ACCUMULATORS. 83 



negative potential on that point, on the nearest surface 

 of the book, in a line between the knobs ; repelling the 

 electricity of the book along that line to the opposite 

 surface, which would thus become highly positive. 



The paper being a very imperfect conductor, the 

 charges thus induced do not spread rapidly, but remain 

 concentrated for a moment on small circular spaces 

 around each of these points ; the greatest intensity 

 being at the centers. Hence there is a powerful at- 

 traction between the knob of the jar and this negative 

 point on the surface of the book ; and also between the 

 knob of the discharger and the positive point on the 

 other surface ; under the influence of which the paper 

 on each surface gives way and bursts outward toward 

 the knobs ; that surface next the knob of the jar being 

 attracted, and that next the knob of the discharger 

 repelled. 



As each outward leaf bursts, the next, becoming 

 then the outer one, bursts also, till the perforation is 

 complete from the center each way. All of which 

 occurs instantaneously. 



Meantime the electricity from the knob of the jar 

 follows up this inductive effect on the electricity of the 

 book; but meeting great resistance from the imper- 

 fectly conducting paper, and the air between the leaves, 

 it is concentrated on each leaf successively ; so that the 

 inductive force is constantly in advance of the charge, 

 the leaves and layers of air between them constituting 

 the dielectric. 



It will be noticed, then, that this is not a case of 

 energy going through a passive medium, but of energy 

 acting on the energy of that medium, causing it to become 

 active and perform work. 



