Page:Popular Science Monthly Volume 6.djvu/778

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not more than one in a hundred of such so-called coal-beds having any value whatever. Unlike the true coal of the carboniferous rocks formed from tree-ferns, algæ, and other plants of low organization, that of the Pacific coast contains the remains of coniferous and dicotyledonous trees, and belongs to the cretaceous rocks, or is of even later origin. It is the lignite of geologists. Many of the beds of this material are too thin to work, a thickness of two feet being the minimum that can be economically taken out. For all practical purposes this lignite in many localities is as good as the older coal, but the thinness of most of the beds makes them useless as sources of supply.


How the Amœba takes its Food.—Prof. Leidy has observed an amœba in the act of taking in its food, and, at a recent meeting of the Philadelphia Academy of Sciences, showed that these curious animals, at least in some instances, employ their pseudopods as instruments for capturing the minute creatures on which they prey. It has commonly been supposed that the amœba's food simply sticks to its body and "falls through" into the stomach-sac. Prof. Leidy saw the two pseudopods of an Amœba princeps gradually approach, come in contact, and then actually become fused—thus securing between them a flagellate infusorium. The infusorium continued to move back and forth, endeavoring to escape. "At the next moment a delicate film of the entosarc proceeded from the body of the amœba, and gradually extended outwardly, so as to convert the circle of the pseudopods into a complete sac, inclosing the infusorium."


A Fresh-water Sponge.—At a recent meeting of the New Jersey Microscopical Society, at New Brunswick, its Secretary, Prof. Lockwood, exhibited specimens of a fresh-water sponge, discovered by himself in a pond at Port Republic, New Jersey. The sponge grew in masses, covering several square yards of surface, with a thickness varying from an inch to two inches. It has a dichotomous habit of growth, and the sarcode, or sponge-flesh, was of an intensely dark-green color. It seemed quite closely related to the Spongilla fluviatilis. Some slides were shown with the spicules cleaned by treatment with boiling nitric acid. With a new lens of low power (seventy-five diameter), just made by George Wale, and of most excellent definition, the silica-spicules were finely brought out. They are cylindrical, curved, and pointed at both ends. They are limited to one form, and are arranged in little fascicles of about twelve spicules in each bundle.


A. Crum Brown on Chemical Theory.—In his address, as President of the Chemical Section of the British Association, Dr. A. Crum Brown defined chemical constitution as the order in which the constituents are united in the compound, and pointed out that the study of chemical changes (composition and decomposition) cannot lead us to a knowledge of the relative position of the atoms. But such a knowledge is required before a real theory of chemistry can be attained, and a knowledge of the intimate structure of matter may be looked for from an examination of the physical properties of substances, and a comparison of these with their chemical constitution. This, he maintained, is truly a branch of chemistry, and the greatest progress in it had been made by chemists, as might be proved by reference to the works of Faraday, Graham, and Andrews. By pursuing this branch, discoveries might be made which would lead to an hypothesis directly connecting chemistry with dynamics, and enabling us to apply mathematics directly to chemistry. The theory of chemistry would then be a particular case of the theory of dynamics. Such a result must be expected by all who believe in the progress of human knowledge and in the consistency of Nature.


Changes attending the Process of Germination.—In the course of their researches on germination, Messrs. Dehérain and Landrin have discovered that, when moist seeds are kept for two or three days in a closed tube above a column of mercury, the volume of air decreases even before carbonic acid has made its appearance. Moist seeds have, therefore, the property of condensing gases after the manner of porous bodies. But no gas can lose the aëriform state without at the same time giving up