of Duplex Telegraphy. 119 



None of the above methods, however, came to have ex- 

 tended, or indeed any, practical application. They appear to 

 have been attempted doubtingly and without .confidence; and 

 although the trials are generally reported to have been suc- 

 cessful, yet the methods were rejected as impracticable, and 

 came to be regarded as merely of scientific interest*. 



Only recently, after a torpid existence of almost twenty 

 years, has duplex telegraphy been revived, and come to be the 

 leading topic in telegraphy, securing after such a lapse of 

 time the amount of public interest it rightly deserves. 



To Mr. Stearns, an American telegraph-engineer, is due 

 the honour of having appreciated the real value of duplex tele- 

 graphy, and of having (by giving the system, modified by im- 

 provements of his own, an extended application on the lines of 

 the United States) proved its thorough practicability. 



Inquiry into the Causes which have delayed the introduction of 

 the System. 



When Steinheil in 1837 announced his discovery of the feasi- 

 bility of employing the earth to complete the electric circuit in- 

 stead of a return-wire, telegraph-engineers immediately recog- 

 nized its immeuse mercantile value, and did not delay to verify 

 his results. 



Now, in the career of telegraphy, the invention of duplex work- 

 ing ranks second only in importance to SteinheiPs discovery. 

 The utilization of the earth reduced by one half the number of 

 wires requh-ed to carry a given traffic : duplex telegraphy again 

 almost halves this number. In the face of this fact it is not easy 

 to understand why the one idea received immediate and universal 

 application, while the other, of only about ten years more recent 

 date, has met, until now, with universal neglect; but on closer 

 examination it will be found that there have been perfectly com- 

 prehensible, although not all rational, influences at work. 



An inquiry into the circumstances, therefore, that have caused 

 the discovery of a system, the introduction of which must mark 

 the second great era in telegraphy, to lie fallow for nearly twenty 

 years is of the utmost interest, and canuot fail to be instructive 

 with regard to the prospects of future progress. 



From an examination of the methods originally proposed for 

 duplex working, it will be found that they do not in any way 

 essentially differ from those which may now come into actual 

 use. The causes, therefore, which have prevented the intro- 

 duction of the system must be sought for external to the 

 methods. 



* For the light in which duplex telegraphy was regarded till quite lately, 

 see Schellen, Dub, Sabine, Blavier, Kuhn, &c. 



