84 ELECTRIC LIGHTING. 



In the machine we are now speaking of, the brush rubbers, 

 which act as collectors for the induced current, are carried 

 on a kind of balance, which by a mere inclination in one 

 direction or the other and by a change of the wires allows 

 the induced currents to be obtained in either direction at 

 pleasure. 



Siemens has recently arranged a new form of this machine, 

 of much smaller dimensions than the preceding, resembling 

 the induction machines of the physical laboratory. This is 

 the form which sets in action the machines by the same 

 maker for reversing the currents, that we shall describe farther 

 on, and in which it is not easy to understand how so small a 

 machine can produce effects so powerful. 



The arrangement of the apparatus represented in Fig. 23 

 is nearly the same as that we have just described, except that 

 the system is placed vertically instead of horizontally, and 

 the induced coil, instead of being provided inside with a 

 framework of iron serving as armature to the electro-magnetic 

 system, is provided with a cylinder formed of a bundle of 

 wires, like the cores of voltaic induction machines. These 

 wires, while acting as an armature, at the same time increase 

 the intensity of the inductive effects, as in the machines of 

 Ruhmkorff and others. 



These machines require, however, a high speed of rotation, 

 from 1,100 to 1,375 turns per minute ; but it does not appear 

 that they heat much. The current they supply is sufficiently 

 powerful to light 16 Jablochkoff candles by passing through 

 a machine of the form of Fig. 35 for dividing and reversing 

 the currents. 



Siemens has also constructed a form of magneto-electric 

 machine arranged nearly under the same conditions as the 

 preceding, and differing from them only that instead of in- 

 ducing electro-magnets there are bundles of magnetized bars 

 separated from each, and bound together by strong iron 

 frames as broad as the length of the induced coil. The 

 machine has also a commutator with four rubbers. 



