330 THE CANADIAN NATURALIST. [Oct. 



therein. Even the wandering meteoric stones, which fall from 

 their courses, and are examined on the earth, betray only well- 

 known mineral elements, though in the manner in which these are 

 combined, some differences appear, which, by chemical research and 

 the aid of transparent sections, Professor Maskelyne and Mr. Sorby 

 are engaged in studying and interpreting (x). 



By the labors of Lavoisier and his contemporaries, chemistry 

 acquired a fixed logic and an accurate nomenclature. Dalton and 

 the great physicists of the early part of this century gave that law 

 of definite combination by proportionate weights of the elements 

 which is for chemistry what the law of gravitation is for celestial 

 mechanics. A great expansion of the meaning of the atomic 

 theory took place, when Mitscherlich announced his views of 

 isomorphous, isomeric, and dimorphous bodies. For thus it came 

 gradually to appear that particular forces resided in crystals in 

 virtue of their structure, lay in certain directions, and exhibited 

 definite physical effects, if the chemical elements, without being 

 the same, were combined in similar proportions and aggregated 

 into similar crystals. Some years later, ozone was discovered by 

 Schonbein, and it concurred with a few other allotropic substances 

 in reviving, among philosophic chemists, the enquiry as to the 

 relative situation of the particles in a compound body, and the 

 effects of such arrangements : an idea which had been expressed 

 by Dalton in diagrams of atoms, and afterwards exercised the 

 ingenuity of Exley, Mac Vicar, and others (y). 

 t Everything connected with this view of the modification of 

 physical properties by the arrangement of the particles — whether 



(x) Professor Maskelyne has made a convenient classification of the 

 large collection of meteorites in the British Museum, under the titles of 

 "Aerolite or Meteoric Stone;" " Aerosiderite or Meteoric Iron:" and 

 " Aerosiderolites," which includes the intervening varieties. Mr. Sorby, 

 whose latest results are unpublished, but "will be communicated to the 

 Royal Society, is of opinion that the substance of meteorites has under- 

 gone changes due to physical conditions in some ancient period not now 

 to be paralleled on our planet, or on the moon, but rather to be looked 

 for only in the immediate neighborhood of the sun. Professor Haidin- 

 ger has also made a special study of meteorites. 



(y) Dalton, Chemistry, vol. i. 1808. A clear view of the simpler 

 Applications of Dalton's ideas is given by the illustrious author in 

 Daubeny's Treatise on the Atomic Theory, 1850. 



Exley, Nat. and Exp. Philosophy, 1829. 



Mac Vicar, Reports of the British Association for 1855. 



