ELECTROMOTIVE FORCES OF THE ELECTRIC ARC. 323 



derived from the direct-current energy supplied to it, the arc acting as a converter. 

 This fact, that the solid arc is capable, under suitable conditions, of automatically 

 transforming energy derived from a source of direct current into alternate-current 

 energy of any frequency over a wide range, is the explanation of the transformation 

 of energy observed in the Musical Arc recently shown for the first time at the 

 Institution of Electrical Engineers.* 



Effect of Varying the Direct Current. 



Having found that with a sufficiently high frequency it was possible to measure 

 the true resistance of the arc, this resistance was measured for arcs of a fixed length 



120 



S B 7 



Direct Current through Arc. 



* ' Journal of the Institution of Electrical Engineers,' 1901, vol. 30, p. 248. 



2 T 2 



