NO. 2 



HISTORY OF ELECTRIC LIGHT — SCHROEDER 



nectecl to a pair of brushes touching a commutator mounted on the 

 shaft holding the magnet, and other brushes carried the current from 

 the commutator so that the alternating current generated was rectified 

 into direct current. 



E. M. Clarke, an Englishman made, in 1834, another dynamo in 

 which the bobbins rotated alongside of the poles of a permanent 



Pixu's Dyna:mo, 1832. 



Pixii made an improvement by rotating a permanent magnet in the 

 neighborhood of coils of wire mounted on a soft iron core. A com- 

 mutator rectified the alternating current generated into direct cur- 

 rent. This dynamo is in the collection of the Smithsonian Institution. 



horseshoe magnet. He also made a commutator so that the machine 

 produced direct current. None of these machines gave more than 

 feeble current at low pressure. The large primary batteries that had 

 been made were much more powerful, although expensive to operate. 

 It has been estimated that the cost of current from the 2000-cell 

 battery to operate the demonstration of the arc light by Davy, was 

 six dollars a minute. At present retail rates for electricity sold by 



