50 ELECTRIC LIGHTING. 



the ends of the induced wire, that is to say, of the wire of the 

 electro-magnet, are connected with a commutator for revers- 

 ing the poles placed on the axis of rotation of the system, 

 the two currents traverse the circuit always in the same 

 direction. Such are the magneto-electric machines, the 

 original type of which is represented in Fig. 12, but their 

 arrangement has, however, been varied in many ways. It 

 is these that have given birth to the powerful machines 

 which in recent times have astonished physicists them- 

 selves. 



While some were making the magneto-electric machines of 

 which we have just spoken, other physicists and mechanicians 

 were setting up new forms of them, by availing themselves of 

 the inductive effects of voltaic coils which allowed induced 

 currents to be obtained without the necessity of turning any 

 machinery. Such coils being placed within the coil intended 

 to supply the induced currents, could play the part of mag- 

 netized bars, since, as Ampere showed, they constituted dy- 

 namical magnets ; and in order to obtain the effects produced 

 by the approach or recession of the inducing coil (that playing 

 the part of a magnet), it sufficed to place in the circuit an 

 automatic interrupter of the current. By the year 1836 Page 

 in America, Masson in France, and Callan in England had 

 in fact constructed machines of this kind, in which the in- 

 duced currents could be thoroughly studied and their character 

 determined; so that it was established with certainty not only 

 that induced currents possessed high tension, but that under 

 certain conditions they were able to produce some effects 

 resembling those of static electricity. These pieces of ap- 

 paratus, improved by Page, Callan, Sturgeon, Gauley, Masson 

 and Breguet, Bachhoffner, Clarke, Golding Bird, Nesbitt, 

 Breton, Fizeau, Ruhmkorff, Cecchi, Hearder, Bright, Pog- 

 gendorff, Foucault, Bently, Ladd, Jean, Ritchie, Gaiffe, and 

 Apps, were not long in becoming powerful generators of high 

 tension electricity, able advantageously to supersede electric 

 machines, and they constitute at the present day the most 



