A /A 1 WILLIAM SIEMENS, F.R.S. 



I I 



A delicate galvanometer was placed with its battery at the end 

 stations, in succession, and the degree of deflection observed. The 

 amount of deflection was inversely as the resistance, and the 

 latter was composed of the resistance of the line wire to the place 

 of leakage, the resistance in the imperfect medium of insulation 

 through which the current escaped into the earth, and finally 

 in the resistance of the earth and battery. The two latter re- 

 sistances would in both cases be the same, and the difference of 

 deflection was, therefore, solely owing to a difference of resistance in 

 the two sections of line wire, which, by Ohm's law, gave a measure 

 of their respective length. 



In the discussion of tlw Paper 



"ON SUBMARINE ELECTRIC TELEGRAPHS," 

 By F. R. WINDOW, 



MR. C. W. SIEMENS* observed, that the subject under discussion 

 involved two principal questions, which should be discussed sepa- 

 rately, namely, the mechanical one of insulating, shielding, and 

 submerging the metallic conductor, and the electrical question of 

 transmitting messages through it when laid. 



The first question had been treated by the author of the paper, 

 and by most of the previous speakers, purely from a historical point 

 of view ; and some erroneous statements had been made, which it 

 was important to correct. The non-conducting property of gutta- 

 percha was discovered, in 1846, by Mr. Werner Siemens, of Berlin. 

 Being appointed a member of a Royal Commission, charged with 

 devising a plan for the establishment of electric telegraphs in 

 Prussia, he proposed, in the spring of 1847, the adoption of under- 

 ground line wires, coated with gutta-percha. In the autumn of 

 the same year, he completed the first experimental line of twenty 

 miles in length, between Gros Beren and Berlin, which was found 



* Excerpt Minutes of Proceedings of the Institution of Civil Engineers, Vol. 

 XVI. Session 1856-1857, pp. 218-220. 



