Light, Heat, Electricity and Magnetism. 177 



the zinc disc, 3° to 5° towards the copper. These experi- 

 ments correspond 'with the jphcenomcna of electro-motion — zinc 

 robbing copper. 



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. 



Exp. 34. May 2. A copper disc ryxbhedhy a rod o^hismuih, 

 current produced vibrating to 30°, stationary at 15° towards 

 the bismuth from the copper. 



Exp. 35. A rod of zinc against the same copper, the edges 

 of the disc being made sharp, 2i° towards the copper, with a 

 good cutting edge, 4° constant; the zinc by this means being 

 well cut. Repeated 4°. Zinc robbing copper, as in exp. 31. 



Exp. 36. A piece of iron made sharp with filing, when used 

 with a large copper disc 3^^ inches in diameter, gave a current 

 of 8° stationary, while the edge remained good and removed 

 shavings from the iron towards the copper, iron positive. 



Exp. 37. Employed a piece of rod copper in friction against 

 the revolving copper disc, and not the least indication of cur- 

 rent was observed. 



Exp. 38. Silver thus employed against the copper disc, gave 

 a slight current of 1° from the silver towards the disc. 



Exp. 39. With a steel tool, a constant current of 2\° to- 

 ijoards the copper. 



Exp. 40. A brass rod turning instead of a disc, and steel 

 tool, current 5° from the tool towards the brass. 



Magnetism. 



Exp. 41. By filing iron with a steel file, a current of 77^° is 

 produced from the iron towards the file, and the two metallic 

 bodies become oppositely magnetic, as shown by the following 

 experiments. 



The steel surface becomes positive and the iron negative, 

 which are electro- polar conditions. 



It will be immediately seen, that not only does the friction 

 of a file upon a piece of soft iron induce two oppositely elec- 

 trical conditions of surface, but that this electrical state is also 

 a tridij magnetic condition, and offers an explanation how, or 

 in "what manner the varioiis mechanical operations, screw-taj}- 

 ping, drilling, filing, ^~c. evince magnetic phicnomena. An 

 attempt to establish the opinion of magnetism being a static 

 electro-polar condition, was by the author of this paper brought 

 forward, and published in the Report of the British Associa- 

 tion for 1812, page 17. 



Exj). Having selected a steel file and piece of fine iron wire 

 Phil. Mag. S. 3. Vol. 32. No. 214. March 1848. N 



