MAGNETO-ELECTRIC MACHINES. 55 



CHAPTER VII. 



ARTIFICIAL EXCITATION OF LIGHT BY MAGNETO- 

 ELECTRIC MACHINES. 



"V/TORE than thirty years ago, attempts were 

 made to utilize the excitation of voltaic bat- 

 teries for illumination. The subsequent plan of 

 exciting electric light by revolving magnets has 

 revived hopes of success. Professor Faraday, the 

 originator of this mode of producing electric exci- 

 tation, was employed by the British government 

 to construct for a lighthouse on the shores of the 

 British channel a magneto-electric machine, ope- 

 rated by a steam-engine of three-horse power. A 

 like machine, afterward placed in a lighthouse on 

 the opposite French coast, is described as "making 

 three hundred revolutions per minute, and pro- 

 ducing a light equal to that of nine hundred Car- 

 cel burners." " The lines of the spectrum, and the 

 photographic pictures thereby produced, are equal 

 to those produced by sunshine." 



In this machine, " the heat transmitted by the 

 electric current through a platinum wire of No. 

 1 8 gauge and eight feet long, instantaneously 

 fused the wire. A round file, four inches long 

 and half an inch diameter, was burnt away in five 

 minutes." 



