88 THE SCIENTIFIC PAPERS OF 



effects of earth currents upon the working of submarine telegraphs. 

 It would appear, from Mr. Varley's observations on the former 

 occasion, that the disturbing influence of these currents was very 

 great, whereas, in point of fact, they were of no practical importance. 

 The earth was no doubt a powerful magnet, as was proved by the 

 appearance of the magnetic light at the polar surfaces, but no 

 current would result from the terrestrial magnetism, except at the 

 time of any change occurring in its intensity, and it was well 

 known that these changes took place only very gradually. In 

 making the necessary arrangements for the working of the Malta 

 and Alexandria line, he had made no provision against earth 

 currents, and the fact that the battery power in working this line 

 had been limited to eight cells was the best proof that no such 

 provision was necessary. 



In the discussion of the Paper 



"ON THE ART OF LAYING SUBMARINE CABLES 

 FROM SHIPS," by Capt. J. SELWYN, R.N. 



ME. C. W. SIEMENS * said they must all feel much indebted to 

 Capt. Selwyn for having brought this subject so fully and ably 

 before them. He (Mr. Siemens) could not, however, go so far as 

 to say he entirely agreed with him in all his statements. The 

 curve made by the cable while being laid was no doubt a very im- 

 portant consideration in dealing with this subject, and he did not 

 agree with Capt. Selwyn that its form was such as he had described 

 it to be. He thought it was capable of demonstration, that when 

 a ship was proceeding at a uniform rate of speed, and paying out 

 a cable of fixed density, the latter must descend in a direct inclined 

 plane. Capt. Selwyn had stated that the moment the cable left 

 the ship it would commence its downward course, at the rate of 



* Excerpt Journal of the Society of Arts, Vol. XIII. 1864-65, p. 434. 



