324 ELECTRICITY. 



by means of points, collect the electric fluid from 

 their inner surfaces only. 



When the cylinder of the electrical machine is 

 whirled round, the friction of the glass against the 

 rubber makes the electric fluid which was in the 

 rubber pass to the glass, from whence it is con- 

 veyed to the prime conductor, the points of which 

 are presented to every part of the globe in succes- 

 sion : and, as the friction is continued, there will, 

 by this means, be a constant supply of the electric 

 matter to the prime conductor, which, when other 

 bodies are presented to it, will keep discharging all 

 the while in visible sparks. The hand, in the case 

 of a glass tube, and the rubber in the electrical 

 machine, which had parted with their share of the 

 electric fluid to the glass against which they were 

 rubbed, receive an immediate supply from the 

 conducting substances in contact with them ; and 

 these are again supplied by the general mass of the 

 fluid that is lodged in the earth. 



Electrical Attraction and Repulsion. 



Two bodies possessing different states of elec- 

 tricity, that is, one being positively, and the other 

 negatively electrified, attract each other j but two 

 bodies which are either both positively or both 

 negatively electrified, repel each other. 



A convenient way of showing electrical attrac- 

 tion and repulsion, is by fastening two small balls 

 made of the pith of elder of the size of peas, by 

 threads of three or four inches long, to a small 

 stem, and putting them on the prime conductor : 

 when the machine is turned, the balls repel each 



