Electricity 



the economy of a hundred years ago, and motive 

 power thus derived is the main source of modern 

 electric currents. In metallurgy there has long 

 been an unwitting preparation for the advent of 

 the electrician, and here the services of fire within 

 the nineteenth century have won triumphs upon 

 which the later successes of electricity largely 

 proceed. In producing alloys, and in the singu- 

 lar use of heat to effect its own banishment, 

 novel and radical developments have been re- 

 corded within the past decade or two. These, 

 also, make easier and bolder the electrician's 

 tasks. The opening chapters of this book will, 

 therefore, bestow a glance at the principal uses 

 of fire as these have been revealed and applied. 

 This glance will make clear how fire and electrici- 

 ty supplement each other with new and re- 

 markable gains, while in other fields, not less 

 important, electricity is nothing else than a 

 supplanter of the very force which made possible 

 its own discovery and impressment. 



[Here follow chapters which outline the chief 

 applications of flame and of electricity.] 



Let us compare electricity with its precursor, 

 fire, and we shall understand the revolution by 

 which fire is now in so many tasks supplanted by 

 the electric pulse which, the while, creates for it- 

 self a thousand fields denied to flame. Copper is 

 an excellent thermal conductor, and yet it trans- 

 mits heat almost infinitely more slowly than it 

 conveys electricity. One end of a thick copper 

 rod ten feet long may be safely held in the hand 

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