XVI PREFACE. 



observations, and express them in the form of 

 equations, these answers are obtained without diffi- 

 culty. 



However numerous our observations may be, yet, 

 if they only bear on one side of a question, they 

 will never enable us to penetrate the essence of a 

 natural phenomenon in its full significance. If we 

 are to derive any advantage from them, they must 

 be directed to a well-defined object ; and there 

 must be an organized connection between them. 



Mechanical philosophers and chemists justly 

 ascribe to their methods of research the greater 

 part of the success which has attended their labours. 

 The result of every such investigation, if it bear in 

 any degree the stamp of perfection, may always be 

 given in few words ; but these few words are eter- 

 nal truths, to the discovery of which numberless 

 experiments and questions were essential. The 

 researches themselves, the laborious experiments 

 and complicated apparatus, are forgotten as soon as 

 the truth is ascertained. They were the ladders, 

 the shafts, the tools, which were indispensable to 

 enable us to attain to the rich vein of ore ; they 

 were the pillars and air passages which protected 

 the mine from water and from foul air. 



Every chemical or physical investigation, how- 

 ever insignificant, which lays claim to attention, 



