VARIOUS GENERATORS OF ELECTRIC LIGHT. 75' 



Like most important machines, the Gramme machine has 

 since its first invention undergone many transformations, and 

 at the present day it is still constructed in several forms, 

 adapted for special applications ; but as we have here to 

 consider only apparatus for light, we shall describe only the 

 form most commonly used, which is represented in Fig. 19. 



FIG. 19. 



This machine is based upon the effects described on page 

 53, resulting from the successive reversing of the polarity of 

 a magnetic body passing rapidly before an inducing magnet, 

 and particularly from the induced currents which are pro- 

 duced on the passage of the spires of an induced coil before 

 the same inducing magnet. In order to obtain these effects 

 continuously the electro-magnetic elements must be arranged 

 in such a manner that the inducing action shall never be in- 



