Popular Science Monthly/Volume 26/November 1884/Popular Miscellany
POPULAR MISCELLANY.
British Association Addresses.—Professor Roscoe's address before the Chemical Section was on "The Progress of Chemistry since 1848." The author made the year 1848 a dividing line between the epoch of Berzelius, which closed then, and that of Dumas and Wurz, which closed in 1884. The differences between the two epochs are shown in the distinct views which were entertained as to the nature of a chemical compound. According to the older notions, the properties of compounds were determined largely by the qualitative nature of their constituent atoms, and these were arranged so as to form a binary system. According to the newer view, it is mainly the number and arrangement of the atoms in a molecule that regulate the characteristics of a compound, which is to be regarded, not as built up of two constituent groups of atoms, but as forming a single group. The theory of substitutions, the relation of atomic weights and volume-combination, the prominent part assigned to organic radicals, the doctrine of valency or atomicity, and Mendelejeff and Lothar Meyer's periodic law, under which we may predict the nature and place of as yet undiscovered elements, and the study of isomeric phenomena, are also distinctive marks of the later chemistry. The artificial synthesis of a few coloring-matters and of kairine, a febrifuge as powerful as quinine, are among its most noteworthy achievements. Of the work that has been done in the determination of chemical constants, the labors of Mallet on aluminum, of J. P. Cooke on antimony, and of Thorpe on titanium, are especially mentioned. The speaker gave accounts of the progress that has been made in spectrum analysis, and the close distinctions of the molecular properties and constitution of bodies which it has made possible. Other indications of progress are given in Sir William Thomson's speculations on the probable size of the atoms; Helmholtz's discussion of the relation of electricity and chemical energy; and the theory of the vortex-ring constitution of matter, as suggested by Sir William Thomson and worked out by Mr. J. J. Thomson. Much experimental attention is now given to thermo-chemistry. The discovery of the liquefaction of the gases by Pictet and Cailletet, including Andrews's discovery of the critical point, indicates a connection, long unseen, between the liquid and the gaseous states. Deville's investigations of the laws of dissociation have opened out entirely fresh fields for research, and given new, important, and interesting views concerning the stability of chemical compounds. Professor Roscoe considered the best method of educating chemists to consist in giving them as sound and extensive a foundation in the theory and practice of the science as their abilities will allow, rather than in forcing them prematurely into original preparations and investigations.
Mr. W. T. Blanford, President of the Geological Section, presented some remarks upon contradictions which had been observed in certain districts, in the determination of the age of geological formations as indicated by their fossils. The most of them occur where a land or fresh-water fauna or flora assigned to a particular formation rests upon a marine bed of apparently later origin: as in Greece, where the supposed Miocene fauna of the Pikermi beds overlie strata with Pliocene mollusca; and in certain described places in India, Australia, and South Africa. Only one case of contradiction between two marine formations is known, and that is in dispute. In making choice between the two witnesses, geologists take the marine formations; for marine faunas and floras are more widely diffused than those of the land, and more nearly uniform throughout the world. Thus, of fishes, eighty families are typically marine, and twenty-nine are confined to fresh water; of the first, fifty are universally or almost universally distributed; while of the second, only one is found in five of Wallace's regions, and not one is met with in all the six regions. Among plants, so uniform is the marine vegetation of the world, that no separate regions can be established in the ocean, while Drude makes fourteen on the land. It appears to the author that at the present day the difference between the land faunas of different parts of the world is so vastly greater than that between the marine faunas that, if both were found fossilized, while there would be but little difficulty in recognizing different marine deposits as of like age from their organic remains, terrestrial and fresh-water beds would in all probability be referred to widely differing epochs, and that some would be more probably classed with a past period than with others of the present time. The idea that marine and terrestrial faunas and floras were similar throughout the world's surface in past times is so ingrained in paleontological science that it will require many years yet for the fallacy of the assumption to be generally admitted. No circumstance has contributed more widely to the belief than the supposed universal diffusion of the carboniferous flora. The evidence that the plants which prevailed in the coal-measures of Europe were replaced by totally different forms in Australia, despite the closest similarity between the marine inhabitants of the two areas, should go far to dispose of this belief. Hence, determinations of the age of terrestrial beds based upon their fossil faunas and floras should not be accepted as fixed unless they are accompanied by evidence from marine beds.
Discussing the "Physiology of Deep-Sea Life" in the Biological Section, Professor Moseley, of the Challenger Expedition, having recognized the value of the work that had been done in deep-sea investigation in the United States, spoke of the importance to the physiologist of a knowledge of the conditions under which gases occur in a state of absorption in the ocean-waters. Professor Dittmar's researches show that the presence of free carbonic acid in ocean-waters is an exception. Hence, the solution which some shells undergo at certain depths is probably due, not to the presence of free acid, but to the solvent action of the seawater itself. Oxygen is present in all seawater, being derived from the surface, but the amount diminishes, on account of the oxidizing that is always going on, with increase of depth. M. Regnaud's experiments on the effects on organisms of high pressures, corresponding with those of certain sea depths, show that a fish without a swimming-bladder, or one with the bladder emptied of air, may be subjected to a pressure of 100 atmospheres, or 650 fathoms, without injurious effect; at 200 atmospheres, or 1,300 fathoms, it becomes torpid, but soon revives when the pressure is removed; while at 300 atmospheres, or about 2,000 fathoms, the fish dies. The results of these experiments would probably have been greatly modified, if plenty of time could have been given for the fish to accommodate itself to the change of pressures and the conditions in which it moves slowly from one depth to another be imitated. M. Paul Bert's experiments upon the effect on aquatic organisms of water subjected to the pressure of compressed air—a very different condition—show fatal results at fifteen and even at seven atmospheres. A large proportion of the food-supply of the deep-sea animals appears to be derived from life on the ocean-surface, or that which is brought to the surface by rivers from the land sinking down to it. Deep-sea life appears to diminish in abundance as the coasts are receded from. More may be known on this subject when we have learned more about pelagic vegetable life, with which our acquaintance is now imperfect. If it shall be ascertained that the deep sea derived its main supply from the coasts and land-surfaces in the early periods, there can have existed scarcely any deep-sea fauna until the littoral and terrestrial faunas and floras had become well established. It still appears impossible to determine any successive zones of depth in the deep-sea regions, characterized by the presence of special groups of animals. Some groups seem to be characteristic of water of considerable depth, but representatives of them struggle up into much shallower regions. This fact places a difficulty in the way of determining the depths at which the geological deposits were formed. Something may be learned of the depths of modern deposits by the examination of their microscopical composition and the condition of the shells and spicules. Great uncertainty prevails as to whether, or to what extent, the intermediate waters, which are held to include about eight ninths cf the bulk of the entire ocean, are inhabited by animals. A feature of the deep-sea fauna is the general absence from it—except as to mollusks and brachiopods—of palæozoic forms. This fauna has, doubtless, been derived almost entirely from the littoral fauna, which also must have preceded, and possibly given rise to, the entire terrestrial fauna. And because the ancestors of nearly all animals have passed through a littoral phase of existence, preceded mostly by a pelagic phase, the investigations now carried on, on the coasts, in marine laboratories, throw floods of light on all the fundamental problems of geology.
General Lefroy, in his address before the Geographical Section on "Recent Geographical Discovery" referred to the more exact identification of the pole of vertical magnetic attraction or magnetic pole, which was visited by Ross and by officers of the Franklin Expedition, and nearly reached by McClintock and Schwatka; and of the focus of greatest magnetic attraction, which is near Cat Lake, and has never been visited; and the exploration of the newly discovered great lake Misstassini, as worthy objects of Canadian research. Among the later achievements of geographical exploration are the journey of Mr. Thomson through the region between Mount Kilimanjaro, Lake Nyanza, and Mount Kenia, touching Lake M'Baringo on which no European had ever before stood, among tribes who had never seen a white man; Stanley's and De Brazza's continued explorations of the Congo region; and the work of Dr. Pogge, Lieutenant Wissman, and the Portuguese explorers in the southern Congo, Upper Quango, and Loando regions. According to Dr. Pogge, much of the interior of Africa belongs, by reason of its elevation above the sea, to a far more temperate zone, and is better suited to European constitutions than its geographical position promises. In illustration of the rapid extension of white occupation in Central Africa, a table is given of about one hundred and twenty actual centers of communication or trade, or of missionary instruction, now established there. Lake Nyassa is becoming a busy inland sea. There are two steamers upon it, and one on the river Shiré; upon Tanganyika three. Donkeys have been already introduced, with good promise, by the universities' missionaries and the African Lakes Company, although they have not been a success on the Congo. The African Lakes Company, of Glasgow, has ten small depots between Quillimane and Malawanda on Lake Nyassa, and from this place a practicable road of two hundred and twenty miles has been carried to Pambete, on Lake Tanganyika.—In Asia, Mr. W. W. Graham has reached in the Himalayas an elevation of 23,500 feet, or about 2,900 feet above the summit of Chimborazo; some progress has been made, by the aid of disguised Indians, in the surveys of territories from which Europeans are excluded; the primary triangulation of India, begun in 1800, is practically completed; and the upper Oxus has been traced from its sources in the Punjaub. Australia has been crossed again from east to west, and also through four hundred miles of new country north of Cowarie Station on the Warburton River, and the usefulness of camels in that service has been demonstrated.—The international circumpolar expeditions have added, perhaps, to local knowledge, but not much, so far as reported, to geography generally. The discoveries made by Greely's party are mentioned appreciatively. The results of the marine researches of the Talisman and the Dacia in the Atlantic Ocean are of great value. Reference was made to the extension of railroads in Mexico, South America, the Senegal, the Caucasus, and Central Asia, as marking steps in the advance of man's mission to subdue the earth and replenish it; and the importance was insisted upon of obtaining accurate map delineations in aid of the exact determination of boundary-lines and the avoidance of disputes about them.
"The Relation of Mechanical Science to the other Sciences" was the topic of Sir F. J. Bramwell's address before the Mechanical Section, lie called attention to the fact that it was the engineer who had made a meeting of the Association in Canada possible. Every one must agree that the engineers are those who make the greatest practical use, not only of the science of mechanics, but of the researches and discoveries of the members of the other sections of the Association. Knowledge of the laws of heat is requisite in the construction of thermal motors; in the applications to metallurgy, as exemplified in the hot blast, in the regenerative furnace, in the dust-furnace of Crampton, in the employment of liquid fuel, and also in operations connected with the rarer metals, the oxygen-furnace, and the atmospheric gas-furnace, and, in its incipient stage, the electrical furnace. The success of air-refrigerating machines and the economic distillation of sea-water arc dependent on the same knowledge. Engineering and electrical science are brought into close relations in the construction of telegraph and cable lines, in the development and application of dynamo-machines and dynamo-energy, and in electric lighting, telephony, and microphony. In navigation, the engineer avails himself of optical science in the equipment of lighthouses; of pneumatics in Sir William Thomson's apparatus for taking quick soundings, and of magnetic science in his adjustment of improved compasses. Mathematical principles enter into the construction of ship-models. In the processes of the preparation from the ore of various metals, "it is essential that the engineer and the chemist should either be combined in one and the same person, or go hand in hand." The chemist and the microscopist have to be called in to ascertain the purity of every contemplated source of water-supply; and the chemist, when it is desired to convert a hard water into soft. Engineers must consult the geologist before they can intelligently make estimates of the works they are about to undertake. In biology, the engineer learns from the botanist the qualities of the various woods he occasionally uses in his work, and has the "germs" in view in arranging for the purity of water-supply and for ventilation. Lastly, great works of engineering facilitate geographical exploration, and are called into existence by the dictates of the economist. The speaker closed his address with a tribute to the memory of Sir William Siemens.
Cultivation of Cacao,—The cacao-tree flourishes in the hot regions of America, and has been cultivated since the conquest in Mexico, Guatemala, and Nicaragua. To secure success, the cacao-plantation must be made in new land, for the tree requires a rich, deep,' and moist soil, and heat. The best situation is cleared forest-land, so inclined as to permit its being irrigated. The cultivation of the trees often ceases to be profitable when the temperature falls below 73°. The cacao seldom blossoms till it is thirty months old. The planters destroy the first flowers, in order to prevent fruiting before the fourth year. There are few plants in which the flower is so small and so disproportioned to the size of the fruit. A bud measured by M. Boussingault, at the time of its expansion was not more than four millimetres broad. The flesh-colored corolla was composed of ten petals surrounding five silver-white stamens. The flowers did not appear singly, but in bouquets on every part of the trunk, on the principal branches, and even on the salient wood-roots. The fruit comes to maturity in about four months after the fall of the flowers. It is about ten inches long and three or four inches in diameter, slighty curved, weighs three hundred or five hundred grammes, and is divided into three lobes. Its color varies from a greenish-white to a red-violet. The pericarp is furrowed longitudinally within; the flesh or pulp is rosy-white and acid, and generally envelops twenty fine, white, oily kernels which in drying assume a superficial brown tint. Two principal crops are harvested every year, but on large plantations the gathering is going on all the time, and it is not uncommon to see trees bearing both flowers and fruits at the same time. After breaking the shell, the nuts are taken out and exposed to the sun. In the evening they are piled up under a shed. An active fermentation soon sets in, which must not be allowed to go too far, and, accordingly, the nuts are on the next day spread out in the air. The cultivation of a cacao-plantation does not demand much labor. One man can take care of a thousand trees. The most serious difficulties are the dangers from storms, which are very destructive to the fruit; otherwise the principal duty of the attendant is to protect the crop from animals. The cacao is shelled by roasting at a moderate heat, in which process it acquires, like the coffee-bean, an odor arising from a minute proportion of a volatile principle which it contains. This is the peculiar aroma which we perceive in chocolate. The cacao-beans are rich in nutritious principles, containing a fat, nitrogenous substance analogous to albumen and caseine, theobromine and ternary compounds, all of which vary somewhat in their relative quantities. The theobromine is almost identical with the caffeine of coffee and the theine of tea, and is essentially the same principle that gives value to those substances and to the maté of Paraguay and the coca of Peru. Thus, in the several drinks prepared from these substances, the Chinese, the Arabs, and the Indians of Mexico and South America enjoy the influence of the same cheering but not inebriating agent. Cacao and chocolate differ from the other beverages named in that they contain a notable proportion of nutritious elements which exist in the others only in minute quantities.
The Question of Short-Sightedness in French Schools.—A commission appointed by the French Government to investigate the question of short-sightedness in schools recently made a report through Dr. Gariel. It declares that the affection is caused by the efforts of the pupil to accommodate his vision to the requirements of the position in which he finds himself, and by his bending over. These effects are provoked by defective lighting, badly fitting seats and desks, bad methods of writing, premature instruction, and too fine print. The commission recommend, for books, yellowish-tinted paper; that each line with its white should occupy a minimum vertical space of 3·384 millimetres; and that there should not be more than seven letters to each current centimetre of text. Furthermore, every book should be rejected which is not readable to good eyes eighty centimetres or thirty-one inches off in the fight of a standard candle one metre away, and every map that is not distinct under the same conditions at a distance of forty centimetres, or sixteen inches. In regard to habit in writing the committee exacts George Sand's condition of "straight writing, on straight paper, with a straight body." Instruction should not begin too early, at least not in writing on paper; and the child should not be put at it till it has learned to trace the letters on a board, upright, and without linking them together. In the matter of seats and desks, the committee appear to exact that the horizontal distance between the edge of the desk and the front of the seat one or two places back shall be rigorously negative; then the child will not be able to bring his chin down to his desk. The back should be inclined to fit the pupil's back and give a position of rest, and the desks should slant so that the paper lying on them should be perpendicular to the visual rays. The larger classes should have movable chairs. If there is not enough light, the pupils should be allowed to hold their books so that they can get the most of it. An Italian journal has published a model of a seat well adapted to fit the back of various sizes to suit deficient eyes, and so adjusted that the child can take a nap, if sleepy, without suffering. The hardest question the committee had to meet was that regarding the admission of light. It was agreed that a sufficient illumination of the darkest part of the room should be the standard, and that a bit of sky not less than thirty centimetres, or twelve inches, in vertical diameter ought to be visible from the least favored spot; but the expediency of bilateral illumination does not yet seem to be determined to the satisfaction of all: some thought cross-lights might give trouble; others suggested that this could be avoided by making the light from one side much stronger than from the other, or by making the light come from above or from behind.
Natural Gas as a Source of Fuel.—An important change in the conditions of manufacturing in Pittsburg is promised by the introduction of natural gas as fuel in place of coal. The gas, which is principally carbureted hydrogen, or the fire-damp of the mines, is obtained abundantly in the neighborhood of the city, and even within its corporate limits, by boring wells. Much of it has been met in the past in boring for petroleum, and when found under such circumstances it was regarded as a nuisance. Some of the wells thus discovered have already been applied to economical uses, and found as valuable as if they had been petroleum-wells. Such wells are employed for burning brick at New Cumberland, and in the manufacture of pottery at East Liverpool, of cutlery at Beaver Falls, and of glass-ware at Rochester. The gas of six wells is brought through pipes twenty miles to the city and used to heat the boilers of an iron-manufactory; and it has been found that, where the distance of the supply is so short that the gas can be brought in without its pressure being wholly lost in piping, it can be made a valuable addition to the resources for fuel. A very fine vein of gas has been found by sinking a well within the limits of the city, and several manufacturers have begun boring for it on their premises. Twenty-six wells are now furnishing gas to manufacturers in the Pittsburg district, and new ones are added from time to time. They are estimated to be furnishing a supply of fuel equivalent to from 5,000 to 7,000 tons of coal daily, or from 1,800,000 to 2,500,000 tons a year. The gas makes a nice and even fire in grates and stoves, but objection is made to its use in private houses on account of its freedom from odor, by which the detection of leaks is prevented, and the danger is incurred of the air of the house being fatally poisoned before any, one becomes aware that anything is wrong. Its light is too weak to make it suitable for illuminating purposes. Its advantages over coal lie in the possibility of supplying it at much less expense, and in its entire freedom from soot and smoke—a matter of extreme importance in such a city as Pittsburg.