1876.] 



Electricity between Non- Conductors. 



171 



virtue of which the work done bj rubbing them together is converted into 

 electrical separation. 



The following experiment, suggested bj Dr. Schuster, was also tried : 

 the needle was taken out of a Thomson's quadrant electrometer and 

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







B ^ 













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 position that when the quadrants A, B were 

 charged with negative and positive electricity respectively, the needle 

 rotated in the direction of the hands of a watch, and when A and B were 

 charged with positive and negative electricity respectively, the needle 

 rotated in the opposite direction. 



When two non-conductors, A, B, are placed in contact, the electricity 

 will not be distributed through the whole of A and B ; and if the dis- 

 placement is from B to A and parallel to the sides of the cake, the only 

 parts electrified will be the middle and ends of the cake ; the A end of the 

 cake will be positively and the B end negatively electrified ; and if A has 

 a greater specific inductive capacity than B the middle will be negatively 

 electrified ; if it has a less specific inductive capacity than B it will be 

 positively electrified. 



I intend to examine more substances, arid to endeavour to make some 

 quantitative measurements. The above experiments were made in the 

 Physical Laboratory of Owens College, Manchester ; and I have much 

 pleasure in thanking Dr. Stewart, Dr. Schuster, and Mr, Kingdon for 

 the assistance they have given me. 



