VARIOUS GENERATORS OF ELECTRIC LIGHT. 77 



pose for a moment that there is a wooden ring instead of the 

 iron one. When one of the coils, E, approaches the pole s, 

 turning from right to left, a current will be developed which, 

 according to the law enunciated on page 54, will be direct. 

 If the movement, instead of being continued, were to take 

 place backward, there would still, according to the same law, 

 be a new current which would be inverse, and therefore in 

 the opposite direction to the first ; but if the movement is 

 continued in the same direction this will not occur, for when 

 the coil E has passed the point s the pole will act on it at its 



FIG. 20. 



opposite end ; so that instead of a current in the opposite 

 direction there will be a cr.rrent in the same direction, which 

 will go on decreasing until E' is reached ; at this time the coil 

 will be approaching the pole N, but this acting on the front 

 end of the coil will create a current having the opposite 

 direction to those produced in the coil on approaching s, 

 because this pole is of opposite name. After having passed 

 N, the travelling coil will be influenced by N at its hinder 

 extremity, and a new current in the same direction as the 

 last will be produced, until E" is reached, when the direct 

 currents will again show themselves. These effects are pro- 

 duced in all the coils, those occupying the upper part of the 

 ring being at a given moment traversed by currents in a 

 direction varying according to the winding of the coil and 

 the direction of the movement ; and the coils occupying the 



