DIFFEEENT FORMS OF ATTRACTION. 107 



To-day we come to a kind of attraction even 

 more curious than the last, namely, the attrac- 

 tion which we find to be of a double nature 

 of a curious and dual nature. And I want first 

 of all to make the nature of this doubleness 

 clear to you. Bodies are sometimes endowed 

 with a wonderful attraction, which is not found 

 in them in their ordinary state. For instance, 

 here is a piece of shellac, having the attraction 

 of gravitation, having the attraction of cohesion, 

 and if I set fire to it, it would have the attrac- 

 tion of chemical affinity to the oxygen in the 

 atmosphere. Now all these powers we find in 

 it as if they were parts of its substance ; but 

 there is another property which I will try and 

 make evident by means of this ball, this bubble 

 of air [a light india-rubber ball, inflated and 

 suspended by a thread]. There is no attraction 

 between this ball and this shellac at present ; 

 there may be a little wind in the room slightly 

 moving the ball about, but there is no attrac- 

 tion. But if I rub the shellac with a piece of 

 flannel [rubbing the shellac, and then holding 

 it near the ball], look at the attraction which 

 has arisen out of the shellac, simply by this 

 friction, and which I may take away as easily 



