286 MECHANICAL ELECTRICITY. 



20°; the current, in that instance, from the 

 tool towards the disc, tested by voltaic pair. 



Exp. 30. With a zinc disc and steel tool, at 

 first no certain indication of current. Repeated 

 afterwards, with and without steam power, current 

 3% and afterwards 5°, constant, from the tool to- 

 wards the zinc. 



Exp. 31. With the extremity of the copper 

 connecting wire, current 2^° from the zinc towards 

 the wire. Repeated with steam power, 3° towards 

 the copper. 



May 1st, 1846. With a sharp cutting edge of 

 copper against the zinc disc, 3° to 5° towards the 

 copper. These experiments correspond with the 

 phenomena of electro-motion — zinc robbing cop- 

 per. 



Exp. 32. With a Bismuth rod against the zinc 

 cylinder, a current of 12° was evinced from the 

 zinc towards the Bismuth. 



Exp. 33. With a piece of iron sharpened, 

 current 4° to 5° from the iron towards the zinc, 

 iron positive, zinc negative. 



