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THE POPULAR SCIENCE MONTHLY. 



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, algaa, and oth- 

 er plants of low organization, that of the 

 Pacific coast contains the remains of conif- 

 erous and dicotyledonous trees, and be- 

 longs 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 Amoeba takes Us Food. Prof. 

 Leidy has observed an amoeba in the act 

 of taking in its food, and, at a recent meet- 

 ing of the Philadelphia Academy of Sciences, 

 showed that these curious animals, at least 

 in some instances, employ their pseudo- 

 pods as instruments for capturing the mi- 

 nute creatures on which they prey. It has 

 commonly been supposed that the amoeba's 

 food simply sticks to its body and " falls 

 through " into the stomach-sac. Prof. Leidy 

 saw the two pseudopods of an Amoeba prin- 

 ceps gradually approach, come in contact, 

 and then actually become fused thus se- 

 curing 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 pro- 

 ceeded from the body of the amoeba, and 

 gradually extended outwardly, so as to con- 

 vert 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. Lockvvood, exhibited specimens of a 

 fresh-water sponge, discovered by himself 

 in a pond at Port Republic, New Jersey. 

 The sponge grew in masses, covering sev- 

 eral square yards of surface, with a thick- 

 ness varying from an inch to two inches. 

 It has a dichotomous habit of growth, and 

 the sarcode, or sponge-flesh, was of an in- 

 tensely dark-green color. It seemed quite 

 closely related to the Spongilla Jluviatilis. 

 Some slides were shown with the spicules 



cleaned by treatment with boiling nitric 

 acid. With a new lens of low power (sev- 

 enty-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. Cmm Brown on Chemical Theory. 



In his address, as President of the Chemi- 

 cal Section of the British Association, Dr. 

 A. Crum Brown defined chemical constitu- 

 tion 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 po- 

 sition of the atoms. But such a knowl- 

 edge is required before a real theory of 

 chemistry can be attained, and a knowl- 

 edge 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 dynam- 

 ics, and enabling us to apply mathematics 

 directly to chemistry. The theory of chem- 

 istry would then be a particular case of the 

 theory of dynamics. Such a result must 

 be expected by all who believe in the prog- 

 ress of human knowledge and in the con- 

 sistency of Nature. 



Changes attending the Process of Germi- 

 nation. In the course of their researches 

 on germination, Messrs. Deherain and Lan- 

 drin have discovered that, when moist seeds 

 are kept for two or three days in a closed 

 tube above a column of mercury, the vol- 

 ume of air decreases even before carbonic 

 acid has made its appearance. Moist seeds 

 have, therefore, the property of condens- 

 ing gases after the manner of porous 

 bodies. But no gas can lose the aeriform 

 state without at the same time giving up 



