order the facts speak for themselves. They show that from
first to last no doubt concerning what was seen existed in the minds of
those competent to judge by systematic study of the planet at first
hand, and furthermore, from their mutual corroboration, that this
confidence was well placed. For, far from there being any conflict of
authorities in the case, those entitled to an opinion in the matter
prove singularly at one.
Beginning with Maedler in 1840 the gallery of such portraitures of the
planet comprises those by Kaiser, Green and Schiaparelli, continued
since Schiaparelli’s time by the earlier ones of the present writer. To
this list has been added one by Flammarion, which though not solely
from his own work gives so just a representation of what was known at
the date, 1876, as to merit inclusion. The remarkable drawings of Dawes
and the excellent ones of Lockyer in 1862-1864 were never combined into
maps by the observers, and though the former’s were so synthesized by
Proctor in 1867, the result was conformed to what Proctor thought ought
to be and so is not really a transcript of the drawings themselves.
Each of the maps presented marked in its day the point areography had
reached; and each tells its own story better than any amount of text.
They are all made upon Mercator’s projection and omit in consequence
the circumpolar regions. The later ones give, too, only so much of the
surface as was shown at the opposition they record, for Mars, being
tipped now one way, now another, regards the earth differently
according to its orbital position. In comparing them, therefore, the
equator must be taken for medial line. Mercator’s projection has been
the customary one for portraying Mars except for such oppositions as
chiefly disclose the arctic pole. And this, too, with a certain poetic
fitness. For it comes by right of priority to delineation of a new
world; seeing that Mercator was the first to represent in a map the
mundane new world in its entirety, by the rather important addition of
North America to the southern continent already known, and to give the
whole the title America with ‘Ame’ at the top of the map and ‘rica’ at
the bottom.
In looking at the maps it is to be remembered that they are what we
should call upside down, south standing at the top and north at the
bottom. Inverted they show because this is the way the telescopic
observer always sees the planet. The disk would seem unnatural to
astronomers were it duly righted. Just the same do men in the southern
hemisphere look at our own Earth topsy-turvy according to our view, the
Sun being to the north of them and the cold to the south. Certain
landmarks distinguishable in all the maps may serve for specific
introduction. The V-shaped marking on the equator pointing to the north
is the Syrtis Major, the first marking ever made out upon the planet
and drawn by the great Huyghens in 1659. The isolated oval patch in
latitude 26° south is the Solis Lacus, the pupil of the eye of Mars;
while the forked bay on the equator, discovered by Dawes, is the
Sabaeus Sinus, the dividing tongue of which, the Fastigium Aryn, has
been taken for the origin of longitudes on Mars.
Twelve maps go to make the series. They are as follows:—
MAKER DATE
I. Map of Beer and Maedler 1840
II. Map of Kaiser 1864
III. Map of Flammarion (Résumé) 1876
IV. Map of Green 1877
V. Map of Schiaparelli 1877
VI. Map of Schiaparelli 1879
VII. Map of Schiaparelli 1881
VIII. Map of Schiaparelli 1884
IX. Map of Lowell 1894
X. Map of Lowell 1896
XI. Map of Lowell 1901
XII. Map of Lowell 1905
If these maps be carefully compared they will be found quite remarkably
confirmatory each of its predecessor. To no one will their
inter-resemblance seem more salient than to draughtsmen themselves. For
none know better how surprisingly, even when two men have the same
thing under their very noses to copy, their two versions will differ.
Judgment of position and of relative size is one cause of variation;
focusing of the attention on different details another. What slight
discrepancies affect the maps are traceable to these two human
imperfections. Maps IV and V make a case in point: it was to his
new-found canals that Schiaparelli gave heed to the neglect of a due
toning of his map; while Green, less keen-eyed but more artistic,
missed the delicate canaliform detail to make a speaking portraiture of
the whole.
Amid the remarkable continuity of progression here shown, in which each
map will be seen to be at once a review and an advance, we may,
nevertheless, distinguish three stages in the perception of the
phenomena. Thus we may mark:—
I. A period of recognition of larger markings
only; 1840-1877
II. A period of detection of canals intersecting
the bright regions or lands; 1877-1892
III. A period of detection of canals traversing
the ‘seas’ and of oases scattered over
the surface; 1892-1905
Each period is here represented by four charts; and each expresses the
result of a more minute and intimate acquaintance with the disk than
was possible to the one that went before. To realize, however, how
accurate each was according to his lights it is only necessary to have
the seeing grow steadily better some evening as one observes. He will
find himself recapitulating in his own person the course taken by
discovery for all those who went before, and in the lapse of an hour
live through the observational experience of sixty years; in much the
same way that the embryological growth of an individual repeats the
development historically of the race.
Two verses of Ovid, which the poet puts into the mouth of Pythagoras,
outline with something like prophetic utterance the special discoveries
which mark the three periods apart. Ovid makes Pythagoras say of the
then world:—
Vidi ego, quod fuerat quondam solidissima tellus
Esse fretum; vidi factas ex aequore terras;
—OVID, _Metamorphoses_ XV, 262.
(Where once was solid ground I’ve seen a strait;
Lands I’ve seen made from out the sea.)
True as the verses are of Earth, the poet could not have penned them
otherwise had he meant to record the course of astronomic detection on
Mars. For they sound like a presentiment of the facts. A surface
thought at first to be part land, part water; the land next seen to be
seamed with straits; and lastly the sea made out to be land. Such is
the history of the subject, and words could not have summed it more
succinctly. “Vidi ego, quod fuerat quondam solidissima tellus esse
fretum” rings like Schiaparelli’s own announcement of the discovery of
the ‘canals.’ Indeed, I venture to believe he would have made it had he
chanced to recall the verse. So “vidi factas ex aequore terras” tells
what has since been learned of the character of the seas.
Of the three periods the first was that of the main or fundamental
markings only. It came in with Beer and Maedler, the inaugurators of
areography. That they planned and executed their survey with but a
four-inch glass shows that there is always room for genius at the top
of any profession and that instruments are not for everything in its
instrumentality. Up to their day the reality of the planet’s features
had been questioned by some people in spite of having been certainly
seen and drawn by Huyghens and others. Beer and Maedler’s labors proved
them permanent facts beyond the possibility of dispute.
The second period was the period of the discovery of the now famous
canals,—a new era in the study of Mars opened by Schiaparelli in 1877
(Map V). Unsuspicious of what he was to stumble on, he seized the then
favorable opposition to make, as he put it, a geodetic survey of the
planet’s surface. He hoped this undertaking feasible to the accuracy of
micrometric measurement. His hopes did not belie him. He found that it
was possible to measure his positions with sufficient exactness to make
a skeleton map on which to embody the markings in detail—and thus to
give his map vertebrate support. But in the course of his work he
became aware of hitherto unrecognized ligaments connecting the seas
with one another. Instead of displaying a broad unity of face the
bright areas appeared to be but groundwork for streaks. The streaks
traversed them in all directions, tesselating the continents into a
tilework of islands. Such mosaic was not only new, but the fashion of
the thing was of a new order or kind. Straits, however, Schiaparelli
considered them and gave them the name _canali_, or channels. How
unfamiliar and seemingly impossible the new detail was is best
evidenced by the prompt and unanimous disbelief with which it was met.
[Illustration: Map I. Beer and Maedler, 1840.]
[Illustration: Map II. Kaiser, 1864.
(From Flammarion’s _Mars_.)]
[Illustration: Map III. Résumé by Flammarion, 1876.
(From Flammarion’s _Mars_.)]
[Illustration: Map IV. Green, 1877.
(From Flammarion’s _Mars_.)]
Unmoved by the universal scepticism which rewarded what was to prove an
epoch-making discovery, Schiaparelli went on, in the judgment of his
critics, from bad to worse—for in 1879 (Map VI) he took up again his
scrutiny of the planet to the detecting of yet more particularity. He
re-observed most of his old canals and discovered half as many more;
and as his map shows he perceived an increased regularity in his lines.
In 1881-1882 (Map VII) he attacked the planet again and with results
yet further out of the common. His lines were still there with more
beside. If they had looked strange before, they now appeared positively
unnatural. Not content with a regularity which seemed to the sceptics
to preclude their being facts, he must needs see them now in duplicate.
To the eyes of disbelief this was the crowning stroke of factitiousness.
In consequence no end of adverse criticism was heaped upon his
observations by those who could not see. But curiously enough,—what
did not attract attention,—the blindness of the critics was as much
mental as bodily. For they failed to perceive that the very
unnaturalness which seemed to them to discredit his observations really
proved their genuineness. His discoveries were so amazing that any
change in strangeness simply went to confirm the universal scepticism
and clouded logic. Yet properly viewed, a pregnant deduction stands
forth quite clearly on a study of the maps.
[Illustration: Map V. Schiaparelli, 1877.
(From Schiaparelli’s _Memoria_.)]
[Illustration: Map VI. Schiaparelli, 1879.
(From Schiaparelli’s _Memoria_.)]
[Illustration: Map VII. Schiaparelli, 1881.
(From Schiaparelli’s _Memoria_.)]
[Illustration: Map VIII. Schiaparelli, 1884.
(From Schiaparelli’s _Memoria_.)]
On comparing maps V, VI and VII an eye duly directed is struck by a
difference in the aspect of the lines. In his first map the ‘canals’
are depicted simply as narrow winding streaks, hardly even roughly
regular and by no means such departures from the plausible as to lie
without the communicatory pale. Indeed, to a modern reader prepared
beforehand for geometric construction they will probably appear no
‘canals’ at all. Certainly the price of acceptance was not a large one
to pay. But like that of the Sibylline Books it increased with putting
off. What he offered the public in 1879 was much more dearly to be
bought. The lines were straighter, narrower, and in every way less
natural than they had seemed two years before. In 1881-1882 they
progressed still more in unaccountability. They had now become regular
rule and compass lines, as straight, as even, and as precise as any
draughtsman could wish and quite what astronomic faith did not desire.
Having thus donned the character, they nevermore put it off.
Now, this curious evolution in depiction points, rightly viewed, to an
absence of design. It shows that Schiaparelli started with no
preconceived idea on the subject. On the contrary, it is clear that he
shared to begin with the prevailing hesitancy to accept anything out of
the ordinary. Nor did he overcome his reluctance except as by degrees
he was compelled. For the canals did not change their characteristics
from one opposition to another; the eye it was that learned to
distinguish what it saw, and the brain made better report as it grew
familiar with the messages sent it. In other words, it is patent from
these successive maps that the geometrical character of the ‘canals’
was forced upon Schiaparelli by the things themselves, instead of
being, as his critics took for granted, foisted on them by him. We have
since seen the regularity of the canals so undeniably that we are not
now in need of such inferential support to help us to the truth; but
too late, as it is, to be of controversial moment the deduction is none
the less of some corroboratory force.
With the third period enters what has been done since Schiaparelli’s
time. For that master was obliged, from failing sight, to close his
work with the opposition of 1890. In 1892 W. H. Pickering at Arequipa
was the chief observer of the planet and made two important
discoveries: one was the detection of small round spots scattered over
the surface of the planet and connected with the canal system; the
other the perception of what seemed to him more or less irregular lines
traversing the Mare Erythraeum. Both were notable detections. The first
set of phenomena he called lakes, the second river-systems, sometimes
schematically ‘canals,’ but without committing himself to canaliform
characteristics as his drawings make clear. The same phenomena were
seen at that opposition at the Lick, by Schaeberle, Barnard and others,
and called streaks. These discoveries took from the _maria_ their
supposed character of seas—a most important event in knowledge of Mars.
[Illustration: Map IX. Lowell, 1894.]
[Illustration: Map X. Lowell, 1896.]
[Illustration: Map XI. Lowell, 1901.]
[Illustration: Map XII. Lowell, 1905.]
The next advance was the detection at Flagstaff in 1894 of their
canaliform characteristics by my then assistant Mr. Douglass, who in
place of the irregular streaks and river-systems of his predecessors
found the seas to be crossed by lines as regular and as regularly
connected as the canals in the light regions. To him they appeared
broad and ill defined, but so habitually did to him the canals in the
light areas, while for directness and uniformity the one set showed as
geometrically perfect as the other. All the dark _maria_ of the
southern hemisphere he found to be laced with them and that they formed
a network over the dark regions, counterparting that over the light.
Still more significant was the fact that their points of departure
coincided with the points of arrival of the bright-region canals, so
that the two connected to form in its entirety a single system. After
the publication of his results (Lowell Observatory Annals, Volume I,
1895) Schiaparelli identified some of those in the Syrtis with what he
had himself seen there in 1888 (_Memoria_, VI, 1899), though his own
had not been sufficiently well seen of him to impress him as canals.
Of other additions to our knowledge since made by the writer the
present book treats; as also of the theory they originally suggested to
him and which his later observations have only gone to confirm.
CHAPTER IV
THE POLAR CAPS
Almost as soon as magnification gives Mars a disk that disk shows
markings, white spots crowning a globe spread with blue-green patches
on an orange ground. The smallest telescope is capable of this far-off
revelation; while with increased power the picture grows steadily more
articulate and full. With a two and a quarter inch glass the writer saw
them thirty-five years ago.
After the assurance that markings exist the next thing to arrest
attention is that these markings move. The patches of color first made
out by the observer are shortly found by him to have shifted in place
upon the planet. And this not through mistake on his part but through
method in the phenomena; for all do it alike. In orderly rotation the
features make their appearance upon the body’s righthand limb (in the
telescopic image), travel across the central meridian of the disk and
vanish over its lefthand border. One follows another, each rising,
culminating and setting in its turn under the observer’s gaze. A
constantly progressing panorama passes majestically before his sight,
new objects replacing the old with a march so steady and withal so
swift that a few minutes will suffice to mark unmistakably the fact of
such procession. But for all this ceaseless turning under his gaze,
after a certain lapse of time it is evident that the same features are
being shown him over again. With such recognition of recurrence comes
the first advance toward acquaintance with the Martian world. For that
in all their journeying their configuration alters not, proves them
permanent in place, part and parcel of the solid surface of that other
globe. This surface, then, lies exposed to view and by its turning
shows itself subject, like our earth, to the vicissitudes of day and
night.
In such self-exposure Mars differs from all the four great planets,
Jupiter, Saturn, Uranus and Neptune. Features, indeed, are apparent on
the first two of these globes and dimly on the other two as well, but
they lack the stability of the Martian markings. They are forever
exchanging place. In the case of Jupiter what we see is undoubtedly a
cloud-envelop through which occasional glimpses may possibly be caught
of a chaotic nucleus below. With Saturn it is the same; and the
evidence is that the like is true of Uranus and Neptune. What goes on
under their great cloud canopies we can only surmise. With Mars,
however, we are not left to imagination in the matter but so far as our
means permit can actually observe what there takes place. Except for
distance, which, through science, year by year grows less, it is as if
we hovered above the planet in a balloon, with its various features
spread out to our gaze below.
Attention shows these areographic features to be on hand with punctual
precision for their traverse of the disk once every twenty-four hours
and thirty-seven minutes. For over two hundred years this has been the
case, their untiring revolutions having been watched so well that we
know the time they take to the nicety of a couple of hundredths of a
second. We thus become possessed of a knowledge of the length of the
Martian day and it is not a little interesting to find that it very
closely counterparts in duration our own, being only one thirty-fifth
the longer of the two. We also find from the course the markings pursue
the axis about which they turn; and just as the period of the rotation
tells us the length of the Martian day so the tilt of the axis, taken
in connection with the form of the orbit, determines the character of
the Martian seasons. Here again we confront a curious resemblance in
the circumstances of the two planets, for the tilt of the equator to
the plane of the orbit is with Mars almost precisely what it is for the
Earth. The more carefully the two are measured the closer the
similitude becomes. Sir William Herschel made the Martian 28°,
Schiaparelli reduced this to 25°, and later determination by the writer
puts it nearer 24°. The latter is the one now adopted in the British
Nautical Almanac for observers of the planet. This is a very close
parallelism indeed; so that in general character the Martian seasons
are nearly the counterpart of ours. In length, however, they differ;
first because the year of Mars is almost double the length of the
terrestrial one and secondly because from the greater ellipticity of
Mars’ orbit the seasons are more unequal than is the case with us, some
being run through with great haste, others being lingered on a
disproportionate time. It is usual on the Earth to consider spring as
the period from the vernal equinox, about March 21, to the summer
solstice, about June 20; summer as lasting thence to the autumnal
equinox; autumn from this latter date, about September 20, to the
winter solstice on December 21; and winter from that point on to the
next spring equinox again. On this division our seasons in the northern
hemisphere last respectively: spring, 91 days; summer, 92 days; autumn,
92 days; and winter, 90 days. On Mars these become, reckoned in our
days: spring, 199 days; summer 183 days; autumn, 147 days; and winter,
158 days. If we had counted them in Martian days they would have
totaled about one thirty-fifth less in number each.
In its days and seasons, then, Mars is wonderfully like the Earth;
except for the length of the year we should hardly know the difference
in reckoning of time could we some morning wake up there instead of
here. Only in one really unimportant respect should we feel strange; in
months we should find ourselves turned topsy-turvy. But lunations have
nothing to do with climate nor with the alternation between night and
day; and in these two important respects we should certainly feel at
home.
Though the axis could be determined by the daily march of any marking
and thus the planet’s tropic, temperate and polar regions marked out,
the process is made easier by the presence of white patches covering
the planet’s poles and known, in consequence, as the polar caps. It is
from measures of the patches that the position of the Martian poles has
actually been determined. These polar caps are exactly analogous in
general position to those which bonnet our own Earth. They reproduce
the appearance of the ice and snow of our arctic and antarctic regions
seen from space, in a very remarkable manner. In truth they are things
of note in more ways than one and would claim precedence on many
counts. Priority of recognition, however, alone entitles them to
premier consideration. Among the very first of the disk’s detail to be
made out by man, they justly demand description first.
With peculiar propriety the polar caps have thus the _pas_. Not only do
they stand first in order of visibility, but they prove to occupy a
like position logically when it comes to an explanation of the planet’s
present physical state. It is not matter of hazard that the most
evident of all the planet’s markings should also be the most
fundamental, the fountainhead from which everything else flows. It is
of the essence of the planet’s condition and furnishes the key to its
comprehension. The steps leading to this conclusion are as interesting
as they are cogent. They start at the polar caps’ visibility. For their
size first riveted man’s attention and then attention to them disclosed
that most vital of the characteristics of the planet’s surface: change.
Just as almost all of the features we note are permanent in place,
showing that they belong to the surface, so are they all impermanent in
character. Change is the only absolutely unchanging thing except
position about the features the planet presents to view. It was in the
aspect of the polar caps that this important fact first came to light.
Not only did they thus initially instance a general law, they have
turned out to make it; for by themselves changing they largely cause
change in all the rest. But for a long time they alone exemplified its
workings. To Sir William Herschel we owe the first study of their
change in aspect. This eminent observer noted that their varying size
was subject to a regular rhythmic wax and wane timed to the course of
the seasons of the planet’s year. The caps increased in the winter of
their hemisphere and decreased in its summer and being situate in
opposite hemispheres they did this alternately with pendulum-like
precision. His observations were soon abundantly confirmed, for the
phenomena take place upon a vast scale and are thus easy of
recognition. At their maximum spread the caps cover more than one
hundred times as much ground as when they have shrunk to their minimum.
In the depth of winter they stretch over much more than the polar zone,
coming down to 60° and even 50° of latitude north or south as the case
may be, thence melting till by midsummer they span only five or six
degrees across.
In this they bear close analogue to the behavior of our own. Ours would
show not otherwise were they viewed from the impersonal standpoint of
space. Very little telescopic aid suffices to disclose the Martian
polar phenomena in this their more salient characteristics and convince
an observer of their likeness to those of the earth. Any one may note
what is there going on by successive observations of the planet with a
three-inch glass. Nor is the change by any means slow. A few days at
the proper Martian season, or at most a couple of weeks, produces
conspicuous and conclusive alterations in the size of these nightcaps
of the planet’s winter sleep. Resembling our own so well they were
early surmised to be of like constitution and composed, therefore, of
ice and snow. Plausible on its face, this view of them was generally
adopted and common sense has held to it ever since. It has encountered,
of course, opposition, partly from very proper conservatism, but
chiefly from that earth-centred philosophy which has doubted most
advances since Galileo’s time, and carbonic acid has been put forward
by this school of sceptics to take its place. We shall critically
examine both objections; the latter first, because a certain physical
fact enables us to dispose of it at once. In casual appearance there is
not much to choose between the rival candidates of common sense and
uncommon subtlety, water and frozen carbonic acid gas, both being
suitably white and both going and coming with the temperature. But,
upon closer study, in one point of behavior the two substances act
quite unlike, and had half the ingenuity been expended in testing the
theory as in broaching it this fact had come to light to the suggestors
as it did upon examination to the writer and had served as a touchstone
in the case. At pressures of anything like one atmosphere or less
carbonic acid passes at once from the solid to the gaseous state.
Water, on the other hand, lingers in the intermediate stage of a
liquid. Now, as the Martian cap melts it shows surrounded by a deep
blue band which accompanies it in its retreat, shrinking to keep pace
with the shrinkage in the cap. This is clearly the product of the
disintegration since it waits so studiously upon it. The substance
composing the cap, then, does not pass instantaneously or anything like
it from the solid to the gaseous condition.
This badge of blue ribbon about the melting cap, therefore,
conclusively shows that carbonic acid is not what we see and leaves us
with the only alternative we know of: water.
CHAPTER V
BEHAVIOR OF THE POLAR CAPS
Assured by physical properties that our visual appearances are quite
capable of being what they seem we pass to the phenomena of the cap
itself. Like as are the polar caps of the two planets at first regard,
upon further study very notable differences soon disclose themselves
between the earthly and the Martian ones; and these serve to give us
our initial hint of a different state of things over there from that
with which we are conversant on Earth.
To begin with, the limits between which they fluctuate are out of all
proportion greater on Mars. It is not so much in their maxima that the
ice-sheets of the two planets vary. Our own polar caps are much larger
than we think; indeed, we live in them a good fraction of the time. Our
winter snows are in truth nothing but part and parcel of the polar cap
at that season. Now, in the northern hemisphere snow covers the ground
at sea-level more or less continuously down to 50° of latitude. It
stretches thus far even on the western flanks of the continents, while
in the middle of them and on their eastern sides it extends ten degrees
farther yet during the depth of winter. So that we have a polar cap
which is then ninety degrees across. In our southern hemisphere it is
much the same six months later, in the corresponding winter of its year.
On Mars at their winter maxima the polar caps extend over a similar
stretch of latitude. They do so, however, unequally. The southern one
is considerably the larger. In 1903, 136 days after the winter
solstice, in the Martian calendar February 27, it came down in
longitude 225° to 44° of latitude and may be taken to have then
measured ninety-three degrees across; in 1905, 121 days after the same
solstice, it stretched in longitude 235° to latitude 42°, and 158 days
later, in longitude 221° to latitude 41°; values which, supposing it to
have been round, imply for it a diameter on these occasions of
ninety-six and ninety-seven degrees. It was then February 20 and March
10 respectively of the Martian year. These determinations of its size
at the two oppositions agree sufficiently well considering the great
tilt away from us of the south pole at the time and the horizonward
foreshortening of the edge of the snow. It seems from a consensus of
the measures to have been some five degrees wider in 1903 than in 1905,
which may mean a colder winter preceding the former date. The cap was
still apparently without a dark contour in both years, showing that it
had not yet begun to melt.
[Illustration: South Polar Cap.
(Lowell Observatory, 1905.)]
Less has been learnt of the northern cap. In 1896-1897 when it was
similarly presented skirting the other rim of the disk, a gap occurred
in the observations corresponding to the time by Martian months between
February 24 and March 22. On the former date the cap came down only to
latitude 55° in longitude 352°; on the subsequent one and for several
days after the latitude of the southern limit of the snow was such as
to imply a breadth to it of about eighty degrees. The cap was now
bordered by a dark line, proving that melting had already set in. It
cannot, however, at its maximum have covered much more country than
this, in view of its lesser extent on February 24.
Fair as our knowledge now is of the dimensions of the Martian polar
caps at their maxima, we have much more accurate information with
regard to their minima, and this, too, was obtained much earlier. That
we should first have known their smallest rather than their greatest
extent with accuracy may appear surprising, exactly the opposite being
our knowledge of our own. It is not, however, so surprising as it
appears, inasmuch as it is an inevitable consequence of the planet’s
aspect with regard to the sun. When the tilt of the axis inclines one
hemisphere toward the sun, that hemisphere’s polar cap must melt and
dwindle, while at the same time it is the one best seen, the other
being turned away from the sun and therefore largely from us as well;
so that even such part of the latter as is illumined lies low down
toward the horizon of the disk where a slight change of angle means a
great difference in size.
It has thus come about that both the south and the north polar caps
have been repeatedly well seen and measured at their minimum; and the
measures for different Martian years agree well with one another. For
the northern cap six degrees in diameter is about the least value to
which it shrinks. The south one becomes even smaller, being usually not
more than five degrees across, while in 1894 it actually vanished, a
thing unprecedented. Its absence was detected by Douglass at Flagstaff
and shortly after the announcement of its disappearance the fact was
corroborated by Barnard at the Lick. The position the cap would have
occupied was at the time better placed for observation in America than
in Europe, inasmuch as the cap is eccentrically situated with regard to
the geographic pole and its centre was then well on the side of the
disk presented to us while in Europe it was turned away. This, together
with the fact that it undoubtedly came and went more than once about
this time, accounts for its disappearance not having been recognized
there, haze left by it having apparently been mistaken for the cap
itself.
[Illustration: North Polar Cap.
(Lowell Observatory, 1905.)]
On Earth the minima are much larger. In the northern hemisphere the
line of perpetual snow or pack-ice in longitude 50° east runs about on
the 80° parallel, including within it the southern end of Franz Joseph
Land. Opposite this, in longitude 120° west, above the North American
continent, it reaches down lower still to 75°. So that the cap is then
from twenty to thirty degrees in diameter. In the southern hemisphere
it is even larger. In longitude 170° west the land was found by Ross to
be under perpetual snow in latitude 72°. Cook had reached in longitude
107° east an impassable barrier of ice in latitude 70° 23′. The season
was then midsummer, January 30. So that we are perhaps justified in
considering 71° south as about the average limit of perpetual snow or
paleocrystic ice. This would make the southern cap at its minimum
thirty-eight degrees across. Pack-ice with open spots extends still
farther north. The Pagoda in 1845 was stopped by impenetrable pack-ice
in south latitude 68° and the Challenger in 1874 encountered the pack
in latitude 65° on the 19th of February, which corresponds about to our
19th of August, the time at which the sea should be most open. The
limit of perpetual snow is thus lower in the southern than in the
northern hemisphere. Here again, then, the two minima differ, but in
the reverse way from what they do on Mars.
From this we perceive that the variations in size of the caps are much
more striking on Mars than on the Earth and that these are due chiefly
to the difference in the minima, the maxima not varying greatly.
To explain these interesting diversities of behavior in the several
polar caps we shall have to go back a little in general physics in
order to get a proper take off. It is a curious concomitant of the law
of gravity that the amount of heat received by a planet in passing from
any point of its path to a point diametrically opposite is always the
same no matter what be the eccentricity of the orbit. Thus, a planet
has as many calories falling upon it in travelling from its vernal
equinox to its autumnal as from the autumnal to the vernal again,
although the time taken in the one journey be very different from that
of the other. This is due to the fact that the angle swept over by the
radius vector, that is, the imaginary bond between it and the sun, is
at all points proportional to the amount of heat received; just as it
is of the gravity undergone, the two forces radiating into space as the
inverse square of the distance. Thus the heat received by a point or a
hemisphere, through any orbital angle, is independent of the
eccentricity of the orbit.
But it is not independent of the axial tilt. For the force of the sun’s
rays is modified by their obliquity. The amount of heat received at any
point in consequence of the tilt turns upon the position of the point,
and for any hemisphere taken as a whole it depends upon the degree to
which the pole is tilted to the source of heat. In consequence of being
more squarely presented to its beams, the hemisphere which is directed
toward the sun and therefore is passing through its summer season gets
far more insolation than that which is at the same time in the depth of
its winter. For a tilt of twenty-four degrees, the present received
value for the axis of Mars, the two hemispheres so circumstanced get
amounts of heat respectively in the proportion of sixty-three to
thirty-seven.
But, though the summer and winter insolation thus differ, they are the
same for each hemisphere in turn. Consequently the mere amount of heat
received cannot be the cause of any differences detected between the
respective maxima and minima of the two polar caps. If heat were a
substance which could be stored up instead of being a mode of motion,
the effect produced would be in accordance with the quantity applied
and the two caps would behave alike. As it is the total amount has very
little to say in the matter.
Not the amount of heat but the manner in which this heat is made at
home is responsible for the difference we observe. Now, though the
total amount is the same in passing from the vernal to the autumnal
equinox as from the autumnal to the vernal, the time during which it is
received in either case varies from one hemisphere to the other. It is
summer in the former while it is winter in the latter and the
difference in the length of the two seasons due to the eccentricity of
the orbit makes a vast difference in the result. Winter affects the
maxima, summer the minima, attained. Of these opposite variations
presented to us by the two caps, the maxima, the one most difficult to
detect, is the easiest to explain, for the difference in the maxima
seems to be due to the surpassing length of the antarctic night.
Owing to the eccentricity of the orbital ellipse pursued by Mars and to
the present position of the planet’s solstices, the southern hemisphere
is farther away from the sun during its winter and is so for a longer
time. The seasons are in length, for the northern hemisphere: spring,
199 days; summer, 183 days; autumn, 147 days; and winter, 158 days;
while for the southern hemisphere they are: spring, 147 days; summer,
158 days; autumn, 199 days; and winter, 183 days. The arctic polar
night is thus 305 of our days long; the antarctic, 382. Thus for 77
more days than happens to its fellow the southern pole never sees the
sun. Now, since the total sunlight from equinox to equinox is the same
in both hemispheres, its distribution by days must be different. In the
southern hemisphere the same amount is crowded into a smaller compass
in the proportion of 305 to 382; that being that hemisphere’s relative
ratio of days. But since during winter the cap increases, there is a
daily excess of accumulation over dissipation of snow and each
twenty-four hours must on the average add its tithe to the sum total.
Since the northern days are the warmer each adds less than do the
southern ones; and furthermore there are fewer of them. On both these
scores the amount of the deposition about the northern pole should be
less than about the southern one. Consequently, the snow-sheet there
should be the less extensive and show a relatively smaller maximum,
which explains what we see.
With the minima the action is otherwise. Inasmuch as the greater heat
received during the daylight hours by the southern hemisphere is
exactly offset by the shortness of its season, it would seem at first
as if there could be no difference in the total effect upon the two
ice-caps.
But further consideration discloses a couple of factors which might,
and possibly do, come in to qualify the action and account for the
observed effect. One is that though the total amount of heat received
is the same, the manner of its distribution differs in the two
hemispheres. In the northern one the time from vernal to autumnal
equinox is 382 days against 305 in the southern. Consequently, the
average daily heat is then five fourths more intense in the southern
hemisphere. Indeed, it is even greater than this and nearer four
thirds, because the melting occurs chiefly in the spring and in the
first two months of summer when the contrast in length of season
between the two hemispheres is at its greatest. Now, a few hotter days
might well work more result than many colder ones. And this would be
particularly true of Mars where the mean temperature is probably none
too much above the freezing-point to start with. Ice consumes so much
caloric in the process of turning into any other state, laying it by in
the form of latent heat before it can turn into water and then so much
more before this water can be converted into steam that a good deal has
to be expended on it before getting any perceptible result. Once
obtained, however, the heat is retained with like tenacity. So that the
process works to double effect! If sufficient heat be received the ice
is first melted, then evaporated and finally formed into a layer of
humid air, the humidity of which keeps it warm. Dry air is unretentive
of heat, moist air the opposite. And for the melting of the ice-cap to
proceed most effectively the temperature that laps it about must be as
high as possible and kept so as continuously as may be. If between days
it be allowed to fall too low at night much caloric must needs be
wasted in simply raising the ice again to the melting-point. This a
blanket of warm air tends to prevent, and this again is brought about
by a few hot days rather than by many colder ones. It is not all the
heat received that becomes effective but the surplus heat above a
certain point. The gain in continuity of action thus brought about is
somewhat like that exhibited between the running of an express and an
accommodation train. To reach its destination in a given time the
former requires far less power because it does not have to get up speed
again after each arrest. Thus the whole effect in melting the snow
would be greater upon that hemisphere whose summer happens to be the
more intense.
The greater swing in size of the cap most exposed to the effects of the
eccentricity is, then, the necessary result of circumstances when the
precipitation is not too great to be nearly carried off by the
subsequent dissipation. This is the state of things on Mars and the
second of the factors above referred to. On the Earth as we have seen
the polar caps are somewhat larger at their maximum and very much so at
their minimum. Now, this is just what should happen were the
precipitation increased. Suppose, for example, that the amount of
precipitation were to increase while the amount of summer melting
remained the same, and this would be the case if the vapor in the air
augmented for one cause or another, and the result of each fresh
deposit was locked up in snow. After a certain point the cap would grow
in depth rather than in extension; the winter deposit would be thicker
but the summer evaporation would remain the same. Now, if this
occurred, it is evident that the minimum size of the cap would increase
relatively much faster than the maximum, and furthermore, that the
relative increase of the minimum in the two caps would be greatest for
that which had seasons of extremes. The result we see in the case of
the Earth. In the arctic cap, where in consequence of the eccentricity
of the orbit the winter is shorter, the maximum is less than in the
antarctic and this extra amount of precipitation cannot be wholly done
away with in its intenser summer, so that the minimum too is greater
there.
We reach, then, this interesting conclusion. We find that eccentricity
of orbit by itself not only causes no universal glaciation in the
hemisphere which we should incidentally suppose likely to show it, but
actually produces the opposite result, in more than offsetting by
summer proximity what winter distance brings about. To cause extensive
glaciation we must have, in addition to favorable eccentricity, a large
precipitation. With these two factors combined we get an ice age, but
not otherwise. The result has an important bearing on geologic glacial
periods and their explanation.
Once formed, an ice-sheet cools everything about it and chills the
climate of its hemisphere. It is a perpetual storehouse of cold. Mars
has no such general glaciation in either hemisphere, and the absence of
it, which is due to lesser precipitation, together with the clearness
of its skies, accounts for the warmth which the surface exhibits and
which has been found so hard hitherto to interpret. Could our earth but
get rid of its oceans, we too might have temperate regions stretching
to the poles.
CHAPTER VI
MARTIAN POLAR EXPEDITIONS
Polar expeditions exert an extreme attraction on certain minds, perhaps
because they combine the maximum of hardship with the minimum of
headway. Inconclusiveness certainly enables them to be constantly
renewed, without loss either of purpose or prestige. The fact that the
pole has never been trod by man constitutes the lodestone to such
undertakings; and that it continues to defy him only whets his endeavor
the more. Except for the demonstration of the polar drift-current
conceived of and then verified by Nansen, very little has been added by
them to our knowledge of the globe. Nor is there specific reason to
suppose that what they might add would be particularly vital. Nothing
out of the way is suspected of the pole beyond the simple fact of being
so positioned. Yet for their patent inconclusion they continue to be
sent in sublime superiority to failure.
Martian polar expeditions, as undertaken by the astronomer, are the
antipodes of these pleasingly perilous excursions in three important
regards, which if less appealing to the gallery commend themselves to
the philosopher. They involve comparatively little hardship; they have
accomplished what they set out to do; and the knowledge they have
gleaned has proved fundamental to an understanding of the present
physical condition of the planet.
The antithesis in pole-pursuing between the two planets manifests
itself at the threshold of the inquiry, in the relative feasibility
with which the phenomena on Mars may be scanned. For, curiously enough,
instead of being the pole and its surrounding paleocrystic ice which
remains hidden on Mars, it is rather the extreme extent of its
extension and the lowest latitudinal deposit of frost which lies
shrouded in mystery. The difficulty there is not to see the pole but to
see in winter the regions from which our own expeditions set out. And
this because the poles are well displayed to us at times which are
neither few nor very far between; while favorable occasions for marking
the edge of the caps when at their greatest have neither proved so
numerous nor so favorable. The tilt of the planet’s axis when
conveniently placed for human observation has been the cause of the one
drawback; the planet’s meteorological condition in those latitudes at
that season the reason for the other.
What knowledge we have of the size of the caps in degrees upon the
surface of the planet at this their extreme equatorward extension has
been given in the last chapter. Their aspect at the time together with
what that aspect betokens was not there touched upon. With it,
therefore, and the peculiarities it presents to view we shall begin our
account of the caps’ annual history.
[Illustration: South Polar Cap in winter.]
When first the hemisphere, the pole of which has for half a Martian
year been turned away from the sun, begins to emerge from its long
hibernation, the snow-cap which covers it down even to temperate
regions presents an undelimited expanse of white, the edges of which
merge indistinguishably into the groundwork color of the regions round
about. Of a dull opaque hue along its border, its contour is not sharp
but fades off in a fleecy fringe without hard and fast line of
demarcation. Such notably was the aspect of the north temperate zone in
1896 when, tilted as it then was away from us into a mere northern
horizon of the planet’s limb, it showed prior to the definite
recognition of the north polar cap in August of that year, and such too
was the look of the disk’s southern edge both before and after the
first certain detection of the southern cap in 1903 and 1905. Each was
then in the depth of winter. For in Martian chronology the season
corresponded in each at the time to what we know in our northern
hemisphere as the latter part of February and the early part of March
and the appearance of the planet’s surface in both was not unlike what
we know at the same season in latitude 45°. Indeed, there is reason to
suppose bad weather there then and the extreme fringe, from the pale
tint it exhibited, to have been cloud rather than snow.
It is quite in keeping with what we know on earth or can conceive of
elsewhere that such aspect should characterize the cap at or near the
attainment of its greatest development. Whether it were not yet quite
arrived at this turning-point of its career or had but slightly passed
it a vagueness of outline would in either event proclaim the fact. For
were the frost still depositing, the cap’s edge would show indefinite;
and on the other hand had it just begun to melt, evaporation would give
it an undefined edge before the melting water had gathered in
sufficient quantities to be itself noticeable.
Its behavior subsequent to recognition bore out the inference from its
aspect when it first appeared. While for many days prior to its coming
unmistakably into view it was impossible to say whether what was seen
of the southern cap in 1903 and 1905 was cloud or snow; so even after
it had definitely disclosed itself it continued to play at odds with
the observer. Showing sharp at the edges one day it would appear but
hazily defined the next, thus clearly demonstrating itself to be at the
then unstable acme of its spread. Such a state of things we are only
too familiar with in our own March weather when after days of sunshine
that have melted off the winter’s white and fringed it with rivulets
and awakening grass, a snow-storm falling upon it powders the ground
again that was beginning to be bare and at one stroke extends the
domain of the snow while mystifying the actual limits it may be said to
occupy. The same condition of things, then, is not unknown on Mars, and
to fix the precise date of so wavering a phenomenon is not so much
matter of difficult observation as of physical impossibility.
[Illustration: Hellas in winter.]
Nor is the southern cap, at this the height of its winter expansion,
confined strictly to its own proper limits. Faint extensions, now so
connected with its main body as to form part and parcel of it, now so
detached and dull of tint as to make the observer doubtful of the exact
relationship, are generally to be seen attendant on it. Hellas in
winter is much given to such questionable garb, and has in consequence
been mistaken by more than one observer for the cap itself, appearing
as it does well upon the southern limb and being often the only region
to show white. Indeed, frost-bound as it then is, to consider it the
polar cap, though possibly geographically incorrect, may
climatologically be sustainable. Its northern extremity extends down to
latitude 30°, a pretty low latitude for frost. Still such equatorward
extension is not without corroborating parallel. In 1903, at what was
in Martian dates April 26, the whole of the region south of the Solis
Lacus and the Nectar showed white, with a whiteness which may as well
have been hoarfrost as cloud. Now, the Nectar runs east and west in
latitude 28°. So that in this instance, too, it is possible that arctic
conditions knocked at the very doors of the tropics. Encroachment of
the sort is equivalent to snow in Cairo and permanent snow at that; not
an occasional snow flurry, but something to linger on the ground and
stay visible sixty millions of miles away.
[Illustration: White south of Nectar and Solis Lacus.]
Knowledge of either cap in this the midwinter of its year has been a
matter of the most recent oppositions of the planet. Up to within the
last few years our acquaintance with either cap was chiefly confined to
the months,—one might almost say the weeks,—immediately surrounding
the summer solstice of its respective hemisphere. The behavior of the
caps during the rest of their career was largely unknown to us, from
the very disadvantageous positions they occupied at the times the
planet was nearest to the earth. Beginning with 1894, however, our
knowledge of both has been much extended, by a proportionate extension
of the period covered by the observations. It used to be thought
impracticable to observe the planet far on either side of opposition;
now it is observed from as much as four months before that event to the
same period after it. The result is a systematic series of observations
which in many ways has given unexpected insight into Martian
conditions. One of the benefits secured has been the lengthening of the
period of study of the cap’s career, a pushing of inquiry farther back
into its spring history and a longer lingering with it in its autumnal
rebuilding. Yet up to the very last opposition a gap in its chronology
still remained between February 25 and April 1. The opposition of 1905
has bridged this hiatus and brought us down to the latter date, at
which the melting of the cap begins in earnest.
From this point, April 1 on, we have abundant evidence of the cap’s
behavior. Its career now for some time is one long chronicle of
contraction. Like Balzac’s _Peau de Chagrin_ it simply shrinks, giving
out of its virtue in the process. The cap proceeds to dwindle almost
under the observer’s eye till, from an enormous white counterpane
spread over all the polar and a large part of the temperate zone, its
area contracts to but the veriest nightcap of what it was before. From
seventy degrees across it becomes sixty, then fifty, then forty, till
by the middle of the Martian May it has become not more than thirty
degrees in diameter. During this time, from the moment the melting
began in good earnest, the retreating white is girdled by a dark band,
of a blue tint, which keeps pace with the edge of the cap, shrinking as
it shrinks, and diminishing in width as the volume of the melting
decreases.
After the melting has been for some time under way and the cap has
become permanently bordered by its dark blue band a peculiar phenomenon
makes its appearance in the cap itself. This is its fission into one or
more parts. The process begins by the appearance of dark rifts which,
starting in from the cap’s exterior, penetrate into its heart until at
last they cleave it in two. Rifts have been seen by several observers
and in both caps; and what is most suggestive they always appear in the
same places, year after year. Sometimes oppositions elapse between
their several detections for they are not the least difficult of
detail; but when they are caught, they prove to lie just where they did
before.
The permanency in place of the rifts, a characteristic true of them
all, shows them to be of local habit. Thus the rift of 1884 and 1897
reappeared again to another observer in the same position in 1901. They
are, therefore, features of, or directly dependent on, the surface of
the planet. But it will not do from this fact to infer that they are
expressive of depressions there. The evidence is conclusive that great
irregularities of surface do not exist on Mars. As we shall see when we
come to consider the orology of the planet it is certain that
elevations there of over two or three thousand feet in altitude are
absent. Differences of temperature, able to explain a melting of the
ice in one locality coincidentally with its retention in an adjacent
one, must in consequence be unknown. And this much more conclusively
than at first appears, for the reason that the smaller the planet’s
mass the less rapidly does its blanket of air thin out in ascent above
the surface. This is in consequence of the greater pull the larger body
exerts and the greater density it imparts to a compressible gas like
our atmosphere. Gravity acts like any force producing pressure and by
it the envelope of air is squeezed into a smaller compass. But as this
is done throughout the atmospheric layer it means a more rapid
rarefaction as one leaves the body. The action is such that the height
necessary to reach an analogic density varies inversely as the gravity
of the mass. In consequence of this, to compass a relative thermometric
fall for which a moderate difference of elevation would suffice on
Earth, an immoderate one must be made on Mars. For gravity there being
but three eighths what it is here, eight thirds the rise must be made
to attain a proportionate lowering of temperature. This fact renders
the above argument against elevation and depression being the cause of
the phenomenon three times as cogent as it otherwise would be.
With so gradual a gradient in barometric pressure there and so low a
set of contour lines, altitude must be a negligible factor in Martian
surface meteorologic phenomena. Both density and temperature can be but
little affected by such cause, and we must search elsewhere for
explanation of what surface peculiarities we detect.
Meanwhile the rifts themselves, from being lines which penetrate the
cap from its periphery in toward its centre, end by traversing it in
its entirety and separating portions which, becoming outlying
subsidiary patches, themselves proceed to dwindle and eventually
disappear. The rifts usually take their rise from such broader parts of
the cap-encircling blue belt as make beads upon that cordon and are
clearly spots where the product of the melting of the cap is either
specially collected, or produces its most visible effect.
So far the description might apply with substantial accuracy to either
cap. Yet the conduct of the two is in some ways diverse and begins to
accentuate itself from this point on.
[Illustration: Northern Cap hooded with vapor.]
From the time that the north polar cap reaches a diameter of about
twenty-five degrees, a singular change steals over it. From having been
up to then of a well-defined outline it now proceeds to grow hazy and
indistinct all along its edge. This change in its character at the same
period of its career has been quite noticeable at each of the three
last oppositions, so that small doubt remains that the metamorphosis is
a regularly recurrent one in the history of the cap. Coincident with
the obliteration of its contour, its dimensions seemingly enlarge. It
is as if a hood had been drawn over the cap of a dull white different
from the dazzling brilliance of the cap itself and covering more
ground. Such is probably what occurs; with vapor for veil. The
excessive melting of the cap produces an extensive evaporation which
then in part condenses to be deposited afresh, in part remains as a
covering, shutting off from our view the outlines of the cap itself. It
would seem that at this time the cap melts faster than the air can
carry it off. A sort of steaming appears to be going on, taking place
_in situ_. For it clearly is not wafted away. The time of its coming
too is significant. For the season is May 15, the height of time for a
spring haze to set in. Then later it dissipates with the same quiet
indefiniteness with which it gathered.
[Illustration: Northern Cap unmasked.]
It is some time in Martian June before the spring haze clears away, and
when it does go, only a tiny polar cap stands revealed beneath it, from
six to eight degrees across, or from a tenth to a fifteenth of what it
was when it passed into its curious spring chrysalis. The date of
emergence varies. In 1903 it occurred early, the haze not being marked
after June 3, though recurring again at intervals for a day or so. In
1905 it was later; perceptibly thin after June 21 it did not certainly
clear away till June 9 and came back again on July 16 and possibly on
the 25th.
These vicissitudes of aspect give us glimpses into a sweet
unreasonableness in Martian weather which makes it seem more akin to
our own. And this on two counts, diurnal and annual. From day to day
atmospheric conditions shift for purely local cause; while,
furthermore, successive Martian years are not alike. In some the season
is early; in others late. So that Mars is no more exempt than are we
from the wantonness of weather.
Clearly disclosed thus reduced to its smallest possible terms it
remains for some months of our days, for six weeks of its own. During
that period it continues practically unchanged, neither increasing nor
decreasing significantly in size, nor altering notably in aspect.
Measures of the drawings of it then make it from five to eight degrees
across and it is possible that it really fluctuates between narrow
limits, though its clear-cut outline at all times renders the variation
difficult to explain. We are not so near it as we could wish; for on
these occasions even at their best it is over two hundred times as
distant as the moon and the greatest magnification possible still
leaves it a hundred thousand miles away.
To the south polar cap a somewhat similar history attaches, but with a
difference. In its case no such regularly recurrent spring haze has yet
been noted. The melting of this cap would seem to be of a more orderly
nature than its fellow and not to outdo what can conveniently be
carried off.
That an excess of evaporation should not take place is the more
peculiar from the fact that at its maximum it is the larger of the two
and therefore has the greater quantity of matter to get rid of. Its
summer, also, is shorter than the arctic one, so that it has the less
time to dispose of its accumulations. The only other respect in which
it seems to be differently circumstanced from its antipodes is in the
character of its surroundings. About it are large blue-green areas
which with intermissions stretch down in places to within less than ten
degrees of the equator; whereas the other pole is continuously
encircled for long distances by practically uninterrupted ochre. The
character of the environment seems thus the only thing that can account
for the difference in behavior and this proves the more plausible when
we come to consider what those two classes of regions respectively
represent.
In other ways as well the southern cap is the more self-contained. The
rifts, indeed, break it up into separate portions and these in part
remain as outlying detachments of the main body, as was notably the
case in 1877 and in 1894, but they hardly have the permanency and
importance of those similarly formed about the arctic pole. Nothing
antarctic for instance compares with the subsidiary patch of the north
polar regions lying in longitude 206°, which both in Schiaparelli’s
time, and during the late oppositions as well was almost as fixed a
feature of the arctic zone as the cap proper. Not quite so constant,
however, and not so solid-looking a landmark is this patch for all its
extent, which nearly equals the area of the more legitimate portion. It
bears on its face a more pallid complexion as if it were thinner, and
this is borne out by the fact that it occasionally disappears, an event
which so far at least has never befallen the northern cap itself.
Less constant the southern one is to its own minimum than the northern.
In some seasons, in most in fact, it reaches like the other a more or
less definite limit of diminution which it does not pass. But this is
not always the case. In 1894 it disappeared entirely at the height of
its midsummer. The season was probably unusually hot then in the
southern hemisphere of Mars.
In position the caps have something to say about physiographic
conditions. Both caps at their minima are then irregular and the centre
of the south one is markedly eccentric to the areographic pole. It lies
some six degrees north along the thirtieth meridian. The northern one
is also probably eccentric, but much less so, with a divergence not
much exceeding a degree and of doubtful orientation. Not only are both
caps not upon their respective poles but they are not opposite each
other, the one lying in longitude 30°, the other in 290°. This speaks,
of course, for local action. In some wise this must depend on the
configuration of the surface, yet so far as markings go there is
nothing to show what the dependence is.
The eccentring of the caps is paralleled by the like state of things on
earth. The pole of cold does not coincide in either hemisphere with the
geographic pole. On the earth its position is largely determined by the
distribution of the land-masses. Continents are not such equalizers of
heat as oceans because of their conductivity on the one hand and their
immobility on the other. In winter they part with their heat more
quickly and convection currents cannot supply the loss. This accounting
for thermal pole eccentricity is inapplicable to Mars because of the
absence there of bodies of water. And it is significant that the degree
the earthly poles of cold are out much exceeds what is the case on
Mars. Possibly areas of vegetation there replace to some effect areas
of water. It is certainly in favor of this view that the arctic regions
there are more desert than the antarctic and that the north pole of
cold occupies more squarely the geographic pole.
Not till 1903 did the actual starting again of either cap chance to be
seen. Nor was this, indeed, a matter of hazard but of persistent
inquiry by observation prolonged after the planet had got so far away
that its scanning had hitherto been discontinued. Such search beyond
the customary limits of observation was essential to success, because
of the relation of the axial tilt to the position of the planet in its
orbit. At an opposition well placed for nearness, the tilt is such as
largely to hide the pole and to present the polar regions too obliquely
to view for effective scanning. This is true both of the arctic and the
antarctic regions in turn. For the Martian axis being inclined somewhat
as our own is to the plane of the planet’s orbit, we at times see well
and at times but poorly the arctic or antarctic zones.
The cap, the starting to form of which was thus caught, was the arctic
one; the date 128 days after the northern summer solstice, or
thereabouts, for as is perhaps natural the advent of the phenomenon
partook of the wavelike advance of such things familiar on earth, an
advance succeeded by a recession and then followed by another advance.
So much is proof of local weather there as here. Hoar-frost was
successively deposited and then melted off.
[Illustration: Deposition of frost.]
What is significant, the deposition of the frost took place
simultaneously over large areas. The very first patch of it, in about
longitude 320°, extended at one stroke down to latitude 55°. For it
actually crossed the Pierius somewhat to the south. A second patch
stretched to the east of the cap. Two wings these made to the kernel of
cap itself. Through the wings could be marked the line of the canal:
the Pierius upon the one side, the Enipeus upon the other. Such
visibility of the canals through the white stretches proved the white
not to be due to cloud suspended between us and them, but a surface
deposit which found no lodgment upon the canals themselves. The same
avoidance of dark markings was evidenced by the showing of the dark rim
round the cap’s kernel. Now, if the deposit were indeed hoarfrost, this
failure to find permanent foothold on the dark markings is what we
should expect to witness. For whether they were vegetation or water,
equally in either case the frost would melt from them first. Probably
they were both vegetal, though some doubt might exist about the latter,
the band around the kernel. It was then August 20 in that hemisphere.
Such deposition over great stretches of country is perhaps not so
surprising as it appears at first sight when seen from without in its
totality. After all, something not unlike it occurs in our snow-storms
when hundreds of square miles are whitened at once. Furthermore, with
an atmosphere as thin as Mars seems to possess the temperature must be
perilously near the freezing-point in the arctic and subarctic regions
at the close of summer.
Steadily, with intermissions, the white sheet increased until even the
dark border to the cap became obliterate, the kernel showing at first
through the veil like the ghost of what it had been, and then ceasing
to be visible at all, its delimitations being buried under deeper and
deeper depositions of frost.
[Illustration: First northern snow.]
The perennial portion of the cap was thus merged in the new-fallen
snow. This marked the on-coming of the arctic winter in full force and
happened even before the polar sun had wholly set. For the pole did not
enter into the shadow till two of our months later, the autumnal
equinox occurring 183 days after the summer solstice or 55 days after
the first fall of frost. Then the pole passed into its star-strewn
arctic night, a polar night of twice the duration of our own and the
circumpolar regions entered upon their long hibernation of ten of our
months.
CHAPTER VII
WHITE SPOTS
In addition to the polar caps proper and to the subsidiary polar
patches that often in late summer flank them round about, other white
spots may from time to time be seen upon the disk. In appearance these
differ in no respect, so far as observed, from the arctic subsidiary
snow-fields. Of the same pure argent, they sparkle on occasion in like
manner with the sheen of ice. Equally with the polar caps they remain
permanent in place during the period of their visibility and are
themselves long-lived. Though by no means perpetual their duration is
reckoned by weeks and even months, and they recur with more or less
persistency at successive Martian years. That, when seen, they show in
particular positions apparently unaffected by diurnal change precludes
their being clouds, and this fact taken in connection with the
character of their habitat is the puzzling point about them. For they
affect chiefly the north tropic belt. They, or at least their nuclei,
are small, about two or three degrees in diameter, and are not
particularly easy of detection as a rule, though certain larger ones
are at times conspicuous. Chromatic, rather than formal, definition is
necessary to their bringing out, as is witnessed by the superb colors
the disk presents at the times when they are best seen. It is then that
Mars puts on the look of a fire-opal.
The first such spot to be noticed was one which Schiaparelli detected
in 1879, at the second opposition in which he studied the planet. He
called it the Nix Olympica, showing that he recognized in it a
cousinship to the polar snows. Yet it lay in latitude 20° north,
longitude[1] 131°, in the midst of the ochre stretches of that part of
the disk. It was a small roundish white speck of not more than two
thirds the diameter of the polar cap. Reseen by him in 1881, it failed
to appear at subsequent oppositions and was not caught again until
1888. Then once more it vanished, not to be detected anew till many
years after at Flagstaff, coming out rather surprisingly in 1903. It
showed, however, in the same place as before; so that its position but
not its existence is permanent.
A similar but smaller patch was apparent to Schiaparelli at the same
opposition of 1879. This one which he styled the Nix Atlantica lay
between the Thoth and the Syrtis Major. It was about half the size of
the Nix Olympica and has never since been seen, though it should have
been had it continued to be what it then was.
[Illustration: White in Elysium.]
On the other hand, phenomena of the sort undetected of Schiaparelli
have been remarked at Flagstaff. On May 18, 1901, I was suddenly struck
by the singular whiteness of the southeast corner of Elysium where that
region bordered the Trivium. Elysium has a way of being bright but not
with such startling intensity as this spot presented nor in so
restricted an area as was here the case. The spot was so much whiter
than anything I had ever previously seen outside the polar caps that it
arrested my attention at once. And this the more that I had observed
this same part of the planet the day before and perceived nothing out
of the ordinary. Once detected, however, the spot continued visible.
The next day it was there with equal conspicuousness, and now thrust an
arm across the Cerberus, entirely obliterating the canal for the space
of several degrees. In this salience it remained day after day till the
region passed from sight, to reappear with it six weeks later when the
region again rounded into view. The hour of the Martian day seemed to
make no difference in its visibility. It was seen from early morning
till Martian afternoon, as late as the phase permitted. Clearly there
was nothing diurnal about its revealing, and it lasted for at least
three months and a half, until the planet got so far away that
observations were discontinued.
It was to all appearances and intents snow. But now comes the singular
fact about it. It lay within ten degrees of the equator and showed from
the end of June to the latter part of August. To our ideas there could
be no more inopportune place or time for such an exhibition. For it
cannot have been due to a snow-capped peak, as we know for certain that
there are no mountains in this, or in any other, part of the planet.
Besides, it had not appeared in previous Martian years; which it
infallibly would have done had it been a peak. Indeed, it baffles
explanation beyond any Martian phenomenon known to me. It seems
directly to contradict every other detail presented by the disk.
The phenomenon is thus unique in kind; it is not, however, unique as a
specimen of its kind. The eastern coast of Aeria where that region
borders the Syrtis Major is prone to a brilliance of the same sort. It
is a narrow belt of country that shows thus, nothing but the coastline
itself, but this for a considerable distance stretching several hundred
miles in length. It has stood out saliently bright now at every
opposition which I have observed, beginning with 1894. Sometimes it has
been described in the notes as bright simply, sometimes as white, and
once, in 1901, as glistening at one point like ice. Yet when upon the
terminator it has never stood forth as a mountain range should have
done to declare its character.
It has been evident regardless apparently of the Martian season. In
1894 it was bright from October 25 to January 16 (Martian chronology);
in 1896, from December 22 to January 7; in 1901, from July 13 to the
15th; in 1903, at about the same date and so in 1905. It was whitest
during the latter oppositions, showing that the effect is most marked
in its midsummer. All of the above instances of extra-polar white have
been located within the tropics. Examples of the same thing, however,
occur in the north temperate zone. Tempe, a region just to the west of
the Mare Acidalium, is exceedingly given to showing a small white spot
close upon the Mare’s border in latitude 50° north. This spot, too, on
occasion glitters as it were with ice. It is also at times very small.
So that whereas much of Tempe is by nature bright but a small kernel of
it is dazzling.
The list might be easily extended from the record book. Thus on March 1
and 2, 1903, the disk showed speckled with minute white spots, one in
Arcadia in latitude 41° north, one in Tharsis near the equator, a third
just north of the Phoenix Lucus in 10° south, and a fourth, the Nix
Olympica, and on April 11, a glittering pin-point starred like a
diamond the centre of the Pons Hectoris. On both these occasions the
Martian season was summer; July 9 for the latter, June 21 for the
former date.
[Illustration: White in the Pons Hectoris.]
As one approaches the north pole spots of like character become more
numerous. Especially are such visible north of the Mare Acidalium in
the arctic region thereabout, from 63° to 75° north.
From so widespread a set of instances the only explanation which seems
to fit the phenomena is that the mean temperature of Mars is low, not
very much above freezing, and that whatever causes a local fall in the
temperature results in hoar-frost. Such an explanation accords well
with the distance of the planet from the sun and the thinness of its
atmosphere. At the same time it shows that the mean temperature over
the greater part of the planet the greater part of the time is above
the freezing-point and that consequently it is no bar to vegetation of
a suitable sort.
That the hoar-frost should be found even at the equator may perhaps be
due to the very thinness of the air-covering of Mars, which would tend
to make the actual insolation more of a factor than it is with us, and
by the great length of the Martian seasons. In midsummer the greatest
insolation occurs in the arctic and temperate, not in the tropic
regions; on the other hand, an atmosphere tends to accumulate heat for
the tropics. With us the latter factor is prepotent; it would be less
effective on Mars. Then again the double duration of summer would tend
to emphasize insolation as the important factor in the matter. But it
is possible that greater deposition plays a part in the matter. On
earth the rainfall is greatest near the equator and something of the
sort may be true of the zones of moisture on Mars. That the most
striking spots are found to the west of large dark areas may in this
connection have a meaning inasmuch as, such regions being
vegetation-covered, the air over them is probably more moisture-laden.
One point about the position of the spots is of moment: they have all
been found in the northern hemisphere or within ten degrees of it in
the southern equatorial region. This seems at first a question of
hemispheres; but when we consider that the light areas of the surface
are chiefly in the boreal hemisphere and in the south tropic belt, we
perceive that it may be rather the character of the surface there than
the particular hemisphere in the abstract that is decisive in the
matter. Nevertheless, the austral hemisphere is the hemisphere of
extremes, possessing a shorter, hotter summer and a longer, colder
winter than its antipodes. This would not favor sporadic small
depositions of frost in summer so much as would a climate of a more
mean temperature.
From the relative lack of atmospheric covering over the planet we
should expect the nights to prove decidedly cool, while the days were
fairly warm. Of this we have perhaps evidence in a singular aspect
shown by the Mare Acidalium in June, 1903. The account of it in the
Annals reads thus: “On May 22 an interesting and curious phenomenon
presented itself. On that day, so soon as the Mare Acidalium had well
rounded the terminator on to the disk, at λ352°, the whole of its
central part showed white, the edges of the marking alone remaining as
a shell to this brilliant core. So striking was the effect that beside
appearing in the drawing it found echo in the notes. The next day no
mention is made of it, and a drawing made under λ20° shows the Mare as
usual and the bright spot in Tempe in its customary place. Neither was
anything of the sort noticed on the 24th and 25th. But on the 26th, the
day of the projection (upon the terminator), the effect of the 23d
reappeared, the longitude of the centre being 332°. Fortunately on that
day a further drawing was secured which enabled its subsequent behavior
to be followed. Made three hours later than the other, the longitude of
the centre being 13°, this drawing shows the Mare well on the disk, its
whole area as dark as usual and with Tempe bright to the right of it
toward the terminator. The terminator in question was the sunrise one,
and we are offered two suppositions in explanation of the phenomenon:
either the white was due to a morning deposition of hoar-frost which
dissipated as the sun got up, or obliquity rendered some superficial
deposit visible which more vertical vision hid. That the former
inference is the more probable seems hinted at by the simultaneous
appearance from the 19th to the 26th of other areas of white between
the Mare and the pole. May 26 was 88 days after the northern summer
solstice, and corresponded to July 31 on the earth.” Annals, Volume
III, §564.
In this connection mention may pertinently be made of Schiaparelli’s
repeated observation of regions that whiten with obliquity, a
proclivity to which he particularly noticed Hellas and certain
‘islands’ in the Mare Erythraeum to be prone. Here as with the Mare
Acidalium we certainly seem to be envisaging cases of matutinal frost
melted by midday under the sun’s rays.
-----
Footnote 1:
Martian longitudes are now reckoned from the Fastigium Aryn, the
mythologic cupola of the world, a spot easy of recognition because
making the tongue in the jaws of the Sabaeus Sinus. It further
commends itself because of lying within a degree of the equator. The
longitudes are reckoned thence westward all the way round, or to 360°.
CHAPTER VIII
CLIMATE AND WEATHER
In gazing at the successive phases presented by the polar caps as their
annual history unrolls itself to view, beginning with vast white cloaks
that in winter hide so effectively the planet’s shoulders, to little
round knobs that in summer sit like guardsmen’s caps more or less askew
upon the poles, the bodily eye sees only the glisten of far-off snow.
The mind’s eye, however, perceives something more: the conviction they
carry of the presence of an atmosphere surrounding the planet. Elusive
as water vapor is to sight for its transparency and to spectroscopic
determination for its earthly omnipresence, recognition of its
existence elsewhere by deduction raises such reasoning at once to a
more conspicuous plane than it might otherwise assume. Especially is
this true where the deduction is itself conclusive, as is here the
case. For it depends on phenomena not its own, but which are in their
turn dependent on it. We are not even beholden to any knowledge of the
substance composing the caps for the fundamental inference that an
atmosphere surrounds them. Whatever that substance were, the fact that
the caps dissipate and reform shows us with absolute certainty that
they pass into the gaseous state, to be later solidified afresh. This
gas constitutes of itself an atmosphere; while another phenomenon, to
wit, their blue girdles as they melt, affirming their substance to be
snow and ice, enables us to precise the fact that this gas is water
vapor.
From such premise given us by the polar caps we are able to infer much
more by the help of the kinetic theory of gases. But the speed of
parting by a planet with its gases is conditioned by the mean speed of
each gas. Water vapor will, therefore, go before nitrogen, oxygen or
carbonic acid gas. If, then, we find it present over the surface of a
planet we are assured of the possibility that the other three may be
there too, and from the similarity of matter in space strong reason to
suspect that they actually are.
Corroborative evidence of the accuracy of the deduction as to the
presence of a Martian air is shown in several other ways; in the
existence of clouds to begin with. Rare as they are, these certainly
float at times over parts of the planet, although it is doubtful
whether they can then be seen. Fortunately for assurance we have other
ways of ascertaining their presence than that of obscuration. Nor is it
of account to the argument that they should be few and far between, as
they unquestionably are. One single instance of such mediumistic
support is enough to support the theory of a medium; and that instance
has been more than once observed.
Direct evidence of atmosphere is further forthcoming in the limb-light.
This phenomenon might be described as a brilliant obscuration. It is a
circlet of illumination that swamps the features as they near the full
edge of the disk, the limb of the planet as it is called. Obliteration
of the sort is evident, more or less markedly, at all times, and is not
due to foreshortening, as the broadest areas are affected. The fading
out of the detail at the limb suggests nothing so much as a veil drawn
between us and it, lighter in tint than what it covers. Such a veil can
be none other than air or the haze and cloud that air supports. From
its effect, impartial in place and partial in character, cloud is
inadmissible as a cause and we are left with air charged with dust or
vapor in explanation. Obscuration due to it should prove most dense at
the limb, since there the eye has to penetrate a greater depth of it;
just as on the earth our own air gives azure dimness to the distance in
deepened tinting as the mountains lie remote.
Another bit of evidence lies in the apparent detection of a twilight
arc. In 1894 measures made of the polar and equatorial diameters of the
planet showed certain systematic residuals left after all known
corrections had been applied. The only thing which would account for
them was the supposition that a twilight arc had been unconsciously
seen and as unconsciously measured. In delicate quantities of the sort
too great reliance cannot be put, but if the residuals be not referable
to other cause they give us not only further evidence of an atmosphere,
but at the same time our only hint of that atmosphere’s extent. From
them it would seem that the air must be rare, not more than about four
inches of barometric pressure, as we reckon it, and probably less; a
thin, high air more rarefied than prevails upon our highest mountain
tops.
Corroborative of this is the aspect of the planet. From the general
look of the disk a scant covering of air is inferable. For one of the
striking things about the planet’s features is their patent exposure to
our sight. Except in the winter time of its hemisphere or in the spring
after the greatest melting of the polar cap, nothing seems to stand in
our way of an uninterrupted view of the surface, whether in the arctic,
temperate, or tropic zones. From the openness of its expression,
however, too much case should not be made as we really know but little
of how an atmosphere-enshrouded planet would look. We find no
difficulty in seeing objects a hundred miles away across the surface of
the earth and yet the thickness of the air strata in such horizontal
traversing is many fold what it is when we look directly up. It is also
out of all proportion laden with dust and smoke. In the purer regions
of the earth, a clear air imposes but little bar to sight, and conjures
up far things startlingly distinct.
Nevertheless, every evidence points to a thin air upon Mars: _a priori_
reasoning, indirect deduction and direct sight. Now, from a thinness of
atmosphere it would follow, other things equal, that the climate was
cold. About this there has been much question, but less of answering
reply. From the distance of the planet from the sun it is certain less
heat is received by it than falls upon the earth in something like the
ratio of one to two. But that the amount effective is as the amount
received is far from sure. The available heat is much affected by the
manner of its reception. A blanket of air acts like the glass of a
conservatory, letting the light rays in, but hindering the heat rays
out. The light rays falling on the ground or the air are transformed
into heat rays that, finding the return journey less easy, are
consequently trapped. All substances are thus calorifiers, but water
vapor is many times more potent than ordinary air to heat-ensnaring. A
humid air has a hothouse tang to it most perceptible. Now, what the
relative percentage of water vapor in the Martian atmosphere may be we
do not know.
The thinness of the Martian air has caused it to be likened to that
upon our highest mountain peaks which are in large part covered with
perpetual snow. But the comparison is not well founded. A peak differs
materially from a plateau in the countenance it gives to the heat
falling upon it. On a plateau each warmed acre of ground helps the
retention of heat by its neighbor; while in addition to being destitute
of side support the higher winds generated about an isolated peak blow
its own caloric away. Still less does any analogy hold between the two
when the plateau is a world-wide one.
From these considerations it is evident glosses are possible upon the
bald idea of a much lower temperature prevailing on the Martian surface
than on the earth’s. Doubtless the theoretic cold has been greatly
overdone. Reversely, recent observations tend to lower the apparent
temperature disclosed by the features of the disk, and between the
rising of the theoretic and the falling of the observed we are left
with a very reasonable compromise and reconcilement as the result.
The various look and behavior of the surface of Mars point to a mean
temperature colder than that of the earth, but above the freezing-point
of water; for regions, at least, outside of the polar caps and during
all but the winter months. Except at certain special spots, and
possibly even there, frost is unknown at all times within the tropics
and except in winter in temperate latitudes. These anomalous
localities, mentioned in the preceding chapter, may be said to be the
exceptions that prove the rule of general non-glaciation. For if they
be snow, they stand witness to its absence elsewhere upon the disk, and
if they are not, they testify the more emphatically to the same effect.
As between different parts of the surface, the tilt of the Martian axis
and the greater length of the Martian seasons, the one the same as, the
other the double of, our own, tend to an accentuation of the heat in
the temperate and arctic or antarctic zones. The greatest insolation on
earth is not, as we might suppose, at the equator, but at the parallels
of 43.°5 north and south; even the poles themselves receiving a quarter
as much heat again on midsummer day as ever falls to the lot of the
line. This broad physical fact is equally true of Mars, while in the
matter of consecutive exposure Mars in summer outdoes the earth. For
the longer the seasons, the more nearly does the effective heat
approach the received amount. Thus both on the score of heat received
and of heat husbanded these zones must be relatively warm. And this
shows itself in the look of the surface. In summer it is clearly warmer
within the polar regions than is the case on earth, to judge by the
effect. In winter the cold is doubtless proportionately severe.
For the diurnal range of temperature we have less data. There is
evidence pointing to chilly nights, but it is meagre, and we are left
to fall back on the cold of our deserts at night for analogic condition
of the state of things over the Martian desert levels after the sun
goes down.
If we are uncertain of the precise character of the Martian climate, we
know on the other hand a good deal about the Martian weather. A
pleasing absence of it over much of the planet distinguishes Martian
conditions from our own. That we can scan the surface as we do without
practical interruption day in and day out proves the weather over it to
be permanently fair. In fact a clear sky, except in winter, and in many
places even then, is not only the rule, but the rule almost without
exceptions. In the early days of Martian study cases of obscuration
were recorded from time to time by observers, in which portions of the
disk were changed or hidden as if clouds were veiling them from view.
More modern observations fail to support this deduction, partly by
absence of instances, partly by other explanation of the facts.
Certainly the recorded instances are very rare. Indeed, occasions of
the sort must to any Martians be events, since only one possible
example has presented itself to me during the course of my
observations, extending more or less over eleven years. Even in this
case there was no obliteration, though a certain whiteness overspread
an area near the equator temporarily. Position seemed to point to its
identity with a cloud which made its appearance about that time upon
the terminator, and lasted for some thirty-six hours. The cloud,
however, showed evidence of being, not the kind with which we are
familiar, but a dust-storm, in keeping, indeed, with the desert region
(Chryse) in which it originated.
With the exception of sporadic disturbance of the sort the whole
surface of the planet outside the immediate vicinity of the polar caps
seems free from cloud or mist and to lie perpetually unveiled to space.
In the neighborhood of the caps, however, and especially round about
their edge, a very distinct pearly appearance is presented during the
months at which the cap is at its maximum, or in other words, in the
depth of its winter. Of a dull white hue and indefinite contour the
phenomenon suggests cloud. Where it lies spread no markings are
visible; an absence explicable by obscuration due an interposed medium,
but equally well by seasonal non-existence of the markings themselves,
which from the general behavior of these markings we know to be to some
extent certainly the fact. Of the regions where the effect is
noticeable, Hellas is the most striking. So conspicuously white during
the winter of the southern hemisphere as to have been often mistaken
for the polar cap, its ghost shows thus almost regularly every Martian
year. What is as suggestive as it is striking, the blanching is
confined to the solid circle constituting Hellas and does not extend
into the dark regions by which it is circumscribed. Hellas is as
self-contained when thus powdered as when, in its normal ochre or
abnormal red, it stretches like a broad buckler across the body of the
disk. That the land there lies at a higher level than its surroundings
is pretty certain, but that the difference can amount to enough to
explain its silveriness as ice is improbable. In latitude Hellas is
distinctly temperate, lying between the parallels of 55° and 30°; but
on Mars this is no warrant of a like climate. Again, though close on
the south to what constitutes the polar cap, it does not strictly form
part of that cap, but occupies both in position and in kind a something
intermediary between the frost-bound regions of periodic snow and the
warmer ones of perpetual sunshine. It seems to be afflicted with the
winter weather of the north of Europe, and to owe its pearly look at
such times to the same cloud canopy that then distressingly covers
those inclement lands.
Similar in behavior to it is the long chain of so-called islands that,
beginning southwest of Thaumasia, runs thence westward even to the
eastern edge of Hellas. These belt the planet in a west-northwesterly
direction by a strip of territory from ten to fifteen degrees wide, the
medial line of which begins at 55° south and ends in about 40°. They
are parted from the main bright areas by blue-green ‘seas’ of about the
same width as themselves, the Mare Sirenum, the Mare Cimmerium and Mare
Tyrrhenum. These ‘seas’ the white that covers the ‘islands’ never
crosses; though the continent, as we may call it for convenience,
descends at the east to 30° south. Since the ‘seas’ are not seas, the
cause which might bound the snow, were they such, cannot be the cause
here. Nevertheless, they have an effect of some sort on the isothermal
lines as is shown not only by latitudinal comparison with the state of
things in Hellas, but with that in Thaumasia as well. For 30° south is
also the limit apparently of the white on Thaumasia, where ochre desert
stretches ten degrees farther south still; the region in its southern
part being white-mantled, in its northern part not. Here again, then,
the ochre areas make exception to what affects the blue-green ones.
Clearly the blue-green regions temper the action of what gives them
wintry cloak. But why they should do this is not easy to explain on any
supposition terrestrial or marine. Bodies of water tend to foster the
formation of clouds; so, less markedly, do areas of vegetation. Neither
the old ideas, then, nor the new lend themselves in explanation. It may
be that while we here seem to be envisaging cloud we are in reality
looking at hoar-frost. On the other hand, light cloud would show less,
superposed over a dark background, than over an ochre one; and this,
the simplest of all explanations, may be the true one. It is facts like
these that intrigue us in the study of the Martian surface by revealing
conditions which render offhand analogy with the earth unsafe. Indeed,
we are more sure of some things which appear too strange to be true
than of others so simple on their face as to enlist belief. Among the
most difficult and perplexing are meteorological problems like the
above. Here we can only say provisionally that while cloud best answers
to the appearance, frost best fits the cause. For vegetation might melt
frost, yet not dissipate cloud. By raising our conception of the mean
temperature the facts can, however, be reconciled and this is probably
the solution of the difficulty after all.
As we saw in the annual history of the polar caps a dimness somewhat
different affects the northern cap in May and June. After the melting
of the cap is well under way a haziness sets in along its edge which
befuddles its outline and effectually hides what is going on within it.
When at last the screen clears away the cap is found to be reduced to
its least dimensions. Such obstructing sheet looks to be more of the
nature of mist caused by the excessive melting of the cap.
Unfortunately, there are here no patches of blue-green to test a
possible partiality in its behavior over such tracts; nor has similar
action ever yet been remarked in the case of the cap of the southern
hemisphere.
Regular recurrence at the appropriate season of the planet’s year,
together with extensive action at the time, takes this springtide mist
to some extent out of the domain of weather into that of climate. For
it prevails all round the cap and repeats itself in place as each fresh
spring comes on. At least it has done so for the past three oppositions
at which it has been possible to observe well the arctic zones. It is
thus both general in its application and fixed in its behavior.
Nevertheless, it betrays something of the fickleness which
characterizes that more inconstant thing: weather. For it comes and
goes, one thinks for good, only to find it there again some days later.
Not less captious is the meteorologic action shown in the making of the
new polar cap. When the northern one starts to form, vast areas of
frost are deposited in a single night. These, however, are not
permanent. The ground thus covered is during the next few days again
partially laid bare. Then a new fall occurs, hiding the surface a
little more completely than before, and the lost domain is more than
regained. By such wavelike advance and recession the tide of frost
creeps over and submerges the arctic regions as the late summer passes
into the autumn. In this alternate coming and going with succeeding
days, we have an unsteadfastness of action most fittingly paralleled by
our own weather. It would seem that local causes there as here are
superposed upon the orderly progress of the seasons and though at the
on-coming of the autumn the cold is steadily gathering strength,
nevertheless warm days occur now and then to stay its hand, only to be
succeeded in their turn by frosts more biting than before. Even on Mars
nothing in the way of weather is absolutely predicable but
impredicability.
CHAPTER IX
MOUNTAINS AND CLOUD
In all ways but one our scrutiny of the planet is confined to such view
as we might get of it from the car of a balloon poised above it in
space; from which disadvantage-point we should see the surface only as
a map spread out below us, a matter of but two dimensions. The
exception consists in the observation of what are called projections;
irregularities visible when the disk is gibbous upon that edge of the
planet where the light fades off. Striking phenomena in themselves they
are of particular value for what may be deduced from them. For by them
we are afforded our only opportunity of gaining knowledge of the
surface other than in plan and thus of determining between peak,
plateau, or plain that to a bird’s-eye view alike lie flattened out to
one dead level.
It might at first be thought that our best chance of noting any
elevations or depressions of the Martian surface lay in catching that
surface in profile, by scanning the bright edge of it which stands
sharp-cut against the sky and is called the limb. For this is
practically what we do on earth when we mark a mountain against the
horizon and measure its height by triangulation. Unfortunately the
method fails in the case of Mars because of the great distance we are
away. Unless the planet were distinctly more generously equipped than
the earth in the matter of mountains, nothing could be hoped from so
forthright an envisaging. So relatively insignificant to the size of
its globe is the relief of the earth’s surface that an orange skin
would seem grossly rough by comparison. The same proves true for Mars.
With the greatest magnification we can produce, the Martian limb still
appears perfectly smooth.
Luckily, while direct vision is thus impossible, oblique illumination
enables us to get an insight into the character of the surface we had
otherwise been denied. When mountains or valleys chance to lie upon the
boundary of light and darkness, the rim of the disk known as the
terminator in contradistinction to the limb where the surface itself
comes to an end, they make their presence evident through an indirect
species of magnification, the elongate effect of oblique lighting. With
a practical instance of it every one is familiar who has walked by
night along a road imperfectly starred at intervals by electric lights.
Startled between posts by what seemed deep holes and high furrows he
has involuntarily imitated a spavined horse for fear of stubbing his
toes, only to encounter when his foot fell a surface on contact
surprisingly smooth. The slant illumination by lengthening the shadows
had painfully deceived him into exaggerated inference of irregularity.
What proves disturbing to a wayfarer misguided by arc lights is made to
do the eye service when it comes to planetary interpretation. On the
boundary of light and shade, those parts of the surface where it is
sunrise or sunset upon the planet, the sun’s rays fall so athwartwise
as to throw enormous shadows from quite small elevations to an eye so
placed as to view the surface with anything approaching
perpendicularity. A mountain mass there will thus proclaim itself by
protracted profile upon the plain in hundredfold magnification.
Similarly a peak there will advertise its height by catching the coming
or holding the lingering light at many times the distance of its own
elevation away from the night side of the planet. Here, if anywhere,
then, could mountains be expected to disclose themselves, and here,
when existent, they have as a matter of fact been found.
Our own moon offers us the first and easiest example of such
vicariously visible relief. When the moon is near the quarter, and for
three or four days on either side of that, a keen eye can usually
detect one or more knobs, like warts, projecting from its terminator,
easily distinguished from the limb both by reason of being less bright
and of being bounded by a semi-ellipse instead of a semicircle. If a
telescope or even an opera-glass be substituted for the eye, it is
possible to see what causes them; the knob resolves itself into the
illuminated rim of a crater separated from the main body of the visible
moon by the seemingly black void of space. The peak has caught the
sunlight, while its foot and the country between it and the illuminated
surface still lies shrouded in shadow.
From measurement of the distance the sun-tipped peak seems to stand
aloof from the line where the plain itself is touched by the light, the
height of it above that plain may be calculated. In this way have been
found the heights of the mountains of the moon. Incidentally, brain
outstrips brawn. For pinnacles no Lunarian could scale, both for their
precipitous inaccessibility and their loftiness, man has measured
without so much as setting foot upon their globe. At each lunar sunrise
and again at lunar sunset these old crater walls show their crescent
coronets tipped the reverse way; and peaks higher than the Himalayas
make gigantic gnomons of themselves with hands outstretched to grasp
the plains.
In this manner a lunar peak of fifteen thousand feet shows its presence
to the unaided eye. With so much for starting-point we can calculate
how low an elevation could similarly be made out on Mars under a like
phase illumination. Now, in spheres of different diameters the distance
out from the terminator for a given height is as the square root of the
diameter. Mars has about twice the size of the Moon. In consequence, if
we saw the planet at the same distance off as the Moon, the height of a
peak upon it sufficient to cast an equal shadow or be seen at an equal
separation from the terminator need be but two thirds as high. To see
it thus equidistant a power of 250 or 300 is necessary, dependent on
the opposition. Twice this power may at times be used, and by the same
reasoning this would reduce the height sufficient to show by four or to
something like 2500 feet. This, then, would be the theoretic limit of
the visible, a limit needing to be somewhat increased because of the
imperfection of our air.
Having found thus what should be visible on Mars we turn now to see
what is. At once we find ourselves confronted with a very unlunar state
of things. Common upon the face of the Moon, excrescences of the
terminator are rare on Mars. The first ever seen was detected by a
visitor at the Lick Observatory in 1888. Since then they have been
repeatedly noticed both at the Lick and elsewhere. But although
observers are now on the watch for them, they are not very frequently
chronicled because not of everyday occurrence. Much depends upon the
opposition; some approaches of the planet proving more prolific of them
than others. How rare they are, however, may be gathered from the fact
that the last three oppositions have disclosed but one apiece.
An account of the great projection of May 25, 1903, will give an idea
of the extent and interest of the phenomenon and will serve to show to
what cause we must attribute all such that have been visible on Mars,
for the behavior of this one was typical of the class.
[Illustration: Projection on terminator.]
About half past eight o’clock in the evening of May 26, 1903, Mr. V. M.
Slipher, astronomer at Flagstaff, shortly after taking over the
telescope then directed upon Mars, suddenly noticed a large projection
about halfway up the terminator of the planet. He at once sent word of
the fact and the observatory staff turned out to see it, for a
projection has for workers on Mars the like interest that a new comet
possesses for astronomers generally. In this case the phenomenon was
specially potent in that it was the first to be detected that year. Its
singularity was amply seconded by its size. For it was very large, its
extent both in length and height being excessive. When I first saw it,
the projection consisted of an oval patch of light, a little to the
north of the centre of the phase ellipse lying parallel to the
terminator but parted from it by darkness to the extent of half the
projection’s own width. It made thus not simply an excrescence but a
detached islet of light. It was easily seen by all those present and
was carefully studied from that time on by Mr. Slipher and me. Both of
us made drawings of it alternately at intervals, as well as micrometer
measures of its position.
Next to its great size, the most striking feature about it was its
color. This, instead of being white or whitish, was ochre orange, a hue
closely assimilated to the tint of the subjacent parts of the disk,
which was the region known as Chryse. This distinctive complexion it
kept throughout the period of its apparition. At the same time Baltia,
a region to the north of it and synchronously visible close upon the
terminator, showed whitish. The seeing was good enough to disclose the
Phison and Euphrates double, the power a magnification of 310 and the
aperture the full aperture of the 24-inch objective.
From the time it was first seen the detached patch of light crept in
toward the disk, the illuminated body of the planet. Four minutes after
I noted it the dark space separating it from the nearest point of the
terminator had sensibly lessened. So it continued, with some
fluctuations intrinsic to the atmospheric difficulties of observations
generally and to the smallness of the object itself, to become
gradually less and less salient. It lasted for about forty minutes from
the moment it had first appeared to Mr. Slipher and then passed from
sight to leave the edge of the planet smooth and commonplace again.
The measures made on it showed that it lay when first seen in longitude
39°.7, latitude 18°.5 north, and that its highest point stood seventeen
miles above the surface of the planet. It was three hundred miles long.
These are my own figures, from which Mr. Slipher’s do not substantially
differ.
The return of the part of the planet where it had been seen was eagerly
awaited the night after by both observers, to see if it would bring the
projection with it. For only once a day is the same region of Mars
similarly presented. But in order not to miss the projection, should it
be ahead of time, observations were begun before it was due. Shortly
after they were started, there appeared higher up the terminator and
therefore farther north than had been the case the night before, a
small projection. It was with difficulty made out and its position
measured. Without careful watching it must have been missed altogether.
As it was, it differed in every respect from that of the preceding day.
It was not nearly so high, not nearly so large, and lay in a different
place on the planet, being now in longitude 31°.7, latitude 25°.5.
Either the two, therefore, were totally different things or the
projection had moved in the elapsed interval of time over seven degrees
of latitude and eight degrees of longitude, a distance of three hundred
and ninety miles in twenty-four hours. Where the previous projection
had been nothing showed. On the following night, May 28, no trace of
anything unusual could be seen anywhere.
We are now concerned to inquire to what this series of appearances
could have been due. The first observers of projections on Mars had
unhesitatingly attributed them to the same cause that produces
projections on the Moon, to wit, mountains. Such they were held to be
in France and at the Lick. This view, however, was in 1892 disputed by
W. H. Pickering who considered them to be not mountains, but cloud. And
this view was strongly supported by A. E. Douglass in a discussion of a
large number of them observed in 1894 at Flagstaff. The mountain theory
of their generation was finally shown to be untenable and their
ascription to cloud conclusively proved to be the correct solution by
the observations of a remarkable one made in December, 1900, and the
careful study to which by the writer they were subjected. We shall now
explain how this was done and we will begin by pointing out that the
fact that only a single specimen of the phenomenon was visible at each
of the three oppositions of 1900, 1903, and 1905 was itself conclusive,
rightly viewed, of their non-mountainous character. This conclusion
follows at once from the isolateness of the phenomenon. For a mountain
cannot change its place. Now, the shift in the aspect presented by the
planet’s disk from one night to the next is not sufficient to alter
perceptibly the appearance shown by anything upon its edge on the two
occasions. If, then, a peak stood out upon it one evening, the peak
should again show salient when the region reached the same position
upon the succeeding night. That nothing then was seen where something
had previously been visible proved the phenomenon not that of a
mountain peak, since what produced the projection was clearly not fixed
in place and therefore not attached to the soil. Now the only other
thing capable of catching the light before it reached the surface would
be something suspended in the air, that is, a cloud. Deduction,
therefore, from the rarity of the phenomenon alone showed that the
projections must be clouds.
Their behavior in detail entirely corroborates this deduction from
their intermittence. Such was shown by the action of the projection of
December 6, 1900, as set forth in a paper before the American
Philosophical Society and such again by that of the one of May 26,
1903, as we shall now note. To begin with, we notice that the
projection seen on May 26 was not found either _in situ_ or in size on
May 27 and had wholly vanished on May 28, though the seeing was
substantially the same if not better on the two nights succeeding that
of its original detection. Hence in its own instance this projection
proved an alibi irreconcilable with the character of a mountain mass.
But it did more. It not only was not on the second evening what and
where it had been on the first, but the remains of it visible on the
second occasion showed clearly that it had moved in the meantime.
Furthermore it was disappearing as it went, for it was very much
smaller after the lapse of twenty-four hours. The something that caused
it was not only not attached to the soil, but was moving and
dissipating as it moved. Only one class of bodies known to us can
account for these metamorphoses and that is: cloud.
But what kind of cloud are we to conceive it to be? Our ordinary vapor
clouds are whitish and this would be still more their color could they
be looked at from above. The Martian cloud was not white but tawny, of
the tint exhibited by a cloud of dust. Nor could this color have very
well been lent it by its sunrise position, for other places equally
situated to be tinged by the hues of that time of day, Baltia to wit,
showed distinctly white. So that we must suppose it to be what it
looked, a something of the soil, not beholden to atmospheric tinting
for its hue; a vast dust-cloud traveling slowly over the desert and
settling slowly again to the ground.
Precisely the same general course of drifting disappearance was taken
by the projection of December 7 and 8, 1900. And this, too, stood an
unique apparition in the annals of its opposition. Clouds, then, and
not mountains are the explanation of the projections on Mars, differing
thus completely from the lunar ones.
CHAPTER X
THE BLUE-GREEN AREAS
Descending now equatorwards from the polar regions, and their in part
paleocrystic, in part periodic, coating of ice, we come out upon the
general uncovered expanse of the planet which in winter comprises
relatively less surface than on Earth, but in summer relatively more.
Forty degrees and eighty-six degrees may be taken as the mean hiemal
and æstival limits respectively of the snow on Mars; forty-five and
seventy-five as those of the Earth. Whatever ground is thus bared of
superficial covering on Mars lies fully exposed to view, thanks to the
absence of obscuring cloud; and it is at once evident that the terrane
is diversified, patches of blue-green alternating with stretches of
reddish ochre. Of the two opaline tints the reddish ochre predominates,
fully five eighths of the disk being occupied by it.
It was early evident in the study of the surface of Mars that its
ochreish disk was not spotless. Huyghens in 1659 saw the Syrtis Major.
From this first fruit of areography dates, indeed, the initial
recognition of the planet’s rotation; for on noting that the marking
changed its place, he inferred a turning of the planet upon itself in
about twenty-four hours. Thirteen years later he observed and drew it
again and this time in company with the polar cap. Again, after eleven
more years, he depicted it for the third time, and now so changed
because of the different tilt of the planet toward the earth that it
may be doubted whether Huyghens himself recognized it for the same. But
that he drew it correctly a globe of Mars will at once show.
From such small beginning did areography progress to the perception of
permanent patches of a sombre hue distributed more or less irregularly
over the disk. Impressing the observers simply as dark at first, they
later came to be recognized as possessing color, a blue-green, which
contrasted beautifully with the reddish ochre of the rest of the
surface. Cassini, Maraldi, Bianchini, Herschel, Schroeter, all saw
markings which they reproduced. Finally, with Beer and Maedler, came
the first attempt at a complete geography. In and out through the ochre
was traced the blue; commonly in long Mediterraneans of shade, but here
and there in isolated Caspians of color. With our modern telescopic
means the dark patches are easily visible, the very smallest glass
sufficing to disclose them. When thus shown they much resemble in
contour the dark patches on the face of the Moon as seen with the naked
eye. Now these patches were early taken for lunar seas and received
names in keeping with the conception; as the Sea of Serenity, the Sea
of Vapors, and so forth. Following the recognition of a like
appearance, like appellatives were given to the Martian markings; and
the Mare Sirenum, or Sea of the Sirens, the Mare Cimmerium, and others
sufficiently proclaim what was thought of them at the time they were
thus baptized. Indeed, if a general similarity be any warrant for a
generic name they were not at the time ill-termed. For, common to all
three bodies, the Earth, the Moon, and the planet Mars, is the
figuration of their surfaces into light areas and dark. In the Martian
disk, as in the lunar one, we seem to be looking at a cartographic
presentation of some strange geography suspended in the sky; the first
generic difference between the two being that the chart is done in
chiaroscuro for the Moon, in color for Mars. On mundane maps, we know
the dusky washes for oceans; so on the Moon it was only natural to
consider their counterparts as _maria_; and on Mars as ‘seas.’ Nor did
the blue-green hue of the Martian ones detract from the resemblance.
But in something other than color these markings are alike. In fact,
color could hardly be excuse for considering the lunar _maria_ what
their name implies, for distinctive tint is lacking in them, even to
the naked eye. It was in form that the likeness lay. Their figures were
such as our own oceans show; and allowing for a sisterly contrast amid
a sisterly resemblance, the lunar _maria_ or the Martian seas might
well have been of similar origin to those with which our schoolboy
study of atlases had made us familiar. Thus did similarity in look
suggest similarity in origin, and intuitive recognition clothe its
objects with the same specific name.
Considerable assumption, however, underlay the pleasing simplicity of
the correlation on other grounds, consequent not so much upon any lack
of astronomic knowledge as, curiously, upon a dearth of knowledge of
ourselves. We know how other bodies look to us, but we ignore how we
look to them. It is not so easy to see ourselves as others see us; for
a far view may differ from a near one, and a matter of inclination
greatly alter the result. Owing both to distance and to tilt we lack
that practical acquaintance with the aspect of our own oceans viewed
from above, necessary to definite predication of their appearance
across interplanetary space. Our usual idea is that seas show dark, but
it is also quite evident that under some circumstances they appear the
contrary. It all depends upon the position of the observer and upon the
position of the Sun. Their usual ultramarine may become even as molten
brass from indirect reflection; while on direct mirroring, they give
back the Sun with such scarce perceptible purloining of splendor as to
present a dazzling sheen not to be gazed upon without regret. Canopied
by a welkin they assume its leaden hue, while at the same time, their
shores, less impressionable to borrowed lighting, show several tints
darker than themselves. Surfaces so sensitive to illumination hardly
admit of more accusable tint than a chameleon. Nevertheless, we are
probably justified in our conviction that perpendicularly visaged, they
would on the whole outdo in sombreness land round about them, and so be
evident as dusky patches against a brighter ground.
One phenomenon we might with some confidence look to see exhibited by
them were they oceans, and that is the reflected image of the Sun
visible as a burnished glare at a calculable point. Specular reflection
of the sort was early suggested in the case of Mars, and physical
ephemerides for the planet registered for many years the precise spot
where the starlike image should be sought. But it was never seen. Yet
not till the marine character of the Martian seas had been otherwise
disproved was the futile quest for it abandoned. Indeed, it was a tacit
recognition that our knowledge had advanced when this column in the
ephemeris was allowed to lapse.
On this general marine ascription doubt was first cast in the case of
the Moon. So soon as the telescope came to be pointed at our satellite,
it was evident that the darker washes were not water surfaces at all,
but very palpably plains. Long low ridges of elevation stood out upon
them like prairie swells, which grew in visible relief according to the
slanting character of the illumination. Cracks or rills, too, appeared
near their edges and craters showed in their very midst. Patently solid
they betrayed their constitution not only by diverse topography but by
diversified tint. All manner of shades of neutral tone mottled their
surface, from seeming porphyry to chalk. Belief perforce departed when
the telescope thus pricked the bubble, evaporating as the water itself
had done long before.
So much was known before the Mars’ markings were named. Nevertheless,
humanity, true to its instincts, promptly proceeded to commit again the
same mistake, and, cheerfully undeterred by the exposure of its errors
in the case of the Moon, repeated the christening in the case of Mars.
So sure was it of its ground that what it saw was not ground, that
though the particular appellatives of the several seas were constantly
altered, rebaptisms, while changing the personal, kept the generic
name. Dawes’ Ocean, for example, later became l’Ocean Newton and later
still the Mare Erythraeum, but remained set down as much a sea as
before. About thirteen years ago, however, what had befallen the seas
of the Moon, befell those of Mars: the loss of their character. It was
first recognized through a similar exposure; but the fact was led up to
and might have been realized in consequence of quite a different line
of evidence. The initial thing to cast doubt upon the seas being what
they seemed to be was the detection of change in their aspect. That the
detection was not made much earlier than actually happened shows how a
phenomenon may elude observation if scrutiny be not persistent, and its
results from time to time not carefully compared. Schiaparelli was the
one who first noticed variation in the look of the seas, and the
discovery was as much due to the assiduity with which he followed the
planet opposition after opposition as to the keenness with which he
scanned it. The noting of change in the blue-green areas constituted,
in fact, one of the first fruits of systematic study of the planet.
Change in configuration, that is, alteration of area, preceded in
recognition alteration of tint. Thus the Syrtis Major showed larger to
him in 1879 than it had in 1877. This was natural; difference of degree
being a more delicate matter to perceive than its effect upon extent.
From change of area his perception went on to change of tone. In his
own words, what he noticed was this: _Memoria_, VI, 1888, “No less
certain is it that, from one opposition to another, one notices in the
seas, very remarkable alterations of tone. Thus the regions called Mare
Cimmerium, Mare Sirenum, and Solis Lacus, which during the years 1877
to 1879 could be numbered among the most sombre on the planet, during
the succeeding oppositions became less and less black, and in 1888 were
of a light gray hardly sufficient to render them visible in the oblique
position in which all three found themselves.... On the other hand, at
the very same moment, the Mare Acidalium and the Lacus Hyperboreus
showed very dark; the latter indeed appeared nearly black, although
seen as tilted as the Syrtis and the equatorial bays. The condition of
the regions called seas is therefore not constant: so much is
unquestionable. Perhaps the change produced in them has to do with the
season of the planet’s year.”
Holding as he did the then prevailing view that the blue-green regions
were bodies of water, he regarded those of intermediate tint as vast
marshes or swamps, and he accounted for change of hue in them as due to
inundations and occasions of drying up. In consequence of losing their
water, the seas, he thought, had in places become so shallow that the
bottom showed through.
Plausible on the surface, this theory breaks down so soon as it is
subjected to quantitative criticism. For the moment we try to track the
water, we detect the inadequacy of the clew. The enormous areas over
which the phenomenon occurs necessitates the establishing an alibi for
all the lost water that has gone. Drying up on such a scale would mean
the removal of many feet of liquid over hundreds of thousands of miles
in extent. To produce any such change in appearance as we witness, even
on the supposition that these seas were none too deep to start with,
would involve lowering the level of the water by from five to twenty
feet throughout two thirds of the whole surface of the southern
hemisphere. This would leave a heap of waters to be accounted for,
bewildering in its immensity. The myriad tons of it must be disposed
of; either by drainage into other regions or by being caught up into
the sky.
In this emergency it might seem at first as if the polar cap of the
opposite hemisphere offered itself as a possible reservoir for the
momentarily superfluous fluid. But such hoped-for outlet to the problem
is at once closed by the simple fact that when the lightening of the
dark regions of the southern hemisphere takes place, the opposite polar
cap has already attained its maximum; in fact, has already begun to
melt. It, therefore, absolutely refuses to lend itself to any such
service. This was not known to Schiaparelli’s time, the observations
which have established it, by recording more completely the history of
the cap, having since been made. Indeed, it was not known even at the
time when the writer, in 1894, showed the impossibility of the transfer
on other grounds; to wit, on the fact of no commensurate concomitant
darkening of the surface elsewhere and on the manifest non-complicity,
if not impotency, of the Martian atmosphere in the process. The
transference of the water to other dark patches in the northern
hemisphere fails of sufficiency of explanation because of the limited
extent of such areas on that side of the globe; while the air is quite
as incapable of carrying away any such body of liquid, though the whole
of it were at the saturation-point, not to mention that there exists no
sign of the attempt. The reader will find this reasoning set forth in
_Mars_, published eleven years ago. He will now note, from what has
been said above about the northern polar cap, that continued
observations since have resulted in opening up another line of proof
which has only strengthened the conclusion there reached.
[Illustration: Lines in dark area.]
The _coup de grâce_, however, to the old belief was given when the
surface of the dark areas was found to be traversed by permanent lines
by Pickering and Douglass. Continued observation showed these lines to
be unchangeable in place. Now permanent lines cannot exist on bodies of
water, and in consequence the idea that what we looked on there were
water surfaces had to be abandoned.
Thus we now know that the markings on both the Moon and Mars which have
been called _maria_ are not in reality seas. Yet we shall do well still
to keep the old-fashioned sonorous names, Mare Erythraeum, Mare
Sirenum, and their fellows, because it is inconvenient to change;
while, if we please, we may see in their consecrated Latin couching the
fit embalming in a dead language of a conception that itself is dead.
CHAPTER XI
VEGETATION
Since closer acquaintance takes from the _maria_ their character of
seas, we are led to inquire again into their constitution. Now, when we
set ourselves to consider to what such appearances could be due we note
something besides sea, which forms a large part of our earth’s surface,
and would have very much what we suppose the latter’s aspect from afar
to be, not only in tone, but in tint. This something is vegetation.
Seen from a height and mellowed by atmospheric distance, great forests
lose their green to become themselves ultramarine.
To dispossess a previous conception is difficult, but so soon as we
have put the idea of seas out of our heads a vegetal explanation proves
to satisfy the phenomena, even at first glance, better than water
surfaces. In their color, blue-green, the dark areas exactly typify the
distant look of our own forests; whereas we are not at all sure that
seas would. From color alone we are more justified in deeming them
vegetal than marine. But the moment we go farther into the matter the
more certain we become of being upon the right road. With increased
detection the markings they reveal and the metamorphoses they undergo,
while pointing away from water, point as directly to vegetation. All
the inexplicabilities which the supposition of water involves find
instant solution on the theory of vegetal growth. The non-balancing of
the areas of shading in their shift from one part of the disk to
another, no longer becomes a circumstance impossible to explain, but a
necessary consequence of their new-found character, denoting the time
necessary for vegetation to sprout. The change of hue of vast areas
from blue-green to ochre no longer presupposes the bodily transference
of thousands of tons of substance, but the quiet turning of the leaf
under autumnal frosts. Even the fact that they occupy those regions
most fitted by figure to contain oceans fits in with the same
conception. For that the Martian equivalents of forest and moorland,
tree and grass, should grow now in the lowest parts of the planet’s
surface is what might not unreasonably be expected from the very fact
of their being low, since what remained of the water would tend both on
the surface and in the air to drain into them.
[Illustration: Mare Erythræum
Martian date. December 30]
For the change in question to be vegetal it must occur at the proper
season of the planet’s year. This we must now consider. We have said
that Schiaparelli detected change in the blue-green regions and
suspected this change of seasonal affiliation. He inferred this from
piecing together the aspects of different seasons of different years as
shown in consecutive Martian oppositions. To mark it actually take
place in a single Martian year came later. In 1894, at Flagstaff, the
southern hemisphere was presented during its late spring and early
summer; it was observed, too, for many of our months in succession.
During this time the planet was specially well circumstanced for study
of the change in that hemisphere, both by reason of the appositeness of
the season and of the unusual size of the disk. Advantage was taken of
the double event to a recording of the consecutive appearances certain
regions underwent, and the contrasted states thus exhibited were such
as clearly to betoken the action of seasonal change. What Schiaparelli
had thus ably inferred from diverse portions of different Martian years
was in this case shown occurring in one and the same semestral cycle.
Usually the change of hue seems essentially one of tone; the blue-green
fades out, getting less and less pronounced, until in extreme cases
only ochre is left behind. It acts as if the darker color were
superimposed upon the lighter and could be to a greater or less extent
removed. This is what Schiaparelli noted and what was seen in 1894 at
Flagstaff. Three views _en suite_ of the chain of changes then observed
are shown in _Mars_, the region known as Hesperia being central in
each. Comparison of the three discloses a remarkable metamorphosis in
that “promontory,” a rise into visibility by a paling of its
complexion. Nor is the contrast confined to it; changes as salient will
be noticed in the pictures over the other parts of the disk.
There have been instances, however, of a metamorphosis so much more
strange as to deserve exposition in detail; one where not tone simply
is involved, but where a quite new tint has surprisingly appeared.
[Illustration: Mare Erythræum
Martian date. January 16]
On April 19, 1903, when, after being hidden for thirty days, owing to
the different rotation periods of the two planets, the Mare Erythraeum,
the largest blue-green region of the disk and lying in the southern
hemisphere, rounded again into view, a startling transformation stood
revealed in it. Instead of showing blue-green as usual, and as it had
done six weeks before, it was now of a distinct chocolate-brown. It had
been well seen at its previous presentation, so that no doubt existed
of its then tint. At that time the Martian season corresponded to
December 30 in our calendar. Eighteen Martian days had since elapsed,
and it was now January 16 there. The metamorphosis had taken place,
therefore, shortly after the winter solstice of that part of the
planet. The color change that had supervened proved permanent. For the
next night the region showed the same brown hue, and so it continued to
appear throughout the days that it was visible. Two months passed, and
then the chocolate hue had vanished,—gone as it had come,—and the
_mare_ had resumed its usual tint, except for being somewhat pale at
the south. It had come to be February 21 on Mars. Timed and tabulated,
the metamorphosis through which the _mare_ passed stands out thus:—
MARE ERYTHRAEUM 1903
============+================+=============+==================
| DAYS BEFORE OR | |
| AFTER SUMMER | |
MUNDANE | SOLSTICE | MARTIAN |
DATE | (BEFORE = - | DATE | ASPECT
| AFTER = +) | |
------------+----------------+-------------+------------------
February 16 | -10 | December 16 | Blue-green
March 20 | +22 | January 1 | Blue-green
April 19 | 52 | January 16 | Chocolate
April 22 | 55 | January 18 | Chocolate
May 26 | 89 | February 4 | Faint chocolate
May 30 | 93 | February 6 | Faint chocolate
June 30 | 123 | February 22 | Faint blue-green
July 7 | 130 | February 25 | Faint blue-green
============+================+=============+==================
The culmination of the transformation seems to have taken place about
60 days after the southern winter solstice, or in the depth of the
Martian winter of that hemisphere. This is certainly just the time at
which vegetation should be at its deadest.
The northern and southern portions of the _mare_ did not behave alike
in taking on the chocolate tint. From the notes made about them during
the opposition it appears that the latter was later than the former in
undergoing the metamorphosis, as will be seen from the following depth
of the blue green estimated in percentages shown at different dates,
calling the deepest tone ever exhibited by it unity.
=========+==========+=========+=========+==========+==========
MARTIAN | DECEMBER | JANUARY | JANUARY | FEBRUARY | FEBRUARY
DATE, | (16) | (1) | (17) | (5) | (24)
---------+----------+---------+---------+----------+----------
| % | % | % | % | %
Northern | 50 | 50 | 0 | 25 | 50
Southern | 50 | 50 | 0 | 0 | 25
=========+==========+=========+=========+==========+==========
From this table we may place the lowest point of the blue-green tint as
reached about the 22d of January for the northern, the 5th of February
for the southern, part. This would indicate that the wave of returning
growth came from the north, not the south; an important fact, as we
shall see later in studying the action of the canals.
[Illustration: Mare Erythræum
Martian date. February 1]
At the next opposition, in 1905, a recurrence of the transformation was
watched for, and not in vain. It occurred, however, somewhat later in
the Martian season. On December 27 of the planet’s current year the
Mare Erythraeum was still as usual, blue-green, nothing out of the
ordinary being remarked in it; and so it was on its January 17,
although the southern edge was darker than the northern. It looked
certainly as if the metamorphosis were this year to be omitted. But
such was not the case. When the region again came round, on February 1
of the Martian calendar, there the strange tint was as unmistakable as
it had been on its original occurrence. Not only was the Mare
Erythraeum so colored, but on February 5 (Martian) the northern portion
of the Mare Cimmerium was observed to be similarly affected. In the
Mare Erythraeum the anomalous chocolate hue was confined to a belt
between the latitudes of 10° and 20° south of the equator; in the Mare
Cimmerium it stretched a little higher, from 10° at the west to 25° at
the east. It is noteworthy that the southern portion of the latter
showed blue at the time the northern showed brown. Then the
metamorphosis proceeded as shown in the following table:—
MARE ERYTHRAEUM 1905
===========+======================+=============+=================
| DAYS AFTER WINTER | |
MUNDANE | SOLSTICE OF SOUTHERN | MARTIAN | ASPECT
DATE | HEMISPHERE | DATE |
-----------+----------------------+-------------+-----------------
January 25 | 12 | December 27 | Blue-green
March 6 | 52 | January 16 | Blue-green
April 4 | 81 | January 31 | Chocolate
April 12 | 89 | February 4 | Chocolate
April 30 | 107 | February 13 | Faint chocolate
May 8 | 115 | February 17 | Faint chocolate
May 12 | 119 | February 19 | Faint blue-green
June 11 | 149 | March 6 | Faint blue-green
June 15 | 153 | March 8 | Faint blue-green
July 16 | 184 | March 23 | Pale bluish green
===========+======================+=============+==================
Here, as in 1903, a chromatic rise and fall is evident; the culmination
of the change occurring in Martian early February about ninety days
after the winter solstice. That it was not of long duration is also
indicated. If we examine the evidence for the two portions of the
_mare_ separately, the northern and the southern, as in 1903, we find
it as follows:—
=========+==========+=========+==========+==========+=======+========
| | | | | |
MARTIAN | DECEMBER | JANUARY | FEBRUARY | FEBRUARY | MARCH | MARCH
DATE, | (27) | (16) | (2) | (16) | (7) | (23)
---------+----------+---------+----------+----------+-------+--------
| % | % | % | % | % | %
Northern | 50 | 50 | 0 | 10 | 25 | 30
Southern | 50 | 50 | 20 | 20 | 25 | 30
=====================================================================
Here again a slight retardation in the advent of the metamorphosis is
observable in the southern portion.
There would seem to be a difference in the time of the change between
the two years of fifteen days, 1905 being by that much the later. But
with points of reference themselves thirty days apart, it is possible
the two more nearly coincided than here appears.
Unlike the ochre of the light regions generally, which suggest desert
pure and simple, the chocolate-brown precisely mimicked the complexion
of fallow ground. When we consider the vegetal-like blue-green that it
replaced, and remember further the time of year at which it occurred
upon both these Martian years, we can hardly resist the conclusion that
it was something very like fallow field that was there uncovered to our
view.
[Illustration: Mare Erythræum
Martian date. February 21]
From the recurrence of the phenomenon on two successive years, it is
likely that it annually takes place. That it is seasonal can scarcely
be doubted from the timeliness of its occurrence, and that different
portions of its terrane successively underwent their metamorphosis
shows further that it followed a law peculiar to the planet, to which
we shall be introduced when we come to consider the phenomena of the
canals.
Instances of relative hue in different dark patches corroboratory of
seasonal variation, and therefore of vegetal constitution, might easily
be adduced. Thus, in 1905 during the summer of the northern hemisphere,
the Mare Acidalium was notably darker than the Mare Erythraeum to the
north of it, which is what the law of seasonal variation would require,
since it was June in the one, December in the other at the time. But we
need not to add example to example or proof to proof, for there are no
phenomena that contradict it. We conclude, therefore, that the
blue-green areas of Mars are not seas, but areas of vegetation. Just as
reasoning to a negative result drifts us to the first conclusion, so
reasoning to a positive one lands us at the second.
CHAPTER XII
TERRAQUEOUSNESS AND TERRESTRIALITY
With the vanishing of its seas we get for the first time solid ground
on which to build our Martian physiography. The change in _venue_ from
oceans to land has produced a complete alteration in our judgment of
the present state of the planet. It destroys the analogy which was
supposed to exist between Mars and our earth, and by abolishing the
actuality of oceans there, seems, metaphorically, to put us at first
all the more at sea in our attempt to understand the planet. But looked
at more carefully, it turns out to explain much that was obscure, and
in so doing gives us at once a wider view of the history of planetary
evolution.
The trait concerned is cosmic. Study of the several planets of our
solar system, notably the Earth, Moon, and Mars, reveals tolerably
legibly an interesting phase of a planet’s career, which apparently
must happen to all such bodies, and evidently has happened or is
happening to these three: the transition of its surface from a
terraqueous to a purely terrestrial condition. The terraqueous state is
well exhibited by our own earth at the moment, where lands and oceans
share the surface between them. The terrestrial is exemplified by both
the Moon and Mars, on whose surfaces no bodies of water at present
exist. That the one state passes by process of development into the
other I shall now give my reasons for believing.
In the first place the appearance of the dark markings both on the Moon
and Mars hints that though seas no longer, they were seas once upon a
time. On the moon, not only does their shape suggest this previous
condition, but the smooth and even look of their surfaces adds to the
cogency of the inference. More important, however, than either of these
characteristics, and confirmatory of both, is the fact that the great
tracts in question seem to lie below the level of the corrugated
surface, which is thickly strewn with volcanic cones. Their level and
their levelness fay in explanation into one another. The first makes
possible the former presence of water; the second speaks of its effect.
For their flat character hints that these areas were held down at the
time when the other parts of the surface were being violently thrown
up. That they can themselves be cooled lava flows, their extent and
position seem enough to negative; to say nothing of the fact that they
should in that case lie above, not below, the general level. Something,
therefore, covered them during the moon’s eruptive youth and
disappeared later. Such superincumbence may well have been water, under
which the now great plains lay then as ocean bottoms. Deep-sea
soundings in our own oceans betray an ocean floor of the same extensive
sort, diversified as on the moon. To call the lunar _maria_ seas may
not be so complete a misnomer after all; but only a resurrecting in
epitaph what was the truth in its day.
Only doubtfully offered here for the Moon, for Mars the inference seems
more sure. Here again the dark regions not only look as they should had
they had an earlier history, but they, too, seem to lie below the level
of the surface round about. When they pass over the terminator they
invariably show as flattenings upon it, as if a slice of the surface
had been pared off. Such profile in such pass is what ground at a lower
level would present. Undoubtedly a part of the seeming depression is
due to relative absence of irradiation consequent upon a more sombre
tint, but loss of light hardly seems capable of the whole effect. In
the case of Mars, then, as with the Moon, a mistaken inference builded
better than it knew, if, indeed, we should rightly consider an
inference to be mistaken which on half data lands us at the right door.
From the aspects of the dark regions we are led, then, to regard Mars
as having passed through that stage of existence in which the earth
finds itself at the moment, the stage at which oceans and seas form a
feature of its landscape and an impediment to subjugation of its
surface in its entirety. What once were ocean beds have become ocean
bottoms devoid of that which originally filled them.
That the process of parting with a watery envelop is an inevitable
concomitant of the evolution of a planet from chaos to world, we do not
have to go so far afield as Mars and the Moon for testimony. Scrutiny
reveals as much in the history of our own globe. Two signposts of the
past, one geologic, the other paleontologic, point unmistakably in this
direction. The geologic guides us the more directly to the goal.
Study of the earth’s surface reveals the preponderating encroachment of
the land upon the sea since both began to be, and demonstrates that,
except for local losses, the oceans have been contracting in size from
archaic times. So much is evidenced by the successive places upon which
marine beds have been laid down. This suggests itself at once as a
theoretic probability to one considering the matter from a cosmic
standpoint, and it is therefore the more interesting and conclusive
that, from an entirely different departure-point, it should have been
one of the pet propositions of the late Professor Dana, who worked out
conclusively the problem for North America, and published charts
detailing the progressive making of that continent.
[Illustration: Map of North America at the close of Archæan time,
showing approximately the areas of dry land. (From Dana’s “Manual of
Geology.”)]
So telling is this reclaiming by nature of land from the sea that it
will be well to follow Dana a little into detail, as the details show
effectively the continuity of the process acting through æons of
geologic time. At the beginning of the Archæan age, or, in other words,
at the epoch when stratified beds were first laid down, the earth
reached a turning-point in its history. Erosion, superficial and
sub-aërial, then set in to help restrict the domain of the sea. At this
juncture North America consisted of a sickle of terrane inclosing
Hudson’s Bay and coming down at its apex to a point not much removed
from where Ottawa now stands, in about latitude 45°—a Labradorian
North America only. This, the kernel of the future continent, curiously
symbolized the form that continent was later to take. For its eastern
edge was roughly parallel to the present Atlantic coastline, although
much within and to the north of it, while its western one was similarly
aligned afar off to the now Pacific slope. Besides this continent
proper, the Appalachian, Rocky Mountain, Sierra Nevada, and Sierra
Madre chains stood out of the ocean in long, narrow ridges of detached
land, outlining in skeleton the bones of the continent that was to be.
The Black Hills of Dakota and other highlands made here and there
islets in the sea.
Much the same backbone-showing of continents yet to be filled out was
true of Europe, Asia, and South America. In Europe the northern
countries constituted all that could be called continental land. Most
of Norway, Sweden, Finland, Lapland, existed then, while the northern
half of Scotland, the outer Hebrides, portions of Ireland, England,
France, and Germany stood out as detached islands. From this, which is
a fair sample of the proportion of land then to land now over the other
continents so far as they are geologically known, we turn to consider
more in detail the history of North America.
By the time the Upper Silurian period came in, the Appalachian
highlands there had been greatly extended and joined to the Labradorian
mainland by continuous territory; otherwise, no important addition had
occurred, though islands emerged in Ohio, Kentucky, and Missouri.
[Illustration: North America at the opening of the Upper Silurian.
(From Dana’s “Manual of Geology.”)]
At the commencement of the Carbonic era what are now the Middle states
had begun to fill up from the north, and Newfoundland, from a small
island in the Upper Silurian, had become a great promontory of
Labrador, while the Eastern states region and Nova Scotia had risen
into being. The movements closing Paleozoic time upheaved from low
islands the Appalachian chain. The earth’s crust here crumpled by
contraction upon itself; and the movement ended, as Dana says, by
making dry land of the whole eastern half of the continent, along
substantially its present lines.
[Illustration: Map of North America after the Appalachian Revolution.
(From Dana’s “Manual of Geology.”)]
Mesozoic time was the period of the making of the West. It was an era
of deposition and coincident subsidence, when the western land had its
nose just above water at one moment to be submerged the next. Though on
the whole this part of the continent was emerging, the fact was that,
synchronously with the sinking of the sea, much of the land from time
to time sank too. The contraction which raised the Appalachian of the
Rockies at its close overdid the necessities of the case and caused
subsidence elsewhere. The southeastern portion of the continent
suffered most, the West on the whole materially gaining. In the
Triassic and Jurassic eras the gain was pronounced; it occurred in the
Cretaceous also, but with much alternation of loss. Finally, at the
close of the Cretaceous, the continent, except for a prolonged Gulf of
Mexico and vast internal lakes, was substantially complete. Mountains
at the beginning of the period and that of the Rockies at its close
overdid the necessities of the case and caused subsidence elsewhere.
The southeastern portion of the continent suffered most, the West on
the whole materially gaining. In the Triassic and Jurassic eras the
gain was pronounced; it occurred in the Cretaceous also, but with much
alternation of loss. Finally, at the close of the Cretaceous, the
continent, except for a prolonged Gulf of Mexico and vast internal
lakes, was substantially complete.
[Illustration: North America in the Cretaceous period. (From Dana’s
“Manual of Geology.”)]
The filling up of these lakes and the reclaiming of land from the Gulf
of Mexico constituted the land-making work of Tertiary times. The
extent of the lakes in the Eocene era is held to show that the general
level of the mountain plateau was low and rose later. So that the gain
by the land at this time was greater than the map allows to appear. By
the beginning of the Quaternary epoch the continents had assumed their
present general area, and since then their internal features have alone
suffered change.
[Illustration: Map of North America, showing the parts under water in
the Tertiary Era; the vertically lined is the Eocene. (From Dana’s
“Manual of Geology.”)]
A similar rising from the sea fell to the lot of Europe, though it has
not been detailed with so much care. The skeleton of that continent was
at the beginning of depositary time much what it is to-day, but a great
inland sea occupied the centre of it, which, as time went on, was
gradually silted in and evaporated away, notably during the Upper
Silurian period.
From all this it is pretty clear that, side by side with alternating
risings and sinkings of the land, there was a tolerably steady gain in
the contest by which dry ground dispossessed the sea. We may, of
course, credit this to a general deepening of the ocean bottoms due to
crumpling of the crust, but we may also impute it to a loss of water,
and that the latter is, at least for a part, in the explanation the
condition of the Moon and Mars makes probable.
Paleontology has the same story of reclamation to tell as geology, and
with as much certainty, though its evidence is circumstantial instead
of direct and speaks for the growing importance of the land in the
globe’s economy since the beginning of depositary time, and thus
inferentially to its increasing extent. Fossil remains of the plants
and creatures that have one after the other inhabited the earth show
that the land has been steadily rising both in floral and faunal
estimation as a habitat from the earliest ages to the present day. The
record lies imprinted in the strata consecutively laid down, and except
for gaps reads as directly on in bettering domicile as in evolutionary
development.
In Archæan times we find no undisputed evidence of life either vegetal
or animal. But beds of graphite and of limestone point to the possible
existence of both. Even anthracite has been found in Archæan rocks in
Norway and also in Rhode Island. Whether Dawson’s Eozoon Canadense be a
rhizopod or a crystal, doctors of science disagree. Dana, while
admitting nothing specific, deems it antecedently probable that algæ
and later microscopic fungi related to bacteria existed then, living in
water well up toward the boiling-point. Indeed, it is practically
certain that invertebrate life existed, because of its already
well-developed character in the next era. The like antedating is
inferable for the whole record of the rocks. Relatively their history
is undoubtedly fairly accurate, but absolutely it must be shifted
bodily backward into the next preceding era to correspond with fact not
yet unearthed.
In the Lower Cambrian, when first the existence of life becomes a
certainty, that life, so far as known, was wholly invertebrate and
wholly marine; rhizopods (probably), sponges and corals, echinoderms,
worms, brachiopods, mollusks, and crustaceans grew amid primitive
seaweed and have left their houses in the shape of shells while
perishing themselves. Their tracks too have thus survived. The
trilobites, crustaceans somewhat resembling our horseshoe crab, were
the lords of the Cambrian seas and marked the point to which organic
evolution had then attained. Their aquatic character as well as their
simple type is shown by their thoracic legs having each a natatory
appendage.
In the next era, the Lower Silurian, the fauna and flora were still
marine, although of a higher order than before, and in the Trenton
period, the upper part of the era, the earliest vertebrates, fishes,
come upon the scene: ganoids and possibly sharks. Nothing terrestrial
of this period has yet with certainty been unearthed in America. Europe
would seem to have either been more advanced then or better studied
since, for there the first plant higher than a seaweed has been dug up,
one of a fresh-water genus betokening the land; while in keeping with
this the first insect, an hemipter, also has been disinterred. Both the
geography and the life of the Eopaleozoic period Dana styles
“thalassic.”
Neopaleozoic time, beginning with the Upper Silurian, marked the
emergence of the continents, and following them the emergence of life
from the water on to this land. In the lower beds of the Upper Silurian
in America we find only the aquatic forms of previous strata, but in a
higher one we come in marshes upon plants related to the equiseta or
horsetails. In England land plants appear for the first time in these
latest Silurian beds and in the schists of Angers have been preserved
ferns. In both the old world and the new fossil fishes are found and
the oldest terrestrial species of scorpions. But the great bulk of
forms was still marine; corals, crinoids, brachiopods, trilobites
constituting the principal inhabitants. At this time the seas were
warm, having much the same temperature between 65° and 80° north as
between 30° and 45°; the prevalence of a general temperate tropicality
being shown by the fact that the common tropical chain corals lived in
latitude 82° north.
In the Devonian era, the Old Red Sandstone, fishes grew and multiplied,
increasing in size apparently through the era, and in the last period
of it reaching their culminating point. These pelagic vertebrates much
surpassed in structure the terrestrial population of the time, which
was of a low type and consisted of invertebrates such as myriapods,
spiders, scorpions, and insects; for the land was only making. In the
mid-Devonian, forests of a primitive kind covered such country as there
was, an amphibious land, composed of jungles and widespread marshes.
Tree ferns made the bulk of the vegetation, but among them grew also
cycads and yews. Mammoth may-flies flitted through the gloom of these
old forests, but no vertebrate as yet had left the sea.
Following upon the Old Red Sandstone were laid down the Carbonic
strata, and with the Carbonic entered upon the scene the advance scouts
of an army of progress evolutionarily impelled to spy out the land—the
first amphibians. They made their début in the Subcarboniferous section
of the era, the oldest of the three periods into which the Carbonic is
divided, crawling out of the sea to return again and leaving but
footprints at first on the sands of time. In the second period, the
Coal-measures proper, they ventured so far as to leave their skeletons
on terra firma, or rather infirma, while their tracks there show them
to have been now in great numbers. In this manner the ancestors of the
oldest land inhabitants began to struggle out of the sea. In the
Permian, the third and latest period of paleozoic times, we find their
descendants established in their new habitat, for in it we come upon
the first reptiles. Such possession marks a distinct step up in
function as in fact, for while amphibians visited dry land, reptiles
made it their home. The getting out of the water had now, in the case
of the more evolved forms, become an accomplished fact. The reptiles
were, indeed, the lowest and most generalized of their class,
Rhynchocephalians, “beak-headed” species that by their teeth proclaim
their marine origin and their relationship to the great amphibians that
still felt undecided where to stay. Meanwhile, in Europe dragon-flies,
two feet across, possessed the air; while amphibians there, as here,
ancestrally preceded reptiles in occupying the land.
Mesozoic times were, _par excellence_, the age of monsters; for the
Triassic (the New Red Sandstone), Jurassic and Cretaceous eras marked
the reign of the reptiles. Great dinosaurs sleep still in the Triassic
strata of the Atlantic border and in the Jurassic of the Western
states, to be unearthed from time to time and be given mausolea in our
museums. Gigantic they were and very literally possessed the earth. In
Europe they were substantially as in America during these mesozoic
eras, and showed their dominance by long survival in time as well as
world-wide distribution in space; for they lived all the way from
Kansas to New Zealand and from the Trias to the Upper Cretaceous. It is
supposed by Professor Osborn that many of them, like the herbivorous
brontosaurus, waded in marshes, not wholly unlike in habit to the
modern hippopotamus. Others were land-stalking carnivores, like the
megalosaurs of a little later date. Of enormous size, the largest
exceeded any animal which has ever lived, the whales alone excepted;
the biggest, the atlantosaurus and the brontosaurus, reaching a length
of sixty feet. For all their bulk they had scant brains, just enough to
enable them to feed and wallow, probably. It is interesting to note
that many of the reptiles, the less adventurous, apparently reverted to
the sea. For though the crocodilians existed already in the Trias, the
plesiosaurians did not come in till the Middle Trias in Europe, and the
sea-serpents (mosasaurus) till the Upper Cretaceous.
Though the dinosaurs dominated life in those days, higher forms, their
descendants, unnoticed were gradually creeping in, eventually to
supplant them. For brain was making its way unobtrusively in the
earliest of the mammals, diminutive creatures at first and of the
lowest type. First appearing in the Trias as something approaching the
missing link between reptiles and mammals, they later developed into
monotremes and marsupials, not rising in differentiation above the
latter order to the end of Mesozoic times. And this both in the old
world and the new. In the Jurassic, too, flying lizards and the first
birds appeared, showing their pedigree in their teeth.
With Cenozoic times we come upon the first true or placental mammals
with their culmination up to date in man. In the Eocene they were of a
primitive type; they were also of a comprehensive one, fitted to eat
anything. From this they specialized, some evolving and some on the
whole devolving; the whale, for instance, taking to the water in the
Eocene through the same degenerate proclivity that had characterized
the sea-saurians ages before. The earth was growing colder, though
still fairly warm, and with the fall in temperature the higher types of
life antithetically rose, evolution gradually fitting them to cope with
more advanced conditions. In this manner did the land supplant the sea
as the essential feature of the earth’s surface, first, in coming into
being, and then, by offering conditions fraught with greater
possibilities, as the habitat of the most advanced forms of life, both
plants and animals.
The possibility of advance in evolution was largely due to the fact
that the land did thus supplant the sea. Spontaneous variation, the as
yet unexplained _primum mobile_ in the genesis of species, is probably
to be referred to chemism and is likely later to receive its solution
at the hands of that science. In the meanwhile it is evident that
unless the variation obtain encouragement from the environment no
advance in type occurs. Now the land offers to an organism sufficiently
evolved to benefit by it, opportunities the sea does not possess. First
of these, undoubtedly, is the care it enables to be given to the young.
To cast one’s brood upon the waters is not the best method of insuring
its bringing up. There is too much of the uncertainties of wave and
current to make the process a healthy one, and even when attached to
rocks and seaweed, the attachment to a mother is to be preferred.
Without a period of infancy, when the young is unable to do for itself,
no great development is possible. In the only striking exception, the
case of the whales, dolphins, and porpoises, size has probably counted
for much in the matter, while the development of the cetaceans is far
behind that of the majority of land mammals.
Change of place, not in distance, but in variety, is another factor.
The sea is same as a habitat, one square mile of it being much like
another, except for gradually changing temperature. The land, on the
other hand, from its accidented surface, presents all manner of
diversity in the conditions. And the more varied the conditions to
which the organism is exposed, the greater its own complexity must be
to enable it to meet them.
That the terrestrial stage of planetary development is subsequent to
the terraqueous one, and must of necessity succeed it if the latter
ever exist on a body, follows from the loss of internal heat on the one
hand and from the kinetic theory of gases on the other. To which of the
two to attribute the lion’s share in the business is matter for doubt;
but that both must be concerned in it we may take for certain.
So long as the internal heat suffices to keep the body fluid, the
liquid itself sees to it that all interstices are filled. As the heat
dissipates, the body begins to solidify, starting with the crust. For
cosmic purposes it undoubtedly still remains plastic, but cracks of
relatively small size are both formed and persist. Into these the
surface water seeps. With continued refrigeration the crust thickens,
more cracks are opened and more water given lodgment within, to the
impoverishment of the seas. The process would continue till the
pressure of the crust itself rendered plastic all that lay below,
beyond which, of course, no fissures could be formed. How competent to
swallow all the seas such earth cuticle cracks may be we ignore; for we
cannot be said to know much of the process. We can only infer that to a
certain extent internal absorption of surface seas must mark a stage of
the evolution by which a star becomes a world and then an inert mass,
one of the dark bodies of which space is full.
Of the other means we know more. We are certain that it must take
place, though we are in doubt as to the amount it has already
accomplished. This method of depletion is by the departure of the water
in the form of gas, in consequence of the molecular motions. If we knew
the temperature and the age of Mars and also the amount of atmosphere
originally surrounding it, we could possibly predicate its state.
Reversely, we can infer something as to age and temperature from its
present condition.
CHAPTER XIII
THE REDDISH-OCHRE TRACTS
Both for their evidence and their extent the great ochre stretches of
the disk claim attention first. Largely unchangeable, these show
essentially the same day after day and from the year’s beginning to its
end. In hue they range from sand color to a brick red; some parts of
the planet being given to the one tint, some to the other. It is to the
latter that the fiery tint of Mars to the naked eye is due. The
differences in complexion are local and peculiar, both in place and
time. For though saffron best paints the greater part of the light
areas, certain localities present at times a red like that of our red
sandstone. Hellas is one of these ruddy regions and Aeria another. It
is only on occasion that they thus show, and to what to assign their
variability is as yet matter of conjecture. Possibly it is owing to
Martian meteorologic condition; possibly to something else. But
whatever its origin, the change is not so much contradictory of, as
supplementary to, the general fact of unalterableness, which is after
all the basic trait about them and the keynote to their condition.
Land the ochre regions have generally been taken for, and land they
still make good their claim to be considered. For the better they are
seen, the greater the ground for the belief. Indeed, they seem to be
nothing but ground, or, in other words, deserts. Their color first
points them out for such. The pale salmon hue, which best reproduces in
drawings the general tint of their surface, is that which our own
deserts wear. The Sahara has this look; still more it finds its
counterpart in the far aspect of the Painted Desert of northern
Arizona. To one standing on the summit of the San Francisco Peaks and
gazing off from that isolated height upon this other isolation of
aridity, the resemblance of its lambent saffron to the telescopic tints
of the Martian globe is strikingly impressive. Far forest and still
farther desert are transmuted by distance into mere washes of color,
the one robin’s-egg blue, the other roseate ochre, and so bathed, both,
in the flood of sunshine from out a cloudless burnished sky that their
tints rival those of a fire-opal. None otherwise do the Martian colors
stand out upon the disk at the far end of the journey down the
telescope’s tube. Even in its mottlings the one expanse recalls the
other. To the Painted Desert its predominating tint is given by the new
red sandstone of the Trias, the stratum here exposed; and this shows in
all its pristine nakedness because of the lack of water to clothe it
with any but the sparsest growth. Limestones that crop out beside it
are lighter yellow, whitish and steel-gray, and seen near give the
terrane the look of a painter’s palette. Seen from far they have rather
the tint of sand; and the one effect, like the other, is Martian in
look. And as if to assimilate the two planetary appearances the more,
the thread of blue-green that attention traces athwart the Painted
Desert marks the line of cottonwoods along the banks of the Little
Colorado River—deserts both, if look be any guarantee of character,
with verdure banding them.
In other ways these earthly deserts offer a parallel to the Martian. No
desert on the Earth is absolutely devoid of life of some kind, vegetal
and animal. The worst conditioned are not what one is taught in
childhood to believe a desert to be—a vast waste of sand, with a camel
and a palm thrown in to heighten the sterility. In all Saharas outside
of the pages of the school books some vegetation grows, though it is
commonly not of a kind to boast of, being rather a _succés d’estime_,
as sagebrush, cacti, and the like. But what is of interest here in the
connection is its color. For it is commonly of a more ochreish tint
than usual, in keeping with its surroundings, a paling out of the green
to something more tawny, indicating a relative reduction of the
chlorophyll and an increase of the lipochromes in the tissues of the
plant, since the one gives the green tint to the leaves, the other the
yellow. As this vegetation, poor as it is, has its annual history, it
must alter the look of the desert at times and produce precisely those
slight variations in tint observable on Mars in like circumstance.
The Arizona desert dates from no further back than early Tertiary
times, as the limestone of the Cretaceous there present shows. Water
then stretched where desert now is, and the limestone beds were laid
down in it. How old the Martian Saharas are we have no means of
knowing. But one thing we may predicate about both: a desert is not an
original, but an acquired, condition of a planet’s surface,
demonstrably so in the case of a planet which has had a sedimentary
epoch in its life-history. In the Arizona desert the surface is
composed of depositary rocks of Mesozoic times, except where lava
streams have flowed down over it since then. The land, then, was once
under water, and cannot but have been fertile for some time after it
emerged.
But we are not left to inference in the matter, however good that
inference may be. A little to the south of the Painted Desert, in the
midst of the barren plateau of northern Arizona, of which the former
makes a part, stand the remains of a petrified forest. Huge chalcedony
trunks of trees, so savingly transmuted into stone that their genus is
still decipherable, lie scattered here over the barren ground in waste
profusion, one of them still spanning a cañon just as it fell in that,
to it, destructive day of a far prehistoric past. The rock stratum on
which their remains lie is of Triassic and Cretaceous times and the
petrifications show that in the Cretaceous a stately forest overspread
the land. In those days at least the spot was fertile where now sparse
sagebrush and cacti find a living hard. Not here alone where the blocks
are so conspicuous as to invite their carrying away is a former
flourishing growth of vegetation attested, but over large adjoining
areas of desert search has brought the like past tenancy to light.
Fragments of what once were trees have been picked up in the Little
Colorado basin and in the neighborhood of Ash Fork, on both sides, that
is, of the present forest crown that covers the higher part of the
plateau from which rise the San Francisco Peaks. In the blue distance
the mountains look down verdure-clad upon a now encircling waste, but
one which in earlier eras was as pine-bearing as they. Their lofty
oasis is all that is now left of a once fertile country; the retreat of
the trees up the slopes in consequence of a diminishing rainfall, until
a rise of two thousand feet from what once was timber-land is necessary
to reach the tree-line of today, being typical of desert lands, and
testifying to greater aqueous affluence in the past. In the same manner
streams descend from the cedar-clad range of the Lebanon to lose
themselves in the Arabian desert just without the doors of Damascus;
and Palestine has desiccated within history times. Palestine, a land
once flowing with milk and honey, can hardly flow poor water now, and
furnishes another straw to mark the ebbing of the water supply.
This making of deserts is not a sporadic, accidental, or local matter,
although local causes have abetted or hindered it. On the contrary, it
is an inevitable result of planetary evolution, a phase of that
evolution which follows from what has been said in Chapter XII on the
abandonment of a planet by its water. Deserts are simply another sign
of the same process. The very aging which began by depriving a body of
its seas takes from it later its forest and its grass. A growing
scarcity of water is bound to depauperate the one, as it depletes the
other. We have positive proof of the action in our own deserts. For
these bear testimony, in places at least, to not having always been so,
but to have gradually become so within relatively recent times. But we
have more general proof of the action from the position occupied on the
earth’s surface by its deserts.
The significant fact about the desert-making so stealthily going on is
that only certain zones of the earth’s surface are affected. Those
belting the two tropics of Cancer and Capricorn, for several degrees on
either side of them, most exhibit the phenomenon. Such positioning of
the deserts is not due to chance. Directly, of course, desertism is due
to dearth of rain. This in turn depends on the character and condition
of the winds. If a wind laden with moisture travel into a colder region
of the globe, its moisture is precipitated in rain and we have a
fertile country; if it voyage into a warmer clime it takes up what
little moisture may be there already and a desert is the result.
Now our system of winds is such as to produce a fall of rain for the
different latitudes, as tabulated by Supan, thus:—
Zone I 40°N-27°N Little rain in summer but much in winter.
II 27 N-19 N Little rain at all seasons.
III 19 N- 7 N Little rain in winter but much in summer.
IV 7 N- 1 N Abundant rain at all seasons.
V 1 N-17 S Little rain in winter but much in summer.
VI 17 S-30 S Little rain at all seasons.
VII 30 S-35 S Little rain in summer but much in winter.
Zones II and VI, the zones of minimum rainfall, are also those in which
the deserts occur. The northern one traverses southern California,
Arizona, New Mexico, the Sahara, Arabia, and the Desert of Gobi; the
southern, Peru, the South African veldt, and central Australia. The
belts are wavy bands which by their form betray both a general
underlying trend to drought at these parallels and also the effect of
local topography in the matter.
From being distributed thus in belts, it is evident that the deserts
are general globe phenomena, and from their being found only in the
zones of least rainfall, that the earth has itself entered, though not
far as yet, upon the desert stage of its history. Once begun, the
desert areas must perforce spread as water becomes scarce, invading and
occupying territory in proportion as the rainfall there grows small.
Now the axial tilt of Mars is almost exactly the same as that of our
Earth, the latest determinations from the ensemble of measures giving
24° for it. Here, then, we have initial conditions reproducing those of
the earth. But from the smaller size of the planet that body would age
the earlier, since it would lose its internal heat the more rapidly,
just as a small stone cools sooner than a larger one. On general
principles, therefore, it should now be more advanced in its planetary
career. In consequence, desertism should have overtaken more of its
surface than has yet happened on earth, and instead of narrow belts of
sterility we should expect to find there Saharas of relatively vast
extent.
Now, such a state of things is precisely what the telescope reveals.
The ochre tracts occupy nine tenths of the northern hemisphere and a
third of the southern. Three fifths, therefore, of the whole surface of
the planet is a desert.
[Illustration: Desert areas.]
Of cosmic as well as of particular import is the correlation thus made
evident between the physical principles that effect the aging of a
planet and the aspect Mars presents. Experimental corroboration of
those laws is thus afforded, while, reversely, confidence in their
applicability is increased. With continued observation the planet
appears more desiccate as improved conditions bring it nearer. Dry land
as it was thought to be proves even drier, something which lacks water
for the ordinary necessities of a living world.
[Illustration: Desert areas.]
The picture the planet offers to us is thus arid beyond present
analogue on Earth. Pitiless as our deserts are, they are but faint
forecasts of the state of things existent on Mars at the present time.
Only those who as travelers have had experience of our own Saharas can
adequately picture what Mars is like and what so waterless a condition
means. Only such can understand what is implied in having the local and
avoidable thus extended into the unescapable and the world-wide; and
what a terrible significance for everything Martian lies in that single
word: _desert_.
CHAPTER XIV
SUMMARY
If, now, we review with the mind’s eye the several features of Mars
which we have surveyed with the bodily one, we shall be surprised to
find to what they commit us. Suggestive as each is considered by
itself, the _ensemble_ into which they combine proves of multiplicate
force in its implication. For each turns out to fit into place in one
consistent whole, a scheme of things in which are present all the
conditions necessary to the existence and continuance of those
processes which constitute what we call life. In short, we are
conducted with a cogency, which grows as we consider it, to the
conclusion that Mars is habitable.
Two ways of appreciating this cogency are open to us. We may treat it
with the simple reasoning of common-sense, as we should a dissected map
or a piece of machinery in which we realize we are right when the
several parts at last fit together and the picture stands revealed or
the machine works. Or we may subject the evidence to quantitative
estimates for and against by the doctrine of probabilities, and thus
evaluate the chances of its being correct. Consciously or
unconsciously, this is what we are about in our decisions every day of
our lives. At the one end of the line are those skillful judgments
where the balance is so keen-edged that the least overweight on the one
side dips the scales to a conclusion. At the other extremity stand
those deductions which we usually speak of as proved, such as the law
of gravitation. But both assurances rest really upon probability and
differ only in degree. What we mean by proof of anything is that a
supposition advanced to account for it explains all the facts and is
not opposed to any of them, and that the balance of probability in
consequence is very largely in its favor.
Now, if several pieces of evidence, distinct in their origin, concur to
a given conclusion, the probability that that conclusion is correct is
far greater than what results from each alone; and mounts up soon to
something much exceeding what bettors at races call certainty odds.
However unversed the average man may be in calculating the probability,
he recognizes the fact in his dealings with his fellows by the way he
attaches weight to concurrent testimony. It is such concurrent evidence
that we have now to consider. To this end we will marshal the several
facts ascertained in a summarized list for their easier intercomparison.
These facts are:—
(1) Mars turns on its axis in 24 h. 37 m. 22.65 s. with reference to
the stars, and in 24 h. 39 m. 35.0 s. (as a mean) with regard to the
Sun. Its day, therefore, is only about forty minutes longer than ours.
(2) Its axis is tilted to the plane of its orbit by about 23° 59′ (most
recent determination, 1905). This gives the planet seasons almost the
counterpart of our own in character; but in length nearly double ours,
for
(3) Its year consists of 687 of our days, 669 of its own.
(4) Polar caps are plainly visible which melt in the Martian summer to
form again in the Martian winter, thus implying the presence of a
substance deposited by cold.
(5) As the polar caps melt, they are bordered by a blue belt, which
retreats with them. This excludes the possibility of their being formed
of carbon dioxide, and shows that of all the substances we know the
material composing them must be water.
(6) In the case of the southern cap, the blue belt has widenings in it
in places. These occur where the blue-green areas bordering upon the
polar cap are largest.
(7) The extensive shrinkage of the polar snows shows their quantity to
be inconsiderable, and points to scanty deposition due to dearth of
water.
(8) The melting takes place locally after the same general order and
method, Martian year after year, both in the south cap,
(9) And in the north one. This is evidenced by the recurrence of rifts
in the same places annually in each. The water thus let loose can,
therefore, be locally counted on.
(10) That the south polar cap is given to greater extremes than the
north one, implies again, in view of the eccentricity of the orbit and
the tilt of the axis, that deposition in both caps is light.
(11) The polar seas at the edges of the caps being temporary affairs,
the water from them must be fresh.
(12) The melting of the caps on the one hand and their reforming on the
other affirm the presence of water vapor in the Martian atmosphere, of
whatever else that air consist.
(13) Since water vapor is present, of which the molecular weight is 18,
it follows from the kinetic theory of gases that nitrogen, oxygen, and
carbonic acid, of molecular weights 28, 32, and 38 respectively, are
probably there, too, owing to being heavier.
(14) The limb-light bears testimony to this atmosphere.
(15) The planet’s low albedo points to a density for the atmosphere
very much less than our own.
(16) The apparent evidence of a twilight goes to confirm this.
(17) Permanent markings show upon the disk, proving that the surface
itself is visible.
(18) Outside of the polar cap the disk is divided into red-ochre and
blue-green regions. The red-ochre stretches have the same appearance as
our deserts seen from afar,
(19) And behave as such, being but little affected by change.
(20) The blue-green areas were once thought to be seas. But they cannot
be such, because they change in tint according to the Martian season,
and the area and amount of the lightening is not offset at the time by
corresponding darkening elsewhere;
(21) Nor by any augmentation of the other polar cap or precipitation
into cloud. It cannot, therefore, be due to shift of substance.
(22) Furthermore, they are all seamed by lines and spots darker than
themselves which are permanent in place; so that there can be no bodies
of water on the planet.
(23) On the other hand, their color, blue-green, is that of vegetation;
this regularly fades out, as vegetation would, to ochre for the most
part, but in places changes to a chocolate-brown.
(24) The change that comes over them is seasonal in period, as that of
vegetation would be.
(25) Each hemisphere undergoes this metamorphosis in turn.
(26) That it is recurrent is again proof positive of an atmosphere.
(27) The changes are metabolic, since those in one direction are later
reversed to a restoration of the original status. Anabolic as well as
katabolic processes thus go on there; that is, growth as well as decay
takes place. This proves them of vegetal origin.
(28) The existence of vegetation shows that carbonic acid, oxygen, and
undoubtedly nitrogen, are present in the Martian atmosphere, since
plants give out oxygen and take in carbonic acid.
(29) The changes in the dark areas follow upon the melting of the polar
caps, not occurring until after that melting is under way;
(30) And not immediately then, but only after the lapse of a certain
time.
(31) Though not seas now, from their look the dark areas suggest old
sea bottoms, and when on the terminator appear as depressions (whether
because really at a lower level or because of less illumination is not
certain).
(32) That they are now the parts of the planet to support vegetation
hints the same past office, as water would naturally drain into them.
That such a metamorphosis should occur with planetary aging is in
keeping with the kinetic theory of gases.
(33) Terminator observations prove conclusively that there are no
mountains on Mars, but that the surface is surprisingly flat.
(34) But they do reveal clouds which are usually rare and are often, if
not always, dust-storms.
(35) White spots are occasionally visible, lasting unchanged for weeks,
in the tropic and temperate regions, showing that the climate is
apparently cold,
(36) But at the same time proving that most of the surface has a
temperature above the freezing-point.
(37) In winter the temperate zones are more or less covered by a
whitish veil, which may be hoar-frost or may be cloud.
(38) A spring haze surrounds the north polar cap during the weeks that
follow its most extensive melting.
(39) Otherwise the Martian sky is perfectly clear; like that of a dry
and desert land.
The way in which these thirty-nine articles fit into one another to a
mortised whole is striking enough at first sight, but becomes more and
more impressive the more one considers it. For some are due to one kind
of observation, some to another. In the taking they are unrelated; yet
in the result they agree. Equally pregnant is the history of their
acquisition. Most of them were detected as the outcome of observations
at the opposition of 1894, and led to the theory which was published in
the writer’s first book on the subject. Others are the result of the
five oppositions that have since occurred. These have proved entirely
corroborative of the previous ones and of the theory then deduced, and
that in two distinct ways: first, by the accumulated evidence they have
brought to the matter along the old lines; and, secondly, by what they
have revealed in new directions. Of these thirty-nine articles of
Martian scientific faith in observation or deduction, (9), (10), (21),
(22), (25), (27), (28), (30), (33), (35), (36), and (38) are in whole
or part new. That continued scrutiny is thus corroborative of the
earlier results, both along the old and along new lines of
investigation, warrants additional confidence in the conclusion.
Considering, now, these counts, we see that they make reasonably
evident on Mars the presence of:—
1. Days and seasons substantially like our own;
2. An atmosphere containing water vapor, carbonic acid, and oxygen;
3. Water in great scarcity;
4. A temperature colder than ours, but above the Fahrenheit
freezing-point, except in winter and in the extreme polar regions;
5. Vegetation.
First and foremost of these is air. In order to make it possible for
vital processes of any sort to take place, the body of a planet must be
clothed with an atmosphere, by the modesty of nature, the old
astronomers would have said. Such a covering subserves two purposes: it
keeps out the cold of space, thus permitting the maintenance of a
temperature sufficient to support life, and it affords a medium through
which metabolism can go on.
Now the presence of air is attested first and foremost by the fact of
change in the Martian markings, (12), (13), (26), (28), and (35). The
changes observed are conspicuous; are both inorganic (in the case of
the polar caps), (12), (13), and (35), and metabolic or organic, (26)
and (28), (in the case of the blue-green areas); that is, they consist
of building up as well as of pulling down and are planet-wide in
occurrence. Such changes could not occur in the absence of an
atmosphere. They show that this atmosphere consists of water vapor,
(5), carbonic acid, and oxygen, (28).
The limb-light, the apparent evidence of a twilight arc and the
planet’s low albedo indicate that this atmosphere is thin. The
appearance of the surface, (35), suggests cold, indicative again of a
thin air. Such tenuity is in accord with what _a priori_ principles
would lead us to expect, and tends to show that reliance on general
principles is here not misplaced, a point of some interest.
Lastly, the occurrence of clouds, (34), visibly floating and traveling
over the surface, and haze at times, (38), proves in another way the
existence of the medium in which alone this could be possible.
Water is the next substance vital to planetary life. As to its actual
presence the polar caps, (4)-(12), have most to say; as to its relative
absence, the rest of the disk, (17)-(22). The forthright conception of
the polar caps as composed of snow and ice is borne out by further
investigation into what could cause the observed phenomenon. Carbonic
acid, the only other substance we know capable in any way of resembling
what we see, turns out not capable of producing one important detail of
the caps’ appearance, the blue band, (5), which accompanies them in
their retreat. Water alone could do this.
The melting of the caps shows that water vapor must be a constituent of
the Martian atmosphere. Moreover, as the molecular weight of water
vapor is less than that of oxygen or nitrogen or carbon dioxide, if the
former can exist in the atmosphere of the planet, _a fortiori_ must
these other gases. So that from this we have knowledge of the
possibility of the presence of oxygen, nitrogen, and carbon dioxide
there. From (28) we saw that their actual existence is demonstrated.
The next step is the ascertainment that the water is in very small
amount. The extensive melting of the caps, (7), shows their quantity to
be inconsiderable, which is the first fact pointing to a dearth of
water. The second comes from the aspect and behavior of the
reddish-ochre regions which proclaim them deserts, (18) and (19); the
third from the detection of the character of the blue-green areas as
not seas, (20), (21), and (22). In several different ways, study of
these regions asserts their non-aquatic constitution, the easiest to
appreciate being that they are traversed by permanent dark lines and
other equally sedentary markings, (22). No bodies of water, therefore,
are to be seen outside of the ephemeral polar seas, immediately
surrounding the caps as they melt.
This leads us to the third presence on Mars indicative of a living
world: vegetation. The other two spoke of substances necessary to life,
the premises in the case, this one of organic existence itself, its
conclusion. The evidence consists of static testimony from the look of
the blue-green areas, (23), and of kinematic derived from their
behavior, (24), (25), (26), and (27). Vegetation would present exactly
the appearance shown by them, and nothing that we know of but
vegetation could. But suggestive as their appearance is, it is as
nothing compared with the cogent telltale character of their behavior.
The seasonal change that sweeps over them is metabolic, constructive as
well as destructive, that is, and proclaims an organic constitution for
them such as only vegetation could produce. In tint their metamorphoses
are those of the same substance. For the blue-green lapses into ochre
and revives again to blue-green just as vegetation does on our own
Earth at the proper season of the year, taking both the Sun and the
advent of water into the reckoning. Furthermore, certain of the largest
dark areas turn to a chocolate-brown at times, which is the color of
fallow ground and suggestive, at least, as occurring where the
blue-green at other seasons is the most pronounced. Lastly, the change
occurs at the epoch at which, from a knowledge of the melting of the
polar caps, theory demonstrates that it ought to take place if it be
due to the action of vegetation.
That this was the case was evident from much less information than is
forthcoming today; but what is significant, each new fact discovered
about the planet goes to show that it is unquestionably true.
PART II
NON-NATURAL FEATURES
CHAPTER XV
THE CANALS
From the detection of the main markings that diversify the surface of
Mars we now pass to a discovery of so unprecedented a character that
the scientific world was at first loath to accept it. Only persistent
corroboration has finally broken down distrust; and, even so, doubt of
the genuineness of the phenomena still lingers in the minds of many who
have not themselves seen the sight because of the inherent difficulty
of the observations. For it is not one where confirmation may be
summoned in the laboratory at will, but one demanding that the watcher
should wait upon the sky, with more than ordinary acumen. This
latter-day revelation is the discovery of the canals.
Quite unlike in look to the main features of the planet’s face is this
second set of markings which traverse its disk, and which the genius of
Schiaparelli disclosed. Unnatural they may well be deemed; for they are
not in the least what one would expect to see. They differ from the
first class, not in degree, but in kind; and the kind is of a wholly
unparalleled sort. While the former bear a family resemblance to those
of the earth; the latter are peculiar to Mars, finding no counterpart
upon the earth at all.
Introduction to the mystery came about in this wise, and will be
repeated for him who is successful in his search. When a fairly acute
eyed observer sets himself to scan the telescopic disk of the planet in
steady air, he will, after noting the dazzling contour of the white
polar cap and the sharp outlines of the blue-green seas, of a sudden be
made aware of a vision as of a thread stretched somewhere from the
blue-green across the orange areas of the disk. Gone as quickly as it
came, he will instinctively doubt his own eyesight, and credit to
illusion what can so unaccountably disappear. Gaze as hard as he will,
no power of his can recall it, when, with the same startling
abruptness, the thing stands before his eyes again. Convinced, after
three or four such showings, that the vision is real, he will still be
left wondering what and where it was. For so short and sudden are its
apparitions that the locating of it is dubiously hard. It is gone each
time before he has got its bearings.
By persistent watch, however, for the best instants of definition,
backed by the knowledge of what he is to see, he will find its coming
more frequent, more certain and more detailed. At last some
particularly propitious moment will disclose its relation to well-known
points and its position be assured. First one such thread and then
another will make its presence evident; and then he will note that each
always appears in place. Repetition _in situ_ will convince him that
these strange visitants are as real as the main markings, and are as
permanent as they.
Such is the experience every observer of them has had; and success
depends upon the acuteness of the observer’s eye and upon the
persistence with which he watches for the best moments in the steadiest
air. Certain as persistence is to be rewarded at last, the difficulty
inherent in the observations is ordinarily great. Not everybody can see
these delicate features at first sight, even when pointed out to them;
and to perceive their more minute details takes a trained as well as an
acute eye, observing under the best conditions. When so viewed,
however, the disk of the planet takes on a most singular appearance. It
looks as if it had been cobwebbed all over. Suggestive of a spider’s
web seen against the grass of a spring morning, a mesh of fine
reticulated lines overspreads it, which with attention proves to
compass the globe from one pole to the other. The chief difference
between it and a spider’s work is one of size, supplemented by greater
complexity, but both are joys of geometric beauty. For the lines are of
individually uniform width, of exceeding tenuity, and of great length.
These are the Martian canals.
Two stages in the recognition of the reality confront the persevering
plodder: first, the perception of the canals at all; and, second, the
realization of their very definite character. It is wholly due to lack
of suitable conditions that the true form of the Martian lines is
usually missed. Given the proper prerequisites of location or of eye,
and their pencil-mark peculiarity stands forth unmistakably confessed.
It is only where the seeing or the sight is at fault that the canals
either fail to show or appear as diffuse streaks, the latter being a
halfway revelation between the reality and their not being revealed at
all. Much misconception exists on this point. It has been supposed that
improved atmospheric conditions simply amount to bringing the object
nearer by permitting greater magnification without altering the hazy
look of its detail.[2] Not so. They do much more than this. They steady
the object much as if a page of print from being violently shaken
should suddenly be held still. The observer would at once read what
before had escaped him for being a blur. So is it with the canals. In
reality, pencilings of extreme tenuity, the agitations of our own air
spread them into diffuse streaks; an effect of which any one may assure
himself by sufficiently rapid motion of a drawing in which they are
depicted sharp and distinct, when he will see them take on the streaky
look. As the writer has observed them under both aspects, and has seen
them pass from the indefinite to the defined as the seeing improved, he
has had practical proof of the fact, and this not once, but an untold
number of times.
Atmospheric conditions far superior to what are good enough for most
astronomic observations are needed for such planetary decipherment, and
the observer experienced in the subject eventually learns how
all-important this is. Under these conditions the testimony of his own
eyesight upon the character of these markings is definite and complete.
And the first trait that then emerges from confusion is that the
markings are _lines_; not simply lines in the sense that any
sufficiently narrow and continuous marking may so be called, but lines
in the far more precise sense in which geometry uses the term. They are
furthermore straight lines. As Schiaparelli said of them: they look to
have been laid down by rule and compass. The very marvel of the sight
has been its own stumbling-block to recognition, joined to the
difficulty of its detection. For not only is the average observatory
not equipped by nature for the task, but what is not good air often
masquerades as such. Trains of air waves exist at times so fine as to
confuse this detail, or even to obliterate it entirely; while at the
same time they leave the disk seemingly sharp-cut, with the result that
one not well versed in such vagaries thinks to see well when in truth
he is debarred from seeing at all. When study of the conditions finally
ends in putting him upon the right road, the sight that rewards him can
hardly be too graphically described.
Next to the fact that they are _lines_, definiteness of direction is
the chief of their characteristics to strike the observer. The lines
run straight throughout their course. This is absolutely true of ninety
per cent of them, and practically so of the remaining ten per cent,
since the latter curve in an equally symmetric manner. Such directness
has I know not what of immediate impressiveness. Quite unlike the
aspect of the main markings, which show a natural irregularity of
outline, these lines offer at the first glance a most unnatural
regularity of look. Nothing on Earth of natural origin on such a scale
bears them analogue. Nor does any other planet show the like. They are,
in fact, distinctively Martian phenomena. This is the first point in
which they differ from the markings we have hitherto described. The
others were generic planetary features; these are specific ones,
peculiar to Mars.[3]
Equally striking is the uniform width of each line from its beginning
to its end, as it stands out there upon the disk. The line varies not
in size throughout its course any more than it deviates in direction.
It counterfeits a telegraph wire stretched from point to point. Like
the latter seen afar, the width, too, is telegraphic. For it is not so
much width as want of it that is evident. Breadth is inferable solely
from the fact that the line is seen at all, and relative size by
difference of insistency. Indeed, the apparent breadth has been
steadily contracting as the instrumental, atmospheric, and personal
conditions have improved. All three of the factors have conduced to
such emaceration, but the middle one the most. For the air waves spread
every marking, and the effect is relatively greatest upon those which
are most slender. As the currents of condensation and rarefaction pulse
along, their denser and their thinner portions refract the rays on
either side of their true place, and thus at the same time confuse a
marking and broaden it. The consequence is that the better the
atmospheric conditions and the more that has been learned about
utilizing them, the finer the lines have shown themselves to be.
Herein we have a specific intrinsic difference between the fundamental
features and these lines: the main markings have extension in two
dimensions, the latter in one.
Distinctive as they thus are, they have, in keeping with their
appearance, been given a distinctive name, that of canal. Useful as the
name is and, as we shall later see, applicable, it must not be supposed
that what we see are such in any simple sense. No observer of them has
ever considered them canals dug like the Suez Canal or the phœnix-like
Panama one. This supposition is exclusively of critic creation.
Their precise width is not precisable. They show no measurable breadth
and their size, therefore, admits for certain only of an outside limit.
They cannot be wider than a determinable maximum, but they may be much
less than this. The sole method of estimating their width is by
comparison of effect with a wire of known caliber at a known distance.
For this purpose a telegraph wire was stretched against the sky at
Flagstaff, and the observers, going back upon the mesa, observed and
recorded its appearance as their stations grew remote. It proved
surprising at what great distances a slender wire could be made out
when thus projected against the sky. The wire in the experiment was but
0.0726 of an inch in diameter and yet could be seen with certainty at a
distance of 1800 feet, at which point its diameter subtended only 0.69
of a second of arc. How small this quantity is may be appreciated from
its taking more than ninety such lines laid side by side to make a
width divisible by the eye. Such slenderness at the then distance of
Mars would correspond, under the magnification commonly used, only to
three quarters of a mile. Theoretically, then, a line three quarters of
a mile wide there should be visible to us. Practically, both light and
definition is lost in the telescope, and it would be nearer the mark to
consider in such case two miles as the limit of the perceptible. With
the planet nearer than this, as is often the case, the width which
could be seen would be proportionally lessened. Perhaps we shall not be
far astray if we put one mile as the limiting width which could be
perceived on Mars at present, with distance at its least and definition
at its best.
That so minute a quantity should be visible at all is due to the line
having a sensible length and by summation of sensations causing to rise
into consciousness what would otherwise be lost. A stimulus too feeble
to produce an effect upon a single retinal rod becomes recognizable
when many in a row are similarly excited.
The experiment furnished another criterion, of importance as regards
the supposition that the lines on Mars are illusory. It showed that
brain-begotten impressions of wires that did not exist could be told
from the real thing when the wire subtended 0.69 of a second of arc or
more; that below this the outside stimulus was too weak to differ
recognizably from optic effects otherwise produced; while when the real
wire was diminished to 0.59′′, it could not be seen at all. Now, the
majority of lines on Mars so far recognized and mapped lie in strength
of impression far above the superior limit of 0.69′′. To one versed in
Martian canal detection there is no possibility of self-deception in
the case, the canals being very much more salient objects to an expert
than those who have not seen them suppose. For it must not be imagined
that, when one knows what to be on the lookout for, they are the
difficult objects they seem to the tyro. Just as the satellites of Mars
were easily seen once they were discovered, so with these lines.
A mile or two we may take, then, with safety as the smallest width for
one of the lines. The greatest was got by comparing what is by far the
largest canal, the Nilosyrtis, with the micrometer thread. From such
determination it appeared that this canal was from 25 to 30 miles wide.
But it is questionable whether the Nilosyrtis can properly be termed a
canal, so much does it exceed the rest. It is certainly far larger than
the majority of them. From comparative estimates between its size and
that of the others, 15 to 20 miles for the width of the larger of the
Martian canals seems the most probable value, and 2 or 3 miles only of
the more diminutive of those so far detected.
[Illustration: Showing the Eumenides-Orcus.]
On the other hand, the length of the canals is relatively enormous.
With them 2000 miles is common; while many exceed 2500, and the
Eumenides-Orcus is 3540 miles from the point where it leaves the Phœnix
Lake to the point where it enters the Trivium Charontis. This means
much more on Mars than it would on Earth, owing to the smaller size of
the planet. Such a length exceeds a third of the whole circumference of
its globe at the equator. But what is still more remarkable, throughout
the whole of the long course taken by the canal, it swerves neither to
the right nor to the left of the great circle joining the two points.
Of these several peculiarities of the individual canal it is difficult
to know to which to allot the palm for oddity,—great circle
directness, excessive length, want of width, or striking uniformity.
Each is so anomalously unnatural as to have received the approving
stamp of incredulity. Yet so much, wonderful as it is, is encountered
on the very threshold of the subject.
-----
Footnote 2:
M. l’abbé Moreux.
Footnote 3:
As some misrepresentation has been made on this subject through
misapprehension of the writer’s observations on Venus and Mercury, it
may be well to state that the tenuous markings on both these other
planets entirely lack the unnatural regularity distinguishing the
canals of Mars. The Venusian lines are hazy, ill-defined, and
non-uniform; the Mercurian broken and irregular, suggesting cracks.
Neither resemble the Martian in marvelous precision, and have never
been called canals by the writer nor by Schiaparelli, but solely by
those who have not seen them and have misapprehended their character
and look.
CHAPTER XVI
THEIR SYSTEM
Much more stands beyond. For, outdoing in suggestiveness the individual
traits of the lines, is the relation shown by them to one another. It
is the communal characteristics of the phenomenon that are most
surprising.
The individual peculiarities of the lines impress themselves at once;
the communal, only as the result of experience, collation, and thought.
As the observer becomes trained, the more lines he is able to make out,
until they fairly seam the whole surface of the light areas of the
planet. Their name collectively is legion; while to name them
individually is fast getting, for the number detected, to be
impossible. As with the increasing family of asteroids, figures alone
will prove adequate to the task.
Interdependence, not independence, marks the attitude of the canals.
Each not only proceeds with absolute directness from one point to
another, but at its terminals it meets canals which have come there
with like forthrightness from other far places upon the planet. Nor is
it two only that thus come together at a common junction. Three, four,
five,—up to as many as fourteen,—thus make rendezvous, and it is a
poor junction that cannot show at least six or seven. The result is a
network which triangulates the surface of the planet like a geodetic
survey into polygons of all shapes and sizes, the Arian areolas. The
size of the pieces forming this tesselate ground depends solely upon
the fineness of the definition. With every increase in the power of
seeing, each areola is cut into still smaller portions, usually by
connection between its corners. Thus a polygon or rhombus is split into
triangles which may themselves be divided in like manner, the mosaic
breaking into bits, the sides of which, however, always remain
clean-cut.
From this arrangement it is at once evident that the canals are not
fortuitously placed. That lines should thus meet exactly and in numbers
at particular points, and only there, shows that their locating is not
the outcome of chance. If very thin rods be thrown haphazard over a
surface, the probability that more than two will cross at the same
point is vanishingly small. Increasingly assured is it that this would
not happen generally. The result we see is therefore not a matter of
chance, but of some law working to that end.
To the detection of what that law is precedes the easier ascertainment
of what it is not. The lines, for example, cannot be rivers, which was
the first explanation offered of them by Proctor many years ago,
because of their peculiar straightness. Nor can they be channels, the
name given to them by Schiaparelli, except in the non-committal sense
in which he used the term. For here again their geometric regularity is
bar to any estuary-like hypothesis. For quite another reason they
cannot be cracks, because of their uniform size throughout. Their
unbroken character is another fatal objection to the same suggestion.
For cracks in ground never pursue for any great distance a continuous
course, any more than they keep uniform or straight. The state of an
old ceiling is a case in point. When it breaks, it does so in fissures
that proceed a certain way, then give out to be continued by others
roughly parallel to the first, but parted from them. The same character
is shown by the rills on the moon. The ‘Straight Wall,’ so called, is
composed of three such sections, and the little rill to the right of
it, west of Birt, of four.
Thus were they seen at Flagstaff, and as, to the writer’s knowledge,
they have not been so depicted elsewhere, the fact may serve to give
some idea of the definition there.
That the underlying cause is not explosion or contraction is also
evidenced by the canals collectively as well as individually, their
arrangement into a system, for cracks, however produced, could only
originate from certain centres and could not fit into those starting
from others, as the canals invariably do. For each canal goes as
undeviatingly to one terminal as it left forthrightly from another. If
one wishes to see what explosion or contraction can do, he has only to
look at the moon through an opera-glass, when he will be shown a very
different sight from what the drawings of Mars detail. Thus just as,
considered individually, the lines cannot be watercourses because of
their straightness, so they cannot be cracks because of dovetailing
into one another.
The fact that they form a system shows that whatever caused them
operated over the whole planet, linked in cause as in effect throughout
each section. This at once negatives any purely physical cause of which
we have cognizance. For upon a globe still so subject to physical
vicissitude as Mars by its aspect shows itself to be, latitude must
tell in the phenomena its zones exhibit. Polar snows that wax and wane
speak of arctic conditions very diverse from temperate and tropic
states, and what would affect the one could not influence the other.
Yet the mesh rises superior to zonal solicitation as to local barrier.
It is not something dependent either on the temperament or the
complexion of the globe’s different parts. It transcends surface
restriction and becomes planet-wide in its working. The importance of
this omnipresence dilates in meaning as one dwells in thought upon it.
Ubiquitous as it is, the mesh which thus covers the Martian surface
like a veil spread completely over it, is unlike a veil in being of
irregular texture. Not only are the interstices of various shape and
pattern, but the mesh itself is of locally differing size. Though the
threads are straight and uniform throughout, they are not all alike,
besides being unsymmetrically interwoven. Some are at least of ten
times the coarseness of others, and from this fact and the bo-peep
effect of our air waves all are not visible at once. In consequence the
network is not so impressive at first glance as it becomes upon a
synthesis of the observations. When this is done, the surface proves to
be fairly evenly cut up, as recourse to the maps printed in this volume
will amply demonstrate. These maps, as on page 31, are made from the
results of but one opposition, and as at each opposition some zone is
in a more canal-showing state than others, owing to the Martian season
at the time, a still greater uniformity in canal distribution results
from a blending of many.
From the completeness of the mesh, it follows that in the course taken
severally by the canals no one direction preponderates over another.
Considered by and large, the canals seem to be equally distributed
round the compass points; and this at all longitudes and nearly all
latitudes. Tropic, temperate, and even arctic canals show a pleasing
impartiality in the matter of the course pursued. The only exceptions
occur in the neighborhood of the pole. There a slight tendency may be
seen to a north and south setting.
Though so much is visible in a general way from the map, it is of
interest to go into the subject with more particularity and to that end
to show it statistically. The several canals traversing each zone were
therefore counted, and the area of the zone computed. The manner of
canal distribution thus found is given in the following table, in the
second column of which stand the areas of the several zones upon the
planet, each ten degrees wide, except the one next the snow, and in the
third the number of canals found traversing them, reduced to
percentages of the 0°-10° zone. A fourth column shows the total length
of the canals in each zone, those from 0° to 20° being taken from the
1896 globe, those from 20° to 90° from the 1903. This is in order to
annul the effect of the seasons upon the showing of the canals as much
as possible.
===============+===============+===============+===============
ZONE | AREA | NO. OF CANALS | ACTUAL LENGTH
| | WTD. |
---------------+---------------+---------------+---------------
0°-10° | 1.00 | 1.00 | 1.00
10°-20° | .97 | .89 | .91
20°-30° | .91 | .93 | .72
30°-40° | .82 | .90 | .71
40°-50° | .71 | .78 | .66
50°-60° | .58 | .64 | .59
60°-70° | .42 | .43 | .42
70°-80° | .26 | .30 | .34
80°-85° | .07 | .12 | .11
===============+===============+===============+===============
The numbers continue fairly non-committal until we begin to approach
the pole, when they commence to increase. Much the same result is got
if we take the actual canal-lengths in each zone, as the fourth column
shows. The crowding of the canals poleward is marked. The canals,
therefore, are phenomena that stand in peculiar relationship to the
polar cap. This corroborates the inference about them due to their
running out of the edge of the snow. They not only emanate from it, but
they do so in numbers surpassing what is elsewhere observable over the
disk.
Otherwise is it with their departure-points. These are not scattered
haphazard over the surface, but bear to its general features definite
relations. If we consider the map, obliterating the lines, and then
seek to connect the most salient points of the planet’s topography by
direct avenues of communication, we shall find that our putative lines
fall exactly where the real ones occur. For the most part, the real
lines emanate from well-marked indentations in the dark regions, fitted
by natural position for departure-points, what, if these were seas, we
should call their most conspicuous bays. They thus leave in the
southern hemisphere the deeper folds of the great diaphragm, for the
most part; though on occasion they run out of them where they will.
From equally conspicuous points in the dark northern areas other lines
proceed; while in the centre of the continents, the canals make for
more or less salient spots, small patches of shading like the Trivium
or the Wedge of Casius, or simply round black radiants, like the Luci
Ismenii.
From this it appears that the lines are locally dependent upon the
general topography of the fundamental features of the surface. For
some reason they connect the very points most suggestive of
intercommunication. As from their characteristics it is perfectly
evident that the lines are neither rivers nor cracks, it follows that
such a communicating habit is of the most telltale character. To be
so dissimilar in kind from the main markings and yet so dependent
upon them, hints that their positioning occurred after the formation
of the main features themselves. We reach thus from the look of the
lines and their location a most striking deduction, that the lines
are not coeval with the main markings, but have come into being later
and with reference to the general topography of the planet. The
network is not only a mesh _de facto_, then, but one _de jure_,
which, subsequent to the fashioning of the seas and continents and
what these have now become, has been superposed upon them.
CHAPTER XVII
GEMINATION OF THE CANALS
Fraught with more difficulty than the detection of the lines alone is
the next discovery made upon the disk: the recognition of pairs of
lines traversing it.
In 1879, while Schiaparelli was engaged in scrutinizing the strange
_canali_ he had discovered on the planet the opposition before, he was
suddenly surprised to mark one of them double. Two closely parallel
lines confronted him where but a single one had previously stood. So
unaccountable did the sight seem, that he hesitated to credit what he
saw, being minded to attribute the vision to illusion of some sort and
the more so that it was not renewed. While he was still wondering what
it meant, the planet parted company with the Earth, carrying its enigma
with it.
When the two bodies again drew near to one another in 1882,
Schiaparelli set himself to watch for a recurrence of the strange
phenomenon. Before long it came, and more bewilderingly than at first;
for not one canal alone, but a score of them now showed in duplicate,
each presenting to his astonished gaze twin lines perfectly matched and
preserving throughout their distance apart. Suspecting diplopia or some
other optical trick, he tried various eyepieces to a test of the cause
but to no change in the effect. The twin lines continued visible, do
what he would, insisting on their own reality in spite of all
solicitation to merge. How cautious he was in the matter, and how
unwilling at first to believe the evidence of his eyes, is shown by the
care he took to guard against deception. It was not until he had
assured himself of the reality of the phenomena that he believed what
he had seen.
It so chanced that my first experience of the thing was almost equally
startling, so unexpected was it and so exceedingly sharp was the
definition at the time. It was in an autumn early twilight, through air
almost perfectly still, as the light went out of the sky and the
markings on the planet began to come forth that the Phison of a sudden
showed in duplicate to me, clear-cut upon the disk, its twin lines like
the rails of a railway track traversing Aeria. Not more vivid do those
of our transcontinental tracks appear as one sees them stretching off
into the distance upon our Western plains. More impressive was the
sight from the fact that I was not looking for it. It simply suddenly
stood forth, this strange parallelism of pencil lines. My surprise
matched the wonder of the sight.
Since then I have witnessed it several hundred times, but never with
more absolute certainty than at that first fortunate revelation. To
this distinctness is due the amazement it then aroused. Not simply
because of its surpassing novelty, but for the insistence with which it
proclaimed itself was the effect to be ascribed. Less well seen, doubt
had robbed it of its full surprise. It requires as a rule steady
definition for its initial unmistakable showing, if one would be
instantly convinced. Except for such it is not usually easy to the
unpracticed, though often discernible to the expert after it has once
been seen. But that it is real no one who had had a good view of the
sight could doubt; still less after the experience had been repeated
over and over again.
What appears to take place is this: where previously a single
pencil-like line joined two well-known points upon the disk, twin
lines, the one the replica of the other, stand forth in its stead. The
two lines of the pair are but a short distance apart, are of the same
size, of the same length, and absolutely equidistant throughout their
course. It is as if a second line had in some way been mysteriously
added to the first since the latter was last seen some weeks before.
This in a word is the phenomenon, technically called the gemination of
the canals, which has since its discovery called forth so much comment.
It is not in reality quite as simple or as sudden as it seems, but this
was the way in which the phenomenon was first seen and in which it
still continues to be criticised.
Self-assertive of reality, the double lines are patently objective to
him who is fortunate enough to see them well. Nevertheless the great
difficulty of detecting them, and the still greater difficulty of
conceiving how such things can be, has led many not versed in the
subject to disbelieve and from that to attempt to explain the sight as
illusory. Scepticism seeks self-justification; what is hard of
acceptance for its strangeness begetting hypotheses of committed error
which find easy credence for their comforting conservatism. Several
such have in consequence been propounded to account for the double
canals. There is the diplopic theory which credits them to
non-focusing; the interferential theory which would make them optical
products of the telescope; and the illusion theory which would have
them quite simply imaginary.
Inasmuch as in any research the assurance that a phenomenon is real is
the first point about it to be established, it is a scientist’s duty,
not only to scan the phenomena with jealous care to that end, but to
scrutinize every theory which would seek otherwise to account for
them—the testing such being only second in importance to observing the
things themselves. Accordingly I have examined each of the optical
theories that have been advanced and critically compared what they
assert and require with the results of observation. The outcome of this
research has proved as negativing to any other origin for the double
canals than reality as direct observations at the telescope are
positive on the point. To show this I shall review each in its
consequences, confronting it with what the telescope has to say on the
subject; for it is of the pith of the matter that the reality should be
as demonstrable on demand as on sight. Furthermore, I shall do this
before embarking on the general account of these strange things,
because it is vital to any interest that one should be assured from the
start of the truth of what he is to read. The preface may seem to him
abstruse and prosy, but it will introduce him to some curious optical
properties and will eventually enhance his concern by proving to him
that what reads like fiction is all the more wonderful for being fact.
_I. The Diplopic Theory_
Diplopia is the property of seeing double with one eye. Surprising as
it sounds it is an effect not unknown to students of optics, though it
usually requires training to produce. It is possible only when the eye
is not focused on the object, and is not always possible then. From my
experiments its feasibility seems to depend upon whether the focus be
beyond or before what it should be. If the eye be focused for a point
beyond the object, the object is doubled, if for a point this side of
it, the latter is simply blurred. When the double is formed, the amount
of the separation of the two images is a function of the distance the
focus is out. The greater the discrepancy, the wider apart is the
ensuing double. Nor does the image, of a line, for example, stop at
doubling. After a certain breadth of separation is reached a third line
appears, bisecting the interval between the other two. With yet greater
widening the third line itself splits into a pair and so the resolution
goes on. In my own experiments I have gone so far as to suspect a fifth
line. Far from being unconscious, the process of producing the
phenomenon is, with some people, of difficult accomplishment. Mr.
Lampland, for instance, of the Flagstaff Observatory, to whom we owe
the first photographing of the canals, and who sees the doubles of Mars
without difficulty, has hitherto found diplopic vision an impossible
feat. Even with the most practiced diplopia is never unconscious except
when the object viewed, as a micrometer wire, has nothing to locate it
in space. Now, the diplopic theory of the double canals supposes that
in all cases the eye of the observer is thus unconsciously out of focus.
To this method of their manufacture the telescopic phenomena prove
unamenable on five counts.
1. Focusing the eye on an object is now a reflex action, so automatic
has it become; in consequence one is commonly directly conscious when
an object is not in focus, always so when the object presents detail.
Were such not the case we should never, except by chance, see anything
defined. Observing through a telescope, after a modicum of practice,
differs in no respect from observing in everyday life. Consequently,
that an experienced observer should not know his business in so primary
a matter is preposterous. One may or may not believe that “the undevout
astronomer is mad,” but that the perpetually unfocused one would be is
beyond debate.
2. Generically unlikely, the failure to focus is here specifically out
of the question. For the observer does not use the canals to focus on
for the simple reason that he cannot. Like all delicate detail, the
doubles appear not continuously but by flashes of revelation, according
as the atmospheric waves permit of passage undisturbed. To focus on
them would be next to impossible even were it resorted to—which it
never is. By the exponents of the theory this important fact is
overlooked: the unforeseen showing of the canals and therefore the
absolute lack of complicity of the eye in the matter. What one focuses
on is the look of the main markings of the disk. Now, to suppose an
observer systematically out in his perceptions of so featureful a
planet as that of Mars, so that he does not know when he sees its image
sharp, implies a lack of knowledge of astronomic observation in the
supposer.
3. Study by the writer shows the width of a given double canal to be
constant for a given date. Within the errors of perception or recording
the twin lines are always at the same epoch the same distance apart.
The greater the number of determinations made, the nearer the result
approaches to this mean; and the greater the care used in delineation,
the less each value departs from it.
Now, if the thing were a matter of mistaken focusing, an eye could not
be thus true to its own mistakes. If it were out in its focus by a
certain amount at one time, it would be likely to be out by a different
amount at another. So that by the very terms of its making a diplopic
double would be sure to vary. Indeed, in laboratory experiments it is
impossible to prevent it. For the eye rests itself automatically by
change of focus, and if it be not consciously kept awry it reverts as
near to the true focus as it can of its own accord.
4. Diplopia might be a respecter of persons, but it certainly could not
be one of canals. For a given observer it must be objectively general
in its application to the same class of objects. Consequently, if the
doubling were diplopic, all canals inclined at the same angle to the
vertical—for the tilt might affect the result were the eye
astigmatic—should be similarly affected. Parallel canals should
parallel each other’s action. With the Martian doubles this is not the
case. Of two canals similarly inclined the one will be double, the
other not, at the same instant and under conditions that are alike. And
this persistently. For gemination is an attribute of certain canals and
never of others. At a given season of the Martian year, some canals are
regularly double, some invariably single. Night after night and
presentation after presentation these idiosyncrasies are preserved: the
doubles, always pairs, the single, always alone. Nor does the strength
of the line affect the action. The single canals are some of them
stronger, some of them weaker, than the doubles seen at the same time.
5. If of diplopic origin the mean width of all the doubles should be
the same. For though the diplopic width would vary for a given canal
according to the moment, a sufficient number of views would yield a
mean width which would be the same for all. Tilt apart, the mean width
of one canal would be that of another. Among Martian doubles, on the
contrary, I have found the width to be a specific property of the
particular canal. Each has its own mean width regardless of
inclination, and this individual width differs as between one and
another by as much as five to two, or, if we consider such canals as
the Nilokeras I and II, by more than ten to two.
Any one of these five points is fatal to the theory; _a fortiori_ all.
_II. The Interference Theory_
From the wave propagation of light it follows that the image of a
bright line made by a lens is not itself a simple bright line but a
bright band flanked by alternate dark and bright ones. It has,
therefore, been suggested that a bright medial line is here concerned
and that the double canal is the first of its dark pair of outriders.
But the suggestion does not bear scrutiny.
1. It presupposes a central streak brighter than the rest of the disk
to give birth to the twin dark lines. This should itself be visible in
the image; but no such bright backbone is seen.
2. It demands a perfectly definite width of separation for a given
aperture—which is not that observed.
3. It makes the width a function of the aperture, decreasing as this
increases—which is not sustained by observation. Different apertures
produce no effect on the widths of the Martian doubles, as the writer
has shown (Lowell Observatory Bulletin, No. 5) by a change of aperture
from twenty-four to six inches.
4. Under like optical conditions the optically produced doubles would
be all of a width; while the Martian ones show idiosyncratic widths,
each peculiar to itself.
_III. The Illusion Theory_
Known also as the Small Boy Theory from the ingenuous simplicity on
which it rests, this theory attacks the reality of the doubles by
questioning that of the canals _en bloc_. Because some boys from the
Greenwich (Reform or) Charity School, set to copy a canal-expurgated
picture of the planet, themselves supplied the lines which had
preceptorily been left out, the Martian canals have been denied
existence; which is like saying that because a man may see stars
without scanning the heavens, therefore those in the sky do not exist.
As to the instructions the boys received we are left in the dark. It
looks as if some leading questions had unconsciously been put to them.
At all events, English charity boys would seem to be particularly
pliant to such imagination, for when Flammarion retried the experiment
with French schoolboys, and even inserted spaced dots for the canals in
the copy, not a boy of them drew an illusory line.
The fact is, this is one of those deceptive half-truths which is so
much more deleterious than an unmitigated mistake. Under certain
circumstances it is quite possible to perceive illusory lines, due
either to shadings otherwise unmarked and thus synthesized or to
immediately precedent retinal impressions transferred to places where
they do not belong by rapid motion of the eye, as I had myself
discovered before the English experiment had been tried. But, as I have
also found out, these effects are produced only at the limit of vision,
and in that limbo of uncertainty the whole art of the observer consists
in learning to distinguish the true from the false. Strength of
impression, renewed effect _in situ_, and a peculiar sense of reality
or the reverse enable him to adjudge the two. More experience than the
boys possessed would have helped them to part the sheep from the goats.
But, furthermore, and fatally to the theory here in question, the
Martian canals when well seen are not at the limit of vision as its
framers supposed, but well within that boundary of doubt; so that the
premise upon which the whole theory rests gives way. Under good
atmospheric conditions the canals are comparable for conspicuousness to
many of the well-recognized Fraunhofer lines and are just as certainly
there.
Thus each attempt to prove the doubles non-objective turns out when
specifically examined to be inconsistent with the facts. With the
assurance of their reality thus made doubly sure, we pass to
consideration of the things themselves.
CHAPTER XVIII
THE DOUBLE CANALS
I
Rightly viewed, no more subtle tribute could be paid to the remarkable
character of the phenomenon of gemination than the scepticism with
which it was immediately received and which it still continues to
elicit. That the sight should be regarded as illusory speaks for its
surpassing strangeness; and so far as oddity goes the encomium is
certainly deserved. Of the bizarre features of this curiously marked
disk, the double canals were at the time of their discovery the
culmination, and though things stranger still if possible have since
been seen there, it is not wonderful that doubt should still
incredulously stare. If the mere account of them reads like romance, to
see them is an experience.
Nothing astronomical that I have ever seen has been so startlingly
impressive as my first view of a double canal. Even in narration the
thing justifies its effect. For a double canal consists of a pair of
twin dark filaments, perfectly parallel throughout their course and
inclosing between them ground of the same ochreish cast as that which
lies without. Only on occasion is this tint of their midway departed
from, and then only toward a darkening, never toward a lightening of
it. Except for appearing paired, the lines resemble precisely the usual
single canals. In length they vary from a few hundred to a few thousand
miles, while in width each component, for narrowness, hardly permits of
definite ascription.
Compared for strength with the usual canal the lines of a double seem
to hold on the average an intermediate position between the larger and
the smaller of the single canals so far detected. Owing, however, to
the massed effect of the pair by reason of their closeness, they have
an advantage in showing over the singles of two to one. And this
renders them among the most conspicuous and important meshes of the
canal network.
Like the single canals, they vary in strength with the Martian time of
year; at certain seasons developing into heavy pencil lines and at
others fading away to the merest gossamers, only just discernible like
cobwebs stretched across the face of the planet.
Although the individual constituent lines vary in aspect and never rise
at their most to cognizable breadth, the distance parting their
centres, or the width of the double, is quite measurable. The only
difficulty in the way of its determination lies in the absence of a
procurable unit small enough to mete it. The usual spider-threads of
the micrometer are colossal in comparison with these filaments and
present a standard only analogic at best. Nevertheless, by means of the
finest threads that could be got, estimates of the distance between the
pairs were made at Flagstaff in 1905, and the results agree as closely
as the means permit with those got by measurement of the doubles as
depicted in the drawings.
[Illustration: Martian doubles.]
Of what they look like, the following illustrations give a fair idea,
only that instead of being more geometrically regular in the drawing
than in reality the fact is the other way. Freehand draftsmanship at
the telescope is incapable of rendering their ruled effect. No railway
metals could be laid down with more precision. As to their size, the
following figures derived from a typical double canal, the Phison, give
some conception. This great artery of intercommunication between the
Sabaeus Sinus and the Nilosyrtis is, roughly speaking, 2250 miles long;
the distance between the centres of the two constituents is about 130
miles, and each line is perhaps 20 miles in breadth, when at its
maximum strength. The pair follow, apparently, the arc of a great
circle from the Portus Sigaeus on the Mare Icarium to the Pseboas Lucus
in latitude 40° north. The Portus Sigaeus consists of two little nicks
in the coastline, looking like the carets one makes in checking off
items down a list, if the space between the down and up strokes were
then filled in; the Pseboas Lucus, on the other hand, is a large round
dot like a small ink spot. To these two differently appearing spots,
the twin lines of the Phison behave differently. While each line leaves
centrally its own caret of the Portus Sigaeus at the south, at the
north each touches peripherally the Pseboas Lucus, on the east and west
sides respectively, the two thus just holding the Lucus between them.
In position the lines are invariable, though in visibility not.
Sometimes only one is seen, sometimes both show faintly, and sometimes
both are conspicuously strong. The delicacy of the observations by
which this detail was established is second only to its importance. It
destroys at a stroke all possibility of diplopic unreality, since were
that the fact the Pseboas Lucus should be doubled, which it is not. At
the same time it opens vistas into the true construction of the things
themselves, at present more suggestive than satisfactory.
[Illustration: Martian doubles (corroborating the above).]
In the great circle character of its course the Phison is quite normal.
The majority of the double canals pursue the like method, running
straight over the surface from one point to another, the constituents
remaining equidistant throughout. But such forthrightness of direction,
though the rule, is not without exceptions. The Thoth-Nepenthes, for
example, sweeps round in a seemingly continuous curve to the
west-southwest from the Aquae Calidae to the Lucus Moeris like some
mighty bow perpetually bent. Nevertheless its lines are no less careful
for all their curving to keep their distance from one end to the other
of their course. The quality of being paired rises superior to change
of direction.
II
Now, the first point to be noticed about the doubles is that
bilateralism, or the quality of being double, is not a universal trait
of the canals, either actually or potentially; it is not even a general
one. Out of the four hundred canals seen at Flagstaff, only fifty-one
have at any time displayed the quality; that is, one eighth roughly of
the whole number observed. This point is most important; for the fact
is of itself enough to disprove any optical origin for the phenomenon.
The characteristic of doubling so confidently ascribed by those who
have not seen it to general optical or ocular principles proves thus
the exception, not the rule, with the canals, and by so doing disowns
the applicability of any merely optical solution. We shall encounter
many more equally prohibitive bars to illusory explanation before we
have done with the doubles, but it is interesting to meet one in this
manner at the very threshold of the subject.
On the other hand, the characteristic when possessed is persistent in
the particular canal, _in posse_ if not _in esse_. Once shown by a
canal, that canal may confidently be looked to at a proper time to
disclose it again. In short, bilateralism, or the state of being dual,
is an inherent attribute of the individual canal, as idiosyncratic to
it as position and size.
The catalogue of canals possessing this property, so far as they have
been detected at Flagstaff to date, number fifty-one if we include in
the list wide parallels like the Nilokeras I and II. Eight of these
were observed in 1894; nineteen more were added in 1896, making
twenty-seven; in 1901 the total was raised to thirty; in 1903 to
forty-eight; and in 1905 to fifty-one. Arranged by years they are
tabulated below, where the numeral to the left registers for each its
first recording and the position held by it in the list. The starred
canals much exceed the others in width, and possibly denote a different
phenomenon.
DATE CONFUSED
1894
1. Ganges
2. Nectar
3. Euphrates
4. [*]Nilokeras I and II
5. Phison
6. Asopus
7. Jamuna
8. Typhon
1896-7
Ganges Typhon
Euphrates Avernus S.
Phison
9. Lethes
Jamuna
10. Dis S.
11. Titan
12. Laestrygon
13. Tartarus
14. Cocytus
15. Sitacus
16. Amenthes
17. Adamas
18. Cerberus N.
19. Cerberus S.
20. Cyclops
21. Gelbes
22. Erebus
23. Avernus N.
24. Gigas
25. Alander
26. Gihon
27. Hiddekel
1900-1
Phison Dis S.
Euphrates Boreas
Hiddekel Cerberus S.
Amenthes Jamuna
Cerberus N. Pyramus
Cyclops Laestrygon
Ganges
28. Deuteronilus
Sitacus
Adamas
29. Djihoun
Gihon
30. Is
1903
Djihoun Typhon
Hiddekel Orontes
Phison
Euphrates
31. Protonilus
Gihon
32. Marsias
Amenthes
Laestrygon
Cyclops
Gigas
*Nilokeras I and II
Ganges
Deuteronilus
33. Pierius
34. Callirrhoe
Jamuna
Sitacus
35. Astaboras S.
36. Nar
37. Chaos
38. Aethiops
39. Hyblaeus
40. Eunostos
41. Thoth
42. Nepenthes
43. Triton
44. Pyramus
45. Fretum Anian
46. Vexillum
Lethes
Cerberus S.
47. Nilokeras I
Cerberus N.
48. Tithonius
1905
Nilokeras Ganges
Hiddekel Chrysorrhoas
Djihoun
Sitacus
Phison
Euphrates
Amenthes
Vexillum
Astaboras S.
Adamas
Cyclops
Cerberus S.
Cerberus N.
Tartarus
49. [*]Propontis
Gigas
Gihon
Nepenthes
Thoth
Laestrygon
50. Polyphemus
Deuteronilus
Triton
Eunostos
Tithonius
Callirrhoe
Pyramus
Nar
Protonilus
51. Naarmalcha
In spite of possessing the property of pairing, a canal may not always
exhibit it. To the production of the phenomenon the proper time is as
essential as the property itself. So far as a primary scanning or first
approximation is capable of revealing, a canal will be single at one
Martian season and double at another. Thus these canals alternated in
their state to Schiaparelli and for the earlier of his own observed
oppositions to the writer. In consequence Schiaparelli deemed
gemination a process which the canal periodically underwent. Three
stages in the development were to him distinguishable: the single
aspect, a short confused aspect, and the clearly dual one.
In the single state the canal remained most of the time. It then
underwent a chrysalid stage of confusion to emerge of a sudden into a
perfect pair. Furthermore, he noted the times at which the pairing took
place, to the formulating of a law in the case—derived from the
observations of more than one opposition. His law was that the
gemination occurred, on the average, three months (ours) after the
summer solstice of the northern hemisphere, lasted four to five months,
then faded out to begin afresh one month after the vernal equinox of
the same hemisphere and continue for four months more. Expressed in
Martian seasonal chronology, the periods would be about half as long.
At certain times then the most pronounced specimens of doubles showed
obstinately single, while the periodic metamorphosis that transformed
them into duplicates was timed to the changes of the planet’s year.
Gemination, then, was a seasonal phenomenon.
Advance in our knowledge of the phenomenon since Schiaparelli’s time,
while still showing the thing to be of seasonal habit, has changed our
conception of it. It now appears that in some cases certainly, and
possibly in all, the dual aspect is not a temporary condition, but the
differing pronouncement of a permanent state, the fact of gemination so
called being confined to a filling out of what is always skeletonly
there. As the canals have come to be better seen, the three stages of
existence have in some cases become recognizable as only different
degrees in discernment of an essential double condition; the single
appearance being due to the relative feebleness of one of the
constituents and the confused showing to the weakness of both, which
are then the more easily blurred by the air waves. In certain canals
the last few oppositions, 1901, 1903, and 1905, have disclosed this
unmistakably to be the case, as with the Phison and Euphrates, for
example. With them the double character has been continuously visible,
appearing not only when by Schiaparelli’s law it should, but at the
times when it should not; only on these latter occasions it was harder
to see, whence the reason it was previously missed. So that further
scrutiny, while in no sense discrediting the earlier observations, has
extended to them some modification, and disclosed the underlying truth
to be the varying visibility, the thing itself, except for strength in
part or whole, persisting the same. Improvement in definition has
lowered the see-level to revelation of continuous presence of the dual
state. It is only on occasion that the improvement is sufficient for
the thing when at its feeblest to loom thus above the horizon of
certainty; yet at such moments of a rise in the seeing it is enough to
allow it to be glimpsed. Thus it fared with the Adamas at the
opposition of 1903, with the Gigas, and with many another in years gone
by. Separation has come with training and generally in the case of the
wider doubles, which leads one to infer that ease of resolution is
largely responsible for assurance of the permanency of the dual state.
Perplexing exceptions, however, remain, so that it is possible at
present only to predicate the principal of most of the double canals
but not of all. Leaving the exceptions out of account for the moment,
we pass to those general characteristics which are intimately linked
with what has just been said.
Inasmuch as the act of getting into a state antedates the fact of being
there, it is logical to let the description of the first precede. An
account of the process of gemination may thus suitably come before that
of its result.
Flux, affecting the double canals in whole or part, is the cause of the
apparent gemination. According as the flux is partitive or total is a
single or a dual state produced. At the depth of its inconspicuousness
the canal may cease to be visible at all; this occurs when both lines
fade out. On the other hand, the one line may outfade the other, and we
are presented with a seemingly single canal, at this its minimum
showing. In such seasons of debility the one line may appear and the
other not, or occasionally the other show and the one not, according to
the air waves of the moment. It is at these times that the double
simulates a single canal, and unless well seen and carefully watched
might easily masquerade successfully as such. The Hiddekel in the depth
of its dead season is peculiarly given to this alternately partitive
presentation. As the flux comes on, one or both lines feel it. If one
only we are likely to have a confused canal; if both, a difficult
double. The strength of the lines increases until at last both attain
their maximum, and the canal stands revealed an unmistakable pair, the
two lines paralleling one another in appearance as in position.
At the canal’s maximum and minimum the equality of its two constituents
is chiefly to be remarked, though it occurs on other occasions as well.
But, what is significant, when the two differ it is always the same one
that outdoes its fellow. It may be the right-hand twin in one pair, the
left-hand one in another; but whichever it be, for the particular canal
its preëminence is invariable. It is this canal which, except for
adventitious help or hindrance from the air-waves, alone shows when the
double assumes the seemingly single state. We may therefore call it the
original canal, the other being dubbed the duplicate. In some cases it
has been possible to decide which is which. It might seem at first
sight as if this point should always be ascertainable. But the
determination is more dilemmic than appears, not from any difficulty in
seeing the canal, but from the absence of distinguishing earmark at its
end. In a long stretch of commonplace coast, the precise point of
embouchure of a solitary canal cannot be so certainly fixed as to be
decisive later between two which show close together in the same
locality. It is only where some landmark points the canal’s terminal
that the problem admits of definite solution. This telltale tag may be
a bay like the Margaritifer Sinus, or double gulfs like the Sabaeus
Sinus, or portions of a marking not too large to permit of partitive
location like the Mare Acidalium, or a canal connection like the
Tacazze which prolongs the one line and not the other. In these and
similar instances the two lines become capable of identification, and
in such manner have been found those comprised in the following list:—
===================+===================+================
| | DATE OF
DOUBLE CANAL | ORIGINAL LINE | ASCERTAINMENT
-------------------+-------------------+----------------
Phison | The Eastern | 1894
Euphrates | The Western | 1894
Titan | The Western | 1896
Hiddekel | The Eastern | 1896
Gihon | The Western | 1896
Gigas | The Northwestern | 1896
Djihoun | The Western | 1901
Laestrygon | The Eastern | 1903
Nilokeras I and II | The Northern | 1903
Astaboras | The Southern | 1903
Jamuna | The Eastern | 1905
Ganges | The Western | 1905
===================+===================+================
In this list of originals the canals stand chronologically marshaled
according to date of detection. The Phison and Euphrates were the first
to permit of intertwin identification in 1894, while the Jamuna and
Ganges were the last to be added to the column in 1905. The list is not
long, though the time taken to compile it was. In the case of the
Ganges and the Jamuna, for example, although suspected for some time on
theoretic grounds, it was only at the opposition just passed that the
fact was observationally established. In his _Memoria_ V, Schiaparelli
has a list of similar detection, and if the present list be compared
with his, the two having been independently made, the concordance of
the result will prove striking, corroborative as it is of both. For the
necessary observations are very difficult.
Having thus realized the original by means of its superior showing, and
then identified it by its position, it is suggestive to discover that
the duplicate betrays its subordinate character, not only by its
relative insignificance, but by its secondary position as well. The
original always takes its departure from some well-marked bay,
seemingly designated by nature as a departure-point, or from a caret
belonging clearly to itself; the adjunct, on the other hand, leaves
from some neighboring undistinguished spot, as in the case of the
additional Djihoun, or makes use of a neighbor’s caret, as in the case
of the second Phison and the supplementary Euphrates. In either case it
plays something of the part of an afterthought; and yet the postscript
when finished reads as an integral part of the letter. An example will
serve to make the connection evident while leaving the character of the
connection as cryptic as ever.
In the long stretch of Aerial coastline bounding the Mare Icarium,
which sweeps with the curve of a foretime beach from the Hammonis Cornu
to the tip of the Edom Promontory, there stand halfway down its
far-away seeming sea-front two little nicks or indentations. Even in
poor seeing they serve to darken this part of the coast while in good
definition they come out as miniature caret-like bays. They are the
Portus Sigaei, and mark the spots where the Phison and the Euphrates
respectively leave the coast. About four degrees apart, the eastern
makes embouchure to the original Phison, the western to the original
Euphrates, and each in some mysterious manner is associated not only in
position but in action with the canal itself. In the single state each
canal leaves the Mare from this its own caret, the Phison proceeding
thence northeast down the disk, the Euphrates nearly due north, so that
starting four degrees apart at the south they are forty degrees asunder
at their northern termini. Clearly at these latter points they are not
even neighbors, and except for the accident of close approach at their
other ends have nothing in common anywhere. And yet when gemination
takes place a curious thing occurs: each borrows its neighbor’s
terminal as departure-point for its own duplicate canal. Having thus
got its base the replica proceeds to parallel its own original canal
without the least reference to the other canal whose own caret it has
so cuckoo-wise appropriated. What the Phison thus does to the
Euphrates, the Euphrates returns the compliment by doing to the Phison.
In this manner is produced an interrelation which suggests, without
necessarily being, an original community of interest; suggests it on
its face and yet appears to be rather of the nature of an adaptation to
subsequent purposes of a something aboriginally there.
[Illustration: _Mouths of Euphrates and Phison._
_June. 1903._]
That such latter-day appropriation is the fact is clearly hinted by the
behavior of another understudy of an original canal, in this case the
duplicate of the Djihoun, which in consequence of the position of its
original finds no neighboring embouchure already convenient to its use.
The single or original Djihoun leaves the tip of the needle-pointed
Margaritifer Sinus, which serves a like end to the Oxus and the Indus,
both single canals. The Sinus is itself a single bay, and so large that
for many degrees its shores on both sides converge smoothly to their
sharp apex. Because of this probably, the coast in the immediate
neighborhood is without canal connection, no canal being known along
either side till one reaches the Hydraotes at the Aromaticum
Promontorium, which marks the western limit of the gulf. The
consequence is that when the Djihoun doubles, the duplicate canal, not
having any terminus ready to its hand, has to make one for itself by
simply running into the Margaritifer Sinus, some distance up its
eastern side. It thus advertises its adjunctival character, and at the
same time the general fact that a neighbor’s terminus, though used from
preference, when convenient, is not an essential in the process.
Gemination occurs of its own initiative, but is conditioned by
convenience.
Whether one canal shows thus to the exclusion of the other, or whether
both stand so confused as not to be told apart, the fact remains that
the double is not always recognizable as such. If we turn to the list
of the doubles on page 222, we shall note that the same canals were not
always seen in the dual condition at successive oppositions. Some,
indeed, are so emphatically of the habit as to appear year after year
in a paired state, but others are not so constant to their
possibilities. Now, when it is remembered that at different oppositions
we view Mars at diverse seasons of its tropical year, we see that this
means that the phenomenon is seasonal; and furthermore that its
exhibition depends upon the canal’s position. Gemination, like the
showing or non-showing of the single canal, is conditioned by the place
of the canal upon the planet.
III
Turning from such generic characteristics to more specific traits, the
first thing to strike an attentive observer is that the doubles differ
in width; that they are not mensurably alike in the property they hold
in common of being paired. In some the twin lines are obviously farther
apart than in others, and the relation persists however repeated the
observations. Of two doubles the one will always surpass its fellow.
This contrasted individuality first struck me in the Phison and the
Euphrates; and from the first moment at which these doubles showed as
such. The Phison pair seemed perceptibly the narrower of the two. A
like distinction was evident at the next opposition and the next; in
fact, at every succeeding one to the present day. Nor was the
recognition of the fact confined to me. If we turn to Schiaparelli’s
Memoriae we shall find that that master had registered the same
idiomatic width for the two canals from first to last throughout his
long series of records. The observation thus made proved to apply to
each and all of these curious twins.
Diversity in width for different doubles appears plainly in drawings
where more than one double is depicted. As an example, two drawings are
here given in the text, made, the one on July 13, 1905, λ15°, and the
other on July 20, λ313°. In them the Phison, Euphrates, Djihoun, and
Thoth appear contrasted as unmistakably as either of them does with the
single canals apparent at the same time. That this drawing is typical
is borne out by all the best measures of the several doubles as seen at
successive oppositions, and marshaled in the subjoined list. How truly
individual the quality is stands proved by the relative values in
different years which are even more accordant than the absolute ones.
The canals were:—
=======================+=====================
| WIDTH
+------+-------+------
| 1903 | 1905 | MEAN
-----------------------+------+-------+------
1. Phison | 3.5 | 3.4 | 3.4
2. Euphrates | 4.0 | 4.2 | 4.1
3. [*]Protonilus | 2.8 | 2.0 | 2.4
4. Deuteronilus | 2.2 | 2.4 | 2.3
5. Pierius | 2.5 | -- | 2.5
6. Callirrhoe | 2.5 |[*]2.1 | 2.3
7. [*]Hiddekel | 3.8 | 4.9 | 4.3
8. [*]Gihon | 3.9 | 4.9 | 4.4
9. Djihoun | 2.0 | 1.9 | 1.9
10. Sitacus | 3.8 |[*]3.3 | 3.6
11. Jamuna | 4.5 | -- | 4.5
12. Ganges | 5.0 | 5.2 | 5.1
13. Nilokeras I and II | 11.0 | 11.7 | 11.3
14. Nilokeras I | 2.3 | -- | 2.3
15. Gigas | 3.5 | -- | 3.5
16. Laestrygon | 2.2 | -- | 2.2
17. Cerberus N. | 4.0 | -- | 4.0
18. Cerberus S. | 4.0 | -- | 4.0
19. Cyclops | 2.9 |[*]2.2 | 2.6
20. Nar | 2.6 | 2.0 | 2.3
21. Fretum Anian | 2.8 | -- | 2.8
22. Aethiops | 3.3 | -- | 3.3
23. Eunostos | 2.8 | -- | 2.8
24. Lethes | 2.9 | -- | 2.9
25. Marsias | 3.2 | -- | 3.2
26. Hyblaeus | 3.0 | -- | 3.0
27. Amenthes | 3.2 | 3.5 | 3.3
28. Thoth | 2.8 | 2.3 | 2.5
29. Nepenthes | 2.8 | 2.3 | 2.5
30. Triton | 2.7 |[*]2.3 | 2.5
31. Pyramus | 2.9 |[*]2.0 | 2.5
32. Astaboras S. | 3.2 | 3.1 | 3.1
33. Tithonius | 2.6 | 2.2 | 2.4
34. Vexillum | 3.5 | 2.9 | 3.2
35. Tartarus | -- | 2.7 | 2.7
=======================+======+=======+======
[*] Poor.
Here we have widths ranging from eleven degrees to two. The widths
given are those when the canal was at or sufficiently near its full
strength, and are measured from the centres of the constituents. We
notice two points: the agreement of the same canal with itself and its
systematic disagreement with others. But what is especially to the
point, if we compare the values found at successive oppositions, we
find that for different canals the values agree in their difference.
This shows that each of these values is, in most cases if not in all, a
norm for that particular canal; a value distinctive of it and to which
it either absolutely or relatively conforms. In other words, the width
of the gemination is a personal peculiarity of the particular canal, as
much an idiosyncrasy of it as its position on the planet.
Two general classes may be distinguished; those up to about five
degrees in width apart and those above this figure. Whether such very
widely separated lines as go to make up the second class, such as the
Nilokeras I and II, constitutes a double is a debatable point.
Schiaparelli thought they did, and so classed them. To me it did not at
first occur so to consider them, and in some instances, such as the
Helicon I and II, later observations seem to justify the omission. With
the Nilokeras I and II the outcome seems the other way. The reasons for
distrust of a physical relation between the constituents is not so much
the distance separating them, nor any lack of parallelism, as the
self-sufficient manner in which they show alone. Even this, however,
tends to be recognized in the narrower pairs as they come to be better
seen. It may be that width alone is wholly competent to selective
showing. For the farther apart two lines are on the planet, the more
opportunity is afforded the air waves to disclose the one without the
other, a relative revelation which is constantly happening to detail in
different parts of the disk. As long as any doubt exists of a physical
community of interest, it seems best to distinguish such possibly
merely parallel canals by suffixed numerals.
Of this class of doubles is the Nilokeras I and II. So wide is it that
Mr. Lampland succeeded in photographing it as such, the two
constituents showing well separated, and if it prove a true double it
will be the first Martian double to leave its impress on a sensitive
plate. Although separated by four hundred miles of territory, the two
lines are parallel so far as observation can detect, which, of course,
is not so very easy with the lines so far apart. In the country between
one crosswise canal certainly lies, the Phryxus, and much shading thus
far unaccounted for. Recent discoveries, however, point to the cause of
such shading as lines imperfectly seen. For in some cases the lines
have actually disclosed themselves, and warrant us in believing that it
is only imperfect seeing that keeps the others hid. Of the pair the
Nilokeras I is itself double, curiously reproducing what sometimes is
seen in the case of double stars, one of whose components turns out to
be itself a binary. The second line of the Nilokeras I lies close to
its primary on the north, and was on the only occasion of its detection
the merest of gossamers, while the Nilokeras I itself stood out strong
and dark. Thus do these Martian details increase and multiply in
intricacy the better the seeing brings them out.
In the case of the other doubles, the doubles proper so to speak, there
is every indication of a physical bond between the pair. What that bond
may be is another matter and seems to be of different divulging,
according to the particular instance. At one end of the subject, both
as the widest of these doubles and one of the most important, stands
the Ganges. The components of the canal are 5°.1 apart. This great
width, joined to the fact of scant extension, gives the canal a stocky
aspect, its breadth being but one sixth of its length. Its width draws
attention to it while the phenomena it exhibits intrigue curiosity.
As early as the first opposition of my observations in 1894, the canal,
as it underwent the process of doubling, showed phases of peculiarity.
It was first caught by me as a double over toward the terminator, or
fading edge of the disk; then as it was brought nearer the centre by
the gaining upon the longitudes, showed as a broad swath of shading of
a width apparently equal to any it later exhibited. In this appearance
it continued for some months, and then in October began to show a
clarification toward the centre. Once started, the lightening of its
midway advanced till at last, on November 13, it stood out an
unmistakable double, the two lines standing where the edges of the
swath had previously been. Had the observations here been all that one
could wish, the method of gemination would have been certain and of
great interest. Unfortunately, the observations left much to be
desired, and those repeated in 1896-1897 and 1901 were of like
doubtfulness. A period of swarthy confusion preceded the plainly dual
state, but whether the double simply clarified or widened as well it
was not possible to assure one’s self. That the canal exhibited plainly
the effects of seasonal development was as unmistakable as the steps
themselves were open to ambiguity. In 1903 the canal was at its minimum
and hardly to be made out. It seemed then to show an actual change in
width coincident with alteration of visibility. But this, too, could
not be predicated with certainty. It was also surmisable that the
westernmost line was the one from which the development proceeded.
In 1905 much more was made out about it, training in the subject and
increased proximity of the planet contributing to the result. It now
became clear to me that the canal did develop from the western side;
for the western edge made a dark line of definite boundary from which
shading proceeded to the eastern side, where it faded almost
imperceptibly off with no defined line to mark its limit. That this
shading gradually darkened was evident, but that when it could be seen
at all it extended to the extreme limit of the eventual double,
restricted the character if not the fact of an actual widening. At this
opposition, too, the canal passed through its period of minimum
visibility and was then seen, whenever it could be caught, as a
confused swath of full width. In the case of this canal, then, a
widening in the sense of a bodily separation of two lines seems
inadmissible. On the other hand, the gradual darkening of the swath,
and especially the advance of the darkening from the western side,
points to an interesting process there taking place.
[Illustration: Peculiar development of the Ganges.]
At the opposite end of the series stands the Djihoun. As the Ganges is
the widest of the instantly impressive doubles, so the Djihoun is the
narrowest the eye has so far been able to make out. Only two fifths of
the width of the Ganges pair, this slender double is very nearly at the
limit of resolvability. So well proportioned are its lines to the space
between them, however, that in ease of recognition it surpasses many
wider pairs. In form, too, it is distinctive, turning by a graceful
curve the trend of the Margaritifer Sinus into the Lucus Ismenius. With
its fundamental branch—the northern of the two—it joins what is
evidently the main line of the Protonilus—also the northern one—to
the Margaritifer Sinus’s tip.
[Illustration: Djihoun, the narrowest double.]
It differs from the Ganges in some other important particulars besides
width. In its case no band of shading distinguishes it at any time. It
has always been two lines whenever it has been seen other than as a
single penciling; the only confusion about it being evidently our own
atmosphere’s affair. These two lines, furthermore, have showed, within
the errors of observation, always the same distance apart. So that not
only no change of intercommunication between the lines but no change in
their places apparently occurs.
Between these extremes in width, two hundred miles more or less for the
Ganges and seventy-five miles for the Djihoun, the distance parting the
pairs of most of the double canals lies. From 3° to 3°.2 on the planet
may be taken as that of the average; the degrees denoting latitudinal
ones on the surface of Mars, the length of which is equal to
thirty-seven of our English statute miles.
Most of the canals conform apparently to the type of the Djihoun rather
than to that of the Ganges. Careful consideration of them fails to find
any increase or decrease of distance, between the pairs of the same
canal at different times, which cannot be referred to errors inevitable
to observation of such minute detail. In short, the double is made by
the addition of a second line in a particular position and not by a
growth out to it of a line coincident to begin with with the first.
I have said that the average width between the two lines of the doubles
was about 3°. It must not be supposed that this average width denotes
anything more than an average; or, in other words, that it denotes
anything in the nature of a norm. The remark is important in view of a
suggestion which I have heard made that we have here a system based on
fundamental Martian units, in which, or in multiples of which, the
dimensions of the canals are implicitly expressed. Such, however, does
not seem to be the case. In some instances, indeed, we have certain
evidence to the contrary and that the width of the double is
conditioned solely by antecedent place. The Phison and Euphrates offer
a case in point. These two important arteries in duplicate leave, as we
saw, from two carets in the Mare Icarium, the Portus Sigaei, held in
common tenancy by both. Each pair then proceeds down the disk inclined
at its own particular angle to the meridian in order to reach by a
great circle course a certain spot; the Pseboas Lucus in one case, the
Luci Ismenii in the other. As one of these angles is thirty-five
degrees while the other is only three, they must, from the
circumstances of their setting out, have not only different widths, but
widths determinately different in advance, since each is, roughly
speaking, foreshortened by the degree of divergence from the meridian.
The one, therefore, must be about four degrees to the other’s something
less than three and a half. This is what they actually are as
determined by measurement from observation. That the calculated value
agrees with that found from observation helps certify to a community of
starting-points, but it completely does away with comprehensive design
in the question of their widths. For if the one were so settled, the
other could not be.
Indeed, the next example seems to deny it to both. This example occurs,
too, not far away from the scene of the first, in the twin bays of the
Sabaeus Sinus, from which depart, _mutatis mutandis_, the double
Hiddekel and the two Gihon. These twin gulfs bear so little imprint of
being other than natural formations, that they have been universally
and very likely quite rightly taken for such ever since Dawes
discovered them in 1859, long before things like canals were dreamed
of. It is strange that when the Hiddekel and the Gihon were found by me
to be double in 1897, with a branch of both leading from each bay, the
connection between the sceptically scouted doubles and the thoroughly
believed-in bays should have been apparent. For to link a ghost to
materiality, if it does not discredit the materiality, serves to
substantialize the ghost. Furthermore, it shows that in this case
neither the one double nor the other can have had its width engineered
on any preconceived scale, unless the twin bays be themselves so
accounted for. So that it seems useless to seek for cryptic standards
in the canals or to think to find them a measure of value from the fact
of their being a medium of exchange.
[Illustration: The Sabaeus Sinus, embouchure for the double Hiddekel
and Gihon.]
A third instance of the same thing in the case of the Ganges and the
Jamuna was proved at the last opposition after having long been
suspected without my being able to make sure of it. These instances,
taken in connection with the wide range of values in the widths
presented by different canals, serve to show that the distance between
the twin lines is an individual characteristic of the particular canal,
and further to point to its cause, in some cases certainly and possibly
in all, as topographical. The duplicate line makes a convenience of a
neighbor, and suits its distance from its fellow to friendly
feasibility. To cut a ‘canal’ to conform to the country seems logical
if not obligatory, and quite in keeping with the nomenclature of the
subject; but here the starting-point appears to be the only thing
considered—the canal once safely launched being left to shift, or
rather not shift, for itself.
IV
Topography thus introduced to our notice for its effect on the breadth
of the doubles proves upon inspection to be of extended application to
the whole subject. Examined for position these canals turn out to have
something to say for themselves bearing on the question of their origin
and office.
With regard to position, probably the first query to suggest itself to
an investigator to ask is of the direction in which they run. Is there
a preponderance manifest in them for one direction over another? Do
they show an inclination to the vertical, to the horizontal, or to some
tilt between? To answer this we may box the compass, and taking the
four cardinal points with the twelve next most important points between
for sectional division segregate the doubles according to their
individual trend. As we have no means of determining in which sense any
direction is to be taken,—if indeed it is not to be taken alternately
in each,—we get eight compartments into one or the other of which all
the doubles must fall. This they do in the following manner:—
S. & N., Laestrygon, [+]Fretum Anian, Aethiops, Amenthes,
Titan, [+]Dis, [+]Is 7
S. S. E. & N. N. W., [+]Gihon, Ganges, [++]Tithonius, Euphrates,
Adamas 5
S. E. & N. W., [+]Eunostos, Triton, Tartarus, Naarmalcha 4
E. S. E. & W. N. W., [+]Astaboras, Typhon, [+]Pierius 3
E. & W., [+]Nar, [+]Protonilus, [*]Propontis, [++]Nectar,
[+]Cocytus, [+]Chaos 6
E. N. E. & W. S. W. [+]Deuteronilus, [+]Callirrhoe, [+]Cerberus N.,
Cerberus S., [+]Sitacus, [+]Erebus 6
N. E. & S. W., [+]Djihoun, [*]Nilokeras I & II, [+]Avernus,
[+]Nepenthes, Gigas, [+]Alander, Polyphemus, [+]Gelbes,
[+]Marsias, [+]Pyramus, [+]Nilokeras I, Asopus 12
N. N. E. & S. S. W., Jamuna, Phison, [+]Hyblaeus, Cyclops,
Lethes, [+]Thoth, [+]Vexillum, [+]Hiddekel 8
--
51
[*] Wide canals.
[+] Northern hemisphere exclusively.
[++] Southern hemisphere exclusively.
No conclusively marked preponderance for one direction over another
manifests itself by this partitionment. Nevertheless, a certain trend
to the east of north, as against the west of north, is discernible.
More than twice as many doubles run northeast and southwest or within
forty-five degrees of this as do similarly northwest and southeast,
there being twelve of the latter and twenty-six of the former. That
this seems to mean something the nearly equal pairing of quadrantal
points goes to show. Thus:—
N. & S. and E. & W. inclined canals number 7 + 6 = 13
N. N. E. & S. S. W. and E. S. E. & W. N. W. inclined
canals number 8 + 3 = 11
N. E. & S. W. and S. E. & N. W. inclined canals
number 12 + 4 = 16
E. N. E. & W. S. W. and N. N. W. & S. S. E. inclined
canals number 6 + 5 = 11
-- -- --
33 18 51
a fairly equable division in direction. A trend to the westward would
be given a particle descending from the north to the equator by the
planet’s rotation, thus turning it southwesterly; and one to the west
to a particle travelling equatorwards from the south, turning it
northwesterly. As the doubles lie in the northern hemisphere, either in
whole or part, to the extent of 93%, this might account for the
preponderating tilt to the east of north and west of south exhibited by
them. It would correspond with the lines of flow.
To see whether this be so we will take only those double canals that
lie exclusively in the northern and southern hemispheres respectively,
and note those in the former that trend to the west of south as against
those that run to the east of it, and _vice versa_ in the southern. In
the northern the proportion of the westerly to the easterly ones is 17
to 4; in the southern, 1 to 0 the other way.
Of those whose course is common to both hemispheres we find for the
ratio of the southwesterly to the southeasterly 8 to 7. But the
proportion of the course of these canals in the two hemispheres is on
the side of this same ratio.
From their direction we now pass to consideration of their distribution
in longitude. It appears that some meridians are more favored than
others. The hemisphere which has the Syrtis Major for centre is more
prolific in them than its antipodes. From longitude 80° to 200° there
are ten doubles, from 200° to 320° twenty-four, and from 320° to 80°
seventeen; or, roughly, in the proportion of 2, 5, and 3. That this
distribution means anything by itself is doubtful; it is much more
likely to be a general topographical consequence of their distribution
in another direction, which proves to be highly significant and which
we shall now expose—that of latitude.
If we separate the surface into zones, each ten degrees wide, and count
the doubles found traversing in whole or part the several zones, we
find the following arrangement:—
Column Headings:
A = At Opposition of 1903 Alone
B = At All Oppositions so far observed at Flagstaff
===========================================================+=====+=====
Double Canals of Mars | |
arranged according to Latitude | A | B
-----------------------------------------------------------+-----+-----
| |
Between 30° S. and 20° S. Tithonius, Nectar, Laestrygon | 2 | 3
| |
Between 20° S. and 10° S. Jamuna, Ganges, Gigas, | |
Laestrygon, Cyclops, Titan, | |
Tartarus, Polyphemus, Tithonius| 7 | 9
| |
| |
Between 10° S. and 0° Jamuna, Ganges, Gigas, | |
Laestrygon, Cyclops, Cerberus | |
S, Aethiops, Lethes, Amenthes, | |
Triton, Phison, Euphrates, | |
Titan, Tartarus, Adamas, | |
Typhon, Vexillum, Asopus, | |
Naarmalcha, Polyphemus | 15 | 20
| |
Between 0° and 10° N. Gihon, Djihoun, Jamuna, Ganges, | |
Gigas, Laestrygon, Cerberus N, | |
Cyclops, Cerberus S, Eunostos, | |
Aethiops, Lethes, Amenthes, | |
Triton, Nepenthes, Phison, | |
Euphrates, Sitacus, Hiddekel, | |
Tartarus, Adamas, Asopus, | |
Typhon, Vexillum, Cocytus, Is, | |
Avernus N, Naarmalcha, | |
Polyphemus | 21 | 29
| |
Between 10° N. and 20° N. Gihon, Djihoun, Jamuna, Nilokeras| |
I and II[4], Nilokeras I, Ganges,| |
Gigas, Eunostos, Aethiops, | |
Lethes, Amenthes, Thoth, | |
Astaboras, Phison, Sitacus, | |
Euphrates, Hiddekel, Adamas, | |
Asopus, Gelbes, Avernus N, | |
Erebus, Naarmalcha, Vexillum, | |
Is, Dis | 18 | 26
| |
Between 20° N. and 30° N. Gihon, Djihoun, Jamuna, | |
Nilokeras I & II,[4] | |
Nilokeras I, Alander, Hyblaeus,| |
Lethes, Amenthes, Thoth, | |
Sitacus, Astaboras, Vexillum, | |
Phison, Euphrates, Hiddekel, | |
Adamas, Eunostos, Aethiops, | |
Gelbes, Avernus N, Naarmalcha, | |
Is | 17 | 23
| |
Between 30° N. and 40° N. Deuteronilus, Alander, Nar, | |
Marsias, Fretum Anian, | |
Amenthes, Thoth, Vexillum, | |
Phison, Euphrates, Hiddekel, | |
Adamas, Eunostos, Djihoun, | |
Gihon, Nilokeras I, Chaos, | |
Gelbes, Aethiops, Naarmalcha | 12 | 20
| |
Between 40° N. and 50° N. Fretum Anian, Pyramus, | |
Protonilus, Propontis[4] | 3 | 4
| |
Between 50° N. and 60° N. Callirrhoe, Fretum Anian, | 3 | 3
Pierius | |
| |
Between 60° N. and 63° N. Pierius, Callirrhoe | 2 | 2
===========================================================+=====+=====
From this tabulating of them it is apparent that the doubles are
practically confined to the zones within forty degrees of the equator.
Only 7% of them straggle farther north than this, while above 63° north
latitude and 35° south latitude there are none. Such a distribution is
not in proportion to the areas of the zones, which though diminishing
toward the poles do so at no such rate. The surface included between
the equator and 40° of latitude is 65% of the hemisphere, whereas the
fraction of the number of doubles found there is 93%. The doubles are,
then, an equatorial feature of the planet, confined to the tropic and
temperate belts.
To perceive the tropical character of the doubles in another way we
have but to consider the zonal distribution of the single canals.
Unlike the former the latter do not thin out as one advances toward the
poles; since in the arctic regions single canals bemesh the surface as
meticulously as elsewhere. It is only that they there replace the
doubles; or, not to put the cart before the horse, it is the doubles
that in part replace the singles in the tropics. And that this
arrangement has something physical behind it by way of cause is
curiously shown by two canals, the Arnon and the Kison, which are
neither of the one kind nor yet the other, but a cross between the two.
For the Arnon and the Kison are convergent doubles; the two lines of
the Kison leaving a common point at the edge of the polar cap and
separating as they travel south, while the two Arnon take up and
continue the divergence, connecting at last with the parallel pair of
the Euphrates. These canals thus make transition between the true
doubles and the true singles, and may be looked upon as endowed with
the potentialities of both. From their association with the double
Euphrates, it is clear that the transition between the two forms is not
only formal but physical, and that the stopping of the dual condition
at the fortieth parallel is not the outcome of chance.
It may occur to the thoughtful that the doubles appear confined to the
more tropical portions of the planet because of a better presentation
of those zones, the reader supposing the planet to be seen axised
perpendicularly to the plane of sight, as geographies represent the
earth’s globe. The supposition, however, is erroneous. We sometimes see
the planet so, but more often not. Such is the tilt of the Martian axis
to the plane of the Martian ecliptic that the different zones are
rarely seen on an even keel, so to speak, their aspects shifting
totally from one opposition to another. What shows in mid-disk on one
occasion may be forty-eight degrees removed from it at another, a
distance amounting to three-quarters of the way from apparent equator
to apparent pole.
Thus the double canals are for some intrinsic reason equatorial
features of the planet as opposed to polar ones. And this not simply
because of greater space there. Duality is a result of conditions
intrinsic to the several localities. What the cause may be is related
to the character of the things themselves, which we shall later
consider. For the moment we may note that the fact disposes quietly of
the diplopic theory of their manufacture. For, for diplopic doubles to
show such respect for the equator would betoken a courtesy in them to
be commended of Sydney Smith.
But this is not their only geographic bias. In addition to not being
partial to the poles, the double canals show a certain exclusiveness
toward the dark areas generally. Not only do they avoid the arctic and
antarctic zones entirely, but they largely shun the blue-green regions.
In these but two suspicions of doubles occur, in the Aonium Sinus,
although single canals there are as numerous as anywhere else on the
planet.
Nevertheless, although they avoid running through them, they run from
them in a manner that is marked. Proceeding from the great diaphragm
are no less than 28 out of the 53 doubles. Connecting directly with
these are 17 more; while the remaining 8 are also associated through
the intermediarism of dark areas, the Solis Lacus and the Trivium.
In like relation to dark regions, they are limited on the north by the
Mare Acidalium, the Propontis, the Wedge of Casius and their
interconnecting bands, the Pierius, Callirrhoe, Helicon. In this manner
do they form a broad girdle round the planet’s waist, leaving the polar
extremities bare.
-----
Footnote 4:
Very wide and possibly not of the same class.
CHAPTER XIX
CANALS IN THE DARK REGIONS
Seventeen years after the recognition of the canals in the light
regions occurred another important event, the discovery of a similar
set in the dark ones. The detection of these markings in the dark areas
was a more difficult feat than the perceiving of those in the light,
and in consequence was later accomplished. Also was it one where
recognition came by degrees.
I have previously pointed out what this discovery did for the
seas—nothing less than the taking away of their character in a
generally convincing manner. To one who had carefully considered the
matter, the seas had indeed already lost it, as was shown in Chapter X,
but to those who had not these canals presented a very instant proof of
the fact.
From such not wholly supererogatory service they went on to furnish
unlooked-for help in other directions. Their discovery showed in the
first place that no part of the planet’s surface was free from canal
triangulation.
But it did more than this. For these canals in the dark regions left
the edge of the ‘continents’ at the very points where the canals of the
light regions entered them, which fact proved for them a community of
interest with the latter. Such continuation was highly significant,
since it linked the two together into a single system, compassing the
whole surface of the planet. Starting from the places where the
light-region canals come out upon the great girdle of seas that
stretches all round the planet, most of the new canals headed toward
the passes between the islands south, as nearly polewards as
circumstances of local topography would permit. In the broader expanses
of the Syrtis Major and the Mare Erythraeum, besides main arteries
others went to spots in their midst after the same fashion as those of
the light regions. These spots differed in no way apparently from their
fellow oases elsewhere. From a spot in the centre of the Syrtis three
great lines thus traveled south: the Dosaron, heading straight up the
Syrtis on the meridian till it struck the northernmost point of Hellas;
the Orosines, inclined more to the right, passing through the dark
channel to the west of that land and so proceeding south; and lastly
the Erymanthus turning eastward till it brought up finally at the
Hesperidum Lucus. Where, on the other hand, the long chain of lighter
land, called by Schiaparelli islands, and stretching from the Solis
Lacus region westward to Hellas, offered only here and there an exit,
the canals made for these exits. The canals in the Mare Sirenum, the
Mare Cimmerium, and the Mare Tyrrhenum struck more or less diagonally
across those seas from their northern termini to the entrances of the
straits between the islands, thus lacing the seas in the way a sail is
rolled to its spar. From the exact manner in which they connected with
the light-region canals they proved the two to be part and parcel of
one system, which in its extension was planet-wide and therefore
proportionately important. Whatever of strange interest the curious
characteristics of the canals themselves suggested was now greatly
increased by this addition; for the solidarity of the phenomenon
affected the cogency of any argument derived from it.
In 1894 only the dark areas of the southern hemisphere were found to be
thus laced with lines. For then so great was the tilt of the planet’s
south pole toward the earth, that while those zones were well displayed
the dark patches of the northern hemisphere were more or less hull-down
over the disk’s northern horizon.
Contrast was the open sesame to their detection. When the _maria_ show
dark, the lines are lost in the sombreness of the background. As the
maria lighten the lines come out. Such was amply witnessed by the
effect in 1894 and 1896. In 1894 I found it impossible to perceive
them, except where the Padargus crossed Atlantis, for the hue of the
_maria_ themselves was then very dark. In 1896, on the other hand, I
saw them without difficulty. What is also of interest: so soon as seen
they appeared small, without haziness or distention.
As the oppositions succeeded one another the northern regions rose into
view, and with their appearance came the detection in them of the same
phenomena. No large dark areas like the diaphragm exist there, but the
smaller patches of blue-green which bestrew them proved to be similarly
meshed. At first canals were evident upon their peripheries, contouring
them about; then the bodies themselves of the patches showed
grid-ironed by lines.
The Mare Acidalium with its adjuncts, the Lucus Niliacus on the south
and the Lacus Hyperboreus on the north, thus stood out in 1901. On a
particularly good evening of definition at the end of May, the Mare
suddenly made background for a sunburst of dark rays, six of them in
all radiating from a point between it and the Lacus Hyperboreus.
Considering how sombre the Mare was at the time, this was as remarkable
a vision as it was striking to see. Although at the moment the sight
was of the nature of a revelation, these lines have been amply verified
since, as the Martian season has proved more propitious.
Similar decipherment has befallen all the other patches of blue-green
in the northern hemisphere; these having shown themselves first
circumscribed and then traversed by canals. Interesting instances were
the Wedge of Casius and the Propontis. These markings, first perceived
years ago as mere patches of shading, then partially resolved by
Schiaparelli, now stood revealed as a perfect network of lines and
spots. So many of both kinds of their detail occupied the ground that
to identify them all was matter of exceeding difficulty. The outcome is
shown in the diagrammatic representations opposite and on page 256.
These drawings disclose better than any description the mass of detail
of which the patches are in reality composed, and serve to convey an
idea of the complexity involved. If the general canal system seems
intricate, here is something which exceeds that as much again.
[Illustration: The Propontis, 1905.]
The extension in this manner of the curious triangulation of the light
areas into and through all the dark areas as well, by thus spreading
the field of its operations over both terranes complexioned so unlike,
greatly increases the cogency of the deduction that this detail is of
later origin than the background upon which it rests. That the mesh of
lines covers not only the ochre stretches of the disk, but the
blue-green parts as well, makes it still more certain that it is not a
simple physical outcome of the fundamental forces that featured the
planet’s face. For in that case it could not with such absolute
impartiality involve both alike. Thus here, again, we find
corroboration by later observations of what earlier ones established.
A last link in the chain of canal sequences remains to be recorded.
Just as the lines in the dark regions continued those in the light, so
they themselves turned out to be similarly prolonged and in no less
suggestive a manner. For when the north polar zone came to be
displayed, canals were evident there, continuing those in the other
zones and running at their northern ends into dark spots at the edge of
the polar cap. Here, then, we have the end of the whole system, or more
properly its origin, in the polar snows. The significance of this will
be seen from other phenomena, to a consideration of which we now
proceed.
CHAPTER XX
OASES
Next to be caught of the details of this most curious network that
meshes the surface of Mars was a set of phenomena stranger even than
the lines; to wit, dark round dots standing at their intersections.
More difficult to make out than the lines, they were in consequence
detected thus later by fifteen years. Once discovered, however, it
became possible to trace their unconscious recognition back in time.
Thus Schiaparelli told the writer in 1895, apropos of those found at
Flagstaff, that he had himself suspected them but could not make sure.
Some of them stand figured in his _Memoria Sesta_ dealing with the
opposition of 1888, but not published till 1899. In such posthumous
recognition, as one may call it, the spots repeated the history of the
canals. For Schiaparelli had himself pointed out a similar preconscious
visioning of the canals in the delicate pencilings of Dawes and the
streaks of Lockyer, Kaiser, and Secchi, now translatable as
representing the Phison, the Euphrates, and half a dozen other canals
imperfectly seen. That both the canals and the oases were thus sketched
before they were seen well enough to be definitely discovered is to an
unprejudiced mind among their strongest credentials to credit.
Nor was Schiaparelli the sole person thus to get proof before letter.
One of their very earliest portrayals appears in a drawing by Otto
Boeddicker, made on December 26, 1881, where the Pseboas Lucus is
clearly represented. In a still more imperfect manner some of the spots
had been adumbrated and their shadows drawn long before that. Thus they
may be deciphered as the cause of patches drawn by Dawes in 1864,
though none of them were in any definite sense detected till 1879, and
only then so ill defined that their true character was not apparent. As
patches they are still commonly seen at observatories where the
observational conditions are not of the best and the study of the
planet not systematically enough pursued to have them disclose their
true shape and size.
The history of their detection is resumed in the experience of the
individual observer. During the course of my own observations I have
had occasion to notice the several stages in recognition of the spots
which have marked their chronologic career. As with the lines, three
stages in the appearance of the spots may be remarked: first, where the
scattering of the rays is so wide that dilution prevents anything from
being seen; second, where the commotion being less the object appears
as a gray patch; and third, where in comparative quiet it condenses
into a black dot. For the two former our own air waves are to blame. In
coursing waves of condensation and rarefaction they spread the image of
the spot as they do that of the canal. Then as the currents calm the
spot shrinks to its normal proportions, and in so doing darkens in
consequence of being less widely diffused. Thus the evolution in
perception which may take place in the course of an hour for a
particular observer represents exactly what has occurred in the person
of the race by the improvement in observational methods and sites.
That the spots, although wider than the canals, remained longer hidden
from human sight, is due to the optico-physic fact that a tenuous line
may be perceived _owing to its length_ when a dot of the same diameter
would be invisible. Summation of impressions is undoubtedly the cause
of this. The mere fact that a row of retinal cones is struck, although
each be but feebly affected, is sufficient to raise the sum total into
the sphere of consciousness.
In the second stage of their visibility, the spots are in danger of
mistake with the smaller true patches of sombre hue which fleck the
northern hemisphere of the planet and from which they differ totally in
kind, totally so far as our present perception goes. Such true patches
consist of a groundwork of shading, upon which, indeed, are superposed
the usual network of lines and spots. Prominent as instances of them
are the Trivium Charontis, the Wedge of Casius, and the Mare Acidalium.
With patches of the sort the spots proper must not be confounded.
Close treading on the heels of the detection of lines athwart the seas
came the recognition of spots there likewise. At the opposition of
1896-1897 the number was added to; and so the tale has been steadily
increased. Their number as found at Flagstaff up to the present time,
that is, to the close of the opposition of 1905, is 186; of which 121
lie in the light regions, 42 in the dark areas of the southern
hemisphere, and 23 in the smaller sombre patches of the northern zones.
From their relationships and behavior it became apparent that the spots
were not lakes but something which answered much more nearly to oases.
Of the spots three kinds may be distinguished: the large, the little,
and the less, if by the latter term it may be permitted to denote what
has but collateral claim to be included and yet demands a certain
recognition. For though not spots like the others, the members of the
third class have certain traits in common with them while differing
radically in others.
To the kind called large belong the greater number of spots so far
found upon the disk. They are large only by comparison with the little.
For they measure according to my latest determinations but seventy-five
or one hundred miles in diameter; on the planet some two degrees
across. Sizable black pin-heads, it is their tone that chiefly catches
the eye, for they are commonly the darkest markings on the disk.
Against the ochre stretches they appear black, and even in the midst of
the dark areas they stand out almost as much contrasted with their
surroundings as these do with the light regions themselves. About a
hundred and forty are now known. Those in the light areas were
discovered first; those in the dark regions being harder to see.
Of this first kind are such spots as the Pseboas Lucus, the Aquae
Calidae, the Lacus Phoenicis, and the Novem Viae; or, in English, the
Grove of Pseboas, the Hot Springs, the Phœnix Lake, and the Nine Ways,
to mention no more. That they bear dissimilar names implies no
dissimilarity in structure. The phenomena are all remarkably alike, and
clearly betoken one and the same class of objects; differing between
themselves at most in size and importance.
In form they all seem to be round. They certainly appear so, and were
it not that retinal images of small areas tend to assume this shape
might implicitly be credited with being what they seem. The reason for
optical circularity probably resides in the shape of the retinal cones
and in their patterning into a mosaic floor. So that unless a
sufficient number of cones be struck the image takes on to
consciousness a roughly circular figure—whether it be so in fact or
not. In the present case, however, they seem to be too well seen for
self-deception of the sort.
The little are distinguished from the large by being pin-points instead
of pin-heads. They are most minute; from fifteen to twenty-five miles
in diameter only. That anything except size distinguishes the two apart
is from their look improbable. In color or rather tone,—for
distinctive color is of such minute objects unpredicable,—they would
seem to be alike. Such is also the case with their distribution and
detail association.
[Illustration: Fons Immortalis, June 19.]
To the second class belong the Fons Juventae,—Schiaparelli’s Fountain
of Youth,—the Fons Immortalis in Elysium in 1905, and the Gygaea
Palus, besides many more. These are all pin-points, just upon the limit
of vision, and noteworthy chiefly for being visible at all. All those
detected so far lie not very distant from the equator, which may or may
not be a matter of accident. It is not one of perception, since this
part of the planet was not the best place for observation at the time
they were discovered. To make out one of these little dots is a
peculiarly pleasing bit of observation, as it requires particularly
good definition. One might almost take them for fly-specks upon the
image did they not move with the disk. They have no perceptible size
and yet are clearly larger in diameter than the canals which run into
them; which proves how very slender the latter must be.
Very early in the detection of the spots it became evident that they
were not scattered haphazard over the surface, but that on the contrary
they were never found except at the meeting-points of the lines. From
this it must not be supposed, as has been done, that the spots are
merely optical reinforcements of the lines at their crossings due to
the more crowded character there of the lines themselves. That they are
not such is demonstrated by the existence of crossings where, either
temporarily or permanently, none appear; which shows that they are far
too well seen for any such illusion about them to be possible. At these
crossings the lines traverse one another without thickening, whether
they be single or double lines. The spots, on the other hand, are much
wider than the lines, giving a beaded look to the threads. In short,
they are the knots to the canal network. All the more important
junctions are characterized by their presence. Such starred junctions
are not confined to the ochre regions; they dot the light and the dark
areas with equal impartiality, thus showing themselves to be
independent of the nature of the ground where large stretches of
country are concerned. On the other hand, they appear to be unusually
numerous in the smaller, isolated, dark areas of the northern
hemisphere, such as the Trivium, the Mare Acidalium, the Propontis, and
the Wedge of Casius. Here they crowd; and one cannot avoid the
inference that their plentifulness in these regions is not due to
chance.
[Illustration: _Utopia regio—1903._]
To the large spots, those of the first class, fall the places of
intersection of the largest and most numerous canals, while the little
spots make termini to fainter lines, ones that bear to them a like
ratio of unimportance. Spots and lines are thus connected not simply in
position but in size. The one is clearly dependent on the other, the
importance of the centre being gauged by the magnitude of its
communications.
From the fact of association we now pass to the manner of it, which is
quite as remarkable. The position of the spot relative to its tributary
canals depends upon the character of the connecting lines. If the canal
be single it runs, so far as may be judged, straight into the middle of
the oasis, or, in other words, the oasis is symmetrically disposed
about its end. This is true of the greater number of the large spots
and of all the little ones, since the latter have as connections only
single canals.
In the case of a double canal arriving at a spot, a different and most
curious dependence is observable. This fact I first noticed in a
general way at the opposition of 1896-1897, the initial appearance of
it being presented on September 30, 1896, by the Coloe Palus and the
Phison. It was again visible in the case of the spots in the Trivium at
the time the canals leading to that place doubled in March, 1897. But
the exact nature of the phenomenon was not fully appreciated till 1903,
when the thing was seen so well as to appear cut on copper plate. It
was this: the spot is exactly embraced between the two arms of the
double canal. It is, moreover, seemingly perfectly round and just fits
in between the parallel lines. The Ascraeus Lucus was the first spot
that showed thus in association with the double Gigas. Others followed
suit in so showing, several specimens presenting themselves so well as
to leave no doubt of the precise connection. The sight presented by
such a spot and its incasing double is a beautiful bit of detail,
perhaps the most beautiful so far to be seen upon the Martian disk. The
distinctness with which it stands out on occasion suggests a steel
engraving, and shows how clear-cut the Martian features really are when
our own air ceases from troubling and allows them to be at rest.
Incidentally, we may note that this phenomenon alone serves to disprove
the diplopic theory of the production of the double canals. For if a
double were a single line seen out of focus, any spot upon it should be
doubled too.
[Illustration: _Ascraeus Lucus and Gigas.—March. 2. 1903._]
It may seem to the reader as if what was seen in 1903 was but an
unimportant advance over the observed phenomena of 1896-1897. Not so,
however. For with the earlier instances it was not possible to be sure
of the precise limits of the spot with regard to the double. The Coloe
Palus, on the one hand, did not fill all the space apparently between
the double Phison; while the Lucus Ismenius more than did so with the
double Euphrates. To have set down the different appearances to
insufficient definition would have been a great mistake, as subsequent
observation has served to show. The Lucus Ismenius instances this. In
1896-1897 it was seen terminating the Euphrates, blocking all the space
between the two lines and extending a little upon either side of them.
Now, from its appearance in 1901 it was evident that the effect had
been produced by twin spots lying along the Deuteronilus, the axis
joining them being perpendicular to the Euphrates. In 1903 the relation
was still better explained by what appeared then, when not only did the
two spots stand out, but the Euphrates showed with a line running
centrally into each.
Although originally seen by Schiaparelli as a single spot and so at
first seen by me, better acquaintance with the disk disclosed to both
observers its really dual character. As this pair has persisted through
all three of the most recent oppositions, it seems fairly certain that
it is always of this character, and more fitting, therefore, to give it
the plural appellative. This is the single instance of a double oasis.
There are many that lie close together and might be taken as such; but
this is the only one where the connection is intrinsic. According to
measures of the drawings of 1905 extending through six presentations,
the distance between the twin oases is 4°.2.
Their relation to the canals which run into them is of the most
complicated description and of the most suggestive character. For to
the twin spots converge no less than seven double canals, one
wedge-shaped pair and three single canals, a most goodly number of
communication lines. Four of the double canals run into the oases with
one line to each; these canals are the Astaboras, the Naarmalcha, the
Euphrates, and the Hiddekel. Three doubles, the Protonilus, the
Djihoun, and the Deuteronilus, embrace the oases between their two
lines, while, in the singles, the canal connects with one or other of
the twins, as the case may be.
Now, there is method as to which of the doubles shall straddle, which
embrace, the two Ismenii. Those which leave the place parallel or
nearly so to the direction joining the Luci, inclose them both; those
of which the setting forth is at an angle to this direction depart,
each line of the pair, from the eastern and the western spot
respectively.
[Illustration: Peculiar association of the Luci Ismenii with double
canals.]
Consider, now, the disposition of these seven pairs of lines. All of
them lie in one semicircle about the Luci, beginning with the
Protonilus on the east and ending with the Deuteronilus on the west.
Furthermore, all follow approximately arcs of great circles, except the
Djihoun, and all send one of their twin lines to one Lucus, one to the
other. The data are enough to make this statement possible. Although
the west line of the Naarmalcha has not been caught entering its oasis,
the east one has been seen to enter the other, and the width of the
double shows that the west one must enter the corresponding spot. In
the case of the Astaboras the double has only been observed as far as
the Vexillum, but the south line has continued on to the west Ismenius,
and here again the width makes it certain that were the canal double
throughout, the other line must enter the east Ismenius. From the base
line of the Proto-Deuteronilus the inclinations of the seven pairs are
as follows:—
Protonilus 0° Due East
Astaboras 40° North of East
Naarmalcha 70° North of East
Euphrates 80° North of West
Hiddekel 55° North of West
Djihoun 0° North of West
Deuteronilus 0° Due West
Now, the width between the two lines of the four canals to the east
increases regularly from the Protonilus round; the Protonilus being the
narrowest double, the Astaboras the next, the Naarmalcha the next, and
the Euphrates the widest. And from the width between the twin oases, it
would seem that they severally enter the centres of them. What takes
place in the case of the Hiddekel, which is wider than its tilt would
imply, and in the Djihoun, which is narrower, is not so clear. But that
they enter the oases in some place is certain.
[Illustration: _Lucus Ismenius. March 1903._]
The spots make common termini for all the canals of a given
neighborhood. In other words, canals converge to the places occupied by
the spots and do not cross haphazard according to the laws of chance.
Only one instance exists where a spot fails to gather to itself the
whole sheaf of canals and even there it collects all but two. This
anomaly is the Pseboas Lucus. The peculiarity of this oasis is that it
lies not on, but just off, the Protonilus. That it does so is exceeding
curious, considering that it is the sole example of such extra-canaline
position. Strictly speaking, it is not the Protonilus but the point
where the Protonilus turns into the Nilosyrtis to which it stands thus
neighboringly aloof. And this may explain the anomaly. For the
Nilosyrtis has not the full geometric regularity of the normal canal,
and seems to have been a more or less fundamental feature of the region.
For the rest, the Lucus has the form and possesses the canal
connections appropriate to its state. It is apparently round, and lies
between the twin lines of the Phison and also between those of the
Vexillum.
Not far from the Pseboas Lucus are to be found all the examples of the
third class of spots; for so far they have not been observed outside of
Aeria, a region peculiarly peopled by double canals. With double canals
they are necessarily associated, inasmuch as they consist of shading in
the form of a square or parallelogram, filling the deltas between two
pairs that cross. Thus have shown the Coloe Palus at the crossing of
the double Phison with the double Astaboras, and the Juturna Fons where
the double Sitacus traverses the double Euphrates.
At these same places a fourth kind is sometimes noticeable: a
four-square set of pin-points or a two-square set of the same at the
corners of the line-made parallelogram. This kind may well be
synchronous with the third, though it has only been noticed at
consecutive presentations. The third, however, has no observed
dependence upon the first or second classes. And this serves to make
more probable the true objectivity of the circular and the square
figures respectively shown by each.
The spots apparent in the dark regions do not appreciably differ in
either size or shape from the bulk of those visible in the light.
Equally with them they seem to be round, small, and nearly black. They
would seem, too, in the great diaphragm—or larger contiguous sombre
region—to be equally plentifully distributed.
CHAPTER XXI
CARETS ON THE BORDERS OF THE GREAT DIAPHRAGM
Functionally related to the canal system, and yet in look and location
contrasted with its other details, is a further set of markings,
detected by me in 1894, and reseen at subsequent oppositions since,
along the north border of the southern seas. They lie upon what used to
be thought the continental coastline, the fringing edge of that almost
continuous band of shading that belts the Martian globe throughout the
southern subtropic zone and called by Schiaparelli the great diaphragm.
The terrane lends itself to the appellative, forming, as it does, a
dark dividing strip of country between the brilliant reddish-ochre
hemisphere on the north and the half-toned islands to the south of it.
By Schiaparelli it was thought to be one long Mediterranean, and though
its marine character is now disproved, that it lies lower than the
bright ochre regions is likely. To this difference of level is probably
due the peculiar phenomenon which there manifested itself to careful
scrutiny in 1894. For it was there only that it occurred.
The phenomenon in question consisted of nicks in the coastline, of
triangular shape and filled with shading. They occurred at intervals
along it and were of the general form of carets, such marks as one
makes in checking items down a list. Their position was always where a
canal debouched from the diaphragm upon its career across the open
continent. The canal itself was by no means necessarily visible. On the
contrary, at first it was usually absent. Such was the case with those
marking the departure-points of the Phison and Euphrates and of the
Amenthes and Lethes, which appeared, without being well defined, from
the moment the planet came to be scanned.
One by one these carets stood out to view, punctuating the points where
canals later were to show or terminating those that already existed.
Strung thus with them at intervals was the whole coastline of the
diaphragm, beginning with the Mare Icarium and stretching round through
the Mare Tyrrhenum, Mare Cimmerium, Mare Sirenum, and Mare Erythraeum
to the Mare Icarium again. As the planet got nearer to the earth their
peculiar shape began to define itself, and it was again in the case of
those giving origin to the Phison and Euphrates that the recognition
came first. What had appeared earlier simply as a spot now stood out as
two triangular notches, indenting the coast and giving exit at their
apices, the eastern one to the Phison, the western to the Euphrates.
These were the things, then, that had constituted the Portus Sigaeus of
Schiaparelli.
Commonly the carets lie at the bottom of well-marked bays, as, for
example, those terminating the Syrtis Minor and the Sinus Titanum. But
frequently they are placed in the very midst of a long and otherwise
unaccented coast, as is the case in mid-course of the Mare Cimmerium
and the Mare Sirenum. Yet in no instance is the thing unassociated with
a canal. In every case one or more canals leave the caret for their
long traverse down the disk.
This is not their only canal connection. When the canals in the dark
regions came to be discovered, each of them was found by me, as nearly
as difficult observations would permit, to be associated with the caret
upon its other side. Thus the lacing of the Mare Cimmerium and Sirenum
used them as its reeving-points. Similarly those at the mouths of the
Phison and Euphrates did duty likewise to the Maesolus and the Ion. In
such manner the carets stood in dual relation to canals; subserving a
purpose to the light-region canals on the one hand and to the
dark-region ones on the other. In a way the caret, then, holds the same
position toward the canals that do the spots in the light or dark
regions. Like them it is a canal-distribution point. Unlike them,
however, in shape it is triangular instead of round, and we are piqued
to inquire to what cause it can owe its different contour. The answer
seems to lie in the character of the locality, not simply in its
complexion. For the spots in both the northern and the southern dark
patches are as circular as those standing in the light, whether they
lie in the centre or upon the edges of them. The edges of the northern
patches, however, and the other sides of the southern ones do not
present the clear-cut character of the northern coast of the diaphragm.
Where they seem to be definitely bounded they are so by darker canals.
This hints that their contours are not defined by antithesis of level,
while that of the northern coast of the great diaphragm is. Difference
of altitude is then concerned in their constitution; the canal system
here falls to a lower level, and these triangular spots instead of
round ones are the result. Topographic only, such explanation leads the
way to a more teleologic one, and serves even on first acquaintance to
stir curiosity to some satisfying cause.
Suggestive in several ways for its resemblance to the carets is another
detail not far distant from the Portus Sigaei, the twin-forked Sabaeus
Sinus. Curiously enough, this feature of Mars, which has been well
known and recognized ever since the eagle-eyed Dawes detected it more
than forty years ago, proves to be a sort of connecting link between
the main markings and the details of more modern detection. The
twin-forked Sabaeus Sinus, as its name implies, is of the form of a
double bay; was considered to be one in fact so long as the _maria_
were held to be seas. It straddles the point of land which, called the
Fastigium Aryn, has been taken for the Greenwich of Martian longitudes.
Each ‘bay’—not in truth a bay at all—indents the ochre in an acute
triangle, from the tip of which many canals proceed like the rays of a
fan from a holding hand. Both tips are darker than the main body of the
dark _mare_ from which they proceed. They thus recall in general
character the carets. They further reproduce specifically the Portus
Sigaei, for they give origin to two doubles, the Gihon and the
Hiddekel, in exactly the same manner that the two nicks of the Portus
Sigaei do to the Phison and Euphrates. Nor are their tips much farther
apart than those of the Portus, five degrees measuring the spread of
the one and four degrees that of the other respectively; the reason for
their earlier discovery lying in their greater size. They thus perform
the same office as the Portus Sigaeus, are quite comparable to it in
width, and differ in shape only as a larger and more acute triangle
differs from a smaller and blunter one. Undreamt of by Dawes and
unheeded since, they were the first hint to the world of the duality
which forms so strangely pervasive a feature of the canal system of the
planet.
Thus the carets stand connected with the canals quite as intimately as
the oases but in a significantly different manner. For, in addition to
their intermediary standing between the light regions and the dark,
their relation to the doubles is peculiar. An instance is offered by
the double Euphrates and another by the Ganges. The Euphrates, as we
saw in Chapter XVIII, leaves the Portus Sigaei at the south, one line
leaving each caret centrally, so that each caret is concerned only with
its own line and has no connection with its fellow. At their northern
ends both lines have similarly each its own Lucus Ismenius. The like
seems to be true of the Ganges. Similarly the twin Titan, have each its
own. Such twin duty in the matter of doubles seems to be the rule with
the carets, even more so than with the oases; and this is probably from
the fact that the coastline is of more limited extent than the interior.
Altogether the carets offer to our inspection glosses in finer print
upon the general text of the canals. Thought upon what they show takes
us a step farther toward the solution of the strange riddle of this
other world, a riddle which he who runs may not read, still less scout,
and which only reasoning, without prejudice or partiality, can unravel.
CHAPTER XXII
THE CANALS PHOTOGRAPHED
Photography holds to-day a place of publicity in the exposition of the
stars. Directed by Draper to the heavens thirty-four years ago, the
camera recorded then the first picture ever taken of the moon. From
this initial peering into celestial matters, practice has progressed
until now the dry plate constitutes one of the most formidable engines
in astronomic research. Not most effectively, however, in the field
which might have been predicted. Beautiful as the lunar presentment
was, as a presentiment of what was coming, it pointed astray. For it is
not in lunar portrayal, superbly as its crater walls in crescent
chiaroscuro or its crags that cast their tapering shadows athwart the
dial of its plains stand out in the latest photographs of our
satellite, that the camera’s greatest service has since been done.
Impressive as they are, these pictorial triumphs are chiefly popular,
and appeal on their face to layman and scientist alike. Not in the
nearest to us of the orbs of heaven, but in the most remote has
celestial photography’s most prolific field been found to lie. Its
province has proved preëminently the stars, especially the farthest
off, and that star-dust, the nebulæ, from out of which the stars are
made. Reason for this explains at once its efficiency and its
limitations.
Its rival, of course, is the eye. It is as regards the eye that its
comparative merits or demerits stand to be judged. Now, thus viewed,
its superiority in one respect is unquestionable; it simply states
facts. But though it cannot misinform, it can color its facts by giving
undue prominence to the effect of some rays and suppressing the
evidence of others, so that its testimony is not, it must be
remembered, always in accord with that of human vision. Speaking
broadly, however, it is so little complicated a machine as to register
its results with more precision than the retina. The evidence of the
camera has thus one important advantage over other astronomic
documents: it is impersonally trustworthy in what it states. Bias it
has none, and its mistakes are few. Imperfections, indeed, affect it,
but they are of purely physical occasion and may be eliminated or
accounted for as well by another as by the photographer himself.
In trustworthiness, then, so far as it goes, it stands commended; not
so much may be said of its ability. This depends upon the work to which
it is put. In certain lines it asserts preëminence; in certain others
it is so far behind as to be out of the race. The reason for both is
one and the same, for, as the French would say: It has the faults of
its quality. The very trait that fits it for one function, bars it from
the other. This excellence is that by which the tortoise outstripped
the hare,—a plodding perseverance. Far less sensitive than the retina
the dry plate has one advantage over its rival,—its action is
cumulative. The eye sees all it can in the twentieth of a second; after
that its perception, instead of increasing, is dulled, and no amount of
application will result in adding more. With the dry plate it is the
reverse. Time works for, not against it. Within limits, themselves
long, light affects it throughout the period it stands exposed and,
roughly speaking, in direct ratio to the time elapsed. Thus the camera
is able to record stars no human eye has ever caught and to register
the structure of nebulæ the eye tries to resolve in vain.
Where illumination alone is concerned the camera reigns supreme; not so
when it comes to a question of definition. Then by its speed and
agility the eye steps into its place, for the atmosphere is not the
void it could be wished, through which the light-waves shoot at will.
Pulsing athwart it are air-waves of condensation and rarefaction that
now obstruct, now further, the passage of the ray. By the nimbleness of
its action the eye cunningly contrives to catch the good moments among
the poor and carry their message to the brain. The dry plate by its
slowness is impotent to follow. To register anything, it must take the
bad with the better to a complete confusion of detail. For the
air-waves throw the image first to one place and then to another, to a
blotting of both.
All of which renders the stars, where lighting counts for so much and
form for so little, the peculiar province of celestial photography.
With the study of the surfaces of the planets the exact contrary is the
case. With most of them illumination is already to be had in abundance;
definition it is that is desired. What succeeds so excellently with the
stars is here put to it to do anything at all. At its best, the camera
is hopelessly behind the eye when it comes to the decipherment of
planetary detail. To say that the eye is ten times the more perceptive
is not to overstep the mark. To try, therefore, here to supplant the
eye by the camera is time thrown away.
Of scant importance to the expert in such matters as Mars, there is a
side of the subject in which service might be hoped of it: that of
elementary exposition. Congenitally incapable of competing with the eye
in discovery, the most that, by any possibility, could be looked for
would be a recording of the coarser details after the fact. For this
reason it had long been a purpose at Flagstaff to photograph some at
least of the canals. But the project seemed chimerical. To get an image
suitable at all some seconds of exposure would be required, and during
such time the shifting air-waves would blur the very detail desired to
be got. It was a problem of essential premises mutually annihilative.
The more the would-be photographer should avoid the one; the more he
would fall into the other.
Nevertheless the thing was tried in 1901. In 1903 the subject was taken
up by Mr. Lampland, then new at the observatory. The results were
better than those of two years before, the images more clear-cut but
still incommunicable of canals. Still they were satisfactory enough to
spur to increased endeavor, and during the following interopposition
preparations were made to grapple with the planet as successfully as
could be devised at its next return. This happened in May, 1905. It
then showed a disk only 17′′ in diameter, or 1/120 that of the
moon,—and this disk Mr. Lampland attacked with the 24-inch and a
negative amplificator that increased the focal length of the former to
143 feet. At such focus the planet’s image was received upon the plate.
Everything that could conduce to success had been put in requisition.
To this end of better definition the color curve of the objective was
first got, and for it a special color screen constructed by Wallace. In
spite of its name no achromatic is so in fact, but brings rays of
different tint to different focus. The color curve shows where these
severally lie, and the color screen, a chemically tinted piece of
glass, is to absorb all those which would blur the image by having a
different focus from the ones retained. Next, all manner of plates were
tried. For in these again it was necessary to reconcile two
contradictory characters, a rapid plate and a well-defining one. For
the coarser the grain the speedier the plate; and coarse grain
disfigures the detail. Both qualities on so small an image were
obligatory and yet both could not be got. Then the clock had to be as
smooth-running as possible. So by a suggestion of Mr. Cogshall’s one
was obtained that filled this requisite, a new form of conical
pendulum. Upon this a further refinement was practiced. Ordinarily
clockwork is timed to follow the stars; this was altered to follow the
planet, and so keep it more nearly motionless while its picture was
being taken. Then the device of capping down the telescope to suit the
air-waves, which had been found so effective to the bringing out of
fine detail, was put in practice. Lastly, all developers were tried,
and those found suited to the finest work were used.
Many pictures were taken on each plate one after the other, both to
vary the exposure and to catch such good moments as might chance. Seven
hundred images were thus got in all; the days of best definition alone
being utilized. The eagerness with which the first plate was scanned as
it emerged from its last bath may be imagined, and the joy when on it
some of the canals could certainly be seen. There were the old
configurations of patches, the light areas and the dark, just as they
looked through the telescope, and never till then otherwise seen of
human eye, and there more marvelous yet were the grosser of those lines
that had so piqued human curiosity, the canals of Mars. He who ran
might now read, so that he had some acquaintance with photography. By
Mr. Lampland’s thought, assiduity, and skill, the seemingly impossible
had been done.
After the initial success was thus assured, plates were taken at other
points around the planet and other well-known features came out;
“continents” and “seas,” “canals” and “oases,” the curious geography of
the planet printed for the first time by itself in black and white. By
chance on one of the plates a temporal event was found registered too,
the first snowfall of the season, the beginning of the new polar cap,
seen visually just before the plate happened to be put in and
reproduced by it unmistakably. Upon the many images thirty-eight canals
were counted in all, and one of them, the Nilokeras, double. Thus did
the canals at last speak for their own reality themselves.
PART III
THE CANALS IN ACTION
CHAPTER XXIII
CANALS: KINEMATIC
So far in our account of the phenomena we have regarded the lines, the
spots, and everything that is theirs solely from the point of view of
their appearance at any one time. In other words, we have viewed them
only from a static standpoint. In this we have followed the course of
the facts, since in this way were the canals first observed. We now
come to a different phase of the matter,—the important disclosure,
with continued looking, that these strange things show themselves to be
subject to change. That is, they take on a kinematic character. This at
once opens a fresh field of inquiry concerning them and widens the
horizon of research. It increases the complexity of the problem, but at
the same time makes it more determinate. For while it greatly augments
the number of facts which must be collected toward an explanation of
what the things are, these once acquired, it narrows the solution which
can apply to them.
The fact of change in the Martian markings forces itself upon any one
who will diligently study the planet. He will be inclined at first to
attribute it to observational mistakes of his own or his predecessor’s
making, preferably the latter. But eventually his own delineations will
prove irreconcilable with one another, and he will then realize the
injustice of his inference and will put the cause, where indeed it
rightly belongs, on the things themselves. Confronted by this fact he
will the more fully appreciate how long and systematic must be the
study of him who would penetrate the planet’s peculiarity. Just as the
recognition of something akin to seasonal change came to Schiaparelli,
because of his attending to the planet with an assiduity unknown to his
predecessors; so it became evident that to learn the laws of these
changes and from them the meaning of the markings, there was necessary
as full and as continuous a record of them as it was possible to
obtain. For this end it was not enough to get observations from time to
time, however good these might be, but to secure as nearly as might be
a complete succession of such, day after day, month after month, and
opposition after opposition. The outcome justified the deduction. And
it is specially gratifying to realize that to no one have the method
and the results thus obtained appealed with more force than to
Schiaparelli himself.
Perseverance in scanning the disk long after the casual observer had
considered it too far away for observational purposes, resulted in
Schiaparelli’s detection of the canals, and this through a
characteristic of theirs destined to play a great part in their
history, their susceptibility to change. He tells us in his _Memoria I_
how Aeria and the adjoining regions showed blank of any markings while
the planet was near in 1877 and the disk large and well shown, and then
how, to his surprise, as the planet got farther away and the disk
shrank, lines began to come out in the region with unmistakable
certainty. Thus to the very variability which had hidden them to others
was due in Schiaparelli’s hands their initial recognition.
Flux affecting the canals was apparent from the outset of my own
observations. No less the subject of transformation than the large dark
regions was the network of tenuous lines that overspread them. At times
they were very hard to make out, and then again they were comparatively
easy. Distance, instead of rendering them more difficult, frequently
did the reverse. Nor was the matter one of veiling. Neither our own
atmosphere nor that of Mars showed itself in any way responsible for
their temporary disappearance. It was not always when our atmospheric
conditions were best that the lines stood out most clearly, and as to
Martian meteorology there was no sign that it had anything whatever to
do with the obliteration. Long before the canals were dreamt of,
veiling by Martian clouds or mist had been considered the cause of
those changes in the planet’s general features, which are too extensive
and deep-toned wholly to escape observation even though none too
clearly seen. It was early evident to me that they were not the cause
of general topographic change, and equally clearly as inoperative in
those that affected the canals. In short, nothing extrinsic to the
canal caused its disappearance; whatever the change was, its action lay
intrinsic to the canal itself.
On occasion canals in whole regions appeared to be blotted out. The
most careful scrutiny would fail to disclose them, where some time
before they had been perfectly clear. And this though distance was at
its minimum and definition at its best. Even the strongest marked of
the strange pencil lines would show at times only as ghosts of their
former selves, while for their more delicate companions it taxed one’s
faith to believe that they could ever really have existed. Illumination
was invoked to account for this, and plays a part in the effect
undoubtedly. For at plumb opposition the centre of the disk for two or
three years has shown less detail than before and after that event.
This is probably due not, as with the moon, to the withdrawal of
shadows, but to the greater glare to which the disk is then subjected.
But this is not the chief cause of the change.
Still more striking and unaccountable was the fact that each canal had
its own times and seasons for showing or remaining hid. Each had its
entrances upon the scene and its exits from it. What dated the one left
another unaffected. The Nilokeras was to be seen when the Chrysorrhoas
was invisible, and the Jamuna perfectly evident when the Indus could
scarcely be made out.
[Illustration: Showing seasonal change.
I.]
So much shows in the two drawings here reproduced. The increase of the
Ganges and the advent of the Chrysorrhoas are noticeable in the second
over the first.
[Illustration: Showing seasonal change.
II.]
Seasonal changes seemed the only thing to account for the phenomena.
And in a general sense this was undoubtedly the explanation. To learn
more about the matter, to verify it if it existed, and to particularize
it if possible, I determined to undertake an investigation permitting
of quantitative precision in the case. A method of doing this occurred
to me which would yield results deserving of consideration from the
amount of data upon which each was based and capable of being compared
with one another upon an equal footing from which relative information
could be derived. It seemed wise to determine from the drawings the
degree of visibility of a given canal at different seasons of the
Martian year, and then to do this for every important canal during the
same period of time. The great number of the drawings suggested this
use to which they might be put. For from a great accumulation of data a
set of statistics on the subject could be secured in which accident or
bias would be largely eliminated and the telling effect of averages
make itself felt.
To render this possible it was necessary that the drawings should be
alike numerous, consecutive, and extended in time. These conditions
were fulfilled by the drawings made by me at the opposition of 1903.
Three hundred and seventy-two drawings had then been secured, and they
covered between them a period of six months and a half. They were also
as consecutive as it was possible to secure. During a part of the
period the planet was seen and drawn at every twenty-four hours, from
April 5, namely, to May 26, or for forty-six consecutive days. Though
the rest of the time did not equal this perfection, no great gap
occurred, and one hundred and forty-three nights were utilized in all.
Furthermore, as these drawings were all made by one man, the personal
equation of the observer—a very important source of deviation where
drawings are to be compared—was eliminated.
But even this does not give an idea of the mass of the data. For by the
method employed about 100 drawings were used in the case of each canal,
and as 109 canals were examined this gave 10,900 separate
determinations upon which the ultimate result depended. That each of
these determinations was independent of the others will appear from a
description of the method itself on which the investigation was
conducted. To understand that method one must begin a little way back.
As the two planets, Mars and the Earth, turn on their axes the parts of
their surfaces they present to each other are constantly changing. For
a feature on Mars to be visible from a given post on earth, observer
and observed must confront each other, and, furthermore, it must be day
there when it is night here. But, as Mars takes about forty minutes
longer to turn than the Earth, such confronting occurs later and later
each night by about forty minutes, until finally it does not occur at
all while Mars is suitably above the horizon; then the feature passes
from sight to remain hidden till the difference of the rotations brings
it round into view again. There are thus times when a given region is
visible, times when it is not, and these succeed each other in from
five to six weeks, and are called presentations. For about a fortnight
at each presentation a region is centrally enough placed to be well
seen; for the rest of the period either ill-placed or on the other side
of the planet.
If a marking were always salient enough it would appear in every
drawing made of the disk during the recurrent fortnights of its
display. If it were weaker than this, it might appear on some drawings
and not on others, dependent upon its own strength and upon the
definition at the moment, and we should have a certain percentage of
visibility for it at that presentation. While if it changed in strength
between one presentation and the next, the percentage of its recording
would change likewise. Definition of course is always varying, but if
its value be noted at the time of each drawing this factor may be
allowed for more or less successfully. Making such allowance, together
with other corrections to produce extrinsic equality, such as the
planet’s distance, which we need not enter upon here, we are left with
only the marking’s intrinsic visibility to affect the percentages; that
is, the percentages tell of the changes it has successively undergone
and give us a history of its wax and wane.
From drawings accurately made it is possible to add to the accuracy of
the percentage by noting in each, not only the presence or absence of
the marking, but the degree of strength with which it is represented.
This was done on the final investigation in the present case, and it
was interesting to note how little difference it made in the result.
The longitude of each canal was known, and the longitude of the central
meridian of each drawing was always calculated and tabulated with the
drawing, so that it was possible to tell which drawings might have
shown the canal. Only when the position of the canal was within a
certain number of degrees of the centre of the drawing (60°) was the
drawing used in the result, allowance being duly made for the loss upon
the phase side. Each drawing, it should be remembered, was as nearly an
instantaneous picture of the disk as possible. It covered only a few
minutes of observation, and was made practically as if the observer had
never seen the planet before. In other words, the man was sunk in the
manner. Such mental effacement is as vital to good observation as
mental assertion is afterward to pregnant reasoning. For a man should
be a machine in collecting his data, a mind in coördinating them. To
reverse the process, as is sometimes done, is not conducive to science.
When the successive true percentages of visibility of a given canal had
thus been found, they were plotted vertically at points along a
horizontal line corresponding in distance from the origin to the number
of days after (or before) the summer solstice of the Martian northern
hemisphere. The horizontal distance thus measured the time while the
vertical height gave the relative visibility. The points so plotted
were then joined by a smooth curve. This curve reproduced the
continuous change in visibility undergone by the canal during the
period under observation. It gave a graphic picture of the canal’s
change of state. It seemed, therefore, proper to call it the canal’s
cartouche or sign manual.
In this manner were obtained the cartouches of 109 canals. Now, as the
presence or absence of any canal in any drawing was entirely
irrespective of the presence or absence of another, each such datum
spoke only for itself, and was an entirely independent observation. The
whole investigation thus rested on 10,900 completely separate
determinations, each as unconditioned by the others as if it existed
alone.
As every factor outside of the canal itself which could affect the
latter’s visibility was taken account of, and the correction due to it
as nearly as possible applied before the cartouches were deduced, the
latter represent the visibility of the canal _due to intrinsic change
alone_. In other words, they give not the apparent only but the real
history of the canal for the period concerned.
Important disclosures result from inspection of the cartouches. This we
shall perceive by considering what different curves mean in the case.
If the canal were an unchangeable phenomenon, for any reason whatever,
its cartouche would be a _straight line parallel to the horizon_ of the
diagram. This is evident from the fact that the visibility would then
never vary. If, on the other hand, it were waxing and waning, and the
wax or wane were uniform, the cartouche would be a straight line
_inclined to the horizontal_; rising if the canal were increasing,
falling when it decreased. Lastly, if the rate of change itself varied,
the cartouche would be a curve concave or convex to the line denoting
the time, according as the rate of change of the growth or decay grew
greater or less.
To see this the more clearly, we may set over against the cartouche the
canal character it signalizes:—
Cartouche. Character.
A horizontal straight line. Canal invariable.
A straight line tilted up on the right. Canal increasing steadily.
A straight line tilted up on the left. Canal decreasing steadily.
A curved line descending, concave from Canal decreasing, but more
above. and more slowly.
A curved line ascending, concave from Canal increasing, but more
above. and more rapidly.
A curved line descending, convex from Canal decreasing more and
above. more rapidly.
A curved line ascending, convex from Canal increasing more and
above. more slowly.
A curved line first descending, then Canal decreasing more and
ascending, concave from above more slowly to a minimum,
throughout. thence increasing
more and more rapidly.
A curved line first descending, then Canal increasing more and
ascending, convex from above more slowly to a maximum,
throughout. thence decreasing
more and more rapidly.
If the cartouche first falls and then rises, this shows the canal to
have passed through a minimum state at the time denoted by the point of
inflection; if it rises first and falls afterward, this betokens in the
same way a maximum. Thus the cartouches reveal to us the complete
history of the canals,—what changes they underwent and the times at
which these occurred. The cartouche, then, is the graphic portrayal of
the canal’s behavior. It not only distinguishes at once between the
dead and the living, as we may call the effect of intrinsic change, but
it tells the exact character of this change,—the way it varied from
time to time, the epoch at which the development was at its minimum or
its maximum for any given canal, and lastly, its actual strength at any
time, thus giving its relative importance in the canal system. For the
height of the curve above the diagrammatic horizon marks the absolute
as well as the relative visibility and enables us to rank the canals
between themselves.
Now, the first point it furnishes a criterion for is the real or
illusory character of the canals. If a line be due to illusion, whether
optical or physical, it can vary only from extrinsic cause, since it
has no intrinsic existence. If, therefore, all extrinsic cause be
allowed for, the cartouche of this ghost must needs be a _horizontal
straight line_. Even if the extrinsic factors to its production be
imperfectly accounted for, their retention could only cause systematic
variations from the straight line in all the lines, which would
themselves vary systematically, and these factors could therefore be
detected.
This criterion is absolute. Unless all the cartouches were
approximately straight lines, no illusion theory of any kind whatever
could explain the facts. Even then the lines might all be real; for
unchangeable reality would produce the same effect on the cartouches as
illusion. In the case therefore of horizontal straight line cartouches,
we should have no guarantee on that score of reality or illusion; but,
on the other hand, curves or inclined straight lines in them would be
instantly fatal to all illusion theories.
Turning now to the 109 cartouches obtained in 1903, the first point to
strike one’s notice is that all but three of them are curves and that
even these three must be accepted with a caveat. Here, then, the
cartouches dispose once and for all of any and every illusion theory.
They show conclusively that the canals are real objects which wax and
wane from some intrinsic cause.
The second result afforded by the cartouches is not of a destructive,
negative character,—however valuable the destruction of bars to
knowledge may be,—but of a constructive, positive one. It does not,
like the first, follow from mere inspection, but is brought to light
only by comparison of all the cartouches. In a positive way, therefore,
its testimony is as conclusive as it was in a negative direction. For
that 10,900 separate and independent data should result in a general
law of development through either conscious or unconscious bias, when
those data would have to be combined in so complicated a manner for the
result to emerge as is here the case, is impossible. Chance could not
do it and consciousness would require a coördinate memory, to which
Murphy’s nine games of chess at once would be child’s play.
Of the 109 canals examined 106 showed by their cartouches that they had
been during the whole or a part of the period in a state of change. But
the change was not the same for all. In some the minimum came early; in
others, late. Some decreased to nothing and stayed there; others
increased from zero and were increasing still at the time observations
closed.
Latitude proved the means of bringing comparative order out of the
chaos. When the canals were ranged according to their latitude on the
planet, a law in their development came to light. To understand it, the
circumstances under which the canals were presented must be considered
as regards the then season of the planet’s year. In 1903 the planet
passed on February 28 through the point of its orbit where the summer
solstice of the northern hemisphere occurs. One hundred and twenty-six
days later took place the first snowfall in the arctic and subarctic
regions, an event that denoted the beginning of the new polar cap; from
which date the snow there gradually increased. Its autumnal equinox the
planet did not reach till August 29. Now, the canals were observed from
thirty-six days before the summer solstice of the northern hemisphere
to one hundred and forty-seven days after that event. We may tabulate
the dates as follows:—
================+===========+================
DAY FROM | VERNAL | CORRESPONDING
SUMMER SOLSTICE | LONGITUDE | DATE ON EARTH
----------------+-----------+----------------
-30 | 77° | June 9
0 | 90° | June 22
+30 | 103° | July 6
+60 | 117° | July 20
+90 | 131° | August 4
+120 | 146° | August 20
+150 | 162° | September 5
================+===========+================
The vernal longitude is the longitude of the planet in its orbit
reckoned from the vernal equinox. From the table it appears that the
cartouches cover the development of the canals from about June 6 to
September 1 of the Martian northern hemisphere for the current but to
us undated year, _ab Marte condita_.
The 109 canals included all the more conspicuous canals on the planet
at that opposition, all those that lent themselves by the sufficient
frequency with which they were seen to a statistical result. They lay
spread all the way between the edge of the polar cap in latitude 87°
north to the extreme limit south, at which the then tilt of the north
pole toward the earth permitted of canal recognition. This southern
limit was in about latitude 35° south. Farther south than this vision
became too oblique, amounting as it did, with an adverse tilt of
twenty-five degrees to start with, to something over sixty degrees, for
detection of such fine markings to be possible. Between the two limits
thus imposed, by the perpetual snow on the one side and the
observational tilt on the other, the 109 canals were distributed by
zones as follows:—
=================+===============+===========
ZONE | LATITUDE | NUMBER OF
| | CANALS
-----------------+---------------+-----------
North Polar | 87° N.-78° N. | 1
Arctic | 78° N.-66° N. | 9
Sub-Arctic | 66° N.-51° N. | 9
North Temperate | 51° N.-37° N. | 11
North Sub-Tropic | 37° N.-24° N. | 18
North Tropic | 24° N.-12° N. | 21
North Equatorial | 12° N.- 0° N. | 14
South Equatorial | 0° N.-12° S. | 17
South Tropic | 12° S.-24° S. | 7
South Sub-Tropic | 24° S.-37° S. | 2
=================+===============+===========
As the latitude of a canal in the investigation was taken as that of
its mid-point, such being the mean value of its successive parts, the
latitudes about which information was obtained lay within the limits
given above, the most northern canal, the Jaxartes N having for its
mid-latitude 78° north, and the most southern, the Nectar, that of 27°
south.
The zones comprised each a belt of territory about thirteen degrees
wide, the first being less solely because in part occupied by the
permanent polar cap.
The curves of all the canals in a given zone have been combined into a
mean curve or cartouche for that zone; and then the cartouches for the
several zones have been represented and ranged according to latitude on
the accompanying plate. Consideration of these mean canal cartouches is
very instructive. In the first place not one of them is a straight
line, either horizontal or inclined. All are curves and, with the
exception of the top one, all show a minimum or lowest point during the
period under observation. From this point they rise with the time, or
to the right on the plate. A black star marks this minimum, and is
found farther and farther to the right as one goes down the plate; that
is, as one travels from the neighborhood of the arctic regions down to
the equator and then over into the planet’s southern hemisphere.
Drawing now a line approximately through the stars and remembering that
the minimum means the date at which the canal started to develop, we
see that the canal development began at the border of the north polar
cap and thence continued down the disk over the planet’s surface, as
far as observation permitted the surface to be seen, which was some
thirty-five degrees into the other hemisphere. This is the first broad
fact disclosed by the cartouches.
[Illustration: _MEAN CANAL CARTOUCHES_
P.L.]
Furthermore, the development took place at an approximately uniform
rate. This is shown by the fact that the line passing through the black
stars is approximately straight; for such straightness means that
progression down the disk as measured by the latitude bore throughout
the same ratio to the time elapsed.
Looking at them again we notice that the three topmost cartouches,
those of the north polar, arctic, and sub-arctic canals respectively,
dip at the right before the end of the observations, while the other
seven were still rising when those observations were brought to a
close. A reason for this, or at least a significant coincidence, is to
be found in the dotted line pendent from the top of the table and
labelled “First Frosts.” This dotted line denotes the date at which the
first extensive frost occurred in the polar regions; for even before
this time patches of white had appeared north of the Mare Acidalium,
denoting the on-coming of the cold. The frost did not last but came and
went and came again just as it does on earth, growing more insistent
and long-lived at each fresh fall. Its sphere of operation was confined
to the three zones in question. Even these zones it by no means
covered, merely blotching them in places with fungi-like patches of
frost. Beyond them south it never extended during the period of the
observations; indeed, it hardly entered the sub-arctic zone at all at
this very beginning of the polar winter. For it was only August 20
then. The coincidence of the isotherm as betrayed by the deposition of
frost with the dividing line between the canal-development curves that
dip down at this season and those that still continue to rise is
suggestive.
It becomes all the more so when the three cartouches are considered
seriatim. The most polewards, the north polar one, had sunk to zero
sometime before the first extensive frost occurred; the second, the
arctic, did so later than its northern neighbor, probably just before
the epoch in question; while the third, practically outside the zone of
deposition, was behind both the others in its descent. Inspection of
the drawings upon which the cartouches are based confirms an inference
deduced from this: that it was cold that killed, not frost that
covered, them, which was responsible for their obliteration. The
drawings show that the canals ceased to be seen before the white
patches were evident. Now this would be the exact behavior of
vegetation. It would be killed, turned brown by freezing, and so
rendered invisible to us against its ochre desert background, before
the cold had grown intense enough to cover that ground with a solid
white carpet of frost. At the opposition of 1905, however, the extreme
northern canals were visible after the snow had covered all the country
about them, being evident as lines threading the new cap.
These three cartouches furthermore show each a maximum, and what is
significant the maximum occurs later in time for each, according as the
zone lies remote from the pole. A red star marks this maximum and shows
that the time of greatest development for the three zones was
respectively:—
41 days after the summer solstice for the North Polar.
61 days after the summer solstice for the Arctic.
95 days after the summer solstice for the Sub-Arctic.
We now pass to the other curves, those that were unaffected by cold.
Though in these the minima themselves show the law of latitudinal
progression, the wavelike character of the advance is even better
disclosed by the curves. As the eye follows them down the page, the
advance of the wave to the right is plainly apparent. The slope of the
wave is much the same for all, implying that a like force was at work
successively down the latitudes.
It will be noticed next that in all the mean cartouches the gradient is
greater after the minimum than before it. The curves fall gently to
their lowest points and rise more steeply from them. Such profile
indicates that the effects of a previous force were slowly dying out
down to the minimum and that then an impulse started in to act afresh.
This explains the attitude of the canals that died out. In them the
effect of the old force shows as in the others, but no impulse came in
their case to resuscitation.
It seems possible to trace this force to an origin at the south. For
beginning with the north sub-tropic zone the gradient on the left shows
less and less steep southward to the south sub-tropic zone. Such a
dying-down swell is what should be looked for in an impulse which had
travelled from the south northward, since the wave would affect the
more northern zones last, and less of a calm period would intervene
between the two impulses from opposite poles.
The cartouches, then, state that the canals began to develop after the
greatest melting of the polar cap had occurred; that this development
proceeded down the latitudes to the equator, and then not stopping
there advanced up the latitudes of the other hemisphere. In the next
place they show that in the arctic region the development was arrested
and devolution or decay set in as it began to get cold there, the most
northern canals being affected first. Finally, that a similar wave of
evolution had occurred from the opposite pole some time before and had
then passed away. And this evidence of the cartouches is direct, and
independent of any theory.
CHAPTER XXIV
CANAL DEVELOPMENT
_Individually Instanced_
As an interesting instance of the law of development we may take the
career of the Brontes during this same Martian year; the Brontes
witnessing individually to the same evolutionary process that the
canals collectively exhibit.
The Brontes is one of the most imposing canals upon the planet. It is
not so much its length which renders it a striking object, though this
length is enough to entitle it to consideration, being no less than
2440 miles. Its direction is what singles it out to notice, for it runs
almost north and south. For this reason it swings into a position to
hold the centre of the stage for a time with the precision of a
meridian, as the planet’s rotation turns its longitude into view. The
points which it connects help also to add to its distinction. For the
Sinus Titanum at its southern end and the Propontis at its northern are
both among the conspicuous points of the disk. The latter is but twelve
degrees farther east than the former, while it is sixty-six degrees
farther north. This long distance,—from nearly the line of the tropics
in the southern hemisphere to mid-temperate regions of the
northern,—the canal runs in an absolutely straight course.
Its north and south character commends it for any investigation of
canal development, since it runs in the general direction that
development takes. Its great latitudinal stretch further fits it for a
recorder of changes sweeping down the disk; so that both in direction
and length it stands well circumstanced for a measure of latitudinal
variations. The fact that it is usually a fairly conspicuous canal does
not detract from its virtue in this respect. It was first recognized at
Flagstaff in 1894. But once realized, so to speak, it was possible to
identify it with a canal seen by Schiaparelli and supposed by him to be
the Titan; indeed, it played hide and seek with that canal throughout
his drawings. In 1894 both it and the Titan were so well seen that its
separate existence was unmistakable, causing it to be both recognized
and named. It is, like the Titan, one of the sheaf of canals descending
the disk from the Sinus Titanum, and lies just to the east of the Titan
in the bunch. In 1896 it was also prominent; and at both these
oppositions most so from its southern end, its northern one being more
or less indefinite, especially in 1894.
In 1901 it was not the same. Instead of being the conspicuous canal it
had been in earlier years, it was now so faint as with difficulty to be
made out. It remained so to the close of observations. It was now under
suspicion. Its behavior in 1896-1897 had led to the supposition that
not only were seasonal changes taking place in it, but that those
changes were such as to point to a law in the case with which its
conduct in 1901 fayed in. The suspicion did not, however, become a
certainty till the opposition of 1903. The length of time during which
the disk was then kept under scrutiny resulted in the method of its
metamorphosis being discovered.
[Illustration: I. February 25.]
At the very start of observations its longitude chanced to be nearly
central and it was made out; but so far off was the planet that only
its northern part could be detected, because, as afterward appeared,
this part was the stronger, the canal being decidedly inconspicuous,
whereas other canals, the northern and even the Pallene and the Dis,
were strongly marked. At the next presentation the planet was nearer,
and details previously hidden for the distance now came out. Among them
was the Brontes, which, showing better than in January, could be traced
all the way to the Sinus Titanum. A drawing (I) made on February 25 and
reproduced in the text shows its appearance at the time. Its emergence
under neared conditions only served to accentuate its relative
inconspicuousness, for it showed now notably inferior to the northern
canals, and this not only in the matter of general visibility, but in
the character it displayed. It was a line of hazy definition,
contrasting thus with the sharp dark forms of its northern neighbors.
[Illustration: II. March 30.]
[Illustration: III. April 3.]
As the planet steadily approached the earth, and the canals to the
north became better and better seen, the Brontes instead of sharing in
the general improvement did exactly the opposite. It grew less visible
when it should have grown more so, if distance had been the cause of
its appearance. It was now only to be seen at the north, even when it
was seen at all; a state of things exemplified in Drawings II and III.
[Illustration: IV. May 4.]
As the planet now went away and detail should have dimmed, the Brontes
proceeded to do the opposite. One had almost said it was actuated by a
spirit of contrariety. For now when it had reason to grow faint it grew
in conspicuousness; just as, before, when it should have become
evident, it had declined. Distinctly farther off and smaller as the
planet was at the next presentation, the Brontes had clearly developed
both in tone and in the amount of it visible. This was in May (Drawings
IV and V). In June bad seeing prevented good observations, but in July,
Drawing VI, when the region again came round, the Brontes, in spite of
the then greatly increased distance, asserted itself so strongly that
even in not very good seeing its presence could not be passed by.
[Illustration: V. May 7.]
This contrariety of behavior had about it one very telling feature.
That the canal waxed or waned in exact opposition to distance and even
toward the last to seeing too, showed conclusively that neither
distance nor definition could in any way be held responsible for its
metamorphoses. A very fortunate circumstance, this of the observations,
for it directly eliminated size of disk, phase, and seeing, for which
correction are none too easy to make, and which in the minds of the
sceptical could always remain as unexplained possibilities of error.
[Illustration: VI. July 18.]
The mean-canal cartouches show synthetically, and all the more
conclusively for being composite, the laws of the flux of the canals.
Something more of vividness, however, is imparted by the actual look of
one of the constituents during the process. It is the difference
between seeing a composite picture made from a given group of men and
the gazing on the actual features of any one of them. So much is gained
by the drawings across the page of the Brontes at different stages of
its evolution during the period here concerned. But in another way,
too, the one canal may be made to yield a more lifelike representation
of the process than a number taken together are capable of affording.
In the mean-canal cartouches each canal is treated as an entity; but it
is possible to consider a canal by parts, and by so doing to see it in
action, as it were. It occurred to me to treat the Brontes in this way.
For this purpose I divided the canal into sections, five of them in
all, between the point where it left the Propontis, at a spot called
the Propropontis, to where it ended in the Sinus Titanum. The first,
the most northern, extended as far as Semnon Lucus, the southernmost
outpost of the Propontis congeries of spots. The second continued on
from these to Eleon, the junction where the Erebus crossed. The third
thence to Utopia, where the canal met the Orcus; the fourth to an
arbitrary point in latitude 8° south, and the fifth and last to the
Sinus Titanum. The lengths of these sections were respectively: 12°,
16°, 15°, 12°, and 13°. Each of the sections was then treated as if it
were a separate canal and its cartouche found. To the cartouches’
determination there were available drawings:
January 21-25 12 drawings.
February 23-March 2 15 drawings.
March 28-April 5 14 drawings.
April 26-May 8 27 drawings.
June 3-16 6 drawings.
July 11-21 16 drawings.
-------------------
90 drawings in all.
The cartouches are given in the plate opposite, which is constructed
precisely like the one for the mean canal cartouches presented on page
298. The mid-latitude of the section and its mid-longitude are given in
the margin with its description.
[Illustration: BRONTES
Showing Successive Development South
_January to July, 1903_
P.L.]
Examining them now we note a family resemblance between the successive
cartouches. All sink slowly on the left to rise sharply from their
lowest point to the right. Such resemblance betokens the action of one
and the same cause.
Next, although the curves are resemblant, each has been, as it were,
sheered to the right as one reads down; that is, the action took place
later and later as the latitude was north.
Lastly, the dying out of a previous impulse can be traced in the
cartouches, which shows that the canals were quickened six months
previously from the south polar cap, as they were now being quickened
from the north polar one.
CHAPTER XXV
HIBERNATION OF THE CANALS
Connected with the conduct of the canals is a phenomenon, examples of
which were early noted in a general way by Schiaparelli and later, but
of which the full import and exhibition only came to light during the
opposition of 1903 by a very striking metamorphosis: what may be called
the hibernation of a canal for a longer or shorter term of years. What
observation discloses is certainly curious. For several successive
oppositions a canal will be seen in a definite locality, as regular in
seasonal recurrence as it is permanent in place, a well-recognized
feature of the disk. Then to one’s surprise, with the next return of
the planet, it will fail to appear, and will proceed to remain
obliterate without assignable cause for many Martian years, until as
unexpectedly it will be found what and where it was before. Neither to
deposition of hoar-frost, such as frequently whitens whole regions of
Mars, nor to other circumstances can be attributed its disappearance.
Without apparent reason it simply ceases to be and then as simply comes
back again.
Such bopeep behavior is quite beyond and apart from the seasonal change
in visibility, to which all the canals are by their nature subject. For
being creatures of the semi-annual unlocking of the water congealed
about the polar caps, they quicken into growth and visibility, each in
its season, and as regularly die out again. Different, however, is the
phenomenon to which I now refer. In it not a seasonal but a secular
change is concerned. The season proper to the canal’s increase will
recur in due course, and the canals round about it will start to life,
yet the canal remains unquickened. Nothing responds where in years the
response was immediate and invariable. The canal lies dormant spite of
seasonal solicitation to stir.
Such curious hibernation was early hinted to the keenness of
Schiaparelli, and most incomprehensible as well as difficult of
verification at that stage the phenomenon was. That the absence was a
fact, however, he assured himself, although he was not able to prove an
alibi. But at the last opposition an event of the sort occurred which,
from the length of time the planet was kept under observation, combined
with continued suitableness of the seeing, unmasked the process. In the
light of what then happened, taken in connection with the side-lights
thrown upon it by the canal’s past and by the knowledge we have
meanwhile gained of the planet’s physical condition, the riddle of the
phenomenon may in part at least be read, and most interesting and
instructive the reading proves to be.
Among the initial canals detected by Schiaparelli, in 1877, was a
tricrural set of lines recalling the heraldic design of three flexed
legs joined equiangularly above the knees. It lay to the east of the
Syrtis Major, and he called its three members the Thoth, the Triton,
and the Nepenthes. Starting from the head of his gulf of Alcyonius, at
a point now known to be occupied by the oasis called Aquae Calidae, the
Thoth started south inclining westward as it went, till in longitude
267° and latitude 15° north, it met the Triton, which had come from the
Syrtis Minor with similar westward inclination. To the same point in
the same manner came the Nepenthes. Part way along the course of the
latter was to be seen a small dark spot, the Lucus Moeris, which he
estimated at four degrees in diameter. Some of the markings were easier
than others, the easiest of all being the Lucus Tritonis, a largish
dark spot at the common intersection of all three canals; but that none
of the markings were remarkably difficult is sufficiently shown by
their detection at this early stage of Schiaparelli’s observations. It
is worth noting also that he discovered the southern ones first; the
Thoth not being seen till March, 1878. As his then recognition of these
canals witnesses, they must have been among the most evident on the
disk. And the point is emphasized by the fact that he failed at this
opposition to detect the Phison and the Euphrates as separate markings.
Much the same the three canals appeared to him at the next opposition
of 1879, the Thoth being seen at its several presentations from October
5, 1879, to January 11, 1880.
At the next opposition a noteworthy alteration occurred, the full
significance of which escaped recognition. Schiaparelli saw, at the
place where the Thoth had been, two lines which he took for a
gemination of that canal, one of which followed the course of the old
Thoth, while the other went straight from the Sinus Alcyonius to the
Little Syrtis, or, more precisely, to the junction of the Triton and
the Lethes. It was not the Thoth, however, but something unsuspected,
of more importance.
In 1884 the Thoth showed really double, the western line being much the
stronger, “una delle piu grosse linee que si vedessero sul disco.” That
neither branch went farther than the meeting-place with the Nepenthes
argues that it was indeed the Thoth that was seen. Schiaparelli himself
had no doubt on the subject, although he drew the double canal he saw
due north and south from the tip of the Sinus Alcyonius to the
junction, but nevertheless along the 263° meridian.
In 1886 and 1888 the system was in all essentials, what it had been in
1877 and 1879, except that the Thoth and Nepenthes were double and were
more minutely seen.
Here, then, was a system of canals and spots which for six Martian
years had been a persistent and substantially invariable feature of the
Martian surface. Any changes in it had been of a secondary order of
importance, while its general visibility was of the first. It is
possible, then, to judge of my perplexity when in beginning my
observations in 1894 no sign of the system could I detect. Of neither
the Thoth, the Triton, the Nepenthes, nor the Lucus Moeris was there
trace. And yet, from the other canals visible, it was evident that the
disk was quite as well seen as it had been by Schiaparelli. Not only
were practically all his canals there, but many much smaller ones were
to be made out. And the same was true of the spots, a host of such not
figured by him appearing here and there over the planet’s surface.
Nor was this all. Instead of the Thoth, another canal showed straight
down the disk from the Syrtis Minor to the Aquae Calidae. This canal
was as unmistakable as the Thoth had been before to Schiaparelli. It
was among the first to be detected, and continued no less conspicuous
to the end, the dates at which it was seen being July 10, August 14,
and October 21. I called it the Amenthes, identifying it with the canal
so named in Schiaparelli’s chart published in _Himmel und Erde_, of the
_ensemble_ of his observations from 1877 to 1888. But in his Memoirs he
never called it so, seeing it, indeed, only in 1881-1882, and deeming
it then the Thoth. Nevertheless, in 1894, it was the conspicuous canal
of the region, and, what is more, had come, as it proved, to stay.
The invisibility of the Thoth continued for me the same during the
succeeding oppositions of 1896-1897 and 1901. At the former opposition
I drew it in 1896 on July 28, August 26, September 2, October 5-9,
seeing it single; and in 1897 on January 12-19, February 21, and March
1. It was single but with suspicions of doubling in January, and was
indubitably double in February. As for the Thoth, I had come to
consider it and the Amenthes one, attributing their diversity of
depiction to errors in drawing. For while the Thoth remained
obstinately invisible, the Amenthes presented itself as substitute so
insistently as to make one of the most obvious canals upon the disk.
One exception only was there to this state of things. On June 16, 1901,
my notes contain this adumbration of a something else: “Amenthes
sometimes appeared with a turn to it two-thirds way up; two canals
concave to the Syrtis Major.”
[Illustration: Amenthes alone in February.]
So matters opened at the opposition of 1903. With the advent of the
planet and the presentation in due course of Libya in February, the
Amenthes duly appeared, much as it had showed at the opposition before,
only less salient. It was a confused and seemingly narrower double.
Suspected on the 16th of that month, it was definitely seen from the
18th to the 23d. Of the Thoth no mention is made either in the notes or
in the drawings. When the region came round again, in March, the
Amenthes was still there, showing more feebly, however, than it had in
February, in spite of better seeing and the fact that the planet had
considerably neared. Clearly the canal was fading out; a fact further
witnessed to by the following note made on March 25: “Throughout this
opposition thus far the dark triangle tipped by Aquae Calidae has been
sharply divided in intensity from the Amenthes, which is very narrow
and exceedingly faint.” Still was there no trace of the Thoth.
[Illustration: Amenthes feebler and still alone in March.]
With the April presentation entered a new order of things. When the
region first became visible, on the 16th, the Amenthes could still be
seen and alone; but on the 19th, as the relative falling back of the
Martian longitudes swung the region nearer the centre of the disk, the
Thoth appeared alongside of it. On the 20th the Thoth showed alone.
Unmistakable it was and just as Schiaparelli had drawn it, accompanied
by the Triton and the curved Nepenthes. The thing was a revelation.
What before I had seen only in the spirit of another’s drawings stood
there patent to me in the body of my own; while the Amenthes, to which
I had so long been accustomed, had vanished into thin air. Only a trace
of it was now and then to be made out. So startlingly strange was the
metamorphosis that I could not at first trust my eyes, and questioned
the broken line, which had replaced the straight, for some ocular
deception. But nothing I could do would rectify it. The Amenthes was
gone and the Thoth stood in its stead.
[Illustration: Appearance of Thoth with Triton and curved Nepenthes.
Amenthes vanished. April 20.]
At the next presentation, May 26 to June 8, the phenomena were
repeated, and with increasing clarity. And then of a sudden, on May 29,
I saw the long-given-up Lucus Moeris. There it was indubitably. And its
definiteness was the most astonishing part of the affair. It was no
question of difficult detection. Indeed, I had not been on the lookout
for it, having searched the region too often fruitlessly before to have
left incentive to search again. And so, when I was not searching, the
thing of its own accord stepped forth to sight. It was a small round
dot, like to any other oasis, and showed, as it were, a black pearl
pendent by the Nepenthes from the Syrtis’s ear. For the Libyan bay made
a dark projection of the sort high up on the Syrtis’s eastern side,
from which the Nepenthes, precisely as Schiaparelli had drawn it,
curved down to the point where the Thoth and Triton met. All three
canals were geminated, the gemination being about three degrees wide.
[Illustration: Advent of the Lucus Moeris. May 29.]
And now occurred the last act in the drama. In July the Amenthes
reappeared, showing alongside of the Thoth-Nepenthes, and thus removing
any possible doubt as to their separate identity. It had, indeed,
become the stronger of the two, having gained in strength in the
interval between June and July and the Thoth-Nepenthes having lost. The
lines were in process of relapsing into the _status quo ante_. Had
these three presentations not been watched, the brief apparition of the
Thoth-Nepenthes had been missed and with it the revealing of its
curious character, and of certain deductions thereupon.
[Illustration: Amenthes with Thoth-Nepenthes. July.]
First among these is a truth of which I have long been convinced; to
wit, that when a seeming discordance arises between the portrayals of a
canal, it is commonly not a case of mistake nor of change, but one of
separate identity. The canal has not shifted its place, nor has an
error been committed; the fact is that one canal has been observed at
one time, another at another.
So it was here, and thus were the old and the new observations
reconciled. There had been no mistake in either. Two separate canals
accounted for the discrepancy, and only an unfounded distrust of the
accuracy possible in such observations was to blame for any failure to
recognize the fact.
Now, scrutiny of the notes upon the appearance of the two canals,
together with their labeling by the seasonal longitudes of the planet
at the dates they were made, discloses a curious relation between the
two. The seasonal longitudes are important, as they date the phenomena
according to the Martian calendar. Ordered thus, the successive aspects
reveal first a seasonal change in each canal and then over and above
this a secular one. And this secular change was such as to cause the
two canals to alternate in visibility. When the one was present the
other was not, and _vice versa_.
[Illustration:
CARTOUCHES
OR
CURVES OF VISIBILITY
OF
AMENTHES, THOTH AND THEIR COMBINATION.]
We shall see this more clearly and at the same time bring out a curious
relation between the two systems, the broken bow of the
Thoth-Nepenthes-Triton and the straight arrow of the Amenthes, while
looking at the cartouches of the Thoth, the Amenthes, and a combination
of both given in the plate on previous page.
The antithetical character of the two canals is apparent. But what is
further interesting, the combination cartouche of both bears a singular
resemblance to that of the mean canal of the north tropic zone, the
zone to which both canals belong. Here, then, is a combination which is
perfectly regular while each of its constituents is anomalous.
And now we come to something as important: at the opposition of 1905
the curious alternation metamorphosis was enacted anew. The Amenthes
appeared, disappeared to be replaced by the Thoth, and then reappeared
again beside the other. This corroboration of behavior showed the
previous observations to have been due to no mistake, and only served
to deepen the interest in this last and more singular phase of canal
conduct.
CHAPTER XXVI
ARCTIC CANALS AND POLAR RIFTS
Last in time but not least in importance of the details of canal
development to be detected is one that connects these strange features
directly with the melting of the polar caps. The cartouches showed that
such connection was to be inferred; the facts now to be recorded depict
it by an identity of place between certain phenomena of the two
subjects following one another in order of time.
On January 8, 1897, while scanning the planet, I was suddenly ware of a
rift in the north polar cap. It ran a little to the west of south from
where it started in at the cap’s edge and went clean through to the
limb, the pole being then slightly tilted away from us. At the time it
seemed to be the first rift ever seen in that cap; but on opening a
little later Schiaparelli’s _Memoria Quarta_, which had just arrived,
the first thing my eye fell on was a drawing of a rift in the north
polar cap observed by him when the planet had held the like attitude
toward the Earth thirteen years before. Reference to its longitude
showed it to be the identical rift, seen again after all these years
and the only one so far seen in the northern cap.
At the next opposition more rifts were detected, one in especial on
December 27, running from Arethusa Lucus, then upon the edge of the
cap, athwart the snow in a northwesterly direction.
In the forepart of the opposition of 1901, which in its Martian season
corresponded to that in 1897, when the rift had been observed, many
rifts were detected in the cap, and among them one traversing the cap
north-northeasterly in longitude 136°.
So far the season when the cap had been observed was that when the
rifts were in process of forming. The ground they and the snow-cap
covered had not yet at any opposition been uncovered.
It was only when my observations began in the latter half of the
opposition of 1901 that, the season on Mars having so far advanced, all
snow in those latitudes had melted. Then appeared, however, the canal
Hippalus, an arctic canal of some importance, lying on that part of the
planet previously occupied by the polar cap. When later studying the
observations on the rifts I remembered this canal, and turning to the
drawing made some months before to compare the two critically,
discovered that the canal occupied the precise position held earlier by
the rift. One had said the rift had never vanished, but that the white
surrounding it had simply turned to ochre. Here, then, was a striking
coincidence of place, too exact to be the result of chance.
Impressed by the identity, I examined all the other rifts seen early in
1901, comparing them with the arctic canals seen later, to the finding
of no less than five cases of the same coinciding positions.
The importance of the identification here made of an arctic canal with
a previous rift in the polar cap has led me to make a list of the
canals thus identified at this opposition.
==========+===========================+=============================
| VISIBLE AS A RIFT | VISIBLE AS A CANAL
----------+---------------------------+-----------------------------
Hypanis | January 1 and February 4 | April 18 (?), May 20, 22,
| | 27, June 4, 5, 6, 7, 8, 25
Hippalus | January 19 and February 4 | April 18, May 27
Rhombites | February 4 | May 27
Python | February 20 | March 31
Zygatis | January 18, 19 | May 7, June 3 to 8
==========+===========================+=============================
If it be asked why these canals do not appear recorded at the March
presentation as either the one phenomenon or the other, the answer is
twofold. First, because they showed as shadings lost amidst a shaded
mass; and, secondly, the observations at several oppositions indicate a
great amount of haze over the region at that season of the Martian year.
We may now go back to the very first rift, that of 1897. The Martian
season grew later with each succeeding opposition, and it so chanced,
abetted by this fact, that the delaying snow was never seen covering
that part of the planet again and so, of course, not the rift. The
Martian summer in those high latitudes came on, and with it brought the
great arctic canal, the Jaxartes, into conspicuousness. The canal in
consequence had been observed for some time before it proclaimed itself
the apotheosis of a rift and that of the first and most important rift
of all. Comparison of position, however, entirely confirmed the
conjecture and added another and the most striking of all to the list.
These six canals, on the whole the largest which run into the northern
cap, have thus a dual character. Starting originally as rifts, they
later come out unmistakably as canals. So that we may say in general
that the two phenomena are different seasonal states of the same thing.
This instantly explains the rifts, the origin of which we found of so
difficult, not to say impossible, interpretation before in these pages,
and incidentally it confirms what we deduced on other grounds as the
character of the canals; to wit, strips of vegetation. For if the cap
covered desert and fertility alike, it is precisely over the latter
that it would first melt.
Vegetation has the property of melting snow. The metabolism of the
plant, like that of the animal, though in a less degree, generates
caloric. A living animal is warm, even the so-called cold-blooded ones,
in some sort, and a growing plant is too. The chemic processes
concerned give off heat, though in such small quantities that we are
often not aware of it. While the plant lies dormant it stays cold, but
the moment its sap begins to run under the rays of the spring sun it
rises in temperature above its winter surroundings. All it needs to
this awakening is sun and water, and both it gets in its place in the
polar cap after the passing of the vernal equinox. The time, therefore,
is suitable, for it is not till after that equinox is passed that any
of the above phenomena occur. In consequence the snow about it melts
and the plants themselves show as dark rifts splitting the cap.
This quite unexpected identity of two seemingly diverse phenomena, and
the unsolicited support its only explanation lends to the general
theory, is an instance of what is constantly occurring as observation
of the planet is pushed farther and farther. Facts every little while
arise which prove to fit into place in the scheme when neither the
facts nor their fitness could have been foreseen.
CHAPTER XXVII
OASES: KINEMATIC
Subject to change also are the oases; and in the same manner apparently
as the canals. They grow less evident at a like season of the Martian
year. They do this seemingly by decreasing in size. Whereas in the full
expanse of their maturity they show as round spots of appreciable
diameter, as the season wanes they contract to the smallest discernible
of dots. All but the kernel, as it were, fades out, and even this may
disappear from sight. The Phœnix Lake in its summer time is a very dark
circular spot, small indeed yet of definite extension; in its winter it
shrinks to a pin point, and is often not visible at all. Sometimes the
husk apparently persists, a ghostlike reminiscence of what it was, with
the kernel showing dark-pointed in its centre. Thus the Lucus Lunae
appeared at the opposition of 1905. A faint wash betokened the presence
of the Lucus, through which now and again a black pin-point pierced.
In this visible decrease of size we get a revelation as to what takes
place impossible in the case of the canals, the tenuous character of
which precludes more than inference as to the process.
Like the canals, latitude, together with the suitable season of the
planet’s year, are the determining factors in their development. In
what corresponded to our July of the northern hemisphere the oases in
the sub-arctic and north temperate zones were conspicuous; black spots
that showed in profusion along the parallels of 40°, 50°, and 60°
north. At the same time the equatorial ones, those along the
Eumenides-Orcus, which had been most evident in 1894, hardly came out.
It had been their time then as it was that of the others now. The law
of development is not so simple as on the earth, depending, like that
of the canals, not only upon the return of the sun, but upon the advent
of the water let loose from about the polar caps. Thus the equatorial
oases are subject to two seasonal quickenings, one from the north, the
other from the south.
In regard to their method of evolution or devolution a most curious
observation happened to me in 1903. Usually the oases are of solid tone
throughout; equally sombre from centre to circumference. But in this
case such uniform complexion found exception. On March 1, 1903, the
Ascraeus Lucus came out strangely differentiated, a dark rim inclosing
a less dark kernel. The sight was odd enough to command comment in the
shape of a sketch which accompanied the note, and the further remark
that other spots had similarly that year affected the like look. That
the effect was optical did not seem to me the case. Other spots at
other times showed nothing of the sort. If it was due to objective
cause it gathers circumstance from what was then the Martian time of
year. For the season was such that the spot should then have been in
process of waning; and the effect would indicate that in so doing the
tone of the centre went first, that of the circumference fading last.
This would be in accordance with a growth proceeding outward and a
decay that followed in its steps.
When to this we add the look of the oases at the antithetic
season,—often a faint shading only, with or without a darker pin-point
at its core,—we are led to the belief that the area of the oasis is
unchangeable and that its growth means a deepening of tint.
So far, then, as it is possible to particularize them, the oases
develop from a small nucleus, perhaps twenty miles in diameter, perhaps
less, and from this spread radially till they attain a width of
seventy-five or one hundred miles. If the oasis be associated with a
double canal, this maximum width exactly fits the space between the
twin lines. Even when no double enters the oasis, the size is about the
same. This size attained, they hold it for some months. Then they
proceed to fade out to their initial nucleus, and after a sufficient
rest the process starts over again.
With the carets something of the same sort seems to take place—if we
may consider as betokening a general law the fact that in 1894 the
carets at the mouths of the Phison and Euphrates developed before their
affiliated canals. But about them much less is yet known, and we must
be content to say that the observations of 1905 made at the opposite
season of the canal’s year seem to bear this out.
PART IV
EXPLANATION
CHAPTER XXVIII
CONSTITUTION OF THE CANALS AND OASES
As rational science does not rest content with raw results, it now
becomes obligatory, by marshaling the facts to suitable discussion, to
seek to find out what they mean. Now, so soon as we scan these
phenomena for some self-interpretation, we perceive one characteristic
of the lines which at once appears to direct us to their nature and
justifies itself as a signpost with increasing certainty as we read on.
This trait is the very simple yet most significant one of showing
intrinsic change: the lines alter in visibility with time. This primary
proclivity we do not even need the cartouches to establish. That the
lines change is palpable to any one who will watch them long enough.
Schiaparelli was struck by the fact early in his study of the planet,
and it forces itself on the notice of any careful observer who compares
his own observations with one another at intervals. But though the
cartouches are not needed to a first revelation of mutability, they
serve to certify and precise it to much further information on the
subject. For, that these changes are not extrinsic, that is, are not
caused by varying definition, distance, or illumination, they make
patent even to those who have never seen the things themselves by
disclosing respective differences of behavior in lines similarly
circumstanced optically. The change is therefore intrinsic, and the
question arises to what can such intrinsic change be due.
In searching for cause, attention is at once attracted by another
series of transmutations that manifests itself upon the disk, in the
orderly melting of the polar caps. For the existence of the two sets of
metamorphoses suggests the possibility of a connection between them.
The inference is strengthened when we note that not only are both
periodic, but that furthermore the period of the two is the same. Each
polar cap runs through its gamut of change in a Martian year; the
canals also complete their cycle of growth and decay in a Martian
twelvemonth. The only difference between the two is that each polar cap
has but one maximum and one minimum in the course of this time, while
most of the canals have two of each, though the maxima are not alike
nor the minima either.
Not only is the period of the two series of changes the same, but the
one follows the other. For the development of the canals does not begin
till the melting of the polar cap is well under way. Now, as the polar
cap disintegrates it gives rise, as we have seen, to a dark belt of
blue-green which fringes its outer edge and retreats with it as it
shrinks. This tells, directly or indirectly, of a product let loose.
After this belt has been formed the canals nearest to it proceed to
darken, then those a little farther off follow suit, and so the wave of
visibility rolls in regular routine down the disk. Here, then, at the
outset we have a chronic connection between the two phenomena, the
disintegration of the cap and the integration of the canals.
Of water we saw that the caps were undoubtedly composed, and to water,
then, let loose by the melting of the cap, we may inferably ascribe the
thaumaturgy in the development of the canals. But it is not necessary
to suppose that this is done directly. That the increased visibility of
the canals can be due to a bodily transference of water seems doubtful,
if for no other reason than the delay in the action. Considerable time
intervenes between the disappearance of the cap and the appearance of
the canals, except in the case of such as have been covered by it.
Transformation consequent upon transference, however, would account for
hesitancy. A quickening to vegetal growth would produce the counterpart
of what we see. If, set free from the winter locking up, the water
accumulated in the cap then percolated equatorward, starting vegetation
in its course, this would cause the increased visibility of the canals
and at the same time explain the seeming delay, by allowing for the
time necessary for this vegetation to sprout. This is certainly the
most satisfactory explanation of the phenomena.
Thus started, the vegetal quickening would pass down the planet’s
surface and give rise to what we mark as seasonal change. But, though
in one sense of seasonal character, a little consideration will show
that it would be quite unlike the seasonal change which we know on
earth.
Could we see our earth from some standpoint in space, we should mark,
with the advent of spring, a wave of verdure sweep over its face. If
freedom from cloud permitted of an unimpeded view, this flush of waking
from winter’s sleep would be quite evident and could be seen to spread.
Starting from the equator so soon as the sun turned north, it, too,
would travel northward, and, distancing the sun, arrive by midsummer
well into the arctic zone. Here, then, we should note, much as we note
it on Mars, a tint of blue-green superpose itself successively upon the
ochre ground; but the mundane and the Martian vegetal awakening would
differ in one fundamental respect; the earthly wave would be seen to
travel from equator to pole, while the Arian travels from pole to
equator. Though clearly seasonal in character, both of them, the
transformations would be opposite in action. Some other cause, then,
must be at work from what we are familiar with on earth. This other
cause is the presence or absence of moisture.
Two factors are necessary to the begetting of vegetal life, the raw
material and the reacting agent. Oxygen, nitrogen, water, and a few
salts make up the first desideratum, the sun supplies the second.
Unless both be present, the quickening to life never comes. Now, the
one may be there and the other not, or the other there and the one not.
On earth the material including water is, except in certain destitute
localities, always present; the sun it is that periodically withdraws.
Observant upon the return of the sun is therefore the annual recurrence
of vegetal growth.
On Mars, on the contrary, water is lacking. This we now know
conclusively from other phenomena the disk presents which have no
connection with the present investigation and are, therefore,
unprejudiced witnesses to the fact. No permanent bodies of water stud
its surface. That the so-called seas are traversed by dark lines
permanent in place is one of several proofs of this. The only surface
water the planet knows comes from the melting of its polar caps.
Vegetation cannot start until this water reaches it. Consequently,
though the sun be ready, vegetation must wait upon the coming of the
water, and starting from near the pole follow the frugal flood
equatorward.
[Illustration: PHENOLOGY CURVES—EARTH.
* = Dead Point of Vegetation.
(From paper in _Proc. Amer. Phil. Soc._, by Percival Lowell.)]
[Illustration: PHENOLOGY CURVES—MARS.
* = Dead Point of Vegetation.
(From paper in _Proc. Amer. Phil. Soc._, by Percival Lowell.)]
Now, such contrariety of progression to what we should observe in the
case of the earth could we view it from afar is exactly what the curves
of visibility of the canals exhibit. Timed primarily, not to the return
of the sun but to the advent of the water, vegetal quickening there
follows, not the former up the latitudes but the latter down the disk.
For better understanding, the two curves of phenological quickening,
the mundane and the Martian, are shown in the diagrams. The plates
represent the surfaces of the two planets, that of the earth being
shown upside down with south at the top so as to agree with the
telescopic depiction of the topography of Mars. The stars mark the
epoch of the dead-point of vegetation at successive latitudes; the time
increasing toward the right. The curves, it will be noticed, are bowed
in opposite ways. The bowed effect is due in part to Mercator’s
projection; in part it may represent a real decrease in speed with
time. But what is strikingly noticeable is the opposite character of
the advance to the right, the one curve running up the disk, the other
down it. This shows that the development of vegetation proceeded in
opposite directions over the surface.
Thus is the opposed action upon the two planets accounted for, and we
are led to the conclusion that the canals are strips of vegetation fed
by water from the polar caps, and that the floral seasons there as
affecting the canals are conditioned, not as they would be with us,
directly upon the return of the sun, but indirectly so through its
direct effect upon the polar snows.
Once adventured on the idea of vegetation, we find that it explains
much more than the time taken by the wave of canal-development down the
disk. It accounts at once for the behavior of the canals in the three
northern zones: the polar, arctic, and sub-arctic. The mean cartouches
of these three zones dip down at their latter end instead of rising
there, as is the case with the cartouches of the mean canals farther
south. This dip denotes that the most northern canals were waning
already by the middle of their August, though the others showed no such
tendency; while the date of the deposition of the frost in these
northern latitudes shows that they were started upon their course
toward extinction before the snow itself had covered them. In other
words, they were not obliterated but snuffed out. That their decline
was thus preparatory to the coming of the first snowfall or frost-fall,
sufficiently severe to whiten the ground so that it did not melt the
next day, is suggestive of their constitution. It is clear that they
were not abruptly cut off by the frost, but were timed by nature to
such extinction. Vegetation would behave in just this way, since
evolution would accommodate the career of a plant to its environment.
The first question to present itself chronologically in the canals’
annual history is connected with the size of the cap. Unfortunately for
the simplicity of the phenomena, the cap is not an extensionless source
of flow, but an extended surface melting from the outer edge in. It
would seem, therefore, that water liberated from the outer parts should
have an effect before the main body of it were ready to begin its
general march down the disk. There should be, one would think, at least
a partial action, locally, before the main action got under way. Now,
there are certain canals that show cartouches increasing apparently
from the time observations began, and the most pronounced is the
Jaxartes, which lies of all the canals observed the farthest north.
Now, the cartouches were founded on canals quickened from the north
polar cap. The farther north the canal, therefore, the greater the
likelihood of its showing the phenomena.
That we note such canals is therefore not only not subversive, but
actually corroboratory, of the law it seems at first to shake. That all
the canals of these zones do not show a like cartouche-profile is not
necessary, a part of them being dependent, not upon the earlier, but
upon the later liberated flow, and thus partaking in the general law,
which grows uniform lower down the latitudes.
As the action from one polar cap proceeds, not only down to the
equator, but across it into the planet’s other hemisphere, it appears
that much, at least, of the surface of Mars has two seasons of vegetal
growth, the one quickened of the north polar cap, the other of the
southern. How far the polar spheres of action overlap it is not
possible at present to affirm, as the canals at this opposition were
only visible to 35° south latitude. That the north polar quickening
goes down so far is vouched for, and it is probable from other observed
phenomena that it goes farther.
The alternate semi-annual quickening also discloses itself directly in
the cartouches; the previous semestral growth from the south polar cap
actually showing in them before the impulse from the north began. The
slow falling of their curves to the minimum preceding their later rise
is nothing less than the dying out of the effect started six months
before from the south. The gentler gradient of their fall proclaims a
gradual lapse, just as the subsequent sharper rise points to the advent
of a fresh impulse. And this deduction seems to be borne out by another
circumstance. There is some evidence of decrease in the pre-minimal
gradient southward. This is telling testimony to the source whence the
impulse came. For if it originated at the south and traveled northward,
the southern canals would be the first to be affected and the first to
die out, and thus show a longer dead season, exhibited in the
cartouches as a more level stretch.
Lastly, the explanation of the canals as threads of vegetation fays in
with the one which has been found to meet the requirements of the
blue-green areas; while the fact that they prove to develop as they do,
reversely to what would take place on earth, is exactly what all we
have latterly learnt about the surface conditions of the planet would
lead us to expect.
From what has just been said we see that the latest observations at
Flagstaff confirm the earlier ones, and, what is especially
corroborative, they do so along another line. The former were chiefly
static, the latter kinematic. In other words, the behavior of the
canals in action bears out the testimony of their appearance at rest.
CHAPTER XXIX
LIFE
Study of the fundamental features of Martian topography has disclosed,
as we have seen, the existence of vegetation on the planet as the only
rational explanation of the dark markings there, considered not simply
on the score of their appearance momentarily, but judged by the changes
that appearance undergoes at successive seasons of the Martian year.
Thus we are assured that plant life exists on the planet. We are made
aware of the fact in more ways than one, but most unanswerably for that
trait to which vegetation owes its very name,—its periodic quickening
to life. Thus the characteristic which has seemed here most distinctive
of this phase of the organic, so that man even christened it in
accordance, has proved equally telltale there.
Important as a conclusion this is no less pregnant as a premise. For
the assurance that plant life exists on Mars leads to a further step in
extramundane acquaintance of far-reaching import. It introduces us at
once to the probability of life there of a higher and more immediately
appealing kind, not with the vagueness of general analogy, but with the
definiteness of specific deduction. For the presence of a flora is
itself ground for suspecting a fauna.
Of a bond connecting the two we get our first hint the moment we look
inquiringly into the world about us, that of our own earth. Common
experience witnesses to a coexistence which grows curious and
compelling as we consider it. For it is not confined to life of any
special order, but extends through the whole range of organisms of both
kinds from the lowest to the highest. Algæ and monera, orchid and
mammal, occur side by side and with a certain considerate poverty or
richness, as the case may be. Luxuriance in the one is matched by
abundance in the other; while a scanty flora means a poor fauna. This
of which we have been aware in regions round about us from childhood
grows in universality as we explore. Wherever man penetrates out of his
proper sphere he finds the same dual possession of the land or the sea,
and a similar curtailing or expanding of both tenantries together. No
mountain top so cold but that if it grow plants, it supports insects
and animals, too, after its kind; no desert so arid but that creeping
things find it as possible a habitat as life that does not stir. Even
in almost boiling geysers animalcula and confervæ share and share
alike. Only where extreme conditions preclude the one do they equally
debar the other.
Proceeding now from the fact to its factors we perceive reasons for
this tenure in common of the land by the vegetal and animal kingdoms.
Examination proves the two great divisions of the organic to be
inextricably connected. It strikes our notice first in the relation of
plants to animals. It is of everyday notoriety that animals eat plants,
though it is less universally understood that in the ultimate they
exist on nothing else. Plants furnish the food of animals; not as a
matter of partial preference but of fundamental necessity. For the
plant is the indispensable intermediary in the process of metabolism.
Without plants animals would soon cease to exist, since they are unable
to manufacture their own plasm out of the raw material offered by
inorganic nature. They must make it out of the already prepared plasm
of plants or out of other animals who have made it from plants. So that
in the end it all comes back to plant production. The plant is able to
build its plasm out of chemical substances; the animal cannot, except
in the case of the nitro-bacteria, begin thus at the lowest rung of the
alimentary ladder.
But the converse of this dependence is also largely true. Plants are
beholden to animals for processes that in return make their own life
possible. The latter minister to the former with unconscious service
all the time, and with no more arrogant independence than do our
domestics generally nowadays. The inconspicuous earthworm is the
fieldhand of nature’s crops, who gets his own living by making theirs.
Without this day and night laborer the soil for want of stirring had
remained less capable of grass. Above ground it is the same story.
Deprived of the ministrations of insects many kinds of plants would
incontinently perish. By the solicited visits of bees and other
hymenoptera—what generically may be classed by the layman as
flutter-bys—is the plant’s propagation made possible. Peculiarly well
named, indeed, are the hymenoptera, seeing that they are the great
matrimonial go-betweens, carrying pollen from one individual to another
and thus uniting what otherwise could not meet. Spectacular as this
widespread commerce is, it forms but portion of the daily drama in
which animals and plants alike take part. From forthright bargainings
of honey for help, we pass to less direct but no less effective
alliance where plants are beholden to animals for life by the killing
of their enemies or the weeding-out of their competitors, and from this
to generic furtherance where the interdependence becomes broadcast. In
the matter of metabolism the advantage is not all upon one side. In the
katabolic process of that which each discards are the two classes of
life mutually complimentary,—the waste of the one being the want of
the other,—carbonic acid gas being given off by the animal, oxygen by
the plant. In biologic economy it is daily more demonstrable that both
are necessary constituents to an advancing whole, and that each pays
for what it gets by what it gives in return.
That they are thus ancillary as well as coexistent today leads us to
confront for them a community of origin in the past; and further study
confirms the inference. Both paleontology and entomology, or the
science of the aged and the science of the young, prove such ancestry
to be a fact. By going back from the present into the past, or, what
amounts to substantially the same thing, by descending in the scale of
life to the lowest known forms of organism, we find proof of
concomitance, cogent because congenital. At the time when inorganic
chemical compounds first passed by evolution into organic ones, the
change was of so general a character that even such tardy
representatives of it as survive today tax erudition to tell to which
of the two great kingdoms they belong, the vegetal or the animal.
Simplest and most primitive of known organisms are the chromacea,
unnucleated single cells as Haeckel has shown, and next to them in
order come many of the bacteria, also of simple unnucleated plasm. So
little do the majority of the bacteria differ morphologically from the
chromacea, that on the score of structure the two are not to be
catalogued apart. Both are as elemental as anything well can be, which
only their diet serves to divide. Each is an organism without organs,
thus belying the dictionary definition of both animals and plants.
Etymologically they are not organic yet manifestly are alive, and only
in their action are unlike. The chromacea are plasm-forming beings, and
therefore they are plants; the bacteria are plasm-eating beings, and so
are animals. Even this distinction is not always preserved. As Haeckel
tells us: “the nitro-bacteria which dwell in the earth having the
vegetal property of converting ammonia by oxidation into nitrous acid
and this into nitric acid, using as their source of carbon the carbonic
acid gas of the atmosphere. They feed, like the chromacea, on simple
inorganic compounds.” Here, then, we have, close to the threshold of
organic life, unorganized organisms, roughly speaking coeval and
differing in a sense but little, either of them, from inorganic
crystals; and yet the one is an animal, the other a plant. Progenitors
of the two great divisions of life, they were themselves concomitantly
evolved, either side by side or as offshoots both of a common stock.
Now, if the ancestors of the two great organic kingdoms were thus
simultaneously produced here, we are warranted in believing that they
would similarly be produced elsewhere, given conditions suitably alike.
In consequence, if we detect the presence of the one, we already have
an argument for inferring the other. Not to complete our syllogism
would be to flaunt a lack of logic in nature’s face.
Rationally viewed, then, the general problem of life in other worlds
reduces itself to a question of conditions. Since certain physical
results follow inevitably upon certain physical premises, if we can
assure ourselves of the proper premises we may look to nature for their
conclusion. _A priori_, then, the possibility of life becomes one of
habitat. If the environment be suitable life will ensue. What makes for
such a mediary _milieu_ is, like most cosmic processes, in its
fundamentals of interesting simplicity; for the production of a proper
nidus depends primarily upon the mere size of the body parentally
concerned. If a planet be big enough it will inevitably bring forth
life, because of conditions suitable to its generating; if too small it
will remain sterile to the end of time.
That size should be the determining factor whether a planet shall be
fecund or barren may seem at first thought strange. Yet that it is so
admits of no rational doubt. All that we see of bodies about us shows
its truth, and what we have learnt of cosmic process enables us in some
sort to discern why. In order for evolution, such as we mark it upon
the earth, to be possible, the parent body must have been at one time
at a high temperature, since only under great heat can the primal
processes occur. But for this generation of caloric the aggregate mass
of the particles, the falling together of which makes the planet, and
their stoppage its internal heat, must be large. The sun’s rays alone
are insufficient to cause the necessary temperature; the heat must come
from within, though it be helped from without. Even here the action is
abetted by a large body. For a planet to entrap the sun’s rays or even
to preserve its own internal warmth, an atmosphere is needed, and it
takes a large body to retain an atmospheric covering sufficiently long.
Yet without it not only would there be no suitable state, but no medium
in which organic or even inorganic reactions could go on. Lastly,
water, the essential nidus for the organism’s early stages, has its
presence similarly conditioned. For this, like the atmosphere, would
from a small body speedily vanish away. Thus the planet itself is the
life-producing body, although the sun furthers the process when once
begun.
That the needed substances are planetarily present, what we know of the
distribution of matter astronomically sufficiently attests. What we
find in meteorites shows that the catastrophe which preceded our
present solar system’s birth scattered its elemental constituents
throughout its domain, and thus when they came to be gathered up again
into planets that these must have been materially the same. The manner,
not the matter, then, is alone that about which we are concerned.
Now, if the mass of matter gravitating together to form a planet be
sufficient to produce the proper inorganic conditions, the organic must
follow as a matter of course. That the organic springs from the
inorganic is not only shown by what has taken place on earth, but is
the necessary logical deduction from its decay back into the inorganic
again. As Nägeli admirably observes: “The origin of the organic from
the inorganic is, in the first place, not a question of experience and
experiment, but a fact deduced from the law of the constancy of matter
and force. If all things in the material world are causally related, if
all phenomena proceed on natural principles, organisms which are formed
of and decay into the same matter must have been derived originally
from inorganic compounds.”
The original oneness of the two, the fact that the organic sprang from
the inorganic, is shown by the cousinly closeness of the lowest organic
with the highest inorganic substances. The monera are suggestive of
crystals in their uniformity of structure. Both are homogeneous or
approximately so. Again, both grow by taking from what they come in
contact with that which they find suitable and so add to their body by
homogeneous accretion. Finally, when grown too large for single life,
they part into similar crystals or split into identical cells. The
difference between the division of the crystal and the fission of the
cell is small in kind; much less than that later differentiation in
genesis into parthenogenesis and sexual reproduction. Yet here we
unhesitatingly trace an assured relationship. It were straining at a
gnat to swallow a camel to doubt it in the other.
Just as the two behave analogically alike in their own action, so do
they observe a like attitude toward nature. They thus point to their
common origin. The monera are resemblant of chemical compounds in their
superiority to external influences. To outward conditions of
temperature and humidity the chromacea are much as sticks and stones.
Some species may remain for long frozen in ice, Haeckel observes, and
yet wake to activity so soon as it thaws. Others may be completely
desiccated, and then resume their life when put in water after a lapse
of several years. Thus both in their deathlike lives and in their
living immortality the chromacea are close to inorganic things.
From preference, however, these lowest forms of life affect what to us
would be unbearable temperatures. Many of the chromacea live in hot
springs at temperatures of 123° to 176° Fahrenheit, in which no other,
that is, no higher, organism can dwell. This choice of habitat is in
line with the other details of their evolutionary career. For it, too,
is in keeping with the conditions of crystalline growth, halfway as it
were on the road to them; the forming of crystals beginning at a
temperature higher still. And we perceive from it that the passing of
the inorganic into the organic is brought about by a lowering of the
temperature of the parent planet. This again, is in line with the
evolution of chemical complexity. Let the heat become less, and higher
and higher chemical compounds, finally the organic ones, become
possible. That evolution is nothing else than such a gradually
increasing chemical synthesis is forced on one by study of the facts.
Once started, life, as paleontology shows, develops along both the
floral and the faunal lines side by side, taking on complexity with
time. It begins so soon as secular cooling has condensed water vapor to
its liquid state; chromacea and confervæ coming into being high up
toward the boiling-point. Then, with lowering temperature come the
seaweeds and the rhizopods, then the land plants and the lunged
vertebrates. Hand in hand the fauna and flora climb to more intricate
perfecting, life rising as temperature lowers.
We perceive then that, considered _a priori_, the possibility of life
on a planet is merely a question of the planet’s size; and then
pursuantly that the character of that life is a matter of the planet’s
age. But age again is a question of size. For the smaller its mass the
quicker the body cools, and with a planet, growing cold means growing
old. Within the bounds that make life possible, the smaller the body
the quicker it ages and the more advanced its denizens must be. Just
how far the advance goes we may not assert dogmatically in a given
case, since not relative age alone but absolute time as well is
concerned in it. It may be that nature’s processes cannot be hurried,
and that for want of time development may in part be missed. But from
general considerations the limit of the time needed seems well within
most planetary careers.
Now, the aspect of the surface of Mars shows that both these conditions
have been fulfilled. Mars is large enough to have begotten vegetation
and small enough to be already old. All that we know of the physical
state of the planet points to the possibility of both vegetal and
animal life existing there, and furthermore, that this life should be
of a relatively high order is possible. Nothing contradicts this, and
the observations of the last ten years have rendered the conclusion
then advanced only the more conclusive. Even the evidence of the past
state of the planet confirms that given by its present one. That with
us life came out of the seas finds its possible parallel in the fact
that seas seem once to have existed there, leaving their mark
discernible to-day. Life, then, had there as here the wherewith to
begin. That we find air and water in both shows that it had the means
to continue once begun. That it then ran a like course is further
witnessed by what we now detect. The necessary premises, then, are
there. More than this. One half of the conclusion, vegetal life, gives
evidence of itself.
CHAPTER XXX
EVIDENCE
Of the existence of animal life upon a far planet any evidence must, of
necessity, assume a different guise from what its flora would present.
Plant life should be, as on Mars we perceive it is, recognizable as
part and parcel of the main features of the planet’s face. In no such
forthright manner could we expect an animal revelation. The sort of
testimony which would render the one patent would leave the other
obstinately hid.
So long as animate life was in the lowest sense animal, it would not be
seen at all, though it were as widespread as the vegetal life all about
it. Reason for this lies in their receptive character. Plants are
fixtures; where they start they stay; while from the nature of their
food, derived directly from the soil and from the air, and conditioned
chiefly by warmth and moisture, like forms inhabit large areas and by
their massed effect make far impression. With animals it is otherwise.
They feed by forage, from beetle to buffalo, roaming the land for
sustenance. Thus, both for paucity of number and from not abiding in
one stay they must escape notice at a distance such that as individuals
they fail to show; to say nothing of the fact that the flora usually
overtop the fauna, and so help to hide the latter while appearing
itself distinct. Any far view of our earth gives instance of this. Seen
from some panoramic height, forest and moorland lie patently outspread
to view, yet imagination is taxed to believe them tenanted at all.
Unless man have marred the landscape not a sign appears of any living
thing. One must be near indeed to note even such unusual sights as a
herd of buffalo in the plains or those immense flights of pigeons, that
in former years occurred like clouds darkening the air. From the
standpoint of another planet, through any such direct showing animal
existence would still remain unknown.
Not until the creatures had reached a certain phase in evolution would
their presence become perceptible; and not then directly, but by the
results such presence brought to pass. Occupancy would be first
evidenced by its imprint on the land; discernible thus initially not so
much by the bodily as by the mind’s eye. For not till the animal had
learnt to dominate nature and fashion it to his needs and ends would
his existence betray itself. By the transformation he wrought in the
landscape would he be known. It is thus we should make our own far
acquaintance; and by the disarrangement of nature first have inkling of
man.
That it is thus we should betray ourselves, a consideration of man’s
history will show. While he still remained of savage simplicity, a mere
child of nature, he might come and go unmarked by an outsider, but so
soon as he started in to possess the earth his handicraft would reveal
him. From the moment he bethought him to till the ground, he entered
upon a course of world-subjugation of which we cannot foresee the end;
but he has already advanced far enough to give us an idea of the
process. It began with agriculture. Deforestation with its subsequent
quartering of crops signalized his acquisition of real estate. His
impress at first was sporadic and irregular, and in so far followed
that of nature itself; but as it advanced it took on a methodism of
plan. Husbandry begot thrift, and augmented wants demanded an
increasing return for toil; and to this desirable end systematization
became a necessity. At the same time gregariousness grew and still
further emphasized the need for economy of space and time. In part
unconsciously, man learnt the laws that govern the expenditure of force
and more and more consciously applied them. Geometry, unloosed of
Euclid, became a part of everyday life as insidiously as M. Jourdain
found that he had been talking prose. Regularity rules to-day, to the
lament of art. The railroad is straighter than the turnpike, as that is
straighter than the trail. Communication is now too urgent in its
demands to know anything but law and take other than the shortest path
to its destination. Tillage has undergone a like rectification. To one
used to the patchwork quilting of the crops in older lands the
methodical rectangles of the farms of the Great West are painfully
exact. Yet it is more than probable that these material manifestations
would be the first signs of intelligence to one considering the earth
from far. Our towns would in all likelihood constitute the next; and,
lastly, the great arteries of travel that minister to their wants.
Their scale, too, would render them the first objects to be observed.
Farming as now practiced in Kansas or Dakota gives it a certain
cosmical concern; fields for miles turning in hue with the rhythm of
the drilled should impress an eye, if armed with our appliances, many
millions of miles away.
Even now we should know ourselves cosmically by our geometrical
designs. To interplanetary understanding it is this quality that would
speak. Still more so will it tell as time goes on. As yet we are but at
the beginning of our subjugation of the globe. We have hardly explored
it all, still less occupied it. When we do so, and space shall have
become enhancedly precious, directness of purpose with economy of
result will have partitioned so regularly the surface of the earth as
to impart to it an artificiality of appearance, and it becomes one vast
coördinated expanse subservient entirely to the wants of its
possessors. Centres of population and lines of communication, with
tillage carried on in the most economic way; to this it must come in
the end.
Nor is this outcome in any sense a circumstance accidental to the
earth; it is an inevitable phase in the evolution of organisms. As the
organism develops brain it is able to circumvent the adversities of
condition; and by overcoming more pronounced inhospitality of
environment not only to survive but spread. Evidence of this thought
will be stamped more and more visibly upon the face of its habitat. On
earth, for all our pride of intellect, we have not yet progressed very
far from the lowly animal state that leaves no records of itself. It is
only in the last two centuries that our self-registration upon our
surroundings has been marked. With another planet the like course must
in all probability be pursued, and the older the life relatively to its
habitat the more its signs of occupation should show. Intelligence on
other worlds could then only make its presence known by such material
revelation, and the sign-manuals of itself would appear more artificial
in look as that life was high in rank. Given the certainty of
plant-life, such markings are what one would look to find. Criticism
which refuses to credit detail of the sort because too bizarre to be
true writes itself down as unacquainted with the character of the
problem. For it is precisely such detail which should show if any
evidence at all were forthcoming.
If, now, we turn our inquiry to Mars, we shall be fairly startled at
what its disk discloses. For we find ourselves confronted in the canals
and oases by precisely the appearances _a priori_ reasoning proves
should show were the planet inhabited. Our abstract prognostications
have taken concrete form. Here in these rectilineal lines and roundish
spots we have spread out our centres of effort and our lines of
communication. For the oases are clearly ganglia to which the canals
play the part of nerves. The strange geometricism which proves
inexplicable on any other hypothesis now shows itself of the essence of
the solution. The appearance of artificiality cast up at the phenomena
in disproof vindicates itself as the vital point in the whole matter.
Like the cachet of an architect, it is the thing about the building
that established the authorship.
Though the Earth and Mars agree in being planets, they differ
constitutionally in several important respects. Even to us the curious
network that enshrouds the Martian disk suggests handicraft; it implies
it much more when considered from a Martian standpoint.
CHAPTER XXXI
THE HUSBANDING OF WATER
That the canals and oases are of artificial origin is thus suggested by
their very look; when we come to go further and inquire into what may
be their office in the planet’s economy, we find that the idea in
addition to its general probability now acquires particular support.
For this we are indebted in part to study of their static aspect, but
chiefly to what has been learnt of their kinematic action.
Dearth of water is the key to their character. Water is very scarce on
the planet. We know this by the absence of any bodies of it of any size
upon the surface. So far as we can see the only available water is what
comes from the semi-annual melting at one or the other cap of the snow
accumulated there during the previous winter. Beyond this there is none
except for what may be present in the air. Now, water is absolutely
essential to all forms of life; no organisms can exist without it.
But as a planet ages, it loses its oceans as has before been explained,
and gradually its whole water supply. Life upon its surface is
confronted by a growing scarcity of this essential to existence. For
its fauna to survive it must utilize all it can get. To this end it
would be obliged to put forth its chief endeavors, and the outcome of
such work would result in a deformation of the disk indicative of its
presence. Lines of communication for water purposes, between the polar
caps, on the one hand, and the centres of population, on the other,
would be the artificial markings we should expect to perceive.
Now, it is not a little startling that the semblance of just such signs
of intelligent interference with nature is what we discern on the face
of Mars,—in the canals and oases. So dominant in its mien is the
pencil-like directness of the canals as to be the trait that primarily
strikes an unprejudiced observer who beholds this astounding system of
lines under favorable definition for the first time, and its
impressiveness only grows on him with study of the phenomena. That they
suggested rule and compass, Schiaparelli said of them long ago, without
committing himself as to what they were. In perception the great
observer was, as usual, quite right; and the better they are seen the
more they justify the statement. Punctilious in their precision, they
outdo in method all attempts of freehand drawing to copy them. Often
has the writer tried to represent the regularity he saw, only to draw
and redraw his lines in vain. Nothing short of ruling them could have
reproduced what the telescope revealed. Strange as their depiction may
look in the drawings, the originals look stranger still. Indeed, that
they should look unnatural when properly depicted is not unnatural if
they are so in fact. For it is the geodetic precision which the lines
exhibit that instantly stamps them to consciousness as artificial. The
inference is so forthright as to be shared by those who have not seen
them to the extent of instant denial of their objectivity. Drawings of
them look too strange to be true. So scepticism imputes to the
draughtsman their artificial fashioning, not realizing that by so doing
it bears unconscious witness to their character. For in order to
disprove the deduction it is driven to deny the fact. Now the fact can
look after itself and will be recognized in time. For that the lines
are as I have stated is beyond doubt. Each return of the planet shows
them more and more geometric as sites are bettered and training
improves.
Suggestive of design as their initial appearance is, the idea of
artificiality receives further sanction from more careful
consideration, even from a static point of view, on at least eight
counts:—
1. Their straightness;
2. Their individually uniform size;
3. Their extreme tenuity;
4. The dual character of some of them;
5. Their position with regard to the planet’s fundamental features;
6. Their relation to the oases;
7. The character of these spots; and, finally,
8. The systematic networking by both canals and spots of the whole
surface of the planet.
Now, no natural phenomena within our knowledge show such regularity on
such a scale upon any one of these eight counts, _a fortiori_ upon all.
When one considers that these lines run for thousands of miles in an
unswerving direction, as far relatively as from London to Bombay, and
as far actually as from Boston to San Francisco, the inadequacy of
natural explanation becomes glaring.
These several counts become more expressive of design the farther one
looks into them. Straightness upon a sphere means the following of an
arc of a great circle. The lines, then, are arcs of great circles. Now,
the great circle course is the shortest distance connecting two given
points. The canals of Mars, then, practice this economy; they connect
their terminals by the shortest, that is, other things equal, by the
quickest and least wasteful path. Their preserving a uniform width
throughout this distance is an equally unnatural feature for any
natural action to exhibit, but a perfectly natural one for an unnatural
agent. For means of communication for whatever cause would probably be
fashioned of like countenance throughout. Their extreme tenuity is a
third trait pointing to artificiality; inasmuch as the narrower they
are, the more probable is their construction by local intelligence.
Even more inexplicable, except from intent, is their dual character.
For them to parallel one another like the twin rails of a railway
track, seems quite beyond the powers of natural causation. Enigmatic,
indeed, from a natural standpoint, they cease to be so enigmatic viewed
from an artificial one; and this the more by reason of what has lately
been learnt of the character of their distribution. That they are found
most plentifully near the equator, where the latitudinal girth is
greatest, and thence diminish in numbers to about latitude 60°, where
they disappear,—and this not relatively to the amount of surface but
actually,—is very significant. It is quite incapable of natural
explanation, and can only be accounted for on some theory of design
such as lines of communication, or canals conducting water down the
latitudes for distribution. So that this distribution of the doubles is
in keeping with the law of development disclosed by the canals _en
masse_. Channels and return-channels the two lines of the pair may be,
but about this we can at present posit nothing. The relation may be of
still greater complexity, and we must carefully distinguish between
surmise and deduction.
The position of the canals, with regard to the main features of the
disk, has a cogency of its own, an argument from time. The places from
which the lines start and to which they go are such as to imply a
dependence of the latter upon the former chronologically. The lines are
logically superposed upon the natural features; not as if they had
grown there, but as if they had been placed there for topographic
cause. Those termini are used which we should ourselves select for
stations of intercommunication. For the lines not only leave important
geodetic points, but they travel directly to equally salient ones.
The connection of the canals with the oases is no less telltale of
intent. The spots are found only at junctions, clearly the seal and
sanction of such rendezvous. Their relation to the canals that enter
them bespeaks method and design. Centring single lines, they are
inclosed by doubles, a disposition such as would be true did they hold
a pivotal position in the planet’s economy.
The shape of the oases also suggests significance. Their form is round,
a solid circle of shading of so deep a tone as to seem black, although
undoubtedly in truth blue-green. Now, a circular area has this peculiar
property, that it incloses for a given length of perimeter the maximum
of space. Any other area has a longer inclosing boundary for the
surface inclosed. Considering each area to be made up of onion-like
envelops to an original core, each similar in shape to the kernel, we
see that the property in question means that the average distance for
points of the circular area from the centre is less than the same
distance for those of any other figure. This has immediate bearing on
the possible fashioning of such areas. For sufficient intelligence in
the fashioners would certainly lead to a construction, where the
greatest area could be attended to at the least expenditure of force.
This would be where the distance to be traveled from the centre to all
the desired points was on the average least; that is, the area would be
round.
But last and all-embracing in its import is the system which the canals
form. Instead of running at haphazard, the canals are interconnected in
a most remarkable manner. They seek centres instead of avoiding them.
The centres are linked thus perfectly one with another, an arrangement
which could not result from centres, whether of explosion or otherwise,
which were themselves discrete. Furthermore, the system covers the
whole surface of the planet, dark areas and light ones alike, a
world-wide distribution which exceeds the bounds of natural
possibility. Any force which could act longitudinally on such a scale
must be limited latitudinally in its action, as witness the belts of
Jupiter or the spots upon the sun. Rotational, climatic, or other
physical cause could not fail of zonal expression. Yet these lines are
grandly indifferent to such compelling influences. Finally, the system
after meshing the surface in its entirety runs straight into the polar
caps.
It is, then, a system whose end and aim is the tapping of the snow-cap
for the water there semiannually let loose; then to distribute it over
the planet’s face.
Function of this very sort is evidenced by the look of the canals.
Further study during the last eleven years as to their behavior leads
to a like conclusion, while at the same time it goes much farther by
revealing the action in the case. This action proves to be not only in
accord with the theory, but interestingly explanatory of the process.
In the first place, the canals have shown themselves, as they showed to
Schiaparelli, to be seasonal phenomena. This negatives afresh the
possibility of their being cracks. But furthermore, their seasonal
behavior turns out to follow a law quite different from what we know on
earth and betokens that they are indebted to the melting of the polar
cap for their annual growth, even more directly than to the sun, and
that vegetation is the only thing that satisfactorily accounts for
their conduct. But again this is not all. Their time of quickening
proceeds with singular uniformity down the disk, not only to, but
_across the equator_. Now, this last fact has peculiar significance.
So large are the planetary masses that no substance can resist the
strains due to the cosmic forces acting on them to change their shape
till it becomes one of stable equilibrium. Thus a body of planetary
size, if unrotating, becomes a sphere except for solar tidal
deformation; if rotating, it takes on a spheroidal form exactly
expressive, as far as observation goes, of the so-called centrifugal
force at work. Mars presents such a figure, being flattened out to
correspond to its axial rotation. Its surface, therefore, is in fluid
equilibrium, or, in other words, a particle of liquid at any point of
its surface at the present time would stay where it was, devoid of
inclination to move elsewhere.
Now, the water which quickens the verdure of the canals moves from the
neighborhood of the pole down to the equator as the season advances.
This it does, then, irrespective of gravity. No natural force propels
it, and the inference is forthright and inevitable that it is
artificially helped to its end. There seems to be no escape from this
deduction. Water flows only downhill, and there is no such thing as
downhill on a surface already in fluid equilibrium. A few canals might
presumably be so situated that their flow could, by inequality of
terrane, lie equatorward, but not all. As we see on the earth, rivers
flow impartially to all points of the compass, dependent only upon
unevenness of the local surface conditions. Now, it is not in
particular but by general consent that the canal system of Mars
develops from pole to equator.
From the respective times at which the minima take place, it appears
that the canal-quickening occupies fifty-two days, as evidenced by the
successive vegetal darkenings to descend from latitude 72° north to
latitude 0°, a journey of 2650 miles. This gives for the water a speed
of fifty-one miles a day, or 2.1 miles an hour. The rate of progression
is remarkably uniform; and this abets the deduction as to assisted
transference. The simple fact that it is carried from near the pole to
the equator is sufficiently telltale of extrinsic aid, but the
uniformity of the action increases its significance.
But the fact is more unnatural yet. The growth pays no regard to the
equator, but proceeds across it as if it did not exist into the
planet’s other hemisphere. Here is something still more telling than
its travel to this point. For even if we suppose, for the sake of
argument, that natural forces took the water down to the equator, their
action must there be certainly reversed and the equator prove a
dead-line to pass which were impossible.
CHAPTER XXXII
CONCLUSION
That Mars is inhabited by beings of some sort or other we may consider
as certain as it is uncertain what those beings may be. The theory of
the existence of intelligent life on Mars may be likened to the atomic
theory in chemistry in that in both we are led to the belief in units
which we are alike unable to define. Both theories explain the facts in
their respective fields and are the only theories that do, while as to
what an atom may resemble we know as little as what a Martian may be
like. But the behavior of chemic compounds points to the existence of
atoms too small for us to see, and in the same way the aspect and
behavior of the Martian markings implies the action of agents too far
away to be made out.
But though in neither case can we tell anything of the Bodily form of
its unit, we can in both predicate a good deal about their workings.
Apart from the general fact of intelligence implied by the geometric
character of their constructions, is the evidence as to its degree
afforded by the cosmopolitan extent of the action. Girdling their globe
and stretching from pole, to pole, the Martian canal system not only
embraces their whole world, but is an organized entity. Each canal
joins another, which in turn connects with a third, and so on over the
entire surface of the planet. This continuity of construction posits a
community of interest. Now, when we consider that though not so large
as the Earth the world of Mars is one of 4200 miles diameter and
therefore containing something like 212,000,000 of square miles, the
unity of the process acquires considerable significance. The supposed
vast enterprises of the earth look small beside it. None of them but
become local in comparison, gigantic as they seem to us to be.
The first thing that is forced on us in conclusion is the necessarily
intelligent and non-bellicose character of the community which could
thus act as a unit throughout its globe. War is a survival among us
from savage times and affects now chiefly the boyish and unthinking
element of the nation. The wisest realize that there are better ways
for practicing heroism and other and more certain ends of insuring the
survival of the fittest. It is something a people outgrow. But whether
they consciously practice peace or not, nature in its evolution
eventually practices it for them, and after enough of the inhabitants
of a globe have killed each other off, the remainder must find it more
advantageous to work together for the common good. Whether increasing
common sense or increasing necessity was the spur that drove the
Martians to this eminently sagacious state we cannot say, but it is
certain that reached it they have, and equally certain that if they had
not they must all die. When a planet has attained to the age of
advancing decrepitude, and the remnant of its water supply resides
simply in its polar caps, these can only be effectively tapped for the
benefit of the inhabitants when arctic and equatorial peoples are at
one. Difference of policy on the question of the all-important water
supply means nothing short of death. Isolated communities cannot there
be sufficient unto themselves; they must combine to solidarity or
perish.
From the fact, therefore, that the reticulated canal system is an
elaborate entity embracing the whole planet from one pole to the other,
we have not only proof of the world-wide sagacity of its builders, but
a very suggestive side-light, to the fact that only a universal
necessity such as water could well be its underlying cause.
Possessed of important bearing upon the possibility of life on Mars is
the rather recent appreciation that the habitat of both plants and
animals is conditioned not by the minimum, nor by the mean temperature
of the locality, but by the maximum heat attained in the region. Not
only is the minimum thermometric point no determinator of a dead-line,
but even a mean temperature does not measure organic capability. The
reason for this is that the continuance of the species seems to depend
solely upon the possibility of reproduction, and this in turn upon a
suitable temperature at the critical period of the plant’s or animal’s
career. Contrary to previous ideas on the subject, Merriam found this
to be the case with the fauna of the San Francisco Peak region in
northern Arizona. The region was peculiarly fitted for a test, because
of rising a boreal island of life out of a sub-tropic sea of desert. It
thus reproduced along its flanks the conditions of climates farther
north, altitude taking the part of latitude, one succeeding another
until at the top stood the arctic zone. Merriam showed that the
existence of life there was dependent solely upon a sufficiency of
warmth at the breeding season. If that were enough the animal or plant
propagated its kind, and held its foothold against adverse conditions
during the rest of the year. This it did by living during its brief
summer and then going into hibernation the balance of the time. Nature
in short suspended its functions to a large extent for months together,
enabling it to resurrect when the conditions turned.
Hibernation proves thus to be a trait acquired by the organism in
consequence of climatic conditions. Like all such it can only be
developed in time, since nature is incapable of abrupt transition. An
animal suddenly transported from the tropic to a sub-arctic zone will
perish, because it has not yet learnt the trick of winter sleeping.
While still characterized by seasonal insomnia it is incapable of
storing its energies and biding its time. But given time enough to
acquire the art, its existence is determined solely by the enjoyment of
heat enough at some season to permit of the vital possibility of
reproducing its kind.
Diurnal shutting off of the heat affects the process but little,
provided the fall be not below freezing at the hottest season. So much
is shown by the fauna of our arctic and sub-arctic zones, but still
more pertinently to Mars by the zones of the San Francisco Peak region,
since the thinner air of altitude, through which a greater amount of
heat can radiate off, is there substituted for the thicker one of
latitudinally equal isotherms. Here again with the diurnal as before
with the seasonal it is the maximum, not the mean, or, till low, even
the minimum temperature, that tells.
Now, with Mars the state of things is completely in accord with what is
thus demanded for the existence of life. The Martian climate is one of
extremes, where considerable heat treads on the heels of great cold.
And the one of these two conditions is as certain as the other, as the
condition of the planet’s surface shows conclusively. In summer and
during the day it must be decidedly hot, certainly well above any
possible freezing, a thinner air blanket actually increasing the amount
of heat that reaches the surface, though affecting the length of time
of its retention unfavorably. The maximum temperature, therefore,
cannot be low. The minimum of course is; but as we have just seen, it
is the maximum that regulates the possibility of life. In spite,
therefore, of a winter probably longer and colder than our own, organic
life is not in the least debarred from finding itself there.
Indeed, the conditions appear to be such as to put a premium upon life
of a high order. The Martian year being twice as long as our own, the
summer is there proportionately extended. Even in the southern
hemisphere, the one where the summer is the shortest, it lasts for 158
days, while at the same latitudes our own is but 90 days. This
lengthening of the period of reproduction cannot but have an elevating
effect upon the organism akin to the prolongation of childhood pointed
out by John Fiske as playing so important a part in the evolution of
the highest animals. Day and night, on the other hand, alternate there
with approximately the same speed as here, and except for what is due
to a thinner air covering reproduce our own terrestrial diurnal
conditions, which as we saw are not inimical to life.
In this respect, then, Mars proves to be by no means so bad a habitat.
It offers another example of how increasing knowledge widens the domain
that life may occupy. Just as we have now found organic existence in
abyssal depths of sea and in excessive degrees of both heat and cold,
so do we find from exploration of our island mountains, which more than
any other locality on earth facsimile the Martian surface, its
possession there as well.
Another point, too, is worth consideration. In an aging world where the
conditions of life have grown more difficult, mentality must
characterize more and more its beings in order for them to survive, and
would in consequence tend to be evolved. To find, therefore, upon Mars
highly intelligent life is what the planet’s state would lead one to
expect.
To some people it may seem that the very strangeness of Martian life
precludes for it an appeal to human interest. To me this is but a
near-sighted view. The less the life there proves a counterpart of our
earthly state of things, the more it fires fancy and piques inquiry as
to what it be. We all have felt this impulse in our childhood as our
ancestors did before us, when they conjured goblins and spirits from
the vasty void, and if our energy continue we never cease to feel its
force through life. We but exchange, as our years increase, the romance
of fiction for the more thrilling romance of fact. As we grow older we
demand reality, but so this requisite be fulfilled the stranger the
realization the better we are pleased. Perhaps it is the more vivid
imagination of youth that enables us all then to dispense with the
hall-mark of actuality upon our cherished visions; perhaps a deeper
sense of our own oneness with nature as we get on makes us insist upon
getting the real thing. Whatever the reason be, certain it is that with
the years a narration, no matter how enthralling, takes added hold of
us for being true. But though we crave this solid foothold for our
conceptions, we yield on that account no jot or tittle of our interest
for the unexpected.
Good reason we have for the allurement we feel toward what is least
like us. For the wider the separation from the familiar, the greater
the parallax the new affords for cosmic comprehension. That which
differs little yields little to the knowledge already possessed. Just
as a longer base line gives us a better measure of the distance of the
sun, so here the more diverse the aspects, the farther back they push
the common starting-point and furnish proportionately comprehensive
insight into the course by which each came to be what it is. By
studying others we learn about ourselves, and though from the remote we
learn less easily, we eventually learn the more. Even on the side,
then, that touches most men, the personal, the strangeness of the
subject should to the far-seeing prove all the greater magnet.
One of the things that makes Mars of such transcendent interest to man
is the foresight it affords of the course earthly evolution is to
pursue. On our own world we are able only to study our present and our
past; in Mars we are able to glimpse, in some sort, our future.
Different as the course of life on the two planets undoubtedly has
been, the one helps, however imperfectly, to better understanding of
the other.
Another, more abstract but no less alluring, appeals to that desire
innate in man to know about the cosmos of which he forms a part and
which we call by the name of science. Study of Mars responds to this
craving both directly by revelation of the secrets of another world and
indirectly by the bearing of what we thus learn upon our understanding
of the laws of the universe. For the facts thus acquired broaden our
conceptions in every branch of science. Some day our own geology,
meteorology, and the rest will stand indebted to study of the planet
Mars for advance along their respective lines. Already the most alert
of those professing them are lending ear to information from this
source, and such cosmopolitanism can but increase as the years roll on.
Today what we already know is helping to comprehension of another
world; in a not distant future we shall be repaid with interest, and
what that other world shall have taught us will redound to a better
knowledge of our own, and of that cosmos of which the two form part.
[Illustration: _Lowell Observatory._ MARS 1905.]
INDEX
_Adamas_, unmistakable double in 1903, 214.
_Aeria_, white in, 76;
ruddy color of, 148.
Air (see Atmosphere), 86;
necessity of, to life, 166, 167;
as important to astronomical calculations, 7.
Air-waves, 250, 251, 273.
Albedo, low, 162, 167.
Algæ, 349.
_Amenthes_, hibernation of, 317-324.
Animalcula, in almost boiling geysers, 349.
_Aonium Sinus_, two doubles suspected in, 242.
_Aquae Calidae_, 208, 253, 315.
Archæan age of the earth, 132, 133, 138.
Areography, 20-31;
beginning and progress of, 109;
three periods in, 24.
Arizona, 16;
in desert belt, 13;
plateau of, 18.
_Arnon_, convergent double, 240.
Artificiality, of canal system, 366, 368, 369, 370, 374;
of oases, 366, 371.
_Ascraeus Lucus_, 331;
embraced by the double Gigas, 257.
_Astaboras_, connection with Lucus Ismenius, 260-263.
Atmosphere, of Mars, 62, 63, 71, 78, 79, 87;
shown to exist, 80, 82, 83, 84, 163, 167;
rare, 85, 86, 162, 167;
effect on temperature, 80;
constituents of, 162, 164, 166, 168.
Autumn, length of Martian, in northern hemisphere, 35, 48;
in southern, 35, 48.
Axial tilt, 34, 36, 55, 155, 161;
determinations of, 34, 36, 155;
determines character of seasons, 34, 36;
effect of, on presentation of arctic and antarctic regions, 70;
effect of, on temperature of arctic and temperate regions, 88.
Bacteria, plasm-eating beings, 353.
Barometric pressure, 63, 85.
Beer, 23, 26, 109.
Bilateralism, 208;
inherent attribute of canals, 209.
Blue band, surrounding polar caps, 39, 40, 42, 43, 56, 61, 63, 71,
161,
162, 168, 338, 339.
Blue-green areas (see Dark Regions), 32, 67, 163;
taken for seas, 110.
British Nautical Almanac, 35.
_Brontes_, development of, 304-312.
Cambrian era of Earth, 139.
Camera, the, 272;
advantage of, 273;
slower than the eye, 273;
stars the peculiar province of, 273, 274.
Canals, 11, 32, 163;
discovery of, 24, 26;
considered straits, 27;
regularity of, 28, 29;
unnatural in look, 173;
manner of introduction of, 174;
conditions necessary to seeing of, 174-177, 282, 283;
pencil-like lines, 177, 179, 367;
definite in direction, 178;
name, 180;
width of, 179, 180, 182;
length of, 183;
visible by virtue of length, 181;
oddities of, 183;
number of, 184;
systematic arrangement of, 184, 185, 187-191, 248;
connect with polar caps, 325, 339, 373;
import of system of, 338, 372, 373;
intrinsic change in, 283, 284, 337, 338;
what they are not, 185-187, 373;
zonal distribution of, 188, 189;
departure-points, 190;
dependent on general topography, 191;
of later origin than main features, 191, 247;
kinematic character of, 281-303;
effect on, of illumination, 284;
drawings of, numerous and
consecutive, 286;
coördination of data, 288, 289;
curves of visibility of (see Cartouches), 289, 290;
geometricism of, 175, 206, 365, 367, 368;
polar, 327.
Canals in the dark regions, 30, 31, 243-248;
of the southern hemisphere, 245;
of the northern hemisphere, 246, 247;
detection of, 243, 245;
deprived seas of marine character, 243;
part of canal system, 244, 245, 247.
Caps (see Polar Caps).
Carbon dioxide, 39, 161, 164-168.
Carbonic era of Earth, 134, 141, 142.
Carets, 265-270;
natural formations, 231, 232;
form and position of, 266, 267;
reason for shape of, 268;
associated with canals, 267, 269;
help in solution of riddle, 270;
act like oases, 333.
Cartouches of the canals, 289-303;
interpretation of, 291-293, 299-303, 344-347;
arranged by latitudes, 294;
showing first frosts, 299;
minimum points of, 297, 344;
maximum point of, 301;
mean canal, 297, 298.
Cenozoic times, 144.
_Cerberus_, obliterated by white spot, 75.
Change, 4, 281;
shown in polar caps, 37, 338;
in blue-green areas, 113, 114, 115, 120, 122-127, 163, 164;
in canals, 168, 169, 205, 283-285, 314, 337, 338;
in oases, 250-252, 330, 331, 337, 338.
Chromacea, 352;
plasm-forming beings, 353;
close to inorganic things, 357;
in hot springs, 357, 358.
_Chryse_, 90, 102.
Climate, 82-89;
one of extremes, 87;
temperature, theoretic and observed, 87;
non-glaciation the rule, 88.
Clouds, 55, 71, 73, 89, 163, 165, 283, 284;
but few exist, 83, 165;
none over blue-green areas, 92;
of tawny dust color, 106;
probably dust storms, 165;
prove existence of atmosphere, 167.
Cold, 87, 167, 299.
_Coloe Palus_, in connection with double canals, 257, 258, 263.
Color, 74, 148;
of Mare Erythraeum, 122.
Confervæ, in almost boiling geysers, 349, 358.
Cretaceous era of the earth, 136, 143, 151, 152.
Crystals, conditions of formation, 357.
Dana, 131, 139, 140.
Dark Regions, 122-125;
thought to be seas, 110, 111;
named in accordance, 110, 113;
change in aspect cast doubt on
marine character of, 113, 114;
change in, considered seasonal, 115, 120, 127, 163, 164;
marine character lost, 30, 115-118, 163, 164;
vegetation tracts, 119-127, 163, 164, 168, 169, 170;
below level of surrounding surface, 130, 164;
former ocean basins, 120, 129, 131;
latitudinal development in, 123, 124, 126, 127.
Dawes, 21, 23, 249, 250, 268.
Day, Martian, length of, 34, 160, 166.
Desert regions of the earth, 13, 149-155;
as observatory sites, 12, 13;
help explain Mars, 16, 17, 156;
color of, 149, 151;
compared with color of Mars, 150, 163;
vegetation in, 150;
position of, 153, 154;
due to winds, 154.
Desertism, 16, 89, 153-158.
Deserts (see Reddish-ochre regions).
_Deuteronilus_, 259-261.
Development of canals, latitudinal law of, 299, 302, 375;
follows melting of polar caps, 302, 338-340;
across equator, 373, 375.
Devonian era of the earth, 141.
Diaphragm, the great, 265.
Diplopia, 196.
_Djihoun_, narrowest double, 228-230;
embouchure of, 219-220;
connection with Luci Ismenii, 260, 262.
Double Canals, first seen by Schiaparelli, 28, 192;
impression of, 193, 204;
two classes of, 224;
require steady definition, 194;
phenomena of, 194, 205, 208, 212, 213;
physical bond between the constituents of, 226;
connection with bays, 232;
optical theories of, 196-203;
not illusions, 195-203, 209;
widths of, 205, 206, 221-224, 229, 230, 233;
length of, 205;
seasonal change in, 205;
constituents of, 204;
original line of, 216, 217;
number of, 205, 209;
list of, 210, 211;
gemination period of, 212, 213;
direction of, 234-236;
zonal distribution of, 236-239, 370;
distribution in longitude, 236;
tropical phenomena, 239, 240, 241, 242;
compared with single canals, 240;
convergent, 240;
avoid blue-green areas, 241;
connect with blue-green areas, 242.
Dust storms, 90, 165.
Earth, tilt of axis of, 34;
seasons on, 35;
polar caps of, 38, 41, 44, 45, 51, 54, 69;
rainfall on, 79;
viewed from space, 340;
vegetal quickening opposite to that on Mars, 344.
Eccentricity of orbit, effect on seasons, 46, 48, 52.
Elevations on limb, 96, 97;
measurement of, 98.
_Elysium_, white in, 75, 76.
Eocene era of the earth, 144.
Eopaleozoic era, 140.
_Euphrates_, 221, 231, 249, 258-261, 266, 267, 316;
continuously double, 213;
curious relation to the Portus Sigaeus and Phison, 218, 219.
Evolution, 362, 366, 367;
planetary, 363, 364;
advance in, dependent on environment, 145, 146.
Exploration, polar, 54.
Eye, relation to camera, 272-274.
Farms in Kansas and Dakota, 363.
_Fastigium Aryn_, 269;
origin of longitudes, 23, 74.
Fauna, 361;
of northern Arizona, 18;
linked with flora, 349, 350, 358.
Flagstaff, Arizona, 16.
Flammarion, 21, 23, 202.
Flora, 361;
linked with fauna, 349, 350, 358;
fixtures, 360.
Focal length, of objective in photographing canals, 275.
Franz Joseph Land, 45.
Frosts, first arctic, 299, 300, 345;
suggestive of, 87.
Galileo, 20, 39.
_Ganges_, 270;
peculiar development of, 226-228;
widest double, 228, 229.
Gemination, 214-221;
seasonal phenomenon, 212, 213;
conditioned by convenience, 218-221.
Geology, shows the growing of the land, 131-138.
_Gigas_, embracing the Ascraeus Lucus, 257.
_Gihon_, embouchure of, 232.
Gravitation, law of, 160.
Gravity, effect on atmosphere, 62;
force of, on Mars, 63.
Green, 21, 23, 24.
Habitability, 159.
Haeckel, 352, 353, 357.
Haze, at melting of caps, 56, 64-66, 90, 93, 165;
recurrent, 94.
Heat, 46, 47, 50, 146, 155.
_Hellas_, 81, 90, 91;
in winter, 58, 59;
ruddy color of, 148.
Herschel, Sir W., 34, 37.
Hibernation of canals, 313-324, 379.
_Hiddekel_, embouchure of, 232;
connection with Luci Ismenii, 260-262.
_Hippalus_, identical with rift, 326, 327.
Hoarfrost, 78, 79, 81;
at equator, 79;
in southern hemisphere, 80, 92.
Huyghens, 23, 26, 108.
Ice sheet, effect of, 52.
Illumination, oblique, 97;
for measuring elevations, 98.
Illusion theories of canals, disproved, 293.
Image of sun, not reflected from dark areas, 112.
Insolation, 47, 79, 91.
Intelligence on other worlds, method of making itself known, 364.
Islands south, 91, 244;
effect of, on isothermal lines, 92.
_Jamuna_, original line of, 216, 217.
_Jaxartes_, polar canal, 328.
Jupiter, 33, 372.
Jurassic era of the earth, 136, 143, 144.
_Juturna Fons_, a square oasis, 263.
Kaiser, 21, 23, 249.
Kinetic theory of gases, 83, 146, 147, 164.
_Kison_, convergent double, 240.
_Lacus Hyperboreus_, 246.
Lampland, 197, 225, 275.
Lick Observatory, 100.
Life, necessity of air and water to, 17, 166, 167, 341;
thin cold air no bar to, 18;
maximum temperature determinative of, 19, 378, 380.
Life on Earth, 349-353;
dependent on conditions, 349-355, 357, 379, 380.
Life on Mars, 169, 376;
vegetal, 348, 359;
probably of high order, 348, 359, 377, 378, 381, 382;
evidence of, 360-365.
Limb-light, evidence of atmosphere, 84, 162, 167.
Longitudes, origin of, 23, 74.
Lowell Observatory, Annals, 31, 81;
Bulletin, 201.
_Lucus Ismenius_, 19, 258;
only double oasis, 259;
association with canals, 260, 261.
_Lucus Lunae_, 330.
_Lucus Moeris_, 208.
Maedler, 21, 23, 26, 109.
Mammal, 349.
Maps, of Mars, 20-24, 26-29.
_Mare Acidalium_, 115, 242, 246-252;
white in, 80;
darker than the Mare Erythraeum, 127.
_Mare Cimmerium_, 267.
_Mare Erythraeum_, 113;
irregular lines in, 30;
in 1903, 122-124;
in 1905, 124-126.
_Mare Icarium_, 207.
_Mare Sirenum_, 92, 110, 114, 267.
Maria, on the moon, 109, 111;
not seas, 112, 113;
on Mars, 110;
not seas, 117;
southern hemisphere, 31.
Matter, distribution of, 355.
Mercator’s projection, 22, 344.
Merriam, 18, 19, 379.
Mesozoic times of the earth, 135, 142, 144, 151.
Meteorology of Mars, 63, 93.
Moisture, 86, 154.
Monera, 349, 357;
suggestive of crystals, 356.
Months, Martian, different from our own, 36.
Mountains, not visible on Mars, 100;
measurement of, 97-100;
limit of height visible, 100;
on Moon, 98, 99.
_Naarmalcha_, association with Luci Ismenii, 260, 261.
Nägeli, 356.
Nansen, 54.
Naval Observatory at Washington, 16.
_Nectar_, shows white, 59.
Neopaleozoic times of the Earth, 140.
Neptune, 33.
Nicks in the coastline (see Carets).
_Nilokeras_, double, 209;
photographed, 225.
_Nilosyrtis_, unlike other canals, 262.
Nitro-bacteria, 350, 353.
Nitrogen, 83, 164, 166, 341.
_Nix Olympica_, 74, 78.
North America, geologic history of, 133-137.
Oases, detected later than canals, 30, 249;
three stages in appearance of, 250-252;
number of, 252;
kinds of, 252-254, 263;
shape of, 253, 371;
position of, 254-257, 263;
connected with canals, 256, 257, 262, 371;
disprove diplopic theory, 258;
objectivity of, 263;
in dark regions, 163, 244, 263, 264;
kinematic character of, 330-333;
latitudinal progress of change in oases, 331;
evolution of, 331, 332;
intrinsic change in, 337, 338;
at junction of canals only, 255, 371.
Observations, mutual corroboration of, 165, 166;
among mountains, 7.
Organic Evolution, origin of, 356.
Orology, of Mars, 62.
Ovid, 25.
Oxygen, 83, 164, 166, 167, 341.
Paleozoic times on the Earth, 135.
Permian period, 142.
Personal equation, eliminated, 287.
Phenological quickening, on Earth, 342;
on Mars, 343.
_Phison_, 221, 231, 249, 258, 266, 267, 316;
continuously double, 213;
connection with Euphrates and Portus Sigaeus, 218, 219.
_Phœnix Lake_, 330.
Photographs of the canals, 225, 275-277.
Photography, celestial, 271-277.
Physiographic conditions, on Mars, 68, 128.
Pickering, W. H., 330.
_Pierius_, 71.
Polar caps, phenomena of, 37, 41, 61;
key to comprehension of planet, 37;
compared with those of earth, 41, 46;
composition of, 39, 161, 168, 339;
making of new, 94;
position of, 68;
aspect of, 56, 57;
maxima and minima of, 38, 41-44, 47-53, 55-57, 66-68, 162;
fission of, 61.
Polar seas (see Blue band);
fresh water, 162.
Poles, Martian, determination of, 36.
_Pons Hectoris_, 78.
_Portus Sigaeus_, nicks in the coastline, 207, 266, 267;
embouchure to Phison and Euphrates, 218.
Precipitation, 51, 79, 154, 155;
effect on glaciation, 52.
Presentation, a, defined, 287, 288.
Probability, law of, 160.
Projections on the terminator, 77, 81, 96, 100, 104, 165;
color of, 102;
cause of, 104-107;
great one of 1903, 101-104;
of 1900, 104.
_Propontis_, the, 242;
canals in, 247;
oases in, 256.
_Protonilus_, association with Luci Ismenii, 260.
_Pseboas Lucus_, 207, 250, 253, 263;
anomalous position of, 262.
Quaternary epoch of the Earth, 137.
Reddish-ochre regions, 153, 155;
deserts, 149, 156, 163;
variations of tint in, 32, 148, 149, 151.
Rifts in polar cap, 61-63, 67, 162, 325-329;
permanent in place, 61, 62;
not depressions, 62, 63, 162;
coincide with canals, 326-328;
explanation of, 328, 329.
Rotation, early noted, 108, 109;
how determined, 34;
time of, 34, 160;
disclosed by markings, 32-34, 108.
_Sabaeus Sinus_, 23, 207, 268, 269.
San Francisco Peaks, 18, 19, 149, 379, 380.
Saturn, 33.
Scepticism, 27, 28, 204.
Schaeberle, 30.
Schiaparelli, 11, 15, 21, 23, 24, 26, 27, 29, 30, 31, 34, 68, 74, 75,
81, 114, 115, 120, 121, 173, 177, 186, 192, 212, 217, 221, 247, 249,
265, 282, 313, 314, 325, 337, 367, 373.
Seas (see Dark Regions).
southern, 92;
formerly on Mars and the Moon, 129;
internal absorption of, 147.
Seasonal change, metabolic, 169;
in canals, 168, 169, 285, 373.
Seasons, like our own, 34, 35, 166;
length of, 48, 79, 161;
of vegetal growth, 346, 347.
Secular change, in canals, 314.
Silurian era of the Earth, 134, 138, 140.
Sky, blotting out of, 14;
measure of extinction of, 16.
Sky, Martian, 89;
clear, 165.
Slipher, 101, 103.
Snow, 345;
limits of, on Earth and Mars, 108.
_Solis Lacus_, 23, 242.
Spring, Martian, 35, 48;
haze in, 94.
S.S. Challenger, concerning south polar cap of earth, 45.
S.S. Pagoda, 45.
Subsidiary snow patches, 67, 73.
Summer, Martian, length of, 35, 48, 381.
Surface, relatively flat, 62, 76, 97, 164;
covered by canal network, 243;
clear-cut in good air, 258;
in fluid equilibrium, 374;
indicative of thin air, 162, 167.
Surface features, reality of, proved, 26, 33.
_Syrtis Major_, 22;
first marking made out, 23.
_Tempe_, white in, 77, 80.
Temperature, 78, 147, 165, 166;
effect on life, 358.
Terminator, projections on, 77, 81, 96, 100-107, 114, 165;
depressions on, 164.
Terrane, 108, 265.
Terraqueousness, shown by earth, 128, 131.
Terrestriality, follows terraqueousness, 129, 131, 137, 144-146;
earth’s oceans contracting in size, 131;
inevitably, 131, 146;
as shown by Mars and the Moon, 128, 130, 131;
as shown by the geologic history of earth, 131-137;
as shown by paleontology, 138-144;
making a better habitat, 145, 146.
Tertiary times of the Earth, 137, 151.
_Thoth-Nepenthes_, peculiar course of, 208;
hibernation of, 315-324.
_Titan_, 305.
Triassic era, 136, 142, 152.
_Trivium Charontis_, canals and oases in, 251, 252, 256.
Twilight arc, shows thin air, 85, 162.
Uranus, 33.
Vegetation, 79, 119-127, 163, 166, 169, 301;
color of Mare Erythraeum, 122-126;
proof of, 170;
theory supported by rifts in polar cap, 329;
most satisfactory explanation of phenomena of canals, 339, 341, 344,
345, 347, 348, 373;
two seasons of growth of, 346;
melts snow, 328.
Water, dearth of, 128, 161, 163, 166, 168, 169, 341, 366;
loss of, inevitable, 131;
speed of flow of, 375;
from polar caps, 340, 374.
Water-vapor, from polar caps, 83;
in atmosphere, 162, 168.
Weather, 66, 89, 95.
_Wedge of Casius_, 242;
canals in, 247;
oases in, 251, 252, 256.
Welkin, man-manufactured, 13-15.
White spots, 32, 165;
similar in look to polar caps, 73;
location and season of, 74, 76-79, 80, 81;
White spots, permanency of, 73, 76;
indication of temperature, 80, 165.
Winds, 154.
Winter, Martian, 35, 48.
World, Mars another, 4, 5, 169;
evolution of a, 16, 128, 131, 155-158, 358.
Year, of Earth, 35;
of Mars, 35, 161.
A COMPENDIUM OF SPHERICAL ASTRONOMY
With its applications to the determination and reduction of positions
of the fixed stars
By SIMON NEWCOMB
Cloth 8vo $3.00 net
--------------
CONTENTS
PART I. PRELIMINARY SUBJECTS
CHAPTER I. INTRODUCTORY. NOTES AND REFERENCES.
CHAPTER II. DIFFERENCES, INTERPOLATION, AND DEVELOPMENT. NOTES AND
REFERENCES.
CHAPTER III. THE METHOD OF LEAST SQUARES. Section I. Mean Values of
Quantities. II. Determination of Probable Errors. III. Equations of
Condition. NOTES AND REFERENCES.
PART II. THE FUNDAMENTAL PRINCIPLES OF SPHERICAL ASTRONOMY
CHAPTER IV. SPHERICAL COÖRDINATES. Section I. General Theory. II.
Problems and Applications of the Theory of Spherical Coördinates.
CHAPTER V. THE MEASURE OF TIME AND RELATED PROBLEMS. Section I. Solar
and Sidereal Time. II. The General Measure of Time. III. Problems
Involving Time.
CHAPTER VI. PARALLAX AND RELATED SUBJECTS. Section I. Figure and
Dimensions of the Earth. II. Parallax and Semi-diameter.
CHAPTER VII. ABERRATION.
CHAPTER VIII. ASTRONOMICAL REFRACTION. Section I. The Atmosphere as a
Refracting Medium. II. Elementary Exposition of Atmospheric
Refraction. III. General Investigation of Astronomical Refraction.
Notes and References to Refraction.
CHAPTER IX. PRECESSION AND NUTATION. Section I. Laws of the
Precessional Motion. II. Relative Positions of the Equator and
Equinox at Widely Separated Epochs. III. Nutation. Notes and
References to Precession and Nutation.
PART III. REDUCTION AND DETERMINATION OF POSITIONS OF THE FIXED STARS
CHAPTER X. REDUCTION OF MEAN PLACES OF THE FIXED STARS FROM ONE EPOCH
TO ANOTHER. Section I. The Proper Motions of the Stars. II.
Trigonometric Reduction for Precession. III. Development of the
Coördinates in the Powers of the Time. NOTES AND REFERENCES.
CHAPTER XI. REDUCTION TO APPARENT PLACE. Section I. Reduction to Terms
of the First Order. II. Rigorous Reduction for Close Polar Stars.
III. Practical Methods of Reduction. IV. Construction of Tables of
the Apparent Places of Fundamental Stars. Notes and References.
CHAPTER XII. METHOD OF DETERMINING THE POSITIONS OF STARS BY MERIDIAN
OBSERVATIONS. Section I. Method of Determining Right Ascensions. II.
The Determination of Declinations.
CHAPTER XIII. METHODS OF DERIVING THE POSITIONS AND PROPER MOTIONS OF
THE STARS FROM PUBLISHED RESULTS OF OBSERVATIONS. Section I.
Historical Review. II. Reduction of Catalogue Positions of Stars to a
Homogeneous System. III. Methods of Combining Star Catalogues.
NOTES AND REFERENCES
List of Independent Star Catalogues.
Catalogues made at Northern Observatories.
Catalogues made at Tropical and Southern Observatories.
APPENDIX
EXPLANATION OF THE TABLES OF THE APPENDIX.—I. Constants and Formulæ in
Frequent Use. II. Tables Relating to Time and Arguments for Star
Reductions. III. Centennial Rates of the Precessional Motions. IV.
Tables and Formulæ for the Trigonometric Reduction of Mean Places of
Stars. V. Reduction of the Struve-Peters Precessions to the Adopted
Values. VI. Conversion of Longitude and Latitude into R. A. and Dec.
VII. Refractions. VIII. Coefficients of Solar and Lunar Nutation. IX.
Three-place Logarithms and Trigonometrical Functions.
--------------
THE MACMILLAN COMPANY, 64-66 Fifth Avenue, New York
Transcriber's Notes
Ditto marks have been replaced by the text they represent.
Some presumed printer's errors have been corrected, including
normalizing punctuation. Further corrections are listed below:
Printed text Corrected text Page
MITGLIED DER MITGLIED DER
ASTRONOMISCHE GESELLSCHAFT ASTRONOMISCHEN GESELLSCHAFT Title page
terrrane terrane 108
seem seems 247
*** End of this LibraryBlog Digital Book "Mars and its Canals" ***
Copyright 2023 LibraryBlog. All rights reserved.