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Title: Scientific American Supplement, No. 365, December 30, 1882
Author: Various
Language: English
As this book started as an ASCII text book there are no pictures available.
Copyright Status: Not copyrighted in the United States. If you live elsewhere check the laws of your country before downloading this ebook. See comments about copyright issues at end of book.

*** Start of this Doctrine Publishing Corporation Digital Book "Scientific American Supplement, No. 365, December 30, 1882" ***

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[Illustration]



SCIENTIFIC AMERICAN SUPPLEMENT NO. 365



NEW YORK, DECEMBER 30, 1882.

Scientific American Supplement. Vol. XIV., No. 365.

Scientific American established 1845

Scientific American Supplement, $5 a year.

Scientific American and Supplement, $7 a year.

       *       *       *       *       *



TABLE OF CONTENTS.


I.    ENGINEERING AND MECHANICS.--Louis Favre, Constructor
      of the St. Gothard Tunnel.--2 figures.--Portrait and
      monument at Turin to commemorate the tunneling of the
      Alps                                                      5817

      The New Harbor of Vera Cruz.--New artificial harbor
      for Vera Cruz.--Capt. Eads's plan.--1 figure.--Plan
      of harbor and improvement                                 5818

      Cost of Power to Make Flour                               5818

      Driving gear Mechanism for Lift Hammers.--2 figures       5819

      De Junker and Ruh's Machine for Cutting Annular
      Wheels.--3 figures                                        5819

      Recent Hydraulic Experiments.--Results of experiments
      on the flow of water in the Ganges Canal                  5819

      The Germ: Shall It be Retained in Flour? By Arthur
      Atkins                                                    5820

      Wheat Tests                                               5820

II.   TECHNOLOGY AND CHEMISTRY.--Apparatus for Manufacturing
      Gaseous or Aerated Beverages.--11 figures.--Bicarbonate
      of soda apparatus. Generator. Washer.--Suction
      pump.--Saturator.--Apparatus for using carbonate of
      lime.--Apparatus completely mechanical in operation       5815

      Detection and Estimation of Fusel Oil                     5816

      On Silicon.--Curious formation of silicide of platinum    5816

      Stannous Nitrates.--The formation of explosive
      compounds in machines by the corrosion of bronze and
      tin solder                                                5816

      Metallic Thorium. By L.F. Nilson                          5816

      Friedrich Wöhler.--Obituary notice of the great German
      chemist                                                   5816

      Apparatus for Printing by the Blue Process. By
      Channing Whitaker.--3 figures                             5820

III.  ELECTRICITY, LIGHT, HEAT, ETC.--Spectrum Gratings         5822

      A New Pocket Opera Glass.--4 figures                      5822

      Atoms, Molecules, and Ether Waves. By JOHN TYNDALL.
      Action of heat and light on molecules.--Heat as an
      agent in exploring molecular conditions.--The results
      of a recent incursion into the extra-sensible world
      of atoms and molecules                                    5823

      Apparatus for Measuring Electricity at the Upper
      School of Telegraphy. By E. MERCADIER.--5 figures.
      Constant vibrator.--The Electrical tuning fork.
      Arrangement for testing electric piles.--Very rapid
      electric tuning fork.--A vibrating micrometer             5824

IV.   NATURAL HISTORY.--Our Origin as a Species. By RICHARD
      OWEN.--The Neanderthal skull.--Differential characters
      between the lowest _Homo_ and the highest _Simia_         5825

      The Aba or Odika. By Dr. W.H. BACHELER.--A remarkable
      tree of West Africa                                       5826

      California Cedars                                         5826

       *       *       *       *       *



APPARATUS FOR MANUFACTURING GASEOUS OR AERATED BEVERAGES.


The apparatus employed at present for making gaseous beverages are
divided into two classes--intermittent apparatus based on chemical
compression, and continuous ones based on mechanical compression.

The first are simple in appearance and occupy small space, but their use
is attended with too great inconveniences and losses to allow them to be
employed in cases where the manufacture is of any extent, so the
continuous apparatus are more and more preferred by those engaged in the
industry.

Continuous apparatus, however, other than those that we now propose to
occupy ourselves with, are not without some defects, for the gas is
produced in them intermittingly and at intervals, and more rapidly than
it is used, thus necessitating the use of a gasometer, numerous and
large washers, complicated piping, and, besides, of an acid cock.

To get rid of such drawbacks, it became necessary to seek a means of
rendering the production of the gas continuous, and of regulating it
automatically without the aid of the operator. Mr. Mondollot has
obtained such a result through a happy modification of the primitive
system of the English engineer Bramah. He preserves the suction and
force pump but, while applying it to the same uses, he likewise employs
it, by the aid of a special arrangement, so as to distribute the
sulphuric acid automatically over the chalk in the generator, and to
thus obtain a regular and continuous disengagement of carbonic acid gas.
The dangers and difficulties in the maneuver of an acid cock are
obviated, the gasometer and its cumbersome accessories are dispensed
with, and the purification is more certain, owing to the regularity with
which the gas traverses the washers.

In the accompanying plate we have figured three types of these
apparatus. The first that we shall describe is arranged for the use of
bicarbonate of soda. This apparatus consists (1) of a _generator_, C D,
(2) of a double _washer_ G G, (3) of a _suction pump_, P, and (4) of a
_saturator_, S (See Figs 1 to 9).

_The Generator._--This consists of a cylindrical leaden receptacle, D,
on the bottom of which rests a leaden bell containing apertures, c, at
its base. A partition, c, into which is screwed a leaden tube, C,
containing apertures divides the interior of the bell into two
compartments. The upper of these latter is surmounted by a mouth, B,
closed by a clamp, and through which the bicarbonate of soda is
introduced. A definite quantity of water and sulphuric acid having been
poured into the receptacle, D, a level tends to take place between the
latter and the bell, C, the liquid passing through the apertures. But
the acidulated water, coming in contact with the soda, sets free
carbonic acid gas, which, having no exit, forces the water back and
stops the production of gas until the apparatus is set in motion. At
this moment, the suction of the pump causes a new inflow of acidulated
water upon the soda, from whence another disengagement of gas, and then
a momentary forcing of the water, whose level thus alternately rises and
falls and causes a continuous production of gas proportionate with the
suction of the pump.

The consumption of soda and acid is about 2 kilogrammes each for
charging 100 siphons or 150 bottles. The bicarbonate is known to be used
up when the liquid in the generator is seen to descend to the bottom of
the water level, n, fixed to the vessel, D.

_The Washer_ (Figs 1 and 4)--The gas, on leaving the generator, enters
the washer through a bent copper pipe, R. The washer is formed of two
ovoid glass flasks G G, mounted on a bronze piece, L, to which they are
fixed by screw rings, l, of the same metal. The two flasks, G G,
communicate with each other only through the tinned-copper tube q,
which is held in the mounting q, of the same metal. This latter is
screwed into the piece, L, and contains numerous apertures, through
which the gas coming in from the pipe, R, passes to reach the upper
flask, G. The gas is washed by bubbling up through water that has been
introduced through the cock, R. After it has traversed both flasks, it
escapes through the copper pipe, p, into which it is sucked by the
pump, P.

_The Pump_ (Figs 1, 5 and 6)--This consists of a cylindrical chamber, P,
of bronze, bolted to a bracket on the frame, and cast in a piece, with
the suction valve chamber, P, in which the valve, p, plays. It is
surmounted by the distributing valve chamber P². This latter is held
by means of two nuts screwed on to the extremity of the rods, p³,
connected with the shell, E, of the distributing-cock, E. In the shell,
E, terminates, on one side, the pipe, p, through which enters the gas
from the washer, and, on the other, the pipe i, that communicates with
a feed-reservoir not shown in the cuts. The cock E, permits of the
simultaneous regulation of the entrance of the gas and water. Its
position is shown by an index e, passing over a graduated dial, _e¹_.
From the distributing valve chamber, P² the pipe, s, leads the
mixture of water and gas under pressure into

_The Saturator_, S (Figs 1, 7 and 9)--This consists of a large copper
vessel, s, affixed to the top of the frame through the intermedium of
a bronze collar h, and a self closing bottom H. This latter is
provided with two pipes, one of which, s, leads the mixture of water
and carbonic acid forced by the pump, and the other, b, communicates
with the siphons or bottles to be filled. The pipe, b, is not affixed
directly to the bottom, but is connected therewith through the
intermedium of a cock, r. The object of the broken form of this pipe
is to cause the pressure to act according to the axis of the screw, r,
which is maneuvered by the key, r².

The water under pressure, having been forced into the vessel, S, is
submitted therein to an agitation that allows it to dissolve a larger
quantity of gas. Such agitation is produced by two pairs of paddles, J
J, mounted at the extremity of an axle actuated by the wheel, A, through
the intermedium of gearings, g and g.

The course of the operation in the saturator may be followed by an
inspection of the water level, n, seen at the front and side in Figs.
2 and 3. This apparatus, in which the pressure reaches 4 to 6
atmospheres in the manufacture of Seltzer water or gaseous lemonade in
bottles, and from 10 to 12 atmospheres in that of Seltzer water in
siphons, is provided also with a pressure gauge, m, and a safety
valve, both screwed, as is also the tube, n², into a sphere, S, on
the top of the saturator.

_Apparatus for Using Carbonate of Lime_ (Figs 2, 3, and 10)--When chalk
is acted upon by sulphuric acid, there is formed an insoluble sulphate
which, by covering the chalk, prevents the action of the acid from
continuing if care be not taken to constantly agitate the materials.
This has led to a change in the arrangement of the generator in the
apparatus designed for the use of chalk.

It consists in this case of a leaden vessel, D, having a hemispherical
bottom set into a cylindrical cast iron base, K, and of an agitator
similar to that shown in Fig. 11, for keeping the chalk in suspension in
the water. These latter materials are introduced through the mouth, B
(Fig. 3). Then a special receptacle, C, of lead, shown in detail in Fig.
10, and the cock, c, of which is kept closed, is filled with sulphuric
acid. The acid is not introduced directly into the vessel, C, but is
poured into the cylinder, C, whose sides contain numerous apertures
which prevent foreign materials from passing into the siphon tube c,
and obstructing it.

To put the apparatus in operation, the acid cock, c, is opened and the
wheel, A, is turned, thus setting in motion both the pump piston, P, and
the agitator, within S and D. Then the play of the pump produces a
suction in the washers and from thence in the generator and causes the
acid in the vessel, C, to flow into the generator through the leaden
siphon tubes, c. Coming in contact with the chalk in suspension, the
acid produces a disengagement of gas which soon establishes sufficient
pressure to stop the flow of the acid and drive it back into the siphon
tube. The play of the pump continuing, a new suction takes place and
consequently a momentary flow of acid and a new disengagement of gas.
Thus the production of the latter is continuous, and is regulated by the
very action of the pump, without the operator having to maneuver an
acid-cock. The latter he only has to open when he sets the apparatus in
operation, and to close it when he stops it.

The arrangement of the washer is the same as in the preceding apparatus,
save that a larger cylindrical copper reservoir, G', is substituted for
the lower flask. The pump and saturator offer nothing peculiar.

A bent tube, u, which communicates with the generator, D, on one side,
and with a cylindrical tube, V, ending in a glass vessel on the other,
serves as a safety-valve for both the generator and the acid vessel.

The consumption of chalk is about 2.5 kilogrammes, and the same of acid,
for charging 100 siphons or 150 bottles. The apparatus shown in the
figure is capable of charging 600 siphons or 900 bottles per day.

_An Apparatus Completely Mechanical in Operation_ (Fig. 11).--This
apparatus consists of two very distinct parts. The saturator, pump, and
driving shaft are supported by a hollow base, in whose interior are
placed a copper washer and the water-inlet controlled by a float-cock.
This part of the apparatus is not shown in the plate. The generator,
partially shown in Fig. 11, is placed on a base of its own, and is
connected by a pipe with the rest of the apparatus. It consists of two
similar generators, D, made of copper lined with lead, and working
alternately, so as to avoid all stoppages in the manufacture when the
materials are being renewed. The pipe, d, connecting the two parts of
the apparatus forks so as to lead the gas from one or the other of the
generators, whence it passes into the copper washer within the base,
then into the glass indicating washer, and then to the pump which forces
it into the saturator.

Each of the generators communicates by special pipes, a, with a single
safety vessel, V, that operates the same as in the preceding apparatus.
The agitator, Q, is of bronze, and is curved as shown in Fig. 11.

The production of this type of apparatus is dependent upon the number of
siphons that can be filled by a siphon filler working without
interruption.--_Machines, Outils et Appareils._

       *       *       *       *       *



DETECTION AND ESTIMATION OF FUSEL OIL.


Until quite recently we have had no accurate method for the
determination of fusel oil in alcohol or brandy. In 1837 Meurer
suggested a solution of one part of silver nitrate in nine parts of
water as a reagent for its detection, stating that when added to alcohol
containing fusel oil, a reddish brown color is produced, and in case
large quantities are present, a dark brown precipitate is formed. It was
soon found, however, that other substances than amyl alcohol produce
brown colored solutions with silver nitrate; and Bouvier[1] observed
that on adding potassium iodide to alcohol containing fusel oil, the
solution is colored yellow, from the decomposition of the iodide.
Subsequently Böttger[2] proved that potassium iodide is not decomposed
by pure amyl alcohol, and that the decomposition is due to the presence
of acids contained in fusel oil. More accurate results are obtained by
using a very dilute solution of potassium permanganate, which is
decomposed by amyl alcohol much more rapidly than by ethyl alcohol.

    [Footnote 1: Zeitschrift f. Anal. Chem. xi., 343.]

    [Footnote 2: Dingler's Polytech. Jour., ccxii., 516.]

Depré[3] determines fusel oil by oxidizing a definite quantity of the
alcohol in a closed vessel with potassium bichromate and sulphuric acid.
after removal of excess of the oxidizing reagents, the organic acids are
distilled, and, by repeated fractional distillation, the acetic acid is
separated as completely as possible. The remaining acids are saturated
with barium hydroxide, and the salts analyzed; a difference between the
percentage of barium found and that of barium in barium acetate proves
the presence of fusel oil, and the amount of difference gives some idea
of its quantity. Betelli[4] dilutes 5 c.c. of the alcohol to be tested
with 6 to 7 volumes of water, and adds 15 to 20 drops of chloroform and
shakes thoroughly. If fusel oil is present, its odor may be detected by
evaporating the chloroform; or, by treatment with sulphuric acid and
sodium acetate, the ether is obtained, which can be readily recognized.
Jorissen[5] tests for fusel oil by adding 10 drops of colorless aniline
and 2 to 3 drops of hydrochloric acid to 10 c.c. of the alcohol. In the
presence of fusel oil a red color is produced within a short time, which
can be detected when not more than 0.1 per cent. is present. But
Foerster[6] objects to this method because he finds the color to be due
to the presence of furfurol, and that pure amyl alcohol gives no color
with aniline and hydrochloric acid.

    [Footnote 3: Pharm. J. Trans. [3] vi., 867.]

    [Footnote 4: Berichte d. Deutschen Chem. Gesellsch., viii., 72.]

    [Footnote 5: Pharm. Centralhalle, xxii., 3.]

    [Footnote 6: Berichte d. Deutsch. Chem. Gesellsch., xv., 230.]

Hager[7] detects fusel oil as follows: If the spirit contains more than
60 per cent. of alcohol, it is diluted with an equal volume of water and
some glycerine added, pieces of filter paper are then saturated with the
liquid and exposed to the After the evaporation of the alcohol, the odor
of the fusel oil can be readily detected. For the quantitative
determination he distills 100 c.c. of the alcohol in a flask of 150 to
200 c.c. capacity connected with a condenser, and so arranged that the
apparatus does not extend more than 20 cm. above the water bath. This
arrangement prevents the fusel oil from passing over. If the alcohol is
stronger than 70 per cent., and the height of the distillation apparatus
is not more than 17 cm., the residue in the flask may be weighed as
fusel oil. With a weaker alcohol, or an apparatus which projects further
out of the water bath, the residual fusel oil is mixed with water. It
can, however, be separated by adding strong alcohol and redistilling, or
by treating with ether, which dissolves the amyl alcohol, and
distilling, the temperature being raised finally to 60°.

    [Footnote 7: Pharm. Centralhalle, xxii., 236.]

Marquardt,[8] like Betelli, extracts the fusel oil from alcohol by means
of chloroform, and by oxidation converts it into valeric acid. From the
quantity of barium valerate found he calculates the amount of amyl
alcohol present in the original solution; 150 c.c. of the spirit, which
has been diluted so as to contain 12 to 15 per cent. of alcohol, are
shaken up thoroughly with 50 c.c. of chloroform, the aqueous layer drawn
off, and shaken with a fresh portion of chloroform. This treatment is
repeated several times. The extracts are then united, and washed
repeatedly with water. The chloroform, which is now free from alcohol
and contains all the fusel oil, is treated with a solution of 5 grammes
of potassium bichromate in 30 grammes of water and 2 grammes of
sulphuric acid, and then heated in a closed flask for six hours on a
water bath at 85°. The contents of the flask are then distilled, the
distillate saturated with barium carbonate, and the chloroform
distilled; the residue is evaporated to a small volume, the excess of
barium carbonate filtered off, and the filtrate evaporated to dryness
and weighed. The residue is dissolved in water, a few drops of nitric
acid added, and the solution divided into two portions. In the first
portion the barium is determined; in the second the barium chloride. The
total per cent. of barium minus that of barium chloride gives the amount
present as barium valerate, from which is calculated the per cent. of
amyl alcohol. By this process the author has determined one part of
fusel oil in ten thousand of alcohol. To detect very minute quantities
of fusel oil, the chloroform extracts are treated with several drops of
sulphuric acid and enough potassium permanganate to keep the solution
red for twenty-four hours. If allowed to stand in a test tube, the odor
of valeric aldehyde will first be noticed, then that of amyl valerate,
and lastly that of valeric acid.--_Amer. Chem. Journal._

    [Footnote 8: Berichte d. Deutsch. Chem. Gesellsch., xv., 1,370
    and 1,663.]

       *       *       *       *       *



ON SILICON.


It is known that platinum heated in a forge fire, in contact with
carbon, becomes fusible. Boussingault has shown that this is due to the
formation of a silicide of platinum by means of the reduction of the
silica of the carbon by the metal. MM. P. Schützenberger and A. Colson
have produced the same phenomenon by heating to white heat a slip of
platinum in the center of a thick layer of lampblack free from silica.

The increase in weight of the metal and the augmentation of its
fusibility were found to be due, in this case also, to a combination
with silicon. As the silicon could not come directly from the carbon
which surrounded the platinum, MM. Schützenberger and Colson have
endeavored to discover under what form it could pass from the walls of
the crucible through a layer of lampblack several centimeters in
thickness, in spite of a volatility amounting to almost nothing under
the conditions of the experiment. They describe the following
experiments as serving to throw some light upon the question:

1. A thin slip of platinum rolled in a spiral is placed in a small
crucible of retort carbon closed by a turned cover of the same material.
This is placed in a second larger crucible of refractory clay, and the
intervening space filled with lampblack tightly packed. The whole is
then heated to white heat for an hour and a half in a good wind furnace.
After cooling, the platinum is generally found to have been fused into a
button, with a marked increase in weight due to taking up silicon, which
has penetrated in the form of vapor through the walls of the interior
crucible.

2. If, in the preceding experiment, the lampblack be replaced by a
mixture of lampblack and rutile in fine powder, the slip of platinum
remains absolutely intact, and does not change in weight. Thus the
titaniferous packing recommended by Sainte-Claire Deville for preventing
the access of nitrogen in experiments at high temperatures also prevents
the passage of silicon. A mixture of carbon and finely divided iron is,
on the contrary, ineffectual. These facts seem to indicate that nitrogen
plays a part in the transportation of the silicon, as this is only
prevented by the same means made use of in order to prevent the passage
of nitrogen.

3. The volatility of free silicon at a high temperature is too slight to
account for the alteration of the platinum at a distance. This can be
shown by placing several decigrammes of crystallized silicon on the
bottom of a small crucible of retort carbon, covering the silicon with a
small flat disk of retort carbon upon which is placed the slip of
platinum. The crucible, closed by its turned cover, is then enveloped in
a titaniferous packing and kept at a brilliant white heat for an hour
and a half. The metal is found to have only very slightly increased in
weight, and its properties remain unaltered. This experiment was
repeated several times with the same result. If, however, the
crystallized silicon be replaced by powdered calcined silica, the
platinum, placed upon the carbon disk, fuses and increases in weight,
while the silica loses weight. The theory of these curious phenomena is
very difficult to establish on account of the high temperatures which
are necessary for their manifestation, but it may be concluded, at
present, that nitrogen and probably oxygen also play some part in the
transportation of the silicon across the intervening space, and that the
carbosilicious compounds recently described by MM. Schützenberger and
Colson also take part in the phenomenon.--_Comptes Rendus_, xciv.,
1,710.--_Amer. Chem. Journal._

       *       *       *       *       *



STANNOUS NITRATES.


At the Royal Powder Works at Spandau, Prussia, frequent ignition of the
powder at a certain stage of the process led to an examination of the
machinery, when it was found that where, at certain parts, bronze pieces
which were soldered were in constant contact with the moist powder, the
solder was much corroded and in part entirely destroyed, and that in the
joints had collected a substance which, on being scraped out with a
chisel, exploded with emission of sparks. It was suspected that the
formation of this explosive material was in some way connected with the
corrosion of the solder, and the subject was referred for investigation
to Rudolph Weber, of the School of Technology, at Berlin. The main
results of his investigation are here given.

The explosive properties of the substance indicated a probable
nitro-compound of one of the solder metals (tin and lead), and as the
lead salts are more stable and better understood than those of tin, it
was resolved to investigate the latter, in hope of obtaining a similar
explosive compound. Experiments on the action of moist potassium nitrate
on pure tin led to no result, as no explosive body was formed. Stannous
nitrate, Sn(NO_{3})_{2}, formed by the action of dilute nitric acid on
tin, has long been known, but only in solution, as it is decomposed on
evaporating. By adding freshly precipitated moist brown stannous oxide
to cool nitric acid of sp. gr. 1.20, as long as solution occurred, and
then cooling the solution to -20°, Weber obtained an abundance of
crystals of the composition Sn(NO_{3})_{2} + 20H_{2}O. They resemble
crystals of potassium chlorate. They cannot be kept, as they liquefy at
ordinary temperatures. An insoluble _basic_ salt was obtained by
digesting an excess of moist stannous oxide in solution of stannous
nitrate, or by adding to a solution of stannous nitrate by degrees, with
constant stirring, a quantity of sodium carbonate solution insufficient
for complete precipitation. Thus obtained, the basic salt, which has the
composition Sn_{2}N_{2}O_{7}, is a snow-white crystalline powder, which
is partially decomposed by water, and slowly oxidized by long exposure
to the air, or by heating to 100°. By rapid heating to a higher
temperature, as well as by percussion and friction, it explodes
violently, giving off a shower of sparks. This compound is also formed
when a fine spray of nitric acid (sp. gr. 1.20) is thrown upon a surface
of tin or solder. It is also formed when tin or solder is exposed to the
action of a solution of copper nitrate, and thus formed presents the
properties already described.

In this, then, we have a probable cause of the explosions occurring in
the powder works; but the explanation of the formation of the substance
is wanting, as potassium nitrate was shown not to give an explosive
substance with tin. A thin layer of a mixture of sulphur and potassium
nitrate was placed between sheets of tin and copper foil, and allowed to
stand, being kept constantly moist. After a time the copper was found to
have become coated with sulphide, while the tin was largely converted
into the explosive basic nitrate. The conditions are obviously the same
as those found in the powder machinery, where bronze and tin solder are
constantly in contact with moist gunpowder. The chemical action is
probably this: the sulphur of the powder forms, with the copper of the
bronze, copper sulphide; this is oxidized to sulphate, which reacts with
the niter of the powder, forming potassium sulphate and copper nitrate;
the latter, as shown above, then forms with the tin of the solder the
explosive basic nitrate, which, being insoluble, gradually collects in
the joints, and finally leads to an explosion.--_Journal für Praktische
Chemie._

       *       *       *       *       *



METALLIC THORIUM.

By L.F. NILSON.


The density of thorium as obtained by reducing the anhydrous chloride by
means of sodium was found by Chydenius, 7.657 to 7.795. The author has
obtained metallic thorium by heating sodium with the double anhydrous
thorium potassium chloride, in presence of sodium chloride in an iron
crucible. After treating the residue with water there remains a grayish,
heavy, sparkling powder, which under the microscope appears to consist
of very small crystals. Metallic thorium is brittle and almost
infusible; the powder takes a metallic luster under pressure, is
permanent in the air at temperatures up to 120°, takes fire below a red
heat either in air or oxygen, and burns with a dazzling luster, leaving
a residue of perfectly white thoria. If heated with chlorine, bromine,
iodine, and sulphur, it combines with them with ignition. It is not
attacked by water, cold or hot. Dilute sulphuric acid occasions the
disengagement of hydrogen, especially if heated, but the metal is acted
on very slowly. Concentrated sulphuric acid with the aid of heat attacks
the metal very slightly, evolving sulphurous anhydride. Nitric acid,
strong or weak, has no sensible action. Fuming hydrochloric acid and
_aqua regia_ attack thorium readily, but the alkalies are without
action. The metal examined by the author behaves with the reagents in
question the same as did the specimens obtained by Berzelius. The mean
specific gravity of pure thorium is about 11. Hence it would seem that
the metal obtained by Chydenius must have contained much foreign matter.
The specific gravity of pure thoria is 10.2207 to 10.2198. The
equivalent and the density being known, we may calculate the atomic
volume. If we admit that the metal is equivalent to 4 atoms of hydrogen,
we obtain the value 21.1. This number coincides with the atomic volumes
of zirconium (21.7), cerium (21.1), lanthanum (22.6), and didymium
(21.5). This analogy is certainly not due to chance; it rather confirms
the opinion which I have put forward in connection with my researches on
the selenites, on certain chloro-platinates and chloro-platinites, etc.,
that the elements of the rare earths form a series of quadrivalent
metals.

       *       *       *       *       *

[AMERICAN CHEMICAL JOURNAL.]



FRIEDRICH WÖHLER.


No one but a chemist can appreciate the full significance of the brief
message which came to us a month ago without warning--"Wöhler is dead!"
What need be added to it? No chemist was better known or more honored
than Wöhler, and none ever deserved distinction and honor more than he.
His life was made up of a series of brilliant successes, which not only
compelled the admiration of the world at large, but directed the
thoughts of his fellow workers, and led to results of the highest
importance to science.

It is impossible in a few words to give a correct account of the work of
Wöhler, and to show in what way his life and work have been of such
great value to chemistry. Could he himself direct the preparation of
this notice, the writer knows that his advice would be, "Keep to the
facts." So far as any one phrase can characterize the teachings of
Wöhler, that one does it; and though enthusiasm prompts to eulogy, let
us rather recall the plain facts of his life, and let them, in the main,
speak for themselves.[1]

    [Footnote 1: See Kopp's "Geschichte der Chemie," iv., 440.]

He was born in the year 1800 at Eschersheim, a village near
Frankfort-on-the-Main. From his earliest years the study of nature
appears to have been attractive to him. He took great delight in
collecting minerals and in performing chemical and physical experiments.
While still a boy, he associated with a Dr. Buch, of Frankfort, and was
aided by this gentleman, who did what he could to encourage in the young
student his inclination toward the natural sciences. The first paper
which bears the name of Wöhler dates from this period, and is upon the
presence of selenium in the iron pyrites from Kraslitz. In 1820 he went
to the University of Marburg to study medicine. While there he did not,
however, neglect the study of chemistry. He was at that time
particularly interested in an investigation on certain cyanogen
compounds. In 1821 he went to Heidelberg, and in 1823 he received the
degree of Doctor of Medicine. L. Gmelin became interested in him, and it
was largely due to Gmelin's influence that Wöhler gave up his intention
of practicing medicine, and concluded to devote himself entirely to
chemistry. For further instruction in his chosen science, Wöhler went to
Stockholm to receive instruction from Berzelius, in whose laboratory he
continued to work from the fall of 1823 until the middle of the
following year. Only a few years since, in a communication entitled
"Jugenderinnerungen eines Chemikers," he gave a fascinating account of
his journey to Stockholm and his experiences while working with
Berzelius. On his return to Germany, he was called to teach chemistry in
the recently founded municipal trade school (Gewerbschule) at Berlin. He
accepted the call, and remained in Berlin until 1832, when he went to
Cassel to live. In a short time he was called upon to take part in the
direction of the higher trade school at Cassel. He continued to teach
and work in Cassel until 1836, when he was appointed Professor of
Chemistry in Göttingen. This office he held at the time of his death,
September 23, 1882.

In 1825 Wöhler became acquainted with Liebig, and an intimate friendship
resulted, which continued until the death of Liebig, a few years ago.
Though they lived far apart, they met during the vacations at their
homes, or traveled together. Many important investigations were
conceived by them as they talked over the problems of chemistry, and
many papers appeared under both their names, containing the results of
their joint work. Among such papers may be mentioned: "On Cyanic Acid"
(1830); "On Mellithic Acid" (1830); "On Sulphotartaric Acid" (1831); "On
Oil of Bitter Almonds, Benzoic Acid, and Related Compounds" (1832); "On
the Formation of Oil of Bitter Almonds from Amygdalin" (1837); and "On
Uric Acid" (1837).

Of the papers included in the above list, the two which most attract
attention are those "On the Oil of Bitter Almonds" and "On Uric Acid."
In the former it was shown for the first time that in analogous carbon
compounds there are groups which remain unchanged, though the compounds
containing them may, in other respects, undergo a variety of changes.
This is the conception of radicals or residues as we use it at the
present day. It cannot be denied that this conception has done very much
to simplify the study of organic compounds. The full value of the
discovery was recognized at once by Berzelius, who, in a letter to the
authors of the paper, proposed that they should call their radical proin
or orthrin (the dawn of day), for the reason that the assumption of its
existence might be likened to the dawn of a new day in chemistry. The
study of this paper should form a part of the work of every advanced
student of chemistry. It is a model of all that is desirable in a
scientific memoir. The paper on uric acid is remarkable for the number
of interesting transformation products described in it, and the skill
displayed in devising methods for the isolation and purification of the
new compounds. Comparatively little has been added to our knowledge of
uric acid since the appearance of the paper of Liebig and Wöhler.

It would lead too far to attempt to give a complete list of the papers
which have appeared under the name of Wöhler alone. In 1828 he made the
remarkable discovery that when an aqueous solution of ammonium cyanate,
CNONH_{4}, is evaporated, the salt is completely transformed into urea,
which has the same percentage composition. It would be difficult to
exaggerate the importance of this discovery. That a substance like urea,
which up to that time had only been met with as a product of processes
which take place in the animal body, should be formed in the laboratory
out of inorganic compounds, appeared to chemists then to be little less
than a miracle. To-day such facts are among the commonest of chemistry.
The many brilliant syntheses of well-known and valuable organic
compounds which have been made during the past twenty years are results
of this discovery of Wöhler.

In 1823 he published a paper on secretion, in the urine, of substances
which are foreign to the animal organism, but which are brought into the
body. He discovered the transformation of neutral organic salts into
carbonates by the process of assimilation.

In 1832 he investigated the dimorphism of arsenious acid and antimony
oxide. In 1841 he made the discovery that dimorphous bodies have
different fusing points, according as they are in the crystallized or
amorphous condition.

Among the more remarkable of his investigations in inorganic chemistry
are those on methods for the preparation of potassium (1823); on
tungsten compounds (1824); the preparation of aluminum (1827); of
glucinum and yttrium (1828). In 1856, working with Ste. Claire Deville,
he discovered crystallized boron.

Analytical methods were improved in many ways, and excellent new methods
were introduced by him. Further, he did a great deal for the improvement
of the processes of applied chemistry.

With Liebig he was associated in editing the "Annalen der Chemie and
Pharmacie" and the "Handwörterbuch der Chemie." He wrote a remarkably
useful and popular "Grundriss der Chemie." The part relating to
inorganic chemistry appeared first in 1831, and was in use until a few
years ago, when Fittig wrote his "Grundriss" on the same plan, a work
which supplanted its prototype.

The above will serve to give some idea of the great activity of Wöhler's
life, and the fruitfulness of his labors. While thus contributing
largely by his own work directly to the growth of chemistry, he did
perhaps as much in the capacity of teacher. Many of the active chemists
of the present day have enjoyed the advantages of Wöhler's instruction,
and many can trace their success to the impulse gathered in the
laboratory at Göttingen. The hand of the old master appears in
investigations carried on to-day by his pupils.

Wöhler's was not a speculative mind. He took very little part in the
many important discussions on chemical theories which engaged the
attention of such men as Dumas, Gerhardt, Berzelius, and Liebig, during
the active period of his life. He preferred to deal with the facts as
such; and no one ever dealt with the facts of chemistry more
successfully. He had a genius for methods which has never been equaled.
The obstacles which had baffled his predecessors were surmounted by him
with ease. He was in this respect a truly great man.

Personally, Wöhler was modest and retiring. His life was simple and
unostentatious. He had a kindly disposition, which endeared him to his
students, to which fact many American chemists who were students at
Göttingen during the time of Wöhler's activity can cordially testify. In
short, it may be said deliberately that Wöhler, as a chemist and as a
man, was a fit model for all of us and for those who will come after us.
Though he has gone, his methods live in every laboratory. His spirit
reigns in many; could it reign in all, the chemical world would be the
better for it.

I.R.

       *       *       *       *       *



LOUIS FAVRE, CONSTRUCTOR OF THE ST. GOTHARD TUNNEL.


It is now already a year that the locomotive has been rolling over the
St. Gothard road, crossing at a flash the distance separating Basle from
Milan, and passing rapidly from the dark and damp defiles of German
Switzerland into the sun lit plains of Lombardy. Our neighbors
uproariously fêted the opening of this great international artery, which
they consider as their personal and exclusive work, as well from a
technical point of view as from that of the economic result that they
had proposed to attain--the creation of a road which, in the words of
Bismarck, "glorifies no other nation." As regards the piercing of the
Gothard, the initiative does, in fact, belong by good right to the
powerful "Iron Chancellor," so we have never dreamed of robbing Germany
of the glory (and it is a true glory) of having created the second of
the great transalpine routes, that open to European products a new gate
to the Oriental world. It seems to us, however, that in the noisy
concert of acclamations that echoed during the days of the fêtes over
the inauguration of the line, a less modest place might have been made
for those who, with invincible tenacity and rare talent, directed the
technical part of the work, and especially those 15 kilometers of
colossal boring--the great St. Gothard Tunnel, which ranks in the
history of great public works side by side with the piercing of the
Frejus, and the marvelous digging of Suez and Panama.

We recall just now the names of those who, during nearly ten years, have
contributed with entire disinterestedness to the completion of this
colossal work. Over all stands a figure of very peculiar
originality--that of M. Louis Favre, the general contractor of the great
tunnel, whose name will remain attached to the creation of this work
through the Helvetian Alps, like that of Sommeiller to the great tunnel
of the Frejus, and that of De Lesseps to the artificial straits that
henceforward join the oceans. Having myself had the honor of occupying
the position of general secretary of the enterprise under consideration,
I have been enabled to make a close acquaintance with the man who was so
remarkable in all respects, and who, after passing his entire life in
great public works, died like a soldier on the field of honor--in the
depths of the tunnel.

[Illustration: LOUIS FAVRE.]

[Illustration: THE DOWNFALL OF THE TITANS, CONQUERED BY THE GENIUS OF
MAN. (Monument at Turin to Commemorate the Tunneling of the Alps.)]

I saw Favre, for the first time, in Geneva, in 1872, a few days after he
had assumed the responsibility of undertaking the great work. He had
been living since the war on his magnificent Plongeon estate, on the
right bank of the lake. There was no need of dancing attendance in order
to reach the contractor of the greatest work that has been accomplished
up to the present time, for M. Favre was easy of access. We had scarcely
passed five minutes together than we we were conversing as we often did
later after an acquaintance of six years. After making known to him the
object of my visit, the desire of being numbered among the _personnel_
of his enterprise, the conversation quickly took that turn of
mirthfulness that was at the bottom of Favre's character. "This is the
first time," said he to me, laughing, "that I ever worked with Germans,
and I had not yet struck the first blow of the pick on the Gothard when
they began to quibble about our contract of the 8th of last August. Ah!
that agreement of August 8th! How I had to change and re-change it,
later on. If this thing continues, we shall have a pretty quarrel,
considering that I do not understand a word of the multiple
interpretations of their _charabia_. I ought to have mistrusted this.
But you see I have remained inactive during the whole of this
unfortunate war. I was not made for promenading in the paths of a
garden, and I should have died of chagrin if such inaction had had to be
prolonged. When one lives, as I have, for thirty years around lumber
yards, it is difficult to accustom one's self to the sedentary and
secluded life that I have led here for nearly two years."

As he said, with just pride, Louis Favre had, indeed, before becoming
the first contractor of public works in the world, lived for a long time
in lumber yards. The years that so many other better instructed but less
learned persons, who were afterward to gladly accept his authority, had
given up to their studies, Favre had passed in the humble shop of his
father, a carpenter at Chêne, a small village at a half league from
Geneva. It soon becoming somewhat irksome for him in the village, he
left the paternal workbench to start on what is called the "tour of
France." He was then eighteen years of age. Three years afterward, he
was undertaking small works. It was not long ere he was remarked by the
engineers conducting the latter, and he was soon called to give his
advice on all difficult questions. Between times, Favre had courageously
studied the principal bases of such sciences as were to be useful to
him. In the evening, he made up at the public school what was lacking in
his early instruction; not that he hoped to make a complete study for an
engineer, but only to learn the indispensable. He was, before all
things, a practical man, who made up for the enforced insufficiency of
his technical knowledge by a _coup d'oeil_ of surprising accuracy.
Here it may be said to me that the piercing of the great St. Gothard
Tunnel was accompanied by considerable loss. That is true, but it must
be recalled also that this colossal work was accomplished amid the most
insurmountable difficulties which ever presented themselves. In spite of
this, the cost of the tunnel per running foot was also a third less than
that of the great Mont Cenis Tunnel.

When Favre undertook the St. Gothard, he already reckoned to his credit
numerous victories in the domain of public works, especially in the
construction of subterranean ones. The majority of tunnels of any length
which, since the beginning of the establishment of railways, have been
considered as works of some proportions (the Blaisy Tunnel, for
instance), were executed by him, in addition to other open air works. So
Favre reached the St. Gothard full of hope. The battle with the colossus
did not displease him, and his courage and his confidence in the success
of the work seemed to increase in measure as the circumstances
surrounding the boring became more difficult. In the presence of the
terrible inundation of the gallery of Airolo and the falling of
aquiferous rocks, creating in the subterranean work so desperate a
situation that a large number of very experienced engineers almost
advised the abandonment of the works, Favre remained impassive. Amid the
general apprehension, which, it may be readily comprehended, was felt in
such a situation he made his confident and cheerful voice heard,
reviving the ardor of all, and speaking disdainfully of "that
insignificant Gothard, which would come out all right." The _personnel_
of the enterprise were not the only ones, however, who were uneasy over
the constantly occurring difficulties in the way of the work, for the
company itself and the Swiss Federal Council made known to Favre their
fears that the execution of the work would be delayed. He, however,
calmed their fears, and exposed his projects to them, and the seances
always ended by a vote of confidence in the future of the undertaking.
Favre certainly did not dissimulate the difficulties that he should have
to conquer, but he execrated those who were timorous and always tried to
put confidence into those who surrounded him. But, singular phenomenon,
he ended by deceiving himself and, at certain times, it would not have
been easy to prove to him that the St. Gothard was not the most easy
undertaking in the world. Those who have lived around him know the jokes
that he sometimes made at the expense of poor Gothard, which paid him
back with interest, however, and did not allow itself to be pierced so
easy after all.

Such confidence as existed in the first years, however, was not to exist
for ever. The tunnel advanced, the heading deepened, but at the price of
what troubles, and especially of how many expenses! Day by day one could
soon count the probable deficit in the affair and the silent partners
began to get a glimpse of the loss of the eight millions of securities
that had had to be deposited with the Swiss Federal Council. For Favre
personally the failure of the enterprise would have been ruin for his
fortune was not so large as has been stated. To fears which Favre
possessed more on account of the associates that he had engaged in the
enterprise than for himself, came to join themselves those troubles with
the Germans that he had spoken to me about on the first day. The St.
Gothard Company, whose troubles are so celebrated, and whose inactivity
lasted until the reconstruction of the affair, was seemingly undertaking
to make Favre, who was directing the only work then in activity, bear
all the insults that it had itself had to endure. And yet, amid these
multiple cares, the contractor of the tunnel did not allow himself to
become disheartened. Constantly at the breach he lived at his works,
going from the gigantic adit of Goschenen to the inundated one of Anolo,
constantly on the mountain, having no heed of the icy and perilous
crossing, and passing days in the torrential rain that was flooding the
tunnel. Who of us does not picture him in mind as he reached the inn at
night, with his high boots still soaking wet, and his gray beard full of
icicles to take his accustomed seat at the table, and, between courses,
to tell some story full of mirth, some joke from the other works whence
he had come, which made us laugh immoderately, and brought a smile to
the faces of the German engineers.

It is a singular coincidence that this confidence in his own work,
despite all the struggles borne, was shared likewise by another man than
Favre--by Germano Sommeiller, the creator of the Mont Cenis Tunnel. When
the work of the first piercing of the Alps was yet in the period of
attacks and incredulity, Sommeiller wrote his brother the following
letter: "Always keep me posted my dear Leander, as to what the laughers
are saying and remember the proverb that 'he will laugh well who laughs
last!' The majority of the people, even engineers, are rubbing their
hands in expectation of the colossal fiasco that awaits us, and it is
for that that the envious keep somewhat silent. I will predict to you
that as soon as success is assured everybody will mount to the house
tops and say 'I told you so! It was an idea of my own!' What great
geniuses are going to spring from the earth! I am in haste, so adieu,
courage, energy, silence and especially cheerfulness! And especially
cheerfulness!" Perhaps this cheerfulness of strong minds is the
invincible weapon of those who, like Sommeiller and Favre, fight against
apathy or the bad faith of their adversaries! Like Favre however
Sommeiller had not the pleasure of being present at the consecration of
his glory, for at the Mont Cenis banquet as at the St. Gothard the place
reserved for the creator of the great work was empty.

As disastrous as was the enterprise from a financial point of view what
a triumph for Favre would have been the day on which he traversed from
one end to the other that 15 kilometers of tunnel that he had walked
over step by step since the first blow of the pick had struck the rock
of the St. Gothard! But such a satisfaction was not to be reserved for
him. Suddenly, on the 19th of July, 1879, less than seven years after
the beginning of the work, and six months before the meeting of the
adits, in the course of one of his visits to the tunnel Favre was
carried off by the rupture of a blood vessel. A year before that epoch,
I had left the enterprise, Favre having confided to me the general
supervision over the manufacture of dynamite that he had undertaken at
Varallo Pombia for the needs of his tunnel, but my friend M. Stockalper,
engineer in chief of the Goschenen section, who accompanied Favre on his
fatal subterranean excursion, has many a time recounted to me the sad
details of his sudden death.

For months before it must be said Favre had been growing old. The man of
broad shoulders and with head covered with thick hair in which here and
there a few silver threads showed themselves, and who was as straight as
at the age of twenty years, had begun to stoop, his hair had whitened
and his face had assumed an expression of sadness that it was difficult
for him to conceal. As powerful as it was this character had been
subjugated. The transformation had not escaped me. Often during the days
that we passed together he complained of a dizziness that became more
and more frequent. We all saw him rapidly growing old. On the 19th of
July, 1879, he had entered the tunnel with one of his friends, a French
engineer who had come to visit the work, accompanied by M. Stockalper.
Up to the end of the adit he had complained of nothing, but, according
to his habit, went along examining the timbers, stopping at different
points to give instructions, and making now and then a sally at his
friend, who was unused to the smell of dynamite. In returning he began
to complain of internal pains. "My dear Stockalper," said he, "take my
lamp, I will join you." At the end of ten minutes not seeing him return,
M. Stockalper exclaimed, "Well! M. Favre, are you coming?" No answer.
The visitor and engineer retraced their steps, and when they reached
Favre he was leaning against the rocks with his head resting upon his
breast. His heart had already ceased to beat. A train loaded with
excavated rock was passing and on this was laid the already stiff body
of him who had struggled up to his last breath to execute a work all
science and labor. A glorious end, if ever there was one!

Favre died in the full plenitude of his forces at less than fifty four
years of age, and I can say, without fear of contradiction, that he was
universally and sincerely regretted by all those who had worked at his
side. Still at the present time when a few of us old colleagues of
Goschenen, Airolo or Altorf meet, it is not without emotion that we
recall the old days, the joyful reunions at which he cheered the whole
table with his broad and genial laugh.--_Maxime Helene, in La Nature._

       *       *       *       *       *



THE NEW HARBOR OF VERA CRUZ.


Besides the enormous engineering work of rendering navigable one of the
mouths of the Mississippi Delta, and the continuous labor of developing
the more original and still bolder project for an Isthmian ship railway,
Mr. James B. Eads has been engaged in the design of new and extensive
harbor works at Vera Cruz, which, when completed, will secure for that
city a commodious and secure port. The accompanying plan shows the
natural features of the locality, as well as the new works. The harbor
is formed by the coast line from the Punta de la Caleta to the Punta de
Hornos, and by La Gallega reef. From the first named point a coral reef,
nearly dry at low water, extends out about 300 yards into the gulf, and
a similar one of about the same length runs out from the Punta de
Hornos. Between these is a bay 2,000 meters wide, and at its northwest
end lies the city of Vera Cruz. The bay is partly inclosed by an island
or reef--La Gallega--which, on the harbor front, has a length of 1,200
meters. Beyond this, and to the southeast, is another small island--the
Lavendera reef. Between the end of this reef and that projecting from
the Punta de Hornos is 320 meters wide. As will be seen from the plan
the natural harbor is exposed to the gale from the north and northwest,
while the formation affords general protection from the northeast and
southeast thanks to five large coral reefs. Not unfrequently, however,
heavy seas sweep through the wide channels between these small islands
interfering seriously with vessels lying alongside the present limited
wharfage. Northeast, La Gallega and Gallaguilla reefs run northward from
the harbor for 3,300 meters and these with the main coast line, form a
bay exposed to the full fury of the winds from the north, and when
northern winds prevail rough water is driven through the passage between
La Gallega and Caleta reefs with great violence, and sets up a rapid and
dangerous current into the harbor.

[Illustration: NEW HARBOR AT VERA CRUZ.]

From the foregoing it will be seen that, while presenting some
advantages, the natural harbor of Vera Cruz possesses many drawbacks and
dangers which the design of Mr. Eads will completely remove. The leading
features of the works about to be carried out are indicated on the plan.
They comprise

1. The construction of a sea wall between La Gallega and the Lavendera
reefs, with an extension over the latter.

2. The construction of a sea wall from Punta de la Caleta to La Gallega.
This part of the work will be begun after the completion of the first
wall to a height of at least 3 ft. above low water.

3. A dike connecting the northern ends of the first two dikes with each
other, and stretching across the southern part of La Gallega, to prevent
the seas which sometimes break over this reef from entering the harbor.
The wall between La Gallega and Lavendera will not only cut off the
rough water during northerly gales, but will also effectually prevent
the deposition of sand in the harbor, because the through passage to the
northwest will be stopped. Passages closed by sluice gates will be
formed through this wall at about low water level, so that at any time
the harbor may be flushed out and stagnation prevented.

4. After the construction of the inclosing walls the harbor will be
dredged out and cleared of coral to a depth of 25 ft. below low water.

5. Following these works of primary importance comes the construction of
a wooden roadway from the Hornos reef to the northwestern dike. This
roadway will form the south front of the harbor, and the excavated
material will be deposited on the space between the roadway and the
existing bottom, so as ultimately to make it a permanent work with a
masonry retaining wall fronting the harbor. The land between the roadway
and the city would also be reclaimed to the extent of more than 740,000
square yards.

6. The construction of wooden piers at right angles to the roadway,
which would be extended to run around the harbor as trade required it,
for ships to be alongside for loading and unloading. The construction of
these short piers would be similar to those used in New York and other
United States ports, and they might afterward be replaced by masonry if
the increase in trade justified so large an expenditure.

7. The erection of a lighthouse, at or near the eastern end of the
Lavendera sea wall of a second on the eastern side of La Gallaguilla
reef, and of another on the west side of La Blanquilla reef. These
houses will be furnished with distinctive signals to enable steamers
running in before another to run with safety between La Gallaguilla and
La Blanquilla as soon as the Lavendera light is seen between the other
two.

The width of deep water at the entrance between the Lavendera and Hornos
reefs will be 1,000 ft. The estimated cost of these extensive works is
ten millions of dollars, a large sum for the Mexican Republic to expend
in harbor improvements at one port but it will doubtless be found a
profitable investment as it will tend greatly to promote trade, and so
increase indefinitely the commerce of the port.

Mr. Eads' plan having been approved by the Mexican Government the work
was formally commenced on the 14th of last August. Plans were also
furnished by him at the request of the Government, for deepening the
mouth of the Panuco River upon which is located the city of Tampico, the
Gulf terminus of the Mexican central railway system.--_Engineering._

       *       *       *       *       *



COST OF POWER TO MAKE FLOUR.


The following estimate of the cost of the power required to manufacture
a barrel of flour is taken from the _Miller_. The calculation would
hardly hold good in this country owing to difference in cost of fuel
attendance etc., but is nevertheless of interest.

"The cost of a steam motor per 20 stone (280 lb.) sack of flour depends
entirely on local circumstances. It depends first, on the amount of
power expended in the production of a sack of flour, that is on its mode
of manufacture, and it depends, secondly, on the cost of the necessary
amount of power, that is, on the cost of fuel burned per horse power The
average consumption of coal of first class steam engines may be taken at
2 lb. per hour per indicated horse power.

"Supposing a mill with six pairs of stones, two pairs of porcelain
roller mills, and the necessary dressing, purifying, and wheat cleaning
machinery to require a steam motor of 100 indicated horse power to drive
it, then the average consumption of fuel in this mill would be 200 lb.
of coal per hour. Such a mill working day and night will turn out about
400 sacks of flour per week of, say, 130 hours, so that 200 X 13 =
26,000 lb. of coal would be required to manufacture 400 sacks of flour.
The cost of this quantity of coal may be taken at, say, £12 (about
$58.32), and for cost of attending engine and boiler, cost of oil, etc.,
another £3 (about $14.58) per week may be added; so that, in this case,
the manufacture of 400 sacks of flour would cause an expenditure of £15
($72.90) for the steam motor. Therefore the cost of the steam motor per
20-stone sack of flour may be taken at 9d. (about 18 cents) per sack, if
an improved low grinding system is used.

"In this case it is supposed that about 55 per cent. of flour is
obtained in the first run, leaving about 30 per cent. of middlings and
about 12 per cent. of bran, which is finished in a bran duster. The
middlings are purified, ground over one pair of middling stones, then
dressed through a centrifugal and the tailings of the latter are passed
over one of the porcelain roller mills, whereas the other porcelain
roller mill treats the second quality of middlings coming from the
purifier. The products from the two porcelain roller mills are dressed
through a second centrifugal, and the whole flour is mixed into one
straight grade. Four pairs of stones are supposed to work on wheat, one
on middlings, and one pair is sharpening. The first run is supposed to
be dressed through two long silk reels. Of course, not every steam motor
has so low a consumption of coal as two pounds per hour per horse power;
it often amounts to three, four, and five pounds per hour. In that case,
of course, the cost of steam power per sack is much greater than 9d. per
sack. A greater number of breaks does not necessarily increase the cost
of steam power per sack of flour. Although more machines may be
employed, each of them may require less horse power; so that the total
amount of power required for manufacturing an equal amount of flour may
not be greater in the case of gradual reduction.

"As, however, the cost of maintenance may be slightly greater in the
latter case, on account of a greater number of more elaborate machines,
the cost of manufacturing a sack of flour may be a little greater when
gradual reduction is employed, taking into account the total expenses of
the mill and interest on the capital employed.

"Water motors are generally a much cheaper source of energy than steam
motors, but they are not so reliable and constant as the latter. The
very irregular supply of water sometimes causes stoppages of the mill,
and often a reserve steam engine has to be provided in order to assist
the water motor when the quantity of water decreases during the summer
months. Wind motors were formerly extensively used for milling purposes,
but they are now gradually disappearing. They are too irregular and
unreliable, although they utilize a very cheap motive power. It is not
advantageous to expend a large amount of capital for a mill which often
is unable to work at the very time when there are favorable
opportunities for doing profitable business. Animal motors are too dear.
They are only suitable for driving very small mills in out of the way
localities."

       *       *       *       *       *



DRIVING GEAR MECHANISM FOR LIFT HAMMERS.


A very interesting system of driving gear for lift hammers was applied
in an apparatus exhibited at Frankfort in 1881 by Mr. Meier of Herzen.
The arrangement of the mechanism is shown in Figs. 1 and 2. In the upper
part of the hammer-frame there is a shaft which is possessed of a
continuous rotary motion, and, with it, there is connected by a friction
coupling a drum that receives the belt from which is suspended the
hammer. In the apparatus exhibited, the mechanism is so arranged that
the hammer must always follow the motion of the controlling lever in the
same direction; but a system may likewise be adopted such that the
hammer shall continue to operate automatically, when and so long as a
lever prepared for such purpose is lowered.

_ab_ is the shaft having a continuous rotary motion, and upon which are
fixed the pulley, c, the fly-wheel, d, and the friction-disk, e.
Upon one of the extremities of the driving shaft is fixed an elongated
sleeve, formed of the drum, g, and of the screw, f, carried by the
nut, h. This latter is supported in the frame in such a way that it
cannot turn, but can move easily in the direction of the axis. Such
motion may be produced by the spring, i, and its extent is such that
the drum, g, is brought in contact with the friction-disk, e.

The hand-lever, k, rod, l, and bent lever, m, serve to bring about
a motion in the opposite direction, and which disengages the drum, g,
from the disk, e, and lets the hammer fall; the drum being then able
to turn freely. If the lever, k, be afterward raised again, the
spring, i, will act anew and couple the drum with the driving-shaft,
so that the hammer will be lifted. In this rotary motion the screw, f,
turns or re-enters into its nut, which it displaces toward the left,
since it cannot itself move in that direction until the rectilinear
motion be wiped out, and the power of the spring be thus overcome. At
the same moment, the screw should naturally also make this rectilinear
movement forward, that is to say, the coupling would be disengaged, if,
at the least lateral motion toward the right, the spring, i, did not
push the system toward the left. There is thus produced a state of
equilibrium such that there is just enough friction between the disk,
e, and the drum, g, to keep the hammer at rest and suspended.
Through the action of an external force which lowers the lever, K, the
hammer at once falls, and the screw issues anew from its nut and brings
the parts into their former positions.

[Illustration: MEIER'S DRIVING GEAR MECHANISM FOR LIFT HAMMERS.]

       *       *       *       *       *



DE JUNKER & RUH'S MACHINE FOR CUTTING ANNULAR WHEELS.


The machine shown in Figs. 1, 2, and 3 has been devised by Messrs.
Junker & Ruh, of Carlsruhe, for cutting internally-toothed gear-wheels.
The progress of the work is such that the wheel is pushed toward the
tool by a piece, n, provided with a curve guide, and that the tool is
raised and separated from the wheel after a tooth has been cut, in order
to allow the wheel to revolve one division further.

The tool is placed in a support, b, which is fixed to the upright,
d, in such away that it may revolve; and this support is connected to
the frame, a, of the machine. A strong flat spring, f, constantly
presses the tool-carrier, b, toward the upright, d, as much as the
screw, g, will permit; and this pressure and the tension of the belt
draw the tool downward. The screws, g, determine the depth of the cut,
and compensate for the differences in the diameter of the tool.

[Illustration: MACHINE FOR CUTTING ANNULAR WHEELS.]

The wheels to be cut are set by pressure into a wrought iron ring, with
which they are placed in a sleeve or support, h. The connection
between the two is assured by means of a nut, c. The axle of the
support, h, is held in the upright of the carriage, k, which
receives from a piece, l, placed on the driving-shaft, n, a slow
forward motion toward the tool, and a rapid motion backward. The
trajectory curve or groove of special form of the piece, l, in which
moves the conducting roller, o, of the carriage, is not closed
everywhere on the two sides, in that the guides that limit it extend
only on the part strictly necessary. This arrangement permits of the
roller being made to leave the trajectory in order that the carriage may
be drawn back to a sufficient distance from the tool when the wheel is
finished, so as to replace the latter by another.

One hollow is cut during each forward travel of the carriage; and, when
such travel is finished, a cam-disk, p, placed on the shaft, n,
lifts the tool-carrier, b, and thus draws the cutting-tool out of the
hollow cut by it, so that the carriage cam can then move back without
restraint. In the interim, the sleeve, h, which supports the wheel,
revolves one tooth through the following arrangement: On the axis, e,
of this sleeve there are two ratchet-wheels, r and s, the number of
whose teeth is equal to that of the teeth to be cut in the wheel. The
wheel, r, produces the rotation of the sleeve, h, and the wheel,
s, keeps the shaft stationary during the operation. The two wheels are
set in motion by a lever, t, or by its click, this lever being raised
at the desired moment on the free extremity of the driving shaft, n,
by a wedge, u. The short arm of the lever, t, engages, through its
point of appropriate shape, with the teeth of the wheel, s, so as to
keep this latter stationary while the tool is cutting out the interspace
between the teeth. When the lever, t, is raised, this point is at
first disengaged from the wheel, s; and the raising of the lever being
prolonged, the button, i, places itself against the upper curve of the
slot in the lever, q, and raises that likewise. q is connected with
the lever, v, which revolves about the axis, e, and v carries the
click, w, so that when the lever, v, is raised, the wheel, r,
turns forward by one tooth. When the lever, t, is lowered, as the
wedge, u, turns more, its click holds the wheel, s, stationary. This
series of operations is repeated until the last interspace between the
teeth has been cut, when the machine stops automatically as follows: A
cam of the disk, A, which receives from the shaft, n, through
cone-wheels, a motion corresponding to that of the wheels, r and s,
abuts against the two-armed lever, z, and this latter then disengages
the rod, y, so that the weight, G, can move the fork, B, in such a way
that the belt shall pass from the fast to the loose pulley.

Motion is communicated to the machine as a whole by the shaft, C, which
is provided with a fast and loose pulley. As shown in the engraving, the
pulley, D, moves the tool, and the pulley, E, causes the revolution of
the shaft, n, through a helicoidal gearing, F.

The construction of the tool carrier is represented in detail in Fig. 3.
The cutting tool, F, rests on a sleeve forming part of the pulley,
r1, against which it is pressed by a nut, while its position is
fixed by a key. The axle, s1, of the tool is held in two boxes, in
which it is fixed by screws. In order that the tool may be placed
exactly in the axis of the wheel to be toothed, and that also the play
produced by lateral wear of the pulley, r1, may be compensated for,
two screws, r2, are arranged on the sides. All rotation of the
shaft, s1, is prevented by a screw, o, which traverses the cast
iron stirrup, C, and the steel axle box.

       *       *       *       *       *



RECENT HYDRAULIC EXPERIMENTS.


At a late meeting of the Institution of Civil Engineers, the paper read
was on "Recent Hydraulic Experiments," by Major Allan Cunningham, R.E.

This paper was mainly a general account of some extensive experiments on
the flow of water in the Ganges Canal, lasting over four years--1874-79.
Their principal object was to find a good mode of discharge measurements
for large canals, and to test existing formulæ. There are about 50,000
velocity, and 600 surface-slope measurements, besides many special
experiments. The Ganges Canal, from its great size, from the variety of
its branches abounding in long straight reaches, and from the power of
control over the water in it, was eminently suited for such experiments.
An important feature was the great range of conditions, and, therefore,
also of results obtained. Thus the chief work was done at thirteen sites
in brickwork and in earth, some being rectangular and others
trapezoidal, and varying from 193 ft. to 13 ft. in breadth, and from 11
ft. to 7 in. in depth, with surface-slopes from 480 to 24 per million,
velocities from 7.7 ft. to 0.6 ft. per second, and discharges from 7,364
to 114 cubic feet per second. For all systematic velocity measurements,
floats were exclusively used, viz., surface floats, double floats, and
loaded rods. Their advantages and disadvantages had been fully discussed
in the detailed treatise "Roorkee Hydraulic Experiments"--1881. They
measured only "forward velocity," the practically useful part of the
actual velocity. The motion of water, even when tranquil to the eye, was
found to be technically "unsteady;" it was inferred that there is no
definite velocity at any point, and that the velocity varies everywhere
largely, both in direction and in magnitude. The average of, say, fifty
forward velocity measurements at any one point was pretty constant, so
that there must be probably average steady motion. Hence average forward
velocity measurements would be the only ones of much practical use. To
obtain these would be tedious and costly, and special arrangements would
be required to obviate the effects of a change in the state of water,
which often occurred in a long experiment, as when velocities at many
points were wanted.

As to surface-slope its measurement--from nearly 600 trials--was found
to be such a delicate operation that the result would be of doubtful
utility. This would affect the application of all formulas into which it
entered. The water surface was ascertained, on the average of its
oscillations, to be sensibly level across, not convex, as supposed by
some writers. There were 565 sets of vertical velocity measurements
combined into forty-six series. The forty-six average curves were all
very flat and convex down stream--except near an irregular bank--and
were approximately parabolas with horizontal axes; the data determined
the parameters only very roughly; the maximum velocity line was usually
below the service, and sank in a rectangular channel, from the center
outward down to about mid-depth near the banks. Its depression seemed
not to depend on the depth, slope, velocity, or wind; probably the air
itself, being a continuous source of surface retardation, would
permanently depress the maximum velocity, while wind failed to effect
this, owing to its short duration. On any vertical the mid-depth
velocity was greater than the mean, and the bed velocity was the least.
The details showed that the mid-depth velocity was nearly as variable
from instant to instant as any other, instead of being nearly constant,
as suggested by the Mississippi experimenters.

The measurement of the mean velocity past a vertical was thought to be
of fundamental importance. Loaded rods seemed by far the best for both
accuracy and convenience in depths under 15 ft. They should be immersed
only 0.94 of the full depth. The chief objection to their use,
that--from not dipping into the slack water near the bed--they moved too
quickly, was thus for the first time removed. A double float with two
similar sub-floats at depths of 0.211 and 0.789 of the full depth would
also give this mean with more accuracy and convenience than any
instrument of its class; this instrument is new. Measurement of the
velocity at five eighths depth would also afford a fair approximation.

One hundred and fourteen average transverse velocity curves were
prepared from 714 separate curves. These average curves were all very
flat, and were convex down stream--over a level or concave bed--and
nearly symmetric in a symmetric section. The velocity was greatest near
the center, or deepest channel, decreased very slowly at first toward
both banks, more rapidly with approach to the banks or with shallowing
of the depth, very rapidly close to the banks, and was very small at the
edges, possibly zero. The figure of the curve was found to be determined
by the figure of the bed, a convexity in the bed producing a concavity
in the curve and _vice versa_, and more markedly in shallow than in deep
water. Curves on the same transversal, at the same site, and with
similar conditions, but differing in general velocity, were nearly
parallel projections. At the edges there was a strong transverse surface
flow from the edge toward mid-channel, decreasing rapidly with distance
from the edge. The discussion showed that it was almost hopeless to seek
the geometric figure of the curves from mere experiment.

Five hundred and eighty-one cubic discharges were measured under very
varied conditions. The process adopted contained three steps: (1)
Sounding along about fifteen float courses, scattered across the site in
eight cross sections; time, say four hours. (2) Measurement of the mean
velocities through the full depths in those float courses, each thrice
repeated; time, say four hours. (3) Computation, say two hours. This
process was direct and wholly experimental; each step was done in a time
which gave some chance of a constant state of water. From an extended
comparison of all results under similar conditions, it appeared that the
above process yielded, under favorable circumstances, results not likely
to differ more than 5 per cent. The sequel showed that in a channel with
variable regimen, a discharge table for a given site must be of at least
double entry, as dependent on the local gauge-reading, and on the
velocity or surface-slope.

Special attention was paid to rapid approximations to mean sectional
velocity. The mean velocity past the central vertical, the central
surface velocity, and Chézy's quasi-velocity--i.e.,

  100 x Sqrt (R x S)

where R = the hydraulic mean depth, and S = surface slope--were tried in
detail; thus 100, 76, and 83 average values thereof respectively were
taken from 581, 313, and 363 detail values. The ratios of these three
velocities to the mean velocity were taken out, and compared in detail
with Bazin's and Cutter's coefficients. Other formulæ were contrasted
also in slight detail. Kutter's alone seemed to be of general
applicability; when the surface slope measurement is good, and the
rugosity coefficient known for the site--both doubtful matters--it would
probably give results within 7½ per cent. of error. Improvement in
formulæ could at present be obtained only by increased complexity, and
the tentative research would be excessively laborious. Now the first two
ratios varied far less than the third; thus their use would probably
involve less error than the third, or approximation would be more likely
from direct velocity measurement than from any use of surface slope. The
connection between velocities was probably a closer one than between
velocity and slope; the former being perhaps only a geometric, and the
latter a physical one. The mean velocity past the central vertical was
recommended for use, as not being affected by wind; the reduction
coefficient could at present only be found by special experiment for
each site. Three current meters were tried for some time with a special
lift, contrived to grip the meter firmly parallel to the current axis,
so as to register only forward velocity, and with a nearly rigid gearing
wire. No useful general results were obtained. Ninety specimens of silt
were collected, but no connection could be traced between silt and
velocity; it seemed that the silt at any point varied greatly from
instant to instant, and that the quantity depended not on the mean
velocity, but probably on the silt in the supply water. Forty
measurements of the evaporation from the canal surface were made in a
floating pan, during twenty five months. The average daily evaporation
was only about 1/10 in. The smallness of this result seemed to be due to
the coldness of the water--only 63 deg. in May, with 165 deg. in the sun
and 105 deg. in shade. Lastly, it must suffice to say that great care
was taken to insure accuracy in both fieldwork and computation.

       *       *       *       *       *



THE GERM.

By ARTHUR ATKINS.


There seems to have sprung up within a few mouths a tendency to revive
the discussion on that hackneyed question, "Shall the germ be retained
in the flour?" This question has been more than once answered in the
negative by both scientific and practical men, but recently certain
prominent persons have come to the conclusion that every one has been
wrong on this point, and the miller should by all means retain the germ.
Now the nutritive value of the germ cannot be disputed, but there are
two circumstances which condemn it us an ingredient of flour. The first
is that the albuminoids which it contains are largely soluble, and this
means that good light bread from germy flour is impossible. I have not
time to go into a detailed explanation of the chemical reasons for this,
but they may be found in a series of articles which appeared in _The
Milling World_ about a year ago. In the next place, the oil contained in
the germ not only discolors the flour, but seriously interferes with its
keeping qualities. Now color is only a matter of taste, and if that were
the only objection to the germ, it might be admitted, but we certainly
do not want anything in our flour to interfere with making light, sweet
bread, and will render it more liable to spoil. If our scientists can
discover some method of obviating these objections, it will then be time
enough to talk about retaining the germ. Meanwhile millers know that
germy flour is low priced flour, and they are not very likely to reduce
their profits by retaining the germ.--_Milling World._

       *       *       *       *       *



WHEAT TESTS.


There was considerable complaint last season, on the part of wheat
raisers in sections tributary to Minneapolis, on account of the rigid
standard of grading adopted by the millers of that city. It was asserted
that the differentiation of prices between the grades was unjustly great
and out of proportion to the actual difference of value. In order to
ascertain whether this was the case or not, the Farmers' Association of
Blue Earth County, Minn., decided to have samples of each grade analyzed
by a competent chemist in order to determine their relative value.
Accordingly specimens were secured, certified to by the agent of the
Millers' Association of Minneapolis, and sent to the University of
Minnesota for analysis. The analysis was conducted by Prof. Wm. A.
Noyes, Ph.D., an experienced chemist, who has recently reported as
follows:

"The analyses of wheat given below were undertaken for the purpose of
determining whether the millers' grades of wheat correspond to an actual
difference in the chemical character of the wheat. For this purpose
samples of wheat were secured, which were inspected and certified to by
M. W. Trexa on April 13th of this year. The inspection cards contained
no statement except the grade of the wheat and the weight per bushel,
but the samples were all of Fife, for the purpose of a better
comparison. The analyses of the wheat were made during October in this
laboratory. In each case the wheat was carefully separated from any
foreign substances before analysis. The results of analysis were as
follows:

                                        Grade     Grade       Grade
                                        No. 1.    No. 2.      No. 3.
  Weight per bushel..................   59 lb.    56½ lb.     55 lb.
  Grains to weigh 10 grains..........    366       474         491
                                        Per ct.   Per ct.     Per ct.
  Foreign matter (seeds, etc.).......    0.41      0.20        1.57
  Nitrogen...........................    2.09      2.08        2.17
  Phosphorus.........................    0.35      0.46        0.46
  Water..............................   12.34     11.31       11.85
  Ash................................    1.59      1.92        1.97
  Albuminoids (nitrogen multiplied
    by 6¼)...........................   13.06     13.00       13.56
  Cellulose..........................    2.03      2.37        2.50
  Starch, sugar, fat, etc............   70.98     71.40       70.12

"The analyses require but little comment. The only substances in which
there is evident connection between the results of analysis and the
grades of wheat are the cellulose, ash, and phosphorus. As regards the
last substance, grades two and three seem to have the greatest food
value. But it seems quite probable from the results that greater
difference would be found between different varieties of wheat of the
same kind than is shown here between different grades of the same
variety of wheat. However, it does not necessarily follow from this that
the different grades of wheat are of nearly equal value to the miller
for the purpose of making flour. That is a question which can be best
answered by determining accurately the amount and character of the flour
which can be made from each grade of wheat. If possible, the
investigation will be continued in that direction."

As Prof. Noyes justly remarks, the value of the different grades of
wheat can best be determined by a comparison of the results of reducing
them to flour, but an intelligent study of the table given above would
of itself be sufficient to indicate the justness of the grading. In the
first place, even were the percentages of the different components
exactly the same in each grade, still the difference in weight would of
itself be sufficient to justify a marked difference in price. This
requires no proof, for, other things being equal, fifty-nine pounds is
worth more than fifty-five pounds. Again, the figures show that No. 3
contained nearly four times as much foreign matter as No. 1. Millers
certainly should not be expected to pay for foreign seeds or other
substances valueless for their purpose, at the price of wheat. Finally,
if the analysis proves anything, it proves that the lower grades contain
a decidedly larger percentage of components which it is generally
agreed, whether directly or the reverse, ought not to be incorporated
with the flour, and are, therefore, of comparatively little value to the
miller. This is shown by the relative amounts of cellulose, ash, and
phosphorus present. Cellulose, as every one knows, is the woody,
indigestible substance which is found in the bran, and the greater the
amount of cellulose, the heavier will be the bran in proportion to the
flour producing elements. According to the figures presented, No. 3
contained nearly one-quarter more cellulose than No. 1, while the amount
in No. 2 was slightly less than in No. 3. The ash, too, which represents
the mineral constituents of the wheat, is directly dependent upon the
quantity of bran. Here, too, the lowest grade is shown to yield about
one-quarter more than the highest. The larger percentage of phosphorus
in the lower grades is suggested by the analyst to indicate their
greater food value in this respect. So it would, were we in the habit of
boiling our wheat and heating it whole, or of using "whole wheat meal."
But, fortunately or unfortunately, the bread reformers have not yet
succeeded in inoculating any considerable portion of the community with
their doctrines, and hence the actual food value of any sample of wheat
must be ascertained, not directly from the composition of the wheat, but
from the composition of the flour made therefrom. Now, as already
stated, phosphorus, like the other mineral components, is found almost
entirely in the bran. Its presence in greater quantity, therefore,
simply adds to the testimony that a larger proportion of the low grade
wheat must be rejected than of the higher grade. It should be evident to
the complaining farmers that the millers were in the right of the
question, on this occasion at least.

It is expected that further analysis will be made, this time of the
flour made from the different grades of wheat. If these investigations
be properly conducted, we have no doubt that they will simply confirm
the evidence of the wheat tests. A chemical analysis alone, however,
will not be sufficient. The quantity of flour obtained from a given
amount of wheat must also be ascertained and its quality further tested
by means best known to millers, as regards "doughing-up," keeping
qualities, color, etc. And then the result can be no less than to show
what millers already knew--that the best quality of flour, commanding
the top prices in the market, cannot be obtained from an inferior
quality of wheat.--_Milling World._

       *       *       *       *       *



APPARATUS FOR PRINTING BY THE BLUE PROCESS.[1]

    [Footnote 1: Read June 21, 1882, before the Boston Society of
    Civil Engineers.]

By CHANNING WHITAKER.


The blue process is well known to the members of the society, and I need
not take time to describe it; but with the ordinary blue process
printing frame the results are sometimes unsatisfactory, and now that
the process has come to be so commonly used I have thought that an
account of an inexpensive but efficient printing frame would be of
interest. The essential parts of the apparatus are its frame, its glass,
its pad or cushion, its clamps, and the mechanism by which the surface
of the glass can easily be made to take a position that is square with
the direction of the sun's rays.

_The Blue Process Printing Frame in Common Use.--Its Defects._--The pad
of the apparatus in common use consists of several thicknesses of
blanketing stretched upon a back board. The sensitized paper and the
negative are placed between the pad and the plate glass, and the whole
is squeezed together by pressure applied at the periphery of the glass
and of the back-board. Both the glass and the back-board spring under
the pressure, and it results that the sensitized paper is not so
severely pressed against the negative near the center of the glass as it
is near the edges. If at any point the sensitized paper is not pressed
hard up against the negative, a bluish tinge will appear where a white
line or surface was expected. With an efficient printing frame and
suitable negatives, these blue lines will never appear, and it was to
prevent the production of defective work that I undertook to improve the
pad of the printing frame.

_The Printing Frame Used in Ordinary Photography._--Very naturally, I
first examined the printing frame used in ordinary photography. This
frame is extremely simple, and is very well adapted to its use. It is,
undoubtedly, the best frame for blue process printing, when the area of
the glass is not too large. The glass is set in an ordinary wooden
frame, while the back-board is stiff and divided into two parts. A flat,
bow-shaped spring is attached by a pivot to the center of each half of
the back-board. The two halves of the back-board are hinged together by
ordinary butts. Four lugs are fastened to the back of the frame, and,
when the back-board is placed in position, the springs may be swung
around, parallel to the line of the hinges, and pressed under the lugs,
so that the back of the back-board is pressed most severely at the
center of each half, while the glass is prevented from springing away
from the back-board by the resistance of the frame at its edges. Unless
the frame is remarkably stiff, it will resist the springing of the glass
more perfectly in the neighborhood of the lugs than elsewhere. It will
now be seen that, on account of the manner in which the pressure is
applied, the back-board tends to become convex toward the glass, while
the adjacent surface of the glass tends to become concave toward the
back-board; and that with such a frame, the pressure upon all parts of
the sensitized paper is more nearly uniform than when the pressure is
applied in the manner before described. With a small frame of this
description, a piece of ordinary cotton flannel is used between the
back-board and the sensitized paper, and, with larger sizes, one or more
thicknesses of elastic woolen blanket are substituted for the cotton
flannel. There is an advantage in having a hinged back-board like that
which has been described, because, when the operator thinks that the
exposure to sunlight has been sufficiently prolonged, he can turn down
either half of the back and examine the sensitized paper, to see if the
process has been carried far enough. If it has not, the back-board can
be replaced, and the exposure continued, without any displacement of the
sensitized paper with respect to the negative. This is an important
advantage.

_An Efficient Blue Process Frame, for Printing from Large Negatives, or
for Printing Simultaneously from many Small Ones._--In order to be
efficient, such a frame must be capable of keeping the sensitized paper
_everywhere tightly pressed against the negative_. Again, such a frame,
being large, is necessarily somewhat heavy. It should be so mounted that
it can be handled with ease; and, in order that it may print quickly, it
should be so arranged that it can be turned without delay, at any time,
into a position that is square with the direction of the sun's rays.

Undoubtedly, if a sufficiently thick plate of glass should be used, the
ordinary photographic printing frames would answer the purpose, whatever
the size, but very thick plate glass is both heavy and expensive.
Commercial plate glass varies in thickness from one-fourth to three
eighths of an inch, and the thicker plates are rather rare. A large
plate of it is easily broken by a slight uniformly distributed pressure.
But the pressure that is required for the blue process printing,
although slight, is much greater than is used in the ordinary
photographic process. For the sensitized paper that is used in the blue
process printing is, comparatively, very thick and stiff, and it may
cockle more or less, while the paper that is used in ordinary
photography is thin and does not cockle. Now, it is easy to see that a
pressure severe enough to flatten all cockles must be had at every part
of the sensitized paper, and that, if the comparatively thin,
inexpensive, light weight, commercial plate glass is to be used, it is
desirable to have the pressure _nowhere much greater than is needed for
that purpose_, lest the fragile glass should be fractured by it. In each
of my large frames I use the commercial plate glass; instead of the
cushion of cotton flannel, or of flannel, I use a cushion filled with
air of sufficiently high pressure to flatten all cockles, and to press
all parts of the sensitized paper closely against the negative; and
instead of the hinged back-board I use a back-board made in one piece
and clamped to the frame of the glass at its edges. Connected with the
cushion is a pressure gauge, and a tube with a cock, for charging the
cushion with air from the lungs. Experience shows what pressure is
necessary with any given paper, and the gauge enables one to know that
the pressure is neither deficient nor in excess of that which is safe
for the glass.

[Illustration: PLAN. COTTON FLANNEL REMOVED.]

[Illustration: SECTION AT CO.]

_The Construction of the Air-Cushion._--The expense of such an
air-cushion seemed at first likely to prevent its being used; but a
method of construction suggested itself, the expense of which proved to
be very slight. The wooden back-board, as constructed, is made in one
piece containing no wide cracks. It has laid upon it some thick brown
Manila paper, the upper surface of which has been previously shellacked
to make it entirely air-tight. Upon this shellacked surface is laid a
single thickness of thin paper of any kind; even newspaper will answer.
Its object is simply to prevent the sheet rubber, which forms the top of
the air-cushion, from sticking to the shellacked paper. The heat of the
sun is often sufficient to bring the shellac to a sticky state. It would
probably answer as well to shellac the under side of the paper, and to
use but one sheet, but I have not tried this plan. Around the periphery
of the pad, there is laid a piece of rubber gasket about one and a half
inches wide, and about one-eighth of an inch thick. In order that the
gasket may not be too expensive, it is cut from two strips about three
inches wide. One of them is as long as the outside length of the frame,
and the other is as long as the outside width of the frame. Each of
these strips is cut into two L-shaped pieces, an inch and a half in
width, with the shorter leg of each L three inches long. When the four
pieces are put together a scarf joint is made near each corner, having
an inch and one-half lap. It is somewhat difficult to cut such a scarf
joint as perfectly as one would wish, and it is best to use rubber
cement at the joints. Over the gasket is laid a sheet of the thinnest
grade of what is called pure rubber or elastic gum. Above this, and over
the gasket, is placed a single thickness of cotton cloth, of the same
dimensions as the gasket, and yet above this are strips of ordinary
strap iron, an inch and a half wide and nearly one eighth of an inch
thick. These strips are filed square at the ends and butt against each
other at right angles. As the edges of the strips are slightly rounded,
they are filed away sufficiently to form good joints wherever the others
butt against them. The whole combination is bound together by ordinary
stove bolts, one quarter of an inch in diameter, placed near the center
of the width of the iron strips, and at a distance apart of about two
and one-half inches. Their heads are countersunk into the strap iron. In
making the holes for the stove bolts through the thin rubber, care
should be taken to make them sufficiently large to enable the bolt to
pass through without touching the rubber, otherwise the rubber may cling
to the bolts, and if they are turned in their holes the rubber may be
torn near the bolts and made to leak. A rough washer, under each nut,
prevents it from cutting into the back-board. For the purpose of
introducing air to, or removing air from, the pad, a three-eighths of an
inch lock nut nipple is introduced through the back-board, the
shellacked paper, and its thin paper covering. Without the back-board a
T connects with the nipple. One of its branches leads, by a rubber tube,
to the pressure gauge, which is a U-tube of glass containing mercury.
The other branch has upon it an ordinary plug cock, and, beyond this, a
rubber tube terminating in a glass mouth-piece. When it is desired to
inflate the air-cushion, it is only necessary to blow into the
mouth-piece. A pressure of one inch of mercury is sufficient for any
work that I have yet undertaken. With particularly good paper, a lower
pressure is sufficient. Upon the top of the pad is laid a piece of
common cotton flannel with the nap outward, and with its edges tacked
along the under edge of the back-board. The cotton flannel is not drawn
tight across the top of the pad. The reason for employing a cotton
flannel covering is this: When the sheet rubber has been exposed for a
few days to the strong sunlight, it loses its strength and becomes
worthless. The cotton flannel is a protection against the destruction of
the rubber by the sunlight. I first observed this destruction while
experimenting with a cheap and convenient form of gauge. I used, as an
inexpensive gauge, an ordinary toy balloon, and I could tell, with
sufficient accuracy, how much pressure I had applied, by the swelling of
the balloon. This balloon ruptured from some unknown cause, and I made a
substitute for it out of a round sheet of thin flat rubber, gathered all
around the circumference. I made holes about one-quarter of an inch
apart, and passing a string in and out drew it tight upon the outside of
a piece of three eighths of an inch pipe, I then wound a string tightly
over the rubber, on the pipe, and found the whole to be air-tight. This
served me for some time, but one day, on applying the pressure, I found
a hole in the balloon which looked as if it had been cut with a very
sharp knife. That it had been so cut was not to be imagined, and on
further examination I found that the fracture had occured at a line
which separated a surface in the strong sunlight from a surface in the
shade, at a fold in the rubber. I saw that all of the rubber which had
been continuously exposed to the intense sunlight had changed color and
had become whiter than before, and that that portion of the balloon had
lost its strength. I then returned to the use of the mercury gauge, and
took the precaution to cover my pad with cotton flannel, as a protection
from the light and from other sources of destruction. This pad is upon
the roof of the Institute; and is exposed to all weathers. As a
protection from the rain and the snow, the whole is covered again with a
rubber blanket. It has withstood the exposure perfectly well for a year,
without injury. The gauge, made from flat rubber, is altogether so cheap
and so convenient that I am now experimenting with one of this
description having a black cloth covering upon the outside. The balloon
is of spherical shape, the black cloth covering is of cylindrical shape,
and I hope that this device will serve every necessary purpose. A
sectional view of the air-cushion is offered as a part of this
communication.

_The Frame, which Contains the Plate Glass_, is made of thick board or
plank, with the broad side of the board at right angles to the surface
of the glass. A rabbet is made for the reception of the glass, and four
strips of strap iron, overlapping both the glass, and the wood, and
screwed to the wood, keep the glass in position. Strips of rubber are
interposed between the glass and the wood and between the glass and the
iron. The frame is hinged to the back-board by separable hinges, so that
the glass can be unhinged from the pad without removing the screws.
Hooks, such as are used for foundry flasks, connect the frame with the
pad upon the opposite side. A frame made in this manner is very stiff
and springs but little, and its depth serves an excellent purpose. The
air-cushion and the frame are so mounted that they can be easily turned
to make the surface of the glass square with the direction of the sun's
rays. It is necessary to have a tell tale connected with the apparatus,
which will show when the surface of the glass has been thus adjusted.
The shadow of the deep frame is an inexpensive tell-tale, and enables
the operator to know when the adjustment is right. I have now described,
in detail, the construction of the air-cushion with its back-board, as
well as that of the frame which holds the plate glass, and I think it
will be evident that the first cost of the materials of which they are
made is comparatively little, and that the workmanship required to
produce it is reduced to a minimum. It will also, I think, be evident
that a uniform pressure, of any desired intensity, can be had all over
the surface of the sensitized paper for the purpose of securing perfect
contact between it and the negative. The blue copies that are taken with
this apparatus are entirely free from blue lines when the negatives,
chemicals, and paper are good.

_The Mechanism for Adjusting the Surface of the Glass, until it shall be
Perpendicular to the Direction of the Sun's Rays._--I have found many
uses for the blue copying process in connection with the work of
instruction at the Massachusetts Institute of Technology. Notes printed
by it are far better and less costly than those printed by papyrograph.
I will not detain you now with an account of the uses that I have made
of it. I will merely say that more than a year ago I found that my
frame, which has a glass 3 feet x 4 feet, was wholly inadequate to the
work in hand, and I tried to increase the production from it by
diminishing the time of printing. The glass of this frame was
horizontal, except when one of its ends was tilted off from the slides
which guided it when pushed out of the window; and I knew that it took
three or four times as long to print when the sun was low as it did when
the sun was near the meridian. I made plans for mounting this frame upon
a single axis, about which it could be turned after it had been pushed
through the window, but I saw that no movement about a single axis would
give a satisfactory adjustment for all times of the year, and I
considered what arrangement of two axes would permit a rapid and perfect
adjustment, at all times, with the least trouble to the operator. It was
evident that when the sun was in the equatorial plane, the surface of
the glass should contain a line which was parallel to the axis of the
earth; and further, that if such a glass was firmly attached to an axis
which was parallel to that of the earth, it would fulfill the desired
purpose. For the glass, being once in adjustment, is only thrown out of
position by the rotation of the earth, and if the glass is rotated
sufficiently about its own axis, in a direction opposite to that of the
earth, it will retain its adjustment. In order to have the adjustment
equally good when the sun was either north or south of the equatorial
plane, it was sufficient to mount a secondary axis upon the primary one
and at right angles to it. About this the glass could be turned through
an angle of 23½°, either way, from the position which it should have
when the sun was in the equatorial plane.

[Illustration: BLUE PROCESS PRINTING APPARATUS.]

_The Construction of the Adjusting Mechanism._--I desired to have the
mechanism as compact and inexpensive as possible, and to have the frame
well balanced about the primary axis, in every position. I also desired
to have a rotation of nearly 180° about the principal axis. The plan
adopted will be most easily understood by referring to the drawing which
illustrates it. The axes are composed chiefly of wood. They are built up
from strips which are 3 inches × 7/8 inch, and from small pieces of 2
inch plank. They are stiffly braced. A pair of ordinary hinges permit
the secondary rotation to occur, while a pair of cast iron dowel pins
with their sockets, such as are used in foundry flasks, serve as pivots
during the primary rotation.

_The Adjustments._--The adjustment about the secondary axis does not
need to be made more frequently than once a week, or once a fortnight.
In order to prevent rotation about this axis when in adjustment, two
cords lead from points which are beneath the back board, and as far
removed from the secondary axis as is convenient. Each cord passes
forward and backward through four parallel holes in a wooden block which
is attached to the primary axis. The cords can be easily slipped in the
holes by pulling their loops, but the friction is so great that they
cannot be slipped by pulling at either end. It takes about twice as long
to make the adjustment as would be necessary if a more expensive device
had been used; but this device is at once so cheap, so secure, and has
so seldom to be used, that it was thought to be best adapted for the
purpose. To prevent rotation from occurring about the primary axis when
it is not desired, a bar parallel to the secondary axis is attached by
its middle point to the primary axis near one end. A cord passes from
either end of this bar through cam shaped clamps, which were originally
designed for clamping the cords of curtains with spring fixtures. These
clamps are cheap. They are easily and quickly adjusted, and are very
secure.

The whole apparatus can be located upon the roof of a building, or, if
convenient, it can be mounted upon slides, and pushed through an open
window when it is to be exposed to the light. If it is to be used upon a
roof, a small hut, or shelter of some sort, near by is a great
convenience to the operator, particularly in winter.

_An Inexpensive Drying Case for Use in Coating the Paper._--When the
apparatus is in continuous use, time may be saved by having a convenient
arrangement for drying the sheets that have been coated with the
sensitizing liquid. I have made an inexpensive drying case which serves
the purpose very well. It consists simply of a light-tight rectangular
case of drawers. There are twenty-five drawers in all. They are
constructed in an inexpensive manner, and are the only parts of the case
that are worth describing. They are very shallow, being but 1-7/8 inches
deep, and as it appeared that the principal expense would be for the
materials of which the bottoms of the drawers should be composed, it was
decided to make the bottoms of cotton cloth. This cloth is stretched
upon a frame, the dimensions of which are greater than that of the paper
to be dried. The stock of which the frame is made is pine, 1¼ inches
wide, and three-eighths of an inch thick. The corners are simply mitered
together and attached to each other by means of the wire staples that
are commonly used for fastening together pages of manuscript, and which
are called "novelty staples." Eight staples are used at each miter, four
above and four below the joint. Two of the staples, at the top and near
the ends of the joint, are set square across it, and two others, at the
top and near the middle of the joint, are placed diagonally across it.
The staples at the bottom are similarly placed. The joint is quite firm
and strong, and is likely to hold for an indefinite period with fair
usage. The cloth, stretched upon the frame, is fastened to it by means
of similar staples. A dark colored cloth not transparent to light is to
be preferred. A strip of pine, 1-13/16 inches wide, and three eighths of
an inch thick, forms the vertical front of the drawer, and prevents the
admission of much light from the front while the sheet is drying. Two
triangular knee pieces, three-quarters of an inch thick, serve to
connect the front board with the frame, and four small screws with a few
brads are used in attaching them. The lower edge of the front board
drops one-quarter of an inch below the bottom of the drawer. My case
stands in a poorly lighted room, and paper dried in this case and
removed to a portfolio as soon as it is dry does not seem to be injured
by the light that reaches it. With the case in a well lighted room, I
should prefer to have outer doors to the case, made of ordinary board
six or eight inches wide, hinged to one end, and arranged to swing
horizontally across the front of the case. These would more completely
prevent the admission of light. The opening of any one of the doors
would allow three or four of the drawers to be filled, while the rest of
the case would be comparatively dark at the same time.[2]

    [Footnote 2: Since this paper was read, I have seen in the
    office of the City Engineer of Boston a drying case which is
    similar in some respects to the one that I have devised. It has
    been longer in use than my own. The drawers are simply the
    ordinary mosquito netting frames covered with cotton netting.
    They have no fronts, but a door covers the front of the case,
    and shuts out the light.]

_The Portfolio for Protecting the Sensitized Paper from Exposure to
Light._--The sensitized paper is very well protected from exposure to
light, if kept in a portfolio or book, the brown paper leaves of which
are considerably larger than the sensitized sheets. The sheets may be
returned to such a book after exposure, and washed at the convenience of
the operator. They can be washed more quickly and perfectly if _two_
water-tanks are provided in which to wash them. A few minutes' soaking
will remove nearly all of the sensitizing preparation which has not been
fixed by the exposure. If the soaking is too long continued in water
that is much discolored by the sensitizing preparation, the sheets
become saturated with the diluted preparation, and they may become
slightly colored by _after_ exposure. If the first soaking is not too
long continued, and if the sheets are transferred at once to a second
bath of clean water, which is kept slowly changing from an open faucet,
they may remain there until the soluble chemicals have been entirely
extracted, and there will be no risk of staining by after exposure.
Washing in two tanks is of more consequence when the ground is white and
the lines blue, than when the ground is blue and the lines white.

_The Grades of Paper that are well Adapted for Blue Process Work._--I
have tested many grades of paper, to ascertain if they were well adapted
for blue process work. Some grades of brown Manila are very good; others
have little specks embedded in their surfaces which refuse to take on a
blue tint; still others, when printed upon, have white lines that are
wider than the corresponding black lines of the negative. The blue
obtained upon bond paper appears to be particularly rich, and the whites
remain pure; but bond paper cockles badly, and the cockles remain in the
finished print. Weston's linen record is an excellent paper. It is
strong, cockles but little, and dries very smooth. A paper that is used
by Allen & Rowell, for carbon printing, is comparatively cheap, and is
an excellent paper. It is not so stiff as the linen record, and the
whites are quite as pure. It does not cockle, neither does it curl while
being sensitized. It comes in one hundred pound rolls, and is about
thirty inches wide. The best papers are those that are prepared for
photographic work. The plain Saxe and the plain Rives both give
excellent results. Blue lines on a pure white ground can be obtained on
these papers, from photographic negatives, without difficulty. None of
the hard papers of good grade require the use of gum in the sensitizing
liquid. The liquid penetrates the more porous papers too far when gum is
not used, and without it good whites are seldom obtained upon porous
paper.

_The Best Chemicals for this Work_ are the _recrystallized_ red
prussiate of potash and the citrate of iron and ammonia, _which is
manufactured by Powers & Wightman_, of Philadelphia. If the red
prussiate has not been recrystallized, the whites will be unsatisfactory
and the samples of citrates of iron and ammonia which have come to us
from other chemists than those named, have all proved unreliable for
this process.

_The Sensitizing Liquid.--Its Proportions._--The blue process was
originally introduced from France, by the late Mr. A. L. Holley. I was
indebted to Mr. P. Barnes, who was with Mr. Holley at the time, for an
early account of it, and I had the first blue process machine that was
in use in New England. Since 1876, instruction in the use of the blue
process has been given to the students of mechanical engineering of the
Massachusetts Institute of Technology, and they have caused its
introduction into many draughting offices. The proportions of the
sensitizing liquid, as originally given me by Mr Barnes, were as
follows:

  Red prussiate of potash............. 8 parts.
  Citrate of iron and ammonia......... 8 parts.
  Gum arabic.......................... 1 part.
  Water.............................. 80 parts.

_Results of Experiments._--In our use, it first appeared that the gum
might be omitted from the preparation when sufficiently hard papers were
used. Next, that a preparation containing

  Red prussiate of potash........ 2 parts,
  Citrate of iron and ammonia.... 3 "
  Water......................... 20 "

printed more rapidly. This preparation I continue to use when much time
may elapse between sensitizing and printing; but, when the paper is to
be printed immediately after sensitizing, I use a larger proportion of
citrate of iron and ammonia. Before arriving at the conclusion that
these proportions were the best to be used, I made a series of purely
empirical experiments, beginning with the proportions:

  Red prussiate of potash.......... 10 parts.
  Citrate of iron and ammonia....... 1 part.
  Water............................ 50 parts.

and ending with the proportions:

  Red prussiate of potash............... 1 part.
  Citrate of iron and ammonia.......... 10 parts.
  Water................................ 50 "

I found the best plan for conducting these experiments to be: To coat a
sheet of the paper with a given mixture; to cut the sheet into strips
before exposure; to expose all the strips of the sheet, at the same
time, to the direct sunlight without an intervening negative; and to
withdraw them, one after another, at stated intervals. I found that with
each mixture there was a time of exposure which would produce the
deepest blue, that with over-exposure the blue gradually turned gray,
and that if a curve should be plotted, the abscissas of which should
represent the time of exposure, and the ordinates of which should
represent the intensity of the blue the curves drawn would have
approximately an elliptical form, so that if one knew the exact time of
exposure which would give the best result with any mixture, one might
deviate two or three minutes either way from that time without producing
a noticeable result. I have found that, with the same paper, the same
blue results with any good proportions of the chemicals named, provided
a sufficient weight of both chemicals is applied to the surface; that an
excess of the red prussiate of potash renders the preparation less
sensitive to light, and very much lengthens the necessary time of
exposure; that the prints are finer with some excess of the red
prussiate; that an excess of the citrate of iron and ammonia hastens the
time of printing materially; that a greater excess of the citrate causes
the whites to become badly stained by the iron, while a still greater
excess of the citrate, in a concentrated solution causes the sensitized
paper to change without exposure to light, and to produce a redder blue
or purple, which does not adhere to the paper, but may be washed off
with a sponge. I have found that the cheapest method of reproducing
inked drawings that have been made on thick paper is not to trace them,
but to print the blues from a photographic glass negative; and also,
that the dry plate process is well adapted to such work in offices, when
one has become sufficiently experienced. Printed matter can also most
easily and inexpensively be reproduced by the same means, when a small
issue is required on each successive year. For the reproduction of
manuscript by the blue process, the best plan that I have found has been
to write the manuscript upon the thinnest blue tinted French note-paper,
with black opaque ink--the stylographic ink is very good--and,
afterward, to dip the paper into melted paraffine, and to dry the paper
at the melting temperature. This operation, if cheaply done, requires
special apparatus. For positive printing from the glass negative, I use
a multiple frame, by the aid of which I can print from 16 negatives at
the same time, upon a single sheet of paper. This frame is
interchangeable with the one that contains the plate glass. The
negatives are so arranged in the frame that the sheets can be cut and
bound, as in the ordinary process of book binding. The time required for
exposure, when printing from glass negatives, varies with the negative;
and, in order to secure satisfactory results with the multiple frame it
is necessary to stop the exposure of some, while the exposure of others
is continued. I insert wooden or cloth stoppers into the frame for the
purpose of stopping the exposure of certain negatives. When paraffined
manuscript is to be printed from, I find it convenient to have it
written on sheets of small size, and to have these mounted upon an
opaque frame of brown Manila paper, printing sixteen or more at a time,
depending upon the size of the printing frame. Many small tracings may
be similarly mounted upon a brown paper multiple frame, and may be
printed together upon a single sheet.

       *       *       *       *       *



SPECTRUM GRATINGS.


At a recent meeting of the London Physical Society, Prof. Rowland, of
Baltimore, exhibited a number of his new concave gratings for giving a
diffraction spectrum. He explained the theory of their action. Gratings
can be ruled on any surface, if the lines are at a proper distance apart
and of the proper form. The best surface, however, is a cylindrical or
spherical one. The gratings are solid slabs of polished speculum metal
ruled with lines equidistant by a special machine of Prof. Rowland's
invention. An account of this machine will be published shortly. The
number of lines per inch varied in the specimens shown from 5,000 to
42,000, but higher numbers can be engraved by the cutting diamond. The
author has designed an ingenious mechanical arrangement for keeping the
photographic plates in focus. In this way photographs of great
distinctness can be obtained. Prof. Rowland exhibited some 10 inches
long, which showed the E line doubled, and the large B group very
clearly. Lines are divided by this method which have never been divided
before, and the work of photographing takes a mere fraction of the time
formerly required. A photographic plate sensitive throughout its length
is got by means of a mixture of eosene, iodized collodion, and bromized
collodion. Prof. Rowland and Captain Abney, R.E., are at present engaged
in preparing a new map of the whole spectrum with a focus of 18 feet.

In reply to Mr. Hilger, F.R.A.S., the author stated that if the metal is
the true speculum metal used by Lord Rosse, it would stand the effects
of climate, he thought; but if too much copper were put in, it might
not.

In reply to Mr. Warren de la Rue, Prof. Rowland said that 42,000 was the
largest number of lines he had yet required to engrave on the metal.

Prof. Guthrie read a letter from Captain Abney, pointing out that Prof.
Rowland's plates gave clearer spectra than any others; they were free
from "ghosts," caused by periodicity in the ruling, and the speculum
metal had no particular absorption.

Prof. Dewar, F.R.S., observed that Prof. Liveing and he had been engaged
for three years past in preparing a map of the ultra-violet spectrum,
which would soon be published. He considered the concave gratings to
make a new departure in the subject, and that they would have greatly
facilitated the preparation of his map.

       *       *       *       *       *



A NEW POCKET OPERA GLASS.


[Illustration: POCKET OPERA GLASS.]

Inasmuch as high power combined with small size is usually required in
an opera glass, manufacturers have always striven to unite these two
features in their instruments, and have succeeded in producing glasses
which, although sufficiently small to be carried in the waistcoat
pocket, are nevertheless powerful enough to allow quite distant objects
to be clearly distinguished. Recently, a Parisian optician has succeeded
in constructing an instrument of this kind that is somewhat of a novelty
in its way, since its mechanism allows it to be closed in such a manner
as to take up no more space than a package of cigarettes (Fig. 1.) It is
constructed as follows:

AB and CD (Fig. 1) are two metallic tubes, in which slide with slight
friction two other tubes. Into the upper part of the latter are inserted
two hollow elliptical eye-pieces, which move therein with slight
friction, and which are united by the two supports tor the wheel, _bb_
(Fig. 4), and endless screw that serve for focusing the instrument. The
eyepieces, TT, are held in the tube by means of two screws, _vv_ (Figs.
2 and 4), in such a way that they can revolve around the latter as axes.
The lenses of the eye-piece are fixed therein by means of a copper ring.
The object glasses are placed in the ends of the tubes, AB and CD, at
_oo_.

When the instrument is closed, it forms a cylinder 35 millimeters in
diameter by 11 centimeters in length. To open it, it is grasped by the
extremities and drawn apart horizontally so as to bring it into the
position shown in Fig. 2. Then it is turned over so that the screw, V,
points upward, while at the same time the two tubes are pressed gently
downward. This causes the eye-pieces to revolve around their axes, _vv_,
and brings the two tubes parallel with each other.--_La Nature._

       *       *       *       *       *



ANCIENT GREEK PAINTING.


A lecture on ancient Greek painting was lately delivered by Professor
C.T. Newton, C.B., at University College, London. The lecturer began by
reminding his audience of the course of lectures on Greek sculpture,
from the earliest times to the Roman period, which he completed this
year. The main epochs in the history of ancient sculpture had an
intimate connection with the general history of the Greeks, with their
intellectual, political, and social development. We could not profitably
study the history of ancient sculpture except as part of the collateral
study of ancient life as a whole, nor could we get a clear idea of the
history of ancient sculpture without tracing out, so far as our
imperfect knowledge permits, the characteristics and successive stages
of ancient painting. Between these twin sister arts there had been in
all times, and especially in Greek antiquity, a close sympathy and a
reciprocal influence. The method in dealing with the history of Greek
painting in this course would be similar to that adopted in the course
on sculpture. The evidence of ancient authors as to the works and
characteristics of Greek painters would be first examined, then the
extant monuments which illustrate the history of this branch of art
would be described. In the case of painting, the extant monuments were
few and far between, but we might learn much by the careful study of the
mural paintings from the buried Campanian cities, Pompeii, Herculaneum,
and those found in the tombs near Rome and Etruria. The paintings on
Greek vases would enable us to trace the history of what is called
ceramographic art from B.C. 600 for nearly five centuries onward.

After noticing the traditions preserved by Pliny and others as to the
earliest painters, the lecturer passed on to the period after the
Persian war. Polygnotos of Thasos was the earliest Greek painter of
celebrity. He flourished B.C. 480-460. At Athens he decorated with
paintings the portico called the Stoa Poikile, the Temple of the
Dioscuri, the Temple of Theseus, and the Pinakotheke on the Akropolis.
At Delphi he painted on the walls of the building called Lesche two
celebrated pictures, the taking of Troy and the descent of Ulysses into
Hades. All these were mural paintings; the subjects were partly
mythical, partly historical. Thus in the Stoa Poikile were represented
the taking of Troy, the battle of Theseus with the Amazons, the battle
of Marathon. In the Temple of Theseus came the battle of the Lapiths and
Centaurs and the battle of the Amazons again. In the other two Athenian
temples he treated mythological subjects. These great public works were
executed during the administration of Kimon, to whom Polygnotos stood in
the same relation us Phidias did to Perikles, the successor of Kimon.
The paintings in the Stoa Poikile were executed by Polygnotos
gratuitously, for which service the Athenians rewarded him with the
freedom of their city. His greatest and probably his earliest works were
the two pictures in the Lesche at Delphi. Of these there was a very full
description in Pausanias. The building called Lesche was thought to have
been of elliptical form, with a colonnade on either side, separated by a
wall in the middle, and to have been about 90 ft in length. The figures
were probably life size.

According to the list given by Pausanias, there were upward of seventy
in each of the two pictures. In that representing the taking of Troy
Polygnotos had brought together many incidents described in the Cyclic
epics: Menelaos Agamemnon, Ulysses, Nestor, Neoptolemos, Antenor, Helen,
Andromache, Kassandra, and many other figures, with which the Homeric
poems have made us familiar, all appeared united in one skillful
composition, arranged in groups. The other picture, the descent of
Ulysses into Hades to interrogate Teiresias, might be called a pictorial
epic of Hades. On one side was the entrance, indicated by Charon's boat
crossing: the Acheron, and the evocation of Teiresias by Ulysses,
besides the punishment of Tityos and other wicked men; on the other side
were Tantalos and Sisyphos. Between these scenes, on the flanks, were
various groups of heroes and heroines from the Trojan and other legends.
From the remarks of ancient critics, it might be inferred that the
genius of Polygnotos, like that of Giotto, was far in advance of his
technical skill. Aristotle called him the most ethical of painters, and
recommended the young artist to study his works in preference to those
of his contemporary Pauson, who was ignobly realistic, or those of
Zeuxis, who had great technical merit, but was deficient in spiritual
conception. The course will comprise four more lectures, as
follows--November 17, "Greek Painters from B.C. 460 to Accession of
Alexander the Great B.C. 336--Apollodoros, Zeuxis, Parrhasios,
Pamphilos, Aristides;" November 24, "Greek Painters from Age of
Alexander to Augustan Age--Apelles, Protogenes, Theon;" December 1,
"Pictures on Greek Fictile Vases;" December 15, "Mural Paintings from
Pompeii, Herculaneum, and other Ancient sites."

       *       *       *       *       *


The new Iowa State Capitol has thus far cost $2,000,000,
and it will require $500,000 to finish it. It is 365 feet long
fron north to south, and measures 274 feet from the sidewalk
to the top of the central dome.

       *       *       *       *       *

[LONGMAN'S MAGAZINE.]



ATOMS, MOLECULES, AND ETHER WAVES.

By JOHN TYNDALL, F.R.S.


I.

Man is prone to idealization. He cannot accept as final the phenomena of
the sensible world, but looks behind that world into another which rules
the sensible one. From this tendency of the human mind, systems of
mythology and scientific theories have equally sprung. By the former the
experiences of volition, passion, power, and design, manifested among
ourselves, were transplanted, with the necessary modifications, into an
unseen universe from which the sway and potency of those magnified human
qualities were exerted. "In the roar of thunder and in the violence of
the storm was felt the presence of a shouter and furious strikers, and
out of the rain was created an Indra or giver of rain." It is
substantially the same with science, the principal force of which is
expended in endeavoring to rend the veil which separates the sensible
world from an ultra-sensible one. In both cases our materials, drawn
from the world of the senses, are modified by the imagination to suit
intellectual needs. The "first beginnings" of Lucretius were not objects
of sense, but they were suggested and illustrated by objects of sense.
The idea of atoms proved an early want on the part of minds in pursuit
of the knowledge of nature. It has never been relinquished, and in our
own day it is growing steadily in power and precision.

The union of bodies in fixed and multiple proportions constitutes the
basis of modern atomic theory. The same compound retains, for ever, the
same elements, in an unalterable ratio. We cannot produce pure water
containing one part, by weight, of hydrogen and nine of oxygen, nor can
we produce it when the ratio is one to ten; but we can produce it from
the ratio of one to eight, and from no other. So also when water is
decomposed by the electric current, the proportion, as regards volumes,
is as fixed as in the case of weights. Two volumes of hydrogen and one
of oxygen invariably go the formation of water. Number and harmony, as
in the Pythagorean system, are everywhere dominant in this under-world.

Following the discovery of fixed proportions we have that of _multiple_
proportions. For the same compound, as above stated, the elementary
factors are constant; but one elementary body often unites with another
so as to form different compounds. Water, for example, is an oxide of
hydrogen; but a peroxide of that substance also exists, containing
exactly double the quantity of oxygen. Nitrogen also unites with oxygen
in various ratios, but not in all. The union takes place, not gradually
and uniformly, but by steps, a definite weight of matter being added at
each step. The larger combining quantities of oxygen are thus multiples
of the smaller ones. It is the same with other combinations.

We remain thus far in the region of fact: why not rest there? It might
as well be asked why we do not, like our poor relations of the woods and
forests, rest content with the facts of the sensible world. In virtue of
our mental idiosyncrasy, we demand _why_ bodies should combine in
multiple proportions, and the outcome and answer of this question is the
atomic theory. The definite weights of matter, above referred to,
represent the weights of atoms, indivisible by any force which chemistry
has hitherto brought to bear upon them. If matter were a _continuum_--if
it were not rounded off, so to say, into these discrete atomic
masses--the impassable breaches of continuity which the law of multiple
proportions reveals, could not be accounted for. These atoms are what
Maxwell finely calls "the foundation stones of the material universe,"
which, amid the wreck of composite matter, "remain unbroken and unworn."

A group of atoms drawn and held together by what chemists term affinity
is called a molecule. The ultimate parts of all compound bodies are
molecules. A molecule of water, for example, consists of two atoms of
hydrogen, which grasp and are grasped by one atom of oxygen. When water
is converted into steam, the distances between the molecules are greatly
augmented, but the molecules themselves continue intact. We must not,
however, picture the constituent atoms of any molecule as held so
rigidly together as to render intestine motion impossible. The
interlocked atoms have still liberty of vibration, which may, under
certain circumstances, become so intense as to shake the molecule
asunder. Most molecules--probably all--are wrecked by intense heat, or
in other words by intense vibratory motion; and many are wrecked by a
very moderate heat of the proper quality. Indeed, a weak force, which
bears a suitable relation to the constitution of the molecule, can, by
timely savings and accumulations, accomplish what a strong force out of
relation fails to achieve.

We have here a glimpse of the world in which the physical philosopher
for the most part resides. Science has been defined as "organized common
sense;" by whom I have forgotten; but, unless we stretch unduly the
definition of common sense, I think it is hardly applicable to this
world of molecules. I should be inclined to ascribe the creation of that
world to inspiration rather than to what is currently known as common
sense. For the natural history sciences the definition may stand--hardly
for the physical and mathematical sciences.

The sensation of light is produced by a succession of waves which strike
the retina in periodic intervals; and such waves, impinging on the
molecules of bodies, agitate their constituent atoms. These atoms are so
small, and, when grouped to molecules, are so tightly clasped together,
that they are capable of tremors equal in rapidity to those of light and
radiant heat. To a mind coming freshly to these subjects, the numbers
with which scientific men here habitually deal must appear utterly
fantastical; and yet, to minds trained in the logic of science, they
express most sober and certain truth. The constituent atoms of molecules
can vibrate to and fro millions of millions of times in a second. The
waves of light and of radiant heat follow each other at similar rates
through the luminiferous ether. Further, the atoms of different
molecules are held together with varying degrees of tightness--they are
tuned, as it were, to notes of different pitch. Suppose, then,
light-waves, or heat-waves, to impinge upon an assemblage of such
molecules, what may be expected to occur? The same as what occurs when a
piano is opened and sung into. The waves of sound select the strings
which respectively respond to them--the strings, that is to say, whose
rates of vibration are the same as their own--and of the general series
of strings these only sound. The vibratory motion of the voice, imparted
first to the air, is here taken up by the strings. It may be regarded as
_absorbed_, each string constituting itself thereby a new center of
motion. Thus also, as regards the tightly locked atoms of molecules on
which waves of light or radiant heat impinge. Like the waves of sound
just adverted to, the waves of ether select those atoms whose periods of
vibration synchronize with their own periods of recurrence, and to such
atoms deliver up their motion. It is thus that light and radiant heat
are absorbed.

And here the statement, though elementary, must not be omitted, that the
colors of the prismatic spectrum, which are presented in an impure form
in the rainbow, are due to different rates of atomic vibration in their
source, the sun. From the extreme red to the extreme violet, between
which are embraced all colors visible to the human eye, the rapidity of
vibration steadily increases, the length of the waves of ether produced
by these vibrations diminishing in the same proportion. I say "visible
to the human eye," because there may be eyes capable of receiving visual
impression from waves which do not affect ours. There is a vast store of
rays, or more correctly waves, beyond the red, and also beyond the
violet, which are incompetent to excite our vision; so that could the
whole length of the spectrum, visible and invisible, be seen by the same
eye, its length would be vastly augmented.

I have spoken of molecules being wrecked by a moderate amount of heat of
the proper quality: let us examine this point for a moment. There is a
liquid called nitrite of amyl--frequently administered to patients
suffering from heart disease. The liquid is volatile, and its vapor is
usually inhaled by the patient. Let a quantity of this vapor be
introduced into a wide glass tube, and let a concentrated beam of solar
light be sent through the tube along its axis. Prior to the entry of the
beam, the vapor is as invisible as the purest air. When the light
enters, a bright cloud is immediately precipitated on the beam. This is
entirely due to the waves of light, which wreck the nitrite of amyl
molecules, the products of decomposition forming innumerable liquid
particles which constitute the cloud. Many other gases and vapors are
acted upon in a similar manner. Now the waves that produce this
decomposition are by no means the most powerful of those emitted by the
sun. It is, for example, possible to gather up the ultra-red waves into
a concentrated beam, and to send it through the vapor, like the beam of
light. But, though possessing vastly greater energy than the light
waves, they fail to produce decomposition. Hence the justification of
the statement already made, that a suitable relation must subsist
between the molecules and the waves of ether to render the latter
effectual.

A very impressive illustration of the decomposing power of the waves of
light is here purposely chosen; but the processes of photography
illustrate the same principle. The photographer, without fear,
illuminates his developing room with light transmitted through red or
yellow glass; but he dares not use blue glass, for blue light would
decompose his chemicals. And yet the waves of red light, measured by the
amount of energy which they carry, are immensely more powerful than the
waves of blue. The blue rays are usually called chemical rays--a
misleading term; for, as Draper and others have taught us, the rays that
produce the grandest chemical effects in nature, by decomposing the
carbonic acid and water which form the nutriment of plants, are not the
blue ones. In regard, however, to the salts of silver, and many other
compounds, the blue rays are the most effectual. How is it then that
weak waves can produce effects which strong waves are incompetent to
produce? This is a feature characteristic of periodic motion. In the
experiment of singing into an open piano already referred to, it is the
accord subsisting between the vibrations of the voice and those of the
string that causes the latter to sound. Were this accord absent, the
intensity of the voice might be quintupled, without producing any
response. But when voice and string are identical in pitch, the
successive impulses add themselves together, and this addition renders
them, in the aggregate, powerful, though individually they may be weak.
It some such fashion the periodic strokes of the smaller ether waves
accumulate, till the atoms on which their timed impulses impinge are
jerked asunder, and what we call chemical decomposition ensues.

Savart was the first to show the influence of musical sounds upon liquid
jets, and I have now to describe an experiment belonging to this class,
which bears upon the present question. From a screw-tap in my little
Alpine kitchen I permitted, an hour ago, a vein of water to descend into
a trough, so arranging the flow that the jet was steady and continuous
from top to bottom. A slight diminution of the orifice caused the
continuous portion of the vein to shorten, the part further down
resolving itself into drops. In my experiment, however, the vein, before
it broke, was intersected by the bottom of the trough. Shouting near the
descending jet produced no sensible effect upon it. The higher notes of
the voice, however powerful, were also ineffectual. But when the voice
was lowered to about 130 vibrations a second, the feeblest utterance of
this note sufficed to shorten, by one half, the continuous portion of
the jet. The responsive drops ran along the vein, pattered against the
trough, and scattered a copious spray round their place of impact. When
the note ceased, the continuity and steadiness of the vein were
immediately restored. The formation of the drops was here periodic; and
when the vibrations of the note accurately synchronized with the periods
of the drops, the waves of sound aided what Plateau has proved to be the
natural tendency of the liquid cylinder to resolve itself into
spherules, and virtually decomposed the vein.

I have stated, without proof, that where absorption occurs, the motion
of the ether-waves is taken up by the constituent atoms of molecules. It
is conceivable that the ether-waves, in passing through an assemblage of
molecules, might deliver up their motion to each molecule as a whole,
leaving the relative positions of the constituent atoms unchanged. But
the long series of reactions, represented by the deportment of nitrite
of amyl vapor, does not favor this conception; for, were the atoms
animated solely by a common motion, the molecules would not be
decomposed. The fact of decomposition, then, goes to prove the atoms to
be the seat of the absorption. They, in great part, take up the energy
of the ether-waves, whereby their union is severed, and the building
materials of the molecules are scattered abroad.

Molecules differ in stability; some of them, though hit by waves of
considerable force, and taking up the motions of these waves,
nevertheless hold their own with a tenacity which defies decomposition.
And here, in passing, I may say that it would give me extreme pleasure
to be able to point to my researches in confirmation of the solar theory
recently enunciated by my friend the President of the British
Association. But though the experiments which I have made on the
decomposition of vapors by light might be numbered by the thousand, I
have, to my regret, encountered no fact which prove that free aqueous
vapor is decomposed by the solar rays, or that the sun is reheated by
the combination of gases, in the severance of which it had previously
sacrificed its heat.


II.

The memorable investigations of Leslie and Rumford, and the subsequent
classical reasearches of Melloni, dealt, in the main, with the
properties of radiant heat; while in my investigations, radiant heat,
instead of being regarded as an end, was employed as a means of
exploring molecular condition. On this score little could be said until
the gaseous form of matter was brought under the dominion of experiment.
This was first effected in 1859, when it was proved that gases and
vapors, notwithstanding the open door which the distances between their
molecules might be supposed to offer to the heat waves, were, in many
cases, able effectually to bar their passage. It was then proved that
while the elementary gases and their mixtures, including among the
latter the earth's atmosphere, were almost as pervious as a vacuum to
ordinary radiant heat, the compound gases were one and all absorbers,
some of them taking up with intense avidity the motion of the
ether-waves.

A single illustration will here suffice. Let a mixture of hydrogen and
nitrogen, in the proportion of three to fourteen by weight, be inclosed
in a space through which are passing the heat rays from an ordinary
stove. The gaseous mixture offers no measurable impediment to the rays
of heat. Let the hydrogen and nitrogen now unite to form the compound
ammonia. A magical change instantly occurs. The number of atoms present
remains unchanged. The transparency of the compound is quite equal to
that of the mixture prior to combination. No change is perceptible to
the eye, but the keen vision of experiment soon detects the fact that
the perfectly transparent and highly attenuated ammonia resembles pitch
or lampblack in its behavior to the rays of heat.

There is probably boldness, if not rashness, in the attempt to make
these ultra-sensible actions generally intelligible, and I may have
already transgressed the limits beyond which the writer of a familiar
article cannot profitably go. There may, however, be a remnant of
readers willing to accompany me, and for their sakes I proceed. A
hundred compounds might be named which, like the ammonia, are
transparent to light, but more or less opaque--often, indeed, intensely
opaque--to the rays of heat from obscure sources. Now the difference
between these latter rays and the light rays is purely a difference of
period of vibration. The vibrations in the case of light are more rapid,
and the ether waves which they produce are shorter, than in the case of
obscure heat. Why, then, should the ultra-red waves be intercepted by
bodies like ammonia, while the more rapidly recurrent waves of the whole
visible spectrum are allowed free transmission? The answer I hold to be
that, by the act of chemical combination, the vibrations of the
constituent atoms of the molecules are rendered so sluggish as to
synchronize with the motions of the longer waves. They resemble loaded
piano strings, or slowly descending water jets, requiring notes of low
pitch to set them in motion.

The influence of synchronism between the "radiant" and the "absorbent"
is well shown by the behavior of carbonic acid gas. To the complex
emission from our heated stove, carbonic acid would be one of the most
transparent of gases. For such waves olefiant gas, for example, would
vastly transcend it in absorbing power. But when we select a radiant
with whose waves the atoms of carbonic acid are in accord, the case is
entirely altered. Such a radiant is found in a carbonic oxide flame,
where the radiating body is really hot carbonic acid. To this special
radiation carbonic acid is the most opaque of gases.

And here we find ourselves face to face with a question of great
delicacy and importance. Both as a radiator and as an absorber, carbonic
acid is, in general, a feeble gas. It is beaten in this respect by
chloride of methyl, ethylene, ammonia, sulphurous acid, nitrous oxide,
and marsh gas. Compared with some of these gases, its behavior, in fact,
approaches that of elementary bodies. May it not help to explain their
neutrality? The doctrine is now very generally accepted that atoms of
the same kind may, like atoms of different kinds, group themselves to
molecules. Affinity exists between hydrogen and hydrogen and between
chlorine and chlorine, as well as between hydrogen and chlorine. We have
thus homogeneous molecules as well as heterogeneous molecules, and the
neutrality so strikingly exhibited by the elements may be due to a
quality of which carbonic acid furnishes a partial illustration. The
paired atoms of the elementary molecules may be so out of accord with
the periods of the ultra red waves--the vibrating periods of these atoms
may, for example, be so rapid--as to disqualify them both from emitting
those waves, and from accepting their energy. This would practically
destroy their power, both as radiators and absorbers. I have reason to
know that a distinguished authority has for some time entertained this
hypothesis.

We must, however, refresh ourselves by occasional contact with the solid
ground of experiment, and an interesting problem now lies before us
awaiting experimental solution. Suppose two hundred men to be scattered
equably throughout the length of Pall Mall. By timely swerving now and
then, a runner from St. James's Palace to the Athenæum Club might be
able to get through such a crowd without much hinderance. But supposing
the men to close up so as to form a dense file crossing Pall Mall from
north to south; such a barrier might seriously impede, or entirely stop,
the runner. Instead of a crowd of men, let us imagine a column of
molecules under small pressure, thus resembling the sparsely distributed
crowd. Let us suppose the column to shorten, without change in the
quantity of matter, until the molecules are so squeezed together as to
resemble the closed file across Pall Mall. During these changes of
density, would the action of the molecules upon a beam of heat passing
among them at all resemble the action of the crowd upon the runner?

We must answer this question by direct experiment. To form our molecular
crowd we place, in the first instance, a gas or vapor in a tube 38
inches long, the ends of which are closed with circular windows,
air-tight, but formed of a substance which offers little or no
obstruction to the calorific waves. Calling the measured value of a heat
beam passing through this tube 100, we carefully determine the
proportionate part of this total absorbed by the molecules in the tube.
We then gather precisely the same number of molecules into a column 10.8
inches long, the one column being thus three and a half times the length
of the other. In this case also we determine the quantity of radiant
heat absorbed. By the depression of a barometric column, we can easily
and exactly measure out the proper quantities of the gaseous body. It is
obvious that one mercury inch of vapor, in the long tube, would
represent precisely the same amount of matter--or, in other words, the
same number of molecules--as 3½ inches in the short one; while 2
inches of vapor in the long tube would be equivalent to 7 inches in the
short one.

The experiments have been made with the vapors of two very volatile
liquids, namely, sulphuric ether and hydride of amyl. The sources of
radiant heat were, in some cases, an incandescent lime cylinder, and in
others a spiral of platinum wire, heated to bright redness by an
electric current. One or two of the measurements will suffice for the
purposes of illustration. First, then, as regards the lime light; for 1
inch of pressure in the long tube, the absorption was 18.4 per cent. of
the total beam; while for 3.5 inches of pressure in the short tube, the
absorption was 18.8 per cent., or almost exactly the same as the former.
For 2 inches pressure, moreover, in the long tube, the absorption was
25.7 per cent.; while for 7 inches in the short tube it was 25.6 per
cent. of the total beam. Thus closely do the absorptions in the two
cases run together--thus emphatically do the molecules assert their
individuality. As long as their number is unaltered, their action on
radiant heat is unchanged. Passing from the lime light to the
incandescent spiral, the absorptions of the smaller equivalent
quantities, in the two tubes, were 23.5 and 23.4 per cent.; while the
absorptions of the larger equivalent quantities were 32.1 and 32.6 per
cent., respectively. This constancy of absorption, when the density of a
gas or vapor is varied, I have called "the conservation of molecular
action."

But it may be urged that the change of density, in these experiments,
has not been carried far enough to justify the enunciation of a law of
molecular physics. The condensation into less than one-third of the
space does not, it may be said, quite represent the close file of men
across Pall Mall. Let us therefore push matters to extremes, and
continue the condensation till the vapor has been squeezed into a
liquid. To the pure change of density we shall then have added the
change in the state of aggregation. The experiments here are more easily
described than executed; nevertheless, by sufficient training,
scrupulous accuracy, and minute attention to details, success may be
insured. Knowing the respective specific gravities, it is easy, by
calculation, to determine the condensation requisite to reduce a column
of vapor of definite density and length to a layer of liquid of definite
thickness. Let the vapor, for example, be that of sulphuric ether, and
let it be introduced into our 38 inch tube till a pressure of 7.2 inches
of mercury is obtained. Or let it be hydride of amyl, of the same
length, and at a pressure of 6.6 inches. Supposing the column to
shorten, the vapor would become proportionally denser, and would, in
each case, end in the production of a layer of liquid exactly one
millimeter in thickness.[1] Conversely, a layer of liquid ether or of
hydride of amyl, of this thickness, were its molecules freed from the
thrall of cohesion, would form a column of vapor 38 inches long, at a
pressure of 7.2 inches in the one case, and of 6.6 inches in the other.
In passing through the liquid layer, a beam of heat encounters the same
number of molecules as in passing through the vapor layer: and our
problem is to decide, by experiment, whether, in both cases, the
molecule is not the dominant factor, or whether its power is augmented,
diminished, or otherwise overridden by the state of aggregation.

    [Footnote 1: The millimeter is 1-25th of an inch.]

Using the sources of heat before mentioned, and employing diathermanous
lenses, or silvered minors, to render the rays from those sources
parallel, the absorption of radiant heat was determined, first for the
liquid layer, and then for its equivalent vaporous layer. As before, a
representative experiment or two will suffice for illustration. When the
substance was sulphuric ether, and the source of radiant heat an
incandescent platinum spiral, the absorption by the column of vapor was
found to be 66.7 per cent. of the total beam. The absorption of the
equivalent liquid layer was next determined, and found to be 67.2 per
cent. Liquid and vapor, therefore, differed from each only 0.5 per
cent.; in other words, they were practically identical in their action.
The radiation from the lime light has a greater power of penetration
through transparent substances than that from the spiral. In the
emission from both of these sources we have a mixture of obscure and
luminous rays; but the ratio of the latter to the former, in the lime
light is greater than in the spiral; and, as the very meaning of
transparency is perviousness to the luminous rays, the emission in which
these rays are predominant must pass most freely through transparent
substances. Increased transmission implies diminished absorption; and
accordingly, the respective absorption of ether vapor and liquid ether,
when the lime light was used, instead of being 66.7 and 67.2 per cent.,
were found to be

  Vapor....................33.3 per cent.
  Liquid...................33.3   "

no difference whatever being observed between the two states of
aggregation. The same was found true of hydride of amyl.

This constancy and continuity of the action exerted on the waves of heat
when the state of aggregation is changed, I have called "the thermal
continuity of liquids and vapors." It is, I think, the strongest
illustration hitherto adduced of the conservation of molecular action.

Thus, by new methods of search, we reach a result which was long ago
enunciated on other grounds. Water is well known to be one of the most
opaque of liquids to the waves of obscure heat. But if the relation of
liquids to their vapors be that here shadowed forth, if in both cases
the molecule asserts itself to be the dominant factor, then the
dispersion of the water of our seas and rivers, as invisible aqueous
vapor in our atmosphere, does not annul the action of the molecules on
solar and terrestrial heat. Both are profoundly modified by this
constituent; but as aqueous vapor is transparent, which, as before
explained, means pervious to the luminous rays, and as the emission from
the sun abounds in such rays, while from the earth's emission they are
wholly absent, the vapor screen offers a far greater hinderance to the
outflow of heat from the earth toward space than to the inflow from the
sun toward the earth. The elevation of our planet's temperature is
therefore a direct consequence of the existence of aqueous vapor in our
air. Flimsy as that garment may appear, were it removed terrestrial life
would probably perish through the consequent refrigeration.

I have thus endeavored to give some account of a recent incursion into
that ultra-sensible world mentioned at the outset of this paper. Invited
by my publishers, with whom I have now worked in harmony for a period of
twenty years, to send some contribution to the first number of their new
Magazine, I could not refuse them this proof of my good will.

J. TYNDALL

Alp Lusgen, September 4, 1882

       *       *       *       *       *


The German empire has now about 34,000,000 acres of
forest, valued at $400,000,000, and appropriates $500,000
even year to increase and maintain the growth of trees.

       *       *       *       *       *



APPARATUS FOR MEASURING ELECTRICITY AT THE UPPER SCHOOL OF TELEGRAPHY.


_Electro Tuning Forks and their Uses._--On a former occasion I described
an instrument to which, in 1873, I gave the name _Electro-Tuning Fork_,
and which is nothing else than a tuning fork whose motion is kept up
electrically in such a way as to last indefinitely, provided that the
elements of the pile are renewed gradually, and that from time to time
the metallic contact is changed, which causes, at every oscillation, the
current to pass from the pile into the magnet, which keeps up the
vibration.

We reproduce herewith, in Fig. 1, a cut showing in projection one of the
simplest forms of the apparatus.

[Illustration: FIG. 1.--CONSTANT VIBRATOR.]

If we imagine the platinum or steel style, s, of the figure to be done
away with, as well as the platinized plate, I, and its communication
with the negative pole of the pile, P, we shall have the ordinary
instrument kept in operation electrically by the aid of the
electro-magnet, E, the style, s, the interrupting plate, I, and the
pile.

If we preserve the parts above mentioned, the instrument will possess
the property of having vibrations of a constant amplitude if sufficient
energy be kept up in the pile. In fact, when the amplitude is
sufficiently great to cause the style, s, to touch the plate, I, it
will be seen that at such a moment the current no longer passes through
the electromagnet, and the vibration is no longer maintained. The
amplitude cannot exceed an extent which shall permit the style, s, to
touch I.

Under such conditions, the duration of the vibrations remains exactly
constant, as does also the vibratory intensity of the entire instrument.
The measurement of time, then, by an instrument of this kind is, indeed,
as perfect as it could well be.

This complication in the arrangement of the apparatus has no importance
as regards those tuning forks the number of whose vibrations exceeds a
hundred per second, for in such a case these are given an amplitude of a
few millimeters only; but it would be of importance with regard to
instruments whose number of vibrations is very small, and to which it
might be desirable to give great amplitude; for then, as I have long ago
shown, the duration of the oscillation would depend a little on the
amplitude, but a very little, it is true.

I shall not refer now to the applications of these instruments in
chronography, but will rather point out first the applications in which
they are destined to produce an effective power.

For this purpose it is necessary to make them pretty massive. The number
of the vibrations depends upon such massiveness, and it is necessity to
know the relation which exists between these two quantities in order to
be able to construct an instrument under determinate conditions. I made
in former years such a research with regard to tuning forks of prismatic
form, that is to say, of a constant rectangular section continuing even
into the bent portion where the parallel branches are united by a
semicylinder, at the middle of which is the wrought iron rod as well as
the branches. The _thickness_ of the instrument is the dimension
parallel to the vibrations; its _width_ is the dimension which is
perpendicular to them, and its _length_ is reckoned from the extremity
of the branches up to the middle of the curved portion.

It is found that the number of vibrations is independent of the width,
proportional to the thickness, and very nearly inverse ratio of the
square of the length, provided the latter exceeds ten centimeters.

If we represent the length by l, the thickness by e, and the number
of vibrations by n, we shall have the following formula:

  n = k x ( e / l² )

in which k is a constant quantity whose value depends upon the nature
of the metal of which the tuning fork is made.

This constant varies very little from steel to malleable cast iron, and
it may be taken as equal to 818270.

Thus, then, we have a means of constructing a tuning fork in which two
of the three quantities, n, e, l, are given in advance. Experience
proves that no errors are committed exceeding one or two per cent.

It is seen from this that there is a means of increasing the mass of the
instrument without changing anything in the thickness, the length or,
consequently, the number of vibrations, and this is by increasing the
_breadth_.

It is in this way that I have succeeded in having long massive tuning
forks made of malleable iron, giving no more than 12 to 15 vibrations
per second, and vibrating with perfect regularity. Fig. 2, annexed,
shows one of these instruments of about 55 centimeters length, whose
breadth, E, is from 5 to 6 centimeters, and which makes about fifteen
double vibrations per second only.

[Illustration: FIG. 2.--THE ELECTRICAL TUNING FORK.]

This number might be still further reduced, but at the expense of our
being led to exaggerate the longitudinal dimensions of the apparatus in
such a way as to make it inconvenient. The object may be attained more
simply by loading the branches with slides supporting leaden weights, M,
of 500 grammes each. By fixing these slides at different points on the
branches, the number of vibrations can be made to vary from simple to
double, and even triple. Thus, by fixing them at the extremity of the
branches the number of the vibrations is reduced to 5 or 6.

There will be seen in the figure the electro-magnet which keeps up the
vibration. This is formed of three simple electro-magnets, whose bobbins
have a resistance of no more than 10 ohms, and which are united in
series. The interrupting plate, P, against which the style, s, rests
at each vibration, is capable of a forward movement, or one of recoil,
by the aid of a screw, V, and of an eccentric movement which is produced
by a small handle, m, and during which its plane remains invariable.
This arrangement permits the point of contact of the style and plate to
be varied without changing the precision with which the contact takes
place, and all the points of the plate to be slowly used in succession
before replacing it. The motion is produced by means of a relatively
weak pile, whose poles are connected to the terminals, A and A'. Three
Callaud elements of triple surface, renewed one after the other every
month at the most, are sufficient to keep up the vibrations
continuously, day and night, without interruption, and that too even
when the instrument is employed in producing a small mechanical power,
as we shall see further on.

We have now seen how electro-tuning forks may be constructed of large
dimensions, of large mass, and giving a small number of vibrations per
second.

Such instruments are well fitted to perform the role of electrical
interrupters, and it was in such a character that one of them figured in
the Exhibition of the Upper School of Telegraphy as a type of an
interrupter for testing piles.

When it is desired to test a pile to ascertain the practicability of
employing it in telegraphy, it is necessary to make it perform a work
which shall be as nearly as possible identical with that which it will
be called on to do, until it is used up, to estimate the duration of
such work, to measure regularly the constants of the pile, the
electro-motive power, and the internal resistance. Usually, in
telegraphy, this work consists in sending over a line of a certain
resistance intermittent currents, through the intermedium of suitable
manipulators. It suffices then to cause the branches of the electro
tuning fork to play the role of one of these manipulators. For doing
this the tuning fork carries two insulating ebonite or ivory strips, B B
(Fig. 3), which, at every oscillation, abut against vertical brass
springs, r. Each of these latter is located in front of the platinized
point of a screw, v, which is affixed to a small metallic tongue. The
springs and tongues are insulated from each other, and are mounted on a
piece which may be moved by a screw, V, so as to cause the springs of
the strips, B B', to approach or recede according to the amplitude of
the instrument's vibrations. Each spring and tongue is connected with
terminals affixed to the base of the apparatus. One of the poles of one
element, P, of the pile is connected with the tongue and corresponding
screw, while the other pole is connected with the screw in front of it
through the intermedium of a galvanometer, g², which gives the
intensity of the intermittent current, and of a resistance coil,
b², which performs the role of an artificial telegraph line. The
apparatus being set in operation, it will be seen that the current from
the pile is emitted once at every vibration.

Thus there may be exhausted as many pile elements as there are springs,
and that, too, simultaneously; and the contacts of the screws and
springs can be regulated in such a way that the duration of the
emissions shall be the same for all.

At the laboratory of the School of Telegraphy one of these instruments
has operated without interruption, day and night, during eighteen
months.

[Illustration: FIG. 4.--VERY RAPID ELECTRIC TUNING FORK]

The apparatus shown in Fig. 4 is also an interrupting electro-tuning
fork, but it makes a much greater number of vibrations than the
preceding, and may serve for other electric tests.

The operation of the tuning fork is kept up electrically by the aid of
the screw, v, and the corresponding plate; of the style, s, and of
the fine wire spiral spring, f, both insulated from the fork, from the
electro-magnet, N, and from the two wires, F F', which communicate with
a pile.

The interrupting system is symmetrical with the first. It consists of
the style, s, of the spiral spring, f, of the screw, v, and of the
plate that this carries at its extremity. The terminal, B, which carries
the spring, f, and the rod which carries the screw being insulated
from each other, it is only necessary to cause to terminate therein the
extremities of a circuit comprising one pile, in order to produce in the
circuit a number of interruptions equal to that of the tuning fork's
vibrations. Provided the lengths of the springs, f and _f'_, are
proper, such vibrations will not be altered.

Moreover, the instrument is so arranged as to produce vibrations whose
_duration can be varied at pleasure and kept constant_ during the whole
time the experiments last. This is done by modifying the _amplitude_ of
the vibrations; for the greater the amplitude, the longer likewise the
duration of the contact of the style, s, on the corresponding plate,
and the shorter the duration of the interruption. In order to modify the
amplitude, the action of the electro-magnet on the branches of the
apparatus is made to vary. To effect this, the electro-magnet is made
movable perpendicularly by the aid of a screw, V, between two slides, so
that the core, N, may be moved with respect to the median line of the
branches, and even be raised above them. Its action diminishes,
necessarily, while it is being raised, and the amplitude of the
vibrations likewise diminishes gradually and continuously. It may thus
be made, without difficulty, to vary from two to three tenths of a
millimeter to three or four millimeters or more.

But it is not sufficient to cause the amplitude to vary; it is necessary
to measure it and to keep it constant at the value desired.

[Illustration: FIG. 5]

The measurement is effected by the aid of a very simple apparatus that I
have before described under the name of the _vibrating micrometer_. This
is a small square of paper carrving a design like that shown in Fig. 5,
and which is seen in Fig. 4 glued to one of the masses, M, which serve
to vary the number of the instrument's vibrations. This figure is in
fact, an angle, one of whose sides is graduated into millimeters, for
example, and the other forms the edge of a wide black band. The apex of
the angle is above and the divided side is perpendicular to the
direction of the vibrations.

Under such conditions, when the fork is vibrating, the apex of the
angle, by virtue of the persistence of impressions upon the retina,
_seems_ to advance along the graduation in measure as the amplitude of
the vibrations increases. If an angle has been drawn such that the slope
of one of its sides to the other is one-tenth, it is easy to see that
for each millimeter passed over _apparently_ by the apex of the angle,
the amplitude will increase by two-tenths of a millimeter.

This is the way, then, that the amplitude is measured. On another hand,
it suffices to keep the apex of the angle of the micrometer immovable,
in order to be sure of the constancy of the tuning fork's amplitude; and
this is done, when necessary, by causing the screw, V, to move slightly.

The instrument represented in Fig. 4 is, moreover, fixed to a support
devised by Mr. A. Duboscq, so as to make it possible to give the tuning
fork every position possible with respect to a vertical plane; to raise
it or lower it, and to move it backward or forward so that it may be
employed for chimography, and in all those experiments in which
electro-tuning folks are used.

E. MERCADIER.

       *       *       *       *       *



LONGMAN'S MAGAZINE.

OUR ORIGIN AS A SPECIES.

By RICHARD OWEN, C.B., F.R.S.


There seems to be a manifest desire in some quarters to anticipate the
looked for and, by some, hoped-for proofs of our descent, or rather
ascent, from the ape.

In the September issue of the _Fortnightly Review_ a writer cites, in
this relation, the "Neanderthal skull, which possesses large bosses on
the forehead, strikingly suggestive of those which give the gorilla its
peculiarly fierce appearance;" and he proceeds: "No other human skull
presents so utterly bestial a type as the Neanderthal fragment. If one
cuts a female gorilla-skull in the same fashion, the resemblance is
truly astonishing, and we may say that the only human feature in the
skull is its size."[1]

    [Footnote 1: Grant Allen, "On Primitive Man," p. 314.]

In testing the question as between Linnæus and Cuvier of the zoological
value of the differences between lowest man and highest ape, a
naturalist would not limit his comparison of a portion of the human
skull with the corresponding one of a female ape, but would extend it to
the young or immature gorilla, and also to the adult male; he would then
find the generic and specific characters summed up, so far, at least, as
a portion or "fragment" of the skull might show them. What is posed as
the "Neanderthal skull" is the roof of the brain-case, or "calvarium" of
the anatomist, including the pent-house overhanging the eye-holes or
"orbits." There is no other part of the fragment which can be supposed
to be meant by the "large bosses" of the above quotation. And, on this
assumption, I have to state that the super-orbital ridge in the
calvarium in question is but little more prominent than in certain human
skulls of both higher and lower races, and of both the existing and
cave-dwelling periods. It is a variable cranial character, by no means
indicative of race, but rather of sex.

Limiting the comparison to that on which the writer quoted bases his
conclusions--apparently the superficial extent of the roof plate--its
greater extent as compared with that of a gorilla equaling, probably, in
weight the entire frame of the individual from the Neanderthal cave, is
strongly significant of the superiority of size of brain in the
cave-dweller. The inner surface moreover indicates the more complex
character of the soft organ on which it was moulded; the precious "gray
substance" being multiplied by certain convolutions which are absent in
the apes. But there is another surface which the unbiased zoologist
finds it requisite to compare. In the human "calvarium" in question, the
mid-line traced backward from the super-orbital ridge runs along a
smooth track. In the gorilla a ridge is raised from along the major part
of that tract to increase the surface giving attachment to the biting
muscles. Such ridge in this position varies only in height in the female
and the male adult ape, as the specimens in the British Museum
demonstrate. In the Neanderthal individual, as in the rest of mankind,
the corresponding muscles do not extend their origins to the upper
surface of the cranium, but stop short at the sides forming the inner
wall or boundary of what are called the "temples," defined by Johnson as
the "upper part of the sides of the head," whence our "biting muscles"
are called "temporal," as the side-bones of the skull to which they are
attached are also the "temporal bones." In the superficial comparison to
which Mr. Grant Allen has restricted himself in bearing testimony on a
question which perhaps affects our fellow-creatures, in the right sense
of the term, more warmly than any other in human and comparative
anatomy, the obvious difference just pointed out ought not to have been
passed over. It was the more incumbent on one pronouncing on the
paramount problem, because the "sagittal ridge in the gorilla," as in
the orang, relates to and signifies the dental character which
differentiates all _Quadrumana_ from all _Bimana_ that have ever come
under the ken of the biologist. And this ridge much more "strikingly
suggests" the fierceness of the powerful brute-ape than the part
referred to as "large bosses." Frontal prominences, more truly so
termed, are even better developed in peaceful, timid, graminivorous
quadrupeds than in the skulls of man or of ape. But before noticing the
evidence which the teeth bear on the physical relations of man to brute,
I would premise that the comparison must not be limited to a part or
"fragment" of the bony frame, but to its totality, as relating to the
modes and faculties of locomotion.

Beginning with the skull--and, indeed, for present aim, limiting myself
thereto--I have found that a vertical longitudinal section brings to
light in greatest number and of truest value the differential characters
between lowest _Homo_ and highest _Simia_. Those truly and indifferently
interested in the question may not think it unworthy their time--if it
has not already been so bestowed--to give attention to the detailed
discussions and illustrations of the characters in question in the
second and third volumes of the "Transactions of the Zoological
Society."[2] The concluding memoir, relating more especially to points
of approximation in cranial and denial structure of the highest
_Quadrumane_ to the lowest _Bimane_, has been separately published.

    [Footnote 2: "Oseteological Contributions to the Natural History
    of the Orangs (_Pithecus_) and Chimpanzees (_Troglodites niger_
    and _Trog. gorilla_)."]

I selected from the large and instructive series of human skulls of
various races in the Museum of the Royal College of Surgeons that which
was the lowest, and might be called most bestial, in its cranial and
dental characters. It was from an adult of that human family of which
the life-characters are chiefly but truly and suggestively defined in
the narrative of Cook's first voyage in the Endeavor.[3]

    [Footnote 3: Hawkesworth's 4th ed., vol. iii., 1770, pp. 86,
    137, 229. The skull in question is No 5,394 of the "Catalogue of
    the Osteology" in the above Museum, 4to, vol. ii, p. 823, 1853.]

Not to trespass further on the patience of my readers, I may refer to
the "Memoir on the Gorilla," 4to, 1865. Plate xii. gives a view, natural
size, of the vertical and longitudinal section of an Australian skull;
plate xi. gives a similar view of the skull of the gorilla. Reduced
copies of these views may be found at p. 572, figs. 395, 396, vol. ii,
of my "Anatomy of Vertebrates."

As far as my experience has reached, there is no skull displaying the
characters of a quadrumanous species, as that series descends from the
gorilla and chimpanzee to the baboon, which exhibits differences, osteal
or dental, on which specific and generic distinctions are founded, so
great, so marked, as are to be seen, and have been above illustrated, in
the comparison of the highest ape with the lowest man.

The modification of man's upper limbs for the endless variety, nicety,
and perfection of their application, in fulfillment of the behests of
his correspondingly developed brain--actions summed up in the term
"manipulation"--testify as strongly to the same conclusion. The
corresponding degree of modification of the human lower limbs, to which
he owes his upright attitude, relieving the manual instruments from all
share in station and terrestrial locomotion--combine and concur in
raising the group so characterized above and beyond the apes, to, at
least, ordinal distinction. The dental characters of mankind bear like
testimony. The lowest (Melanian), like the highest (Caucasian), variety
of the bimanal order differs from the quadrumanal one in the order of
appearance, and succession to the first set of teeth, of the second or
"permanent" set. The foremost incisor and foremost molar are the
earliest to appear in that scries; the intermediate teeth are acquired
sooner than those behind the foremost molar.[4]

    [Footnote 4: "Odontography," 4to, 1840-44, p. 454, plates 117,
    118, 119.]

In the gorilla and chimpanzee, the rate or course of progress is
reversed; the second true molar, or the one behind the first, makes its
appearance before the bicuspid molars rise in front of the first; and
the third or last of the molars behind the first comes into place before
the canine tooth has risen. This tooth, indeed, which occupies part of
the interval between the foremost incisor and foremost molar, is the
last of the permanent set of teeth to be fully developed in the
_Quadrumana_; especially in those which, in their order, rank next to
the _Bimana_. To this differential character add the breaks in the
dental series necessitated for the reception of the crowns of the huge
canines when the gorilla or chimpanzee shuts its mouth.

But the superior value of developmental over adult anatomical characters
in such questions as the present is too well known in the actual phase
of biology to need comment.

In the article on "Primeval Man," the author states that the Cave-men
"probably had lower foreheads, with high bosses like the Neanderthal
skull, and big canine teeth like the Naulette jaw."[5]

    [Footnote 5: _Fortnightly Review_, September, p. 321.]

The human lower jaw so defined, from a Belgian cave, which I have
carefully examined, gives no evidence of a canine tooth of a size
indicative of one in the upper jaw necessitating such vacancy in the
lower series of teeth which the apes present. There is no such vacancy
nor any evidence of a "big canine tooth" in that cave specimen. And,
with respect to cave specimens in general, the zoological characters of
the race of men they represent must be founded on the rule, not on an
exception, to their cranial features. Those which I obtained from the
cavern at Bruniquel, and which are now exhibited in the Museum of
Natural History, were disinterred under circumstances more
satisfactorily determining their contemporaneity with the extinct
quadrupeds those cave-men killed and devoured than in any other spelæan
retreat which I have explored. They show neither "lower foreheads" nor
"higher bosses" than do the skulls of existing races of mankind.

Present evidence concurs in concluding that the modes of life and grades
of thought of the men who have left evidences of their existence at the
earliest periods hitherto discovered and determined, were such as are
now observable in "savages," or the human races which are commonly so
called.

The industry and pains now devoted to the determination of the physical
characters of such races, to their ways of living, their tools and
weapons, and to the relations of their dermal, osteal, and dental
modifications to those of the mammals which follow next after _Bimana_
in the descensive series of mammalian orders, are exemplary.

The present phase of the quest may be far from the bourn to yield
hereafter trustworthy evidence of the origin of man; but, meanwhile,
exaggerations and misstatements of acquired grounds ought especially to
be avoided.

       *       *       *       *       *



THE ABA OR ODIKA.

By W.H. BACHELER, M.D.


Among the many luxuriant and magnificent forest trees of equatorial West
Africa, none can surpass, for general beauty and symmetry, that which is
called by the natives the "aba." When growing alone and undisturbed, its
conical outline and dark green foliage remind one very much of the white
maples of the northern United States, by a distant view, but, on a
nearer approach, a dissimilarity is observed. Wherever, in ravines or
near the banks of rivers, the soil is moist the most part of the year,
there the aba chooses to grow, and during the months of June and July
the falling fruits permeate the atmosphere with a delicious fragrance
not similar to any other. This, in form, size, and general appearance,
is very much like mango apples, so that the natives call mangoes the
"white man's aba;" but the wild aba is not much eaten as a fruit, one or
two being sufficient for the whole season. The kernel, or seed, is the
important and useful part.

When the fallen fruit covers the ground, much as apples do in America,
the natives go in canoes to gather it, and the number harvested will be
in proportion to the industry of the women. The aba plum is about the
size of a goose's egg, of a flattened, ovoid shape, and, when ripe, a
beautiful golden color. It consists of three distinct parts: the rind,
the pulp, and the seed. The pulp consists of a mass extensively
interwoven with strong filaments, which apparently grow out of the seed
and are with great difficulty separated from it. The seed, reniform in
shape, is bivalved, and constitutes about two-thirds of the bulk of the
entire plum, and the inner kernel two-thirds the bulk of the seed.

In consequence of it being such a high tree and growing in such
inconvenient places, I have been unable to procure a specimen of the
flowers.

As soon as the fruit is brought to the village, all the inhabitants
assemble with cutlasses and engage in the work of opening the plums and
removing the kernels. The former are thrown away as useless. The seeds
are evenly spread on the top of a rack of small sticks, under which a
fire is built in the morning, and subjected to the smoke and heat of an
entire day. Toward evening the heat is greatly augmented, and in a
couple of hours the process is completed. The kernels are now soft, and
the oil oozing from them, and while yet in this condition they are
thrown into an immense trough and throughly beaten and mashed with a
pestle.

Baskets, with banana leaves spread in the inside to prevent the escape
of the product, are in readiness, and it is put into them and pressed
down. The next day these baskets are suspended in the sun, and at night
are brought into the houses to congeal. The process is now finished. The
cakes are removed by inversion of the baskets and "bushrope" tied around
them, by which the pieces are carried. As thus prepared, odika is highly
esteemed by the natives as an article of food, being made into a kind of
thick gravy and eaten with boiled plantains.

While at an interior mission station on the Ogowe River, I made some
experiments in soap making. With palm oil I succeeded very well, using
for an alkali the old-fashioned lye of ashes. But I was disappointed
with the odika, though I learned some peculiar characteristics of it as
a grease. By boiling the crude odika, I was unable, as I hoped, to
separate the oleaginous from the extraneous matter, of which it contains
a large proportion, but when the above-mentioned lye was used instead of
water, the mass, instead of saponifying, merely separated; the grease,
resembling very much in all particulars ordinary beef tallow, rising to
the top of the caldron, while the refuse was precipitated.

After clarifying this, it answers instead of oil of theobroma very
nicely, and I have used it considerably in making ointments and
suppositories with pleasing results.

Gaboon, W. Africa, Aug., 1882.--_New Remedies._

       *       *       *       *       *



CALIFORNIA CEDARS.


The incense cedar (_Libocedius decurrens_) is one of the valued trees of
the California coast and mountains. It is eminently noted for great
rapidity of growth, wonderful lightness, stiffness, and extraordinary
durability. A thousand uses have sprung up and are multiplying around
this interesting cedar as its most inestimable qualities become better
known. Fortunately it is one of the most extensively distributed trees
of the Pacific--found from the coast range north, south to San Diego,
Sierra Nevada, southern Oregon, and most of the interior mountain region
from 2,000 to 4,000 feet, and it even thrives quite well at 6,600 feet
altitude, but seeming to give out at 7,000 feet, though said to extend
to 8,500 feet, which is questionable. As usual with the sylva, flora,
and fauna, this also is found lowest along the coast, where it finds the
requisite temperature and other essentials, with combined moisture. The
base and lower trunk somewhat resembles the Western juniper (_J.
occidentalis_). It is to be noted in general that trees of such broad,
outwardly sweeping, or expanded bases seldom blow over, and to the
perceptive and artistic eye their significant character is one of
firmness and stability. One hundred to two hundred feet high, six to
nine feet in diameter (rarely larger) the shaft is often clear of limbs
80 to 100 feet, and although the lower limbs, or even dry branches, may
encumber the middle portion, pin-knots do not damage the timber. The
massive body tapers more rapidly above than redwood, and is less
eccentric than juniper, yet its general port resembles most the best
specimens of the latter. The light cinnamon bark is thick and of
shreddy-fibered texture, but so concretely compacted as to render the
surface evenly ridged by very long, big bars of bark. These sweep
obliquely down on the long spiral twist of swift water lines. The top is
conic, the foliage is in compressed, flattened sprays, upright,
thickened, and somewhat succulent; if not a languid type, at least in no
sense rigid. It bears some resemblance to the great Western arborvitæ
(_Thuja gigantea_), but the tiny leaf-scales are opposite and quite
awl-pointed. The general hue of the foliage is light yellowish green,
warmly tinted, golden and bead tipped, with tiny, oblong male catkins,
as the fruit ripens in October and November. The cones are pendulous
from the tips of twigs, oblong, and seldom over three-quarters of an
inch long, little more than one-third as thick, and for the most part a
trifle compressed. The wood is a pale cream-tint in color--a delicate
salmon shade. This would hardly warrant the name white cedar, sometimes
applied to it, as well as the giant arborvitæ. The extreme lightness of
the lumber and its sweetness for packing boxes will commend it for
express and commercial purposes, for posts and fencing, and especially
railway ties, for sleepers, stringers, and ground timbers of all
varieties, and for unnumbered uses, a tithe of which cannot be told in a
brief notice. Formerly these trees were cut away and burned up, to clear
the track for redwood, tamarack, and ponderous pith-pines, etc.; now all
else is superseded by this incense cedar. Thus is seen how hasty and
ill-advised notions give place to genuine merit.

A fungus (_dædalus_) attacks and honeycombs it; and riddled as it may
occasionally be, still, if spike or nail finds substance enough to hold,
or sufficient solidity to resist crushing, then, for many purposes, even
such lumber is practically as good as the soundest timber; because when
the tree dies the fungus dies, and thenceforth will absorb no more
moisture than the soundest part, and is alike imperishable, contrary to
common experience in similar cases. This is a timber nearly as lasting
as solid granite. For ship or boat lumber, the clear stuff from sound
wood is so exceedingly light, stiff, and durable, and so plenty and
available, that few timbers excel it, unless the yellow cedar or cyprus
(_Cupressus nutkaensis_) is excepted, which is a little tougher,
stronger, perhaps more elastic, and equally durable, if judged apart
from thorough tests and careful data, which, it has been remarked, the
apathy or ignorance of some governments appear to deem unworthy their
sublime attention. There are said to be in California a thousand times
more and better kinds of naval timbers on government lands as important
to preserve as the live oaks of the South Atlantic States. It has been
asserted as probable that, after due investigation, California would be
found to possess a vast amount of the best naval timber in the world, a
hundredfold more lasting than the best now in use, if a few woods are
excepted, of which there is understood to be no very adequate supply.

The great Washington cedar (_Sequoia gigantea_) is another important
California tree. The great sequoian timber belt lies along the Sierras,
upon the first exposed mountain side--moraines of recent retiring
glaciers--that face the Pacific, from Calaveras on the north to near the
head of Deer Creek on the south--a distance of 200 miles, or a little
above 38 degrees north to a little below 36 degrees; altitude 5,000 to
8,000 feet, and rarely 8,400 feet. The belt is broken by two gaps, each
40 miles wide, caused by manifest topographical and glacial reasons, one
gap between Calaveras and Tuolumne, the other between Fresno and King's
River; thence the vast forest trends south, across the broad basins of
Kaweah and Tule, a distance of 70 miles, on fresh moraine soil, ground
from high mountain flanks by glaciers. The inscriptions are scarcely
marred by post glacial agents, and the contiguous water-worn marks are
often so slight in the rock-bound streams as to be measured by a few
inches. Rarely does one of these sound and vigorous cedars fall, and
those that do will lie 800 to 1,000 years, scarcely less perishable than
the granite on which they grew. The great sequoian ditches, dug at a
blow by their fall, and the tree tumuli, always turned up beside the
deep root-bowls, remain; but, scientists assert, not a vestige of one
outside the present forests has yet presented itself, hence the area has
not been diminished during the last 8,000 or 10,000 years, and probably
not at all in post glacial times. These colossal sequoias rise 275, 300,
and even 400 feet aloft; are 20 to 30, and in some rare cases 40 feet in
diameter, looking like vast columnar pillars of the skies. No known
trees of the world compare with them and their kin, the redwoods, for
the focused proximity of such a marvelous amount of timber within
limited areas--as it were, the highest standard of timber-land capacity.
The stage coach passes through one; 120 children and a piano crowd
inside another; a trunk furnishes a house for cotillon parties to dance
"stout on stumps;" a horse and rider travel within the burnt-out hollows
of others, and so on. A single tree would furnish a two-rail fence, 20
to 30 miles long. The tree has great value for wood and lumber.--_N.W.
Lumberman._

       *       *       *       *       *


A catalogue containing brief notices of many important
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MUNN & CO., PUBLISHERS,
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PATENTS.

In connection with the SCIENTIFIC AMERICAN, Messrs. MUNN & CO are
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MUNN & CO., 261 BROADWAY, NEW YORK.

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