[ 221 ] 

 XXXII. Intelligence and Miscellaneous Articles. 



ON SOME EXPERIMENTS INSTITUTED TO SUPPLY ALL THE LINES 



TERMINATING AT THE CALCUTTA TELEGRAPH-OFFICE WITH 



CURRENTS TAPPED FROM THE MAIN CURRENT PRODUCED BY 



A DYNAMO-ELECTRIC MACHINE. BY LOUIS SCHWENDLER, 



ESQ., M.I.C.E., ETC. 

 1X/TR. SCHWEjNTXLEB, gave an outline of his paper explaining 

 -*-*-*■ the latest experiments he had made in order to prove the 

 practicability of his new method of supplying signalling currents. 

 This method was published in the Journal of the Asiatic Society, 

 part 2, vol. xlix. 1880, and in the Philosophical Magazine, No. 52, 

 December 1879, Supplement. After certain incidental delays, the 

 final trial came oh 2 on Sunday the 29th August, 1880. 



One of the dynamo-electric machines employed for lighting the 

 sheds at Howrah Railway-station, produced the required strong 

 main current ; and the signal currents were conveyed from Howrah 

 to the Calcutta Telegraph Office by an ordinary telegraph-line 

 about 2 miles in length. 



In all eleven long main circuits were supplied with telegraph- 

 currents in this manner, viz. the lines to Bombay, Madras, Kurrachee, 

 and Eangoon. The currents sent from Calcutta and the currents 

 received at the out-stations were measured ; and by it the satisfactory 

 result was established that in all the lines, even in the longest, 

 the tapped or machine currents were considerably stronger than the 

 currents produced by the ordinary signalling-batteries at present 

 in use. 



The trial lasted for three hours, under the direct supervision of 

 Mr. C. B. P. Grordon, the Superintendent of the Bengal Division, 

 who carefully watched the working of the office. The traffic was 

 despatched with regularity in the ordinary manner. 



At the beginning of the trial the main current was produced 

 through an iron wire of 0*21" diameter, offering a resistance of 

 1*5 B.A. unit. This main current was carefully measured, and 

 found to be equal to 36801 millioersteds. At the end of the trial 

 the main current was produced through the arc of an electric lamp, 

 giving a light of about 6000 standard candles when measured under 

 an angle of 45° with the horizon. In this latter case the main 

 current amounted to 45706 millioersteds *. 



The total current tapped from the main current (when all the 

 eleven lines were simultaneously sending) equalled 129 milli- 

 oersteds, quite an insignificant fraction of the large main current. 



Mr. Schwendler stated that this practical trial of the method had 

 shown that it was perfectly reliable, and no practical telegraph- 

 engineer would doubt that it was very convenient to produce the 

 currents in this manner. It was therefore under consideration 

 to introduce the system at the Calcutta office. Mr. Schwendler 

 concluded his paper with some suggestions for utilizing the larger 

 portion of the current not required for telegraph-purposes, saying : — 



* One oersted is equal to one weber per second. One millioersted is 

 equal to one milliweber per second. 



Phil. Mag. S. 5. Vol 11. No. 67. March 1881. R 



