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diff --git a/18763-8.txt b/18763-8.txt new file mode 100644 index 0000000..dc28b55 --- /dev/null +++ b/18763-8.txt @@ -0,0 +1,3834 @@ +The Project Gutenberg EBook of Scientific American Supplement, No. 365, +December 30, 1882, by Various + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Scientific American Supplement, No. 365, December 30, 1882 + +Author: Various + +Release Date: July 6, 2006 [EBook #18763] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK SCIENTIFIC AMERICAN *** + + + + +Produced by David King, Juliet Sutherland and the Online +Distributed Proofreading Team at http://www.pgdp.net + + + + + +[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 +scientific papers heretofore published in the SUPPLEMENT, +may be had gratis at this office. + + * * * * * + + +The +SCIENTIFIC AMERICAN SUPPLEMENT. + +PUBLISHED WEEKLY. + +TERMS OF SUBSCRIPTION, $5 A YEAR. + +Sent by mail, postage prepaid, to subscribers in any part of the United +States or Canada. Six dollars a year, sent, prepaid, to any foreign +country. + + * * * * * + +All the back numbers of THE SUPPLEMENT, from the commencement, January +1, 1876, can be had. Price, 10 cents each. + + * * * * * + +All the back volumes of THE SUPPLEMENT can likewise be supplied. Two +volumes are issued yearly. 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