Electricity between Non-conductors. 



391 



deflected from the glass part of the cake, when charged with nega- 

 tive it was attracted towards it. In order to get rid of any electricity 

 which might have got on the cake in the making, the cake was 

 made the day before it was placed on the threads, and the experi- 

 ment was made at least a day, sometimes a week, after pntting 

 the cake on the threads ; pieces of glass and sulphur which had 

 been treated in as nearly as possible the same way as those of which 

 the cakes were made were taken and placed separately on the 

 threads, but no electricity could be detected on them. 

 The following cakes were tried : — 



Grlass and wax glass + , wax — ; 



Grlass and resin glass + , resin— ; 



G-lass and sulphur glass-}-, sulphur— 



Glass and solid paraffin . . glass + , paraffin — 



Zinc and sulphur zinc +, sulphur — 



Sulphur and vulcanite . . vulcanite-!-, sulphur— ; 

 the series so far being in the same order as the frictional series ; 

 this seems to suggest that the electrical displacement which takes 

 place when two non-conductors are put in contact acts as a pre- 

 disposing cause, in virtue of which the work done by rubbing them 

 together is converted into electrical separation. 



The following experiment, suggested by Dr, Schuster, was also 

 tried : the needle was taken out of a Thomson's quadrant elec- 

 trometer and replaced by a needle, half of which was sealing-wax 

 and the other half glass ; the quadrants C and D were connected 

 with the earth ; and it was found possible, after the needle had 





stood undisturbed for ten days, to set the needle in such a posi- 

 tion that when the quadrants A, B were charged with negative 

 and positive electricity respectively, the needle rotated in the di- 

 rection of the hands of a watch, and when A and B were charged 

 with positive and negative electricity respectively, the needle ro- 

 tated in the opposite direction. 



