VARIOUS GENERATORS OF ELECTRI'C LIGHT. 97 



magnetic cores give the means of fixing the rings on the axis 

 of rotation with precision a difficult operation with the 

 Gramme rin'g. In short, this is a very interesting and a very 

 promising machine. 



Trouve's machine. Trouve has also constructed 

 dynamo-electric machines based on nearly the same prin- 

 ciple as the preceding machines, but with a reaction of the 

 inducing magnets on the induced, which is effected at the 

 contact of the magnetic pieces, and by a method similar to 

 that which Larmangeat had applied as early as 1855 in his 

 electro-motor with electro-magnets and revolving armatures. 



In one of these apparatus the inducer is formed of a large 

 straight electro-magnet, movable horizontally on its axis, and 

 with a core provided with two iron discs, as in the circular 

 electro-magnets of Nickles. On these discs turn the iron 

 ends of a certain number of bundles of electro-magnets, 

 arranged in a circle, with their poles thus placed successively 

 in contact with the expanded poles of the inducing electro- 

 magnet, and each giving rise to the induction currents, which, 

 reaching a commutator, traverse the inducing coil and supply 

 at once the working and the exciting current. This arrange- 

 ment is entirely the same as that of Larmangeat's electro- 

 motor. 



In another form of the machine, which is now being made 

 on a large scale, the inducing magnet is arranged as we have 

 just mentioned, but it is constituted of two straight electro- 

 magnets placed parallel to each other, and their iron discs 

 are thick enough to have a groove in which move two rings, 

 similar to those of the Brush machine, having a common 

 axle of iron, and coils so combined as to give currents recti- 

 fied by the inducing electro-magnet. Under these conditions 

 the induced and inducing coils form a closed electro-magnetic 

 system in which the movable electro-magnetic pieces are 

 always in contact, and therefore at the maximum of their 

 power. 



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