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Mr. Lockyer's Theory of "The Cosmos,"—Mr. Lockyer has presented, in a paper to the Royal Society "Spectra of Meteorites," a new hypothesis concerning the origin and nature of the stars and other celestial bodies. Among the fundamental propositions of his theory are those that all self-luminous bodies in the celestial spaces are composed of meteorites, or masses of meteoric vapor, produced by heat brought about by condensation of meteor swarms due to gravity; that the spectra of all bodies depend upon the heat of the meteorites, produced by collisions, and the average space between the meteorites in the swarm, or in the case of consolidated swarms, upon the time which has elapsed since complete vaporization; that the existing distinction between stars, comets, and nebulæ rests on no physical basis; and that the main factor in the various spectra produced is the ratio of the interspaces between the meteorites to their incandescent surfaces. These, with other propositions of more detailed and specific character, are sustained by results of spectroscopic examinations of meteorites and of various substances, which are described particularly. Experiments prosecuted for fourteen years have shown that the luminous phenomena manifested by the several classes of heavenly bodies can be reproduced in the laboratory by subjecting meteorites, as far as possible, to conditions similar to those assumed by the hypothesis to exist in space. Thus, the reproduction of the spectrum of the sun by the fusion of meteorites in the voltaic arc accords with the supposition that it is the result of the condensation to the point of complete volatilization of an originally sparse swarm of meteorites. The spectra of comets when near the sun give the lines of a meteoric body glowing in a dense atmosphere given off by itself when highly heated; while at their greatest observed distances from the sun their spectra are identical with those of the nebulæ, which are supposed by the hypothesis to be "closely associated with a meteorite glowing very gently in a very tenuous atmosphere given off by itself." Hence nebulæ are supposed to be sparse clusters of associated meteorites, and their luminous phenomena to be due to the glow of gases which result from collisions between the individuals of the group. Comets are nebulæ whose proper motions have brought them within the range of the sun's attraction; but when outside of his more immediate influence they exhibit no phenomena which are not also exhibited by nebulæ. The next stage of approximation is exhibited by stars designated as of Class IlIa, and is due to the attraction of gravity among the individual meteorites of the swarm; and the succeeding stages are indicated by the increasing complexity of the spectra, whether of the meteorite itself rendered incandescent by collision of the vapors by which it is immediately surrounded, or of the general interspace between me-