PREFACE. 



THIS work is based upon a course of Lectures delivered by 

 one of us in the College de France in the last few years. 

 It will comprise two parts : the first, which is principally 

 theoretical, forms the present volume ; the second, which 

 will be more experimental in character, will be devoted to 

 the examination of the various phenomena, the methods of 

 measurement, and the principal applications. % 



This method of treatment seemed to us to present great 

 advantages. The phenomena are, in fact, almost always 

 very complicated, especially in the case of electricity; and 

 to understand all the details which these phenomena involve 

 often requires a more extensive knowledge than that fur- 

 nished in the chapters with which they are more immediately 

 connected. The explanation of the experiments will, there- 

 fore, be materially facilitated by a preliminary account of the 

 general principles of the science. 



After having stated and co-ordinated the facts which 

 serve to establish the theory, we have investigated the 

 mechanical consequences. This first volume forms, accord- 

 ingly, a distinct work ; and we might express the idea 

 which has guided us by considering it as an Essay on the 

 Mechanical TJieory of Electricity, if such a title did not 

 seem too ambitious. 



We have endeavoured to bring into prominence the 

 profound views introduced into science by Faraday, and 



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