WILLIAM SIEMENS, F.R.S. 83 



by heat, that it wag affected chemically by every current that 

 passed it, and that it frequently contained cavities. The passage 

 of electricity through gutta-percha was due, not to its con- 

 ductivity, but to a slight decomposition of the water which it 

 contained. The consequence was, that in places where the thick- 

 ness of the covering was much reduced by any accidental cause, a 

 fault would gradually be produced by the electrolytic action of the 

 currents employed. He was, therefore, a strong advocate of low 

 battery power, so long as gutta-percha was employed for the insu- 

 lating medium ; and his instructions to the electrical staff pro- 

 ceeding to Rangoon were, that not more than 22 Daniell's cells 

 should ever be used. India-rubber possessed a much higher 

 power of resistance to electricity than gutta-percha. "Wray's 

 mixture, composed of india-rubber, shellac, and powdered flint, 

 and other compounds of india-rubber possessed valuable properties 

 as insulating materials. He had made some attempts to combine 

 them in a cable, but he should refrain from entering further into 

 this question, for his present object was rather to inquire into the 

 causes of failure of the cables hitherto laid, than to consider the 

 comparative merits of new projects. 



In answer to the PRESIDENT, MR. SIEMENS stated, that the 

 Red Sea telegraph was worked between Aden and Suez from the 

 summer of 1859 till February, 1860. 



MR. C. W. SIEMENS, in answer to a question from the PRESI- 

 DENT, replied, that the testing of the cable had been continued on 

 board the Queen Victoria, with results confirming his previous 

 statements. Unless the cable was effectually cooled by pumping cold 

 water over it daily, the heat increased at the rate of about 3 Fahr. 

 per day. Considering that the weight of cable on board that 

 vessel amounted to more than 1,000 tons, it was evident that the 

 amount of heat generated daily was considerable, and that very 

 effective measures would have to be adopted if it was to reach its 

 destination in safety. 



MR. C. W. SIEMENS, in answer to the PRESIDENT, said that 

 recently, the Quern Victoria, which carried the Rangoon cable, 

 had been wrecked, and the hold being filled with water, the cable 



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