142 POSITIVE AND NEGATIVE ELECTRICITY. 



equal and oppositely directed movements : as when 

 a cannon-ball is put in motion in one direction, 

 an equal motion, or momentum, is imparted to the 

 cannon in an opposite direction. This simple ex- 

 planation resolves the mystery of the opposite 

 movements of bodies toward and from one another 

 into effects produced by oppositely directed im- 

 pulses of mechanical force. This is the obvious 

 way in which every other kind of matter is put in 

 motion. By roughening one end of a glass tube, 

 leaving the other end smooth, the same rubber 

 passed over both surfaces receives different reac- 

 tions, and the electric ether is put in motion in 

 opposite directions on the surfaces of the glass 

 and rubber. 



The terms positive and negative are also ap- 

 plied to denote the two opposite delivering and 

 receiving ends of electric circuits, or poles of 

 voltaic batteries ; which are marked as + and . 

 The present popular theory of electricity being 

 based on' the reciprocal movements of bodies 

 toward and from one another, denoted attraction 

 and repulsion, it remains to show how these move- 

 ments are mechanically produced, instead of 

 ascribing them to self-motive and self-directive 

 powers inherent in the electric ether, or in other 

 matter. 



In accordance with the reciprocal movements 

 of portions of matter toward and from each 

 other, produced by transmitting currents through 



