THEORY OF DEFINITE PROPORTIONS. 285 



which have been given of chemical relations, namely, the views of the 

 electro-chemists. 



But before we do this, we must look back upon a law which ob- 

 tains in the combination of elements, and which we have hitherto not 

 stated ; although it appears, more than any other, to reveal to us the 

 intimate constitution of bodies, and to offer a basis for future generali- 

 zations. I speak of the Atomic TJieory, as it is usually termed ; or, as 

 we might rather call it, the Doctrine of Definite, Reciprocal, and 

 Multiple Proportions. 



CHAPTER VIII. 



THEORY OF DEFINITE, RECIPROCAL, AND MULTIPLE PROPORTIONS. 



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



JDalton. 



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 certain. 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 phenomena, 

 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 reciprocally , 

 and that when, between the same elements, several combining pro- 

 portions occur, they are related as multiples. 



That elements combine in certain definite proportions of quantity, 

 and in no other, was implied, as soon as it was supposed that chemical 

 compounds had any definite properties. Those who first attempted to 

 establish regular formulae 1 for the constitution of sa.ts, minerals, 



1 Thomson, Hist. Chem. vol. ii. p 279 



