HISTORY OF GALVANISM. 63 



vidual as Mr. Peel could be found in Cam- 

 bridge, so that the letter bearing his name is a 

 complete fabrication. It was not, however, en- 

 tirely without its use : for the minute examination 

 of the effects of galvanic electricity upon water to 

 which it gave rise, may probably be regarded, in 

 some measure, as the immediate cause of Sir H. 

 Davy's most brilliant discoveries. 



An elaborate memoir was written by Erman of 

 Berlin, on the conducting power of different 



bodies, which obtained the prize from the French 

 Institute. His object was to remove some anoma- 

 lies, which appeared to exist in the relation of the 

 galvanic electricity to the different conducting 

 substances. 



He divides all bodies into five classes : 1st, Per- 

 fect non-conductors; 2d, Perfect conductors ; 3d, 



Imperfect conductors; 4th, Positive conductors; 

 and 5th, Negative conductors. The nature of the 

 three first classes requires no explanation; the 

 fourth and fifth class of bodies act as perfect 

 conductors, when applied to either of the two 

 poles separately, but when placed between them, 

 insulate either the positive or negative pole 

 respectively, and do not form a communication 

 between them. The flame of a spirit lamp is Flame a 

 described as a positive conductor ; if it be ap- conductor. 

 plied to each pole separately it conducts the 

 electricity ; but if it be placed between the two 

 poles, it will not form a communication be- 

 tween them, in consequence of its insulating 



