198 



FRICTIONAL ELECTRICITY. 



FIG. 137. 



FIG. 138. 



325. Electric Force. We must by this time 

 recognize the fact that we are dealing with a new class of 

 phenomena. We have an agent here capable of producing 

 motion ; we have indisputable evidence of the presence 

 of a force. This force is called electricity. Electricity 

 is a force manifested ~by the peculiar phenomena of 

 attraction and repulsion. It is believed that electricity 

 is a form of molecular motion, but this belief rests upon 

 analogy rather than demonstration. 



326. Two Kinds of Electricity. Prepare two 



electric pendulums. Bring the electrified glass rod near 

 the pith ball of one ; after contact, the ball will be repelled 

 by the glass. Bring the electrified sealing-wax near the 

 second pith ball ; after contact it will be repelled by the 

 wax. Satisfy yourself that the electrified glass will repel 

 the first; that the electrified sealing-wax will repel the 

 second. Let the glass rod and the sealing-wax change 



