QUANTITY OF ELECTRIFICATION 29 



Let a small can B have a lid furnished with an insulating 

 handle h and let the under side of the lid have some arrangement 

 by which the base of A can be attached when A is inverted. Let 

 H be an insulating handle by which the can may be lifted up. Let 

 an insulating base plate be fixed to the can. Let C and D be two 

 other cans similar in general plan to B, but large enough to con- 

 tain it. Let a metal piece S be fastened to the lid of each of the 

 larger cans so as just to touch the smaller can when inside. 



We shall now show that we may give to C a charge equal to 



FIG. 22. 



any positive multiple of the unit, and to D a charge equal to any 

 negative multiple. To charge C with a positive multiple, place 

 the unit within B, place B within C, and put the lid on C, taking 

 care not to touch the conductors in any case, but moving them 

 always by their insulating handles. Then following out the process 

 by the aid of the upper row of diagrams in Fig. 22, it is easy to 

 see that when B is taken out of C, C will have a positive unit on 

 the outside. On taking A out of B, B may be inserted in D, as 

 represented in the lower row, and its negative charge is imparted 

 to I). On taking B out of D, B is free from charge. As A 

 has its original charge we may repeat the process any number of 

 times, each repetition adding a positive unit to C and a negative 

 unit to D. We may imagine the preparation in this way of a 

 series of multiples of the unit, both positive and negative, by having 

 a number of cans like C and D. By making a number^of exactly 

 similar cans, charging one with a unit and sharing this unit 



