18 



ELECTRICITY. 



the two plates, they will exhibit a rapid 

 dance, while they fetch and carry the 

 electricity from the upper to the lower 

 plate ; or contrariwise, if the conductor 

 be in the negative state. 



A* II. 



. (67.) This alternation of attractions 

 and repulsions accompanying the trans- 

 ferring electricity by moveable conduc- 

 tors, is also illustrated by the motions of 

 a ball (fig. 12.), suspended by a silk 



Fig. 12. 



thread, and placed between two bells, of 

 which the one is electrified, and the other 

 communicates with the ground. The 

 alternate motion of the ball between 

 the two bells will produce a continued 

 ringing. As thus described, it is a 

 mere toy, but the same arrangement 

 has been applied to the philosophical 

 purpose of giving notice of changes 

 taking place in the electrical state of the 

 atmosphere. 



(68.) The mutual repulsion of bodies 

 that are similarly electrified gives rise 

 to many amusing appearances. The 

 filaments of a feather will separate from 

 each other and diverge, when electrified, 

 presenting a singular and unnatural 

 appearance. A small figure in the 



shape of a human head, covered with 

 hair, when placed upon the conductor 

 and electrified, will exhibit the appear- 

 ance of terror from the general bristling 

 up and divergence of the hair. A lock 

 of wool highly charged with electricity 

 will, in like manner, swell out to a large 

 size, in consequence of the mutual re- 

 pulsion of the filaments which compose 

 it. On approaching a needle to it, held 

 in the hand, whereby its electricity is 

 quickly drawn off, the cotton will sud- 

 denly shrink into its original dimen- 

 sions. 



(69.) We 'have already adverted to 

 the effects of fusion in rendering some 

 bodies conductors, which in their solid 

 state had the contrary property. This 

 is the case with sealing-wax ; and ac- 

 cordingly, if melted sealing-wax be 

 electrified, its particles will tend to 

 separate by their mutual repulsion, and 

 to draw out into filaments. Let a piece 

 of sealing-wax be fixed on the end of a 

 wire, and be set fire to, but the flame 

 immediately afterwards blown out. 

 While the surface of the wax is still 

 melted, present it, at the distance of 

 some inches, to the electrified conductor, 

 a number of extremely fine filaments 

 will immediately dart out from the 

 sealing-wax to the conductor, on which 

 they will be condensed into a kind of 

 net- work resembling wool. If the wire 

 with the sealing-wax be stuck into one 

 of the holes of the conductor, and a 

 piece of paper be presented at a mode- 

 rate distance to the wax, just after it 

 has been ignited, on setting the machine 

 in motion, a net-work of wax will be 

 formed on the paper. The same effect, 

 but in a slighter degree, will be pro- 

 duced, if the paper be briskly rubbed 

 with a piece of Indian rubber, and the 

 melting sealing-wax be held pretty near 

 the paper immediately after it has been 

 rubbed. If the paper, thus covered 

 with filaments of sealing-wax, be gently 

 warmed before the fire, the wax will 

 adhere to it, and exhibit permanently 

 the result of the experiment. Still more 

 beautiful are the appearances produced 

 by camphor subjected to a similar pro- 

 cess. For the purpose of obtaining them, 

 a spoon, holding a piece of lighted cam- 

 phor, must be kept electrified by work- 

 ing the machine, while it communicates 

 with the conductor ; the camphor will 

 then throw t ut curious ramifications* 

 which appear to shoot like those of a 

 vegetable. 

 (70.) It is on the same principle that 



