14 THE SCIENTIFIC PAPERS OF 



In the discussion of tJw Papers 



" ON SUBMERGING TELEGRAPHIC CABLES," by J. A. 

 LONGRIDGE, M. Inst. C.E., and C. H. BROOKS ; and 



"ON THE PRACTICAL OPERATIONS CONNECTED WITH 

 PAYING OUT AND REPAIRING SUBMARINE TELE- 

 GRAPH CABLES," by F. C. WEBB, Assoc. Inst. C.E. ; 



MR. C. W. SIEMENS * said that he had paid considerable atten- 

 tion to this subject. When assisting at the laying of the Mediter- 

 ranean cable from Cagliari to Bona, his brother, Mr. Werner 

 Siemens, had devised an apparatus similar to that just described, 

 to regulate the strain on the cable, as it was paid out. The 

 results were very favourable. It not only enabled the brakesman 

 to regulate the strain upon the cable with great nicety, by the 

 deflection of the weighted lever, which rested with its pulley upon 

 the cable, between the brake-wheel and the stern-pulley, but it 

 overcame, to a great extent, the bad effects arising from the pitch- 

 ing of the vessel. When the vessel pitched, the weight rose, and 

 allowed more cable to run out, so that the pulleys of the brake 

 travelled at a more uniform velocity. 



With reference to the best form for a submarine cable, he con- 

 sidered that there were several questions involved, which required 

 to be balanced against each other. It had been proved satisfac- 

 torily, by the mathematical investigations in the first paper, that 

 a cable of light specific gravity was best suited for laying in great 

 depths. But the cable was composed of several materials. There 

 was the conductor, which, when of copper, had a specific gravity 

 of 11 ; the gutta-percha insulator, nearly equal in weight to sea- 

 water ; and the iron external covering, having a specific gravity 

 of 7. Taking two cables of the same specific gravity : one might 

 have little strength in the covering and a large central core ; 

 while the other might, have a small core and great strength in 

 the external covering. In analysing what produced weight in the 

 cable, there came first the conductor, which, for electrical reasons, 



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

 Vol. XVII. Session 1857-58, pp. 319-321. 



