ELECTRICAL ATTRACTION AND REPULSION. 109 



other ; but now what happens ? It does not 

 attract ; on the contrary, it very strongly repels, 



Fig. 33. 



and I can thus drive it round to any extent. 

 These, therefore, repel each other, although 

 they are so strongly attractive repel each 

 other to the extent of driving this heavy piece 

 of shellac round and round in this way. But 

 if I excite this piece of shellac as before, and 

 take this piece of glass and rub it with silk, and 

 then bring them near, what think you will 

 happen ? [The Lecturer held the excited glass 

 near the excited shellac, when they attracted 

 each other strongly.] You see, therefore, what 

 a difference there is between these two attrac- 

 tions, they are actually two kinds of attraction 



