120 Experimental Philosophy. [Lecture 9. 



ducting rod should not be too slender, and should 

 extend in the earth beyond the building, to con- 

 vey the electric matter clearly away ; and if it 

 terminates in a pool of water, which is one of the 

 best conductors, it will be still safer. 



I shall conclude this lecture by a short view of 

 that branch of science (for such it is now uni- 

 versally allowed to be) which has been termed 

 GALVANISM, or VOLTAISM. 



It was long known that common electricity 

 could excite a tremulous or convulsive motion in 

 dead animals; but about the year 1791 it was 

 discovered that these effects could be produced 

 without the aid of an electrical apparatus, and 

 apparently by different means, and hence they 

 were at first ascribed to a different power in 

 nature. 



This discovery, like some others of importance 

 in philosophy, was the effect partly of accident. 

 Dr. Galvani (whence the term Galvanism), pro- 

 fessor of anatomy at Bologna, having observed 

 certain involuntary motions or contractions in 

 the muscles of some dead frogs, which had been 

 hooked by the back-bone and suspended from 

 the iron palisades of his garden, was induced to 

 examine more minutely into the cause of these 

 motions; and he found that he could produce 

 them at pleasure, by touching the lifeless animal 

 with two different metals, provided the metals 

 were, at the same time, in contact with each other. 

 From latter observations it appears that these 



