THEORY OF DEFINITE PROPORTIONS. 165 



so on. Thus, if C represent an atom of carbon and 

 O one of oxygen, OC will be an atom of carbonic 

 oxide, and OCO an atom of carbonic acid; and 

 hence it follows, that while both these bodies have 

 a definite quantity of oxygen to a given quantity 

 of carbon, in the latter substance this quantity 

 is double of what it is in the former. 



The consideration of bodies as consisting of 

 compound atoms, each of these being composed of 

 elementary atoms, naturally led to this law of mul- 

 tiple proportions. In this mode of viewing bodies, 

 Mr. Dalton had been preceded (unknown to himself) 

 by Mr. Higgins, who, in 1789, published' his Com- 

 parative View of the Phlogistic and Antiphlogistic 

 Theories. He there says 4 , " That in volatile vitriolic 

 acid, a single ultimate particle of sulphur is united 

 only to a single particle of dephlogisticated air ; and 

 that in perfect vitriolic acid, every single particle of 

 sulphur is united to two of dephlogisticated air, 

 being the quantity necessary to saturation ;" and he 

 reasons in the same manner concerning the con- 

 stitution of water, and the compounds of nitrogen 

 and oxygen. These observations of Higgins were, 

 however, made casually, and not followed out, and 

 cannot affect Dalton's claim to original merit. 



Mr. Dalton's generalization was first suggested 5 

 during his examination of olefiant gas and car- 

 buretted hydrogen gas ; and was asserted generally, 



3 Turner's Chem. p. 217- 4 P. 36 and 37- 



5 Thomson, vol. ii. p. 291. 



