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CHAPTER VIII. 



THEORY OF DEFINITE, RECIPROCAL, AND MULTIPLE 

 PROPORTIONS. 



Sect. 1. Prelude to the Atomic Theory, and its 

 Publication by Dalton. 



THE general laws of chemical combination 

 announced by Mr. Dalton are truths of the 

 highest importance in the science, and are now 

 nowhere contested; but the view of matter as 

 constituted of atoms, which he has employed in 

 conveying those laws, and in expressing his opinion 

 of their cause, is neither so important nor so cer- 

 tain. In the place which I here assign to his 

 discovery, as one of the great events of the history 

 of chemistry, I speak only of the law of pheno- 

 mena, the rules which govern the quantities in 

 which elements combine. 



This law may be considered as consisting of 

 three parts, according to the above description of 

 it ; that elements combine in definite proportions ; 

 that these determining proportions operate reci- 

 procally ; and that when, between the same ele- 

 ments, several combining proportions occur, they 

 are related as multiples. 



That elements combine in certain definite pro- 

 portions of quantity, and in no other, was implied, 



