12 Meldrum, Development of the Atomic Theory. 



that the composition is not in the least a matter of chance. 

 Proust had no conception of the law which regulates 

 multiple proportions. Again, Berthollet believed that one 

 oxide could change into the other by continuous variation 

 in composition, while Dalton's theory not only allowed 

 for the existence of definite intermediate oxides, but 

 could even predict their composition with a considerable 

 degree of certainty. 



The view taken here, that Berthollet's teaching on the 

 subject of chemical composition easily survived Proust's 

 criticism, and received a serious check from Dalton, can 

 be amply illustrated from the literature of the time. 

 William Henry treats the subject of chemical proportion 

 in that sense. " In opposition to the theory that chemical 

 affinity has a strong tendency to unite bodies in unlimited 

 proportions, an hypothesis has lately been proposed by 

 Mr. Dalton, which appears more consonant to the general 

 simplicity of nature." "^ John Murray pits the two doctrines 

 against one another, and actually, as late as the year 

 1809, expresses a strong preference for Berthollet's.'* 

 Indeed, Berthollet felt the challenge to himself implied in 

 Dalton's Atomic Theory; and showed this by criticising 

 it in the Introduction which he contributed to the French 

 translation of Thomson's " System of Chemistry," ^" in 

 which, it will be remembered, the theory is sketched. 



If anyone, inclining to hold to the view of von Meyer 

 and Wurtz that Proust was successful against Berthollet, 

 should doubt whether the prestige of the latter was so 

 great as has been indicated in this paper, he might do 

 well to consider the chemical literature of the time. In 



^^ " Elements of Experimental Chemistry," 6th ed., vol. I, p. Si, 1810. 

 "* "System of Chemistry," 2nd ed., vol. i, p. 627. 

 ^* Riffault's translation, vol. i. pp. 21 — 27, 1809. 



