MA CHINES WI'l *H AL TERN A TE RE VERSIONS. 1 03 



tremities end severally in the commutator M, which enables 

 all the currents they supply to be drawn off separately or col- 

 lectively by means of the rubbers a s. Inside of this ring 

 revolves the inducer, which is so arranged that the magnetic 

 cores of the two systems pass each other without touching. 

 Thus each of the induced systems is magnetized in opposite 

 directions alternately ; for if one of the cores of the inducing 

 system, acting on one of the 'cores of the induced system, is 

 polarized north, the adjoining core of the induced system 

 will be subjected to the action of a south polarity, and a cur- 

 rent will always be produced in the induced system connected 

 with the commutator. When the inducer has advanced, the 

 polarities will have different signs, and a current in the 

 reverse direction will be obtained. 



As the action we have examined will be simultaneously 

 repeated in all the electro-magnetic systems of the induced 

 bobbins, each of these is able to supply its own action and is 

 independent of the rest, an arrangement which allows of the 

 division of the electric effect. Supposing that each of the 

 induced magnetic systems formed of two bobbins is capable 

 of supplying a current powerful enough to maintain an electric 

 light, the machine represented in Fig. 33 would give 12 lights, 

 and if these were desired of different intensities, it would be 

 necessary merely to take away currents from some of the 

 lights and put them in communication with those lamps that 

 are to be brightest. As the induced system is fixed, nothing 

 is easier than to combine the lights in any required manner, 

 and as there are neither rubbers nor revolving contacts no 

 loss of electricity can occur. 



The commutator M is so arranged as to act on as many 

 contact plates as the machine supplies currents available 

 for the production of light. The number of these currents 

 depends on the construction of the machine, and we have 

 seen that the one represented in Fig. 33 furnishes twelve 

 currents. There are therefore twelve contact plates, and to 

 each of these correspond two binding screws, one of which 



