VARIOUS GENERATORS OF ELECTRIC LIGHT. 83 



on the same axle as the cylinder; and against these, 

 as in the Gramme machine, there press two rubbers of 

 metallic wires, which transmit the current supplied by the 

 machine. This cylinder is surrounded by the expanded poles 

 of a dynamo-electric system through which the entire induced 

 current is passed, and these semicircular poles are divided by a 

 certain number of slits in order to facilitate the demagnetiza- 

 tions. The branches of the electro-magnets are also formed 

 by plates of iron wider than they are long, joined two by two 

 by pieces of iron, which ser/e as a frame to the apparatus and 

 form its pillow-blocks. 



Finally, inside of the copper cylinder is placed, opposite 

 the poles of the inducing magnet, an iron framework, termi- 

 nated by arched plates of the same metal, which by forming a 

 kind of armature for the inducing electro-magnets, consider- 

 ably reinforce their power. 



Under these conditions the induced currents are due to 

 the dynamical action which we have explained on page 77, 

 that is to say, to the movement of the galvanometrical coils 

 before the inducing poles, only, the two poles of the magnet 

 act simultaneously on each coil ; and as this double action 

 takes place on the opposite parts of these coils, where the 

 current has necessarily a contrary direction in relation to the 

 axis of figure, the two effects concur in the same result. 

 The change of direction in the currents is, however, produced 

 in the same manner as in the Gramme machine, in the centre 

 of the interpolar space, and it is there that the two rubbers 

 of the collector are applied. It will easily be understood 

 that currents of polar inversion count for nothing in this 

 machine, and, as I have said, the iron framework acts merely 

 by reinforcing the electro-magnetic action. Therefore, if 

 necessary, it may be dispensed with; and this especially 

 distinguishes this system from that of Gramme, since in 

 the latter the iron ring, besides being useful for effective 

 inductive action, serves as a framework for the support of 

 the coils. 



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