HISTORICAL INTRODUCTION. 27 



the simple substances, and of many of their com- 

 pounds, I next wished to examine the composi- 

 tion of a considerable number of salts, to see 

 whether any law would develope itself respecting 

 the quantity of water of crystallization which 

 these bodies frequently contain. \Vith this view 

 a great number of salts were subjected to expe- 

 riment ; but the only obvious result is, that the 

 number of atoms of water in salts, depends more 

 upon the base than upon the acid : for the same 

 base, in general, affects nearly the same number 

 of atoms of water in its salts. But to this law 

 there are many exceptions. 



I now present the result of my investigations 

 to the chemical public with considerable diffi- 

 dence. For though I have been at the utmost 

 pains to ensure accurate results ; and often re- 

 peated what I considered as fundamental expe- 

 riments eight or ten times, before I felt myself 

 finally satisfied ; yet the number of experiments 

 gone through is so great, that it will be won- 

 derful if, in some cases, I have not fallen 

 into mistakes. I have made a point of relating 

 my experiments (where I thought them funda- 

 mental) nearly as they were made : because, as 

 I had no person to go over my calculations, 

 which have been of necessity very numerous, 

 though all of the simplest kind ; it is very likely 

 that I have not been always able to prevent the 

 occurrence of some arithmetical errors in them. 



3 



