JOURNAL 



OF THE 



ASIATIC SOCIETY OF BENGAL 



Part II.— PHYSICAL SCIENCE. 



No. I.— 1880. 



I. — On a Simple Method of using mv insignificant Fraction of the Main 

 Current produced hy a Dynamo-Electric Machine for Telegraph Fur- 

 poses. — JBy Louis Sghwendlek, M. Inst. C. E. &e. 



("jRcceived 29tli October ; read November 5th, 1879.) 



The currents -wliicli a dynamo-electric machine is able to generate 

 through a small external resistance, are so enormously strong and also so 

 constant and exceedingly cheap, that I have always thought it would be 

 of technical as well as of economical importance to use them for signalling 

 purposes. The difficulty only was how to solve the problem practically. 

 Manifestly, the currents could not be produced through the telegraph lines, 

 in the ordinary manner of applying dynamo-electric machines, for, in the 

 first place, telegraph lines offer high resistance, and, in the second place, 

 the use of the closed-circuit system would become imperative. However, 

 some time ago a very simple method occurred to me which appears to con- 

 tain the germs of practical success, and, having lately made some experi- 

 ments on the subject, I do not hesitate to communicate the result. 



Suppose we have a dynamo-electric machine, the two terminals of 

 which are connected by a resistance r through which any kind of useful 

 work is to be performed by the current. 



For instance, during the night, r may consist of an electric arc, and the 

 useful work done by the current is given out as light for the signalling 

 office ; or during the day-time r may consist of another dynamo-electric 

 machiuc which acts as an ordinary electromagnetic engine, performing 

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