18 



STATIC ELECTRICITY 



It is not. always necessary to electrify a field plate to set the- 

 machine in action. There is frequently some charge to begin 

 with, perhaps due to friction of a carrier against a spring, a 

 the two plates are not electrified equally the machine will 

 the larger charge and soon make the smaller charge of the oppo 

 sign to it, if it was not so initially. . 



In 1860 C F. Varley* invented a machine similar in prn 

 to that of Belli, and later Lord Kelvinf devised a modified 

 replenisher " used to charge the jar in his Quadrant El* 



Fir,. 15. 



Other important developments were made in Toeplers machine 

 and Holies machines.! We shall only describe the machine 

 usually employed in this country and introduced by Wimdnmt 

 1883, a modification of the previous machines somewhat moiv 

 certain and convenient in its working. 



The Wimshurst machine. The common form c 

 machine is represented in Fig. 15. It consists of two exactly 

 similar glass plates which are rotated close to each other with equal 



* Specification of Patent, Jan. 27, 1860, No. 200. 

 f Pavers on Electrostatics and Magnetism, p. 2/0. 

 J A full account of Toepler's and Holtz's machines 

 Electrical Influence Machine \ 



