2 INTRODUCTION. 



without the aid of friction, and where we perceive 

 a chemical action to take place between some of 

 the bodies employed. 



Plan of the In treating upon this science, it will be found 

 convenient to arrange the subject into two divi- 

 sions : in the first I shah* give an historical detail 

 of the discoveries that have been successively made 

 from the time of Galvani's first observation to 

 the present period ; and, in the second place, I 

 shall examine the principal theories and hypotheses 

 that have been formed to explain the phenomena 

 of galvanism. 



