THEORY OF DEFINITE PROPORTIONS. 171 



definite proportions. Thus water is composed ex- 

 actly of 100 measures of oxygen and 200 measures 

 of hydrogen. And since these simple ratios 1 and 1 , 

 1 and 2, 1 and 3, alone prevail in such combinations, 

 it may easily be shown that laws like Dalton's law 

 of multiple proportions, must obtain in such cases 

 as he considered (i). 



I cannot now attempt to trace other bearings 

 and developements of this remarkable discovery. I 

 hasten on to the last generalization of chemistry ; 

 which presents to us chemical forces under a new 

 aspect, and brings us back to the point from which 

 we departed in commencing the history of this 

 science. 



