MECHANICAL ELECTRICITY. 289 



Exp. Having selected a steel file and piece 

 of fine iron wire, free from magnetic polarity, I 

 proceeded to draw the file several times over the 

 surface of the wire, when by holding them on 

 each side the north-pole of a suspended magnetic 

 needle, it was found that the wire attracted, 

 and the file repelled this pole with considerable 

 force. 



Exp. a new file attracted both poles of a 

 magnetic needle, or was unmagnetic. A piece of 

 iron wire slightly repelled the pole. After rubbing 

 the wire along its surface, and holding the wire 

 on one side of the north-pole, and the file on 

 other, the needle was attracted hy the wire^ and 

 repelled hy the file. 



Exp. a new file attracted the north-pole of 

 a magnetic needle 10°, a piece of iron wire re- 

 pelled the same. After filing the same, and 

 placing this pole of the needle between them, 

 the file repelled, and the wire attracted the 

 needle. This experiment was repeated with the 

 same result. 



A thick file, and a thick piece of soft iron 

 did not produce any change, the process not 

 pp 



