IO8 THE SCIENTIFIC PAPERS OF 



over a capstan-wheel, by which io is drawn through the three 

 machines, notwithstanding the retarding form applied to the 

 numerous hemp strings constituting the strength of the cable. In 

 passing away from the capstan- wheel, the extended hemp strings 

 would naturally shorten to their original length ; but are prevented 

 by the tight grasp of the metal sheathing. For the same reason 

 they are not at liberty to shrink, when the cable is immersed in 

 water. 



This cable has no tendency to untwist. Its extension, with 

 half the breaking strain upon it, does not exceed 0*3 per cent., 

 and being very strong, and of only double the weight of water, it 

 will support from 7 miles to 8 miles of its own weight in the sea. 



Considering that good ship's sheathing lasts from ten years to 

 twelve years, when the ship is at rest, and that this cable has a 

 double layer of metal, with hardened tar between the layers, it ap- 

 pears not unreasonable to suppose that the sheathing will last, at 

 the tranquil bottom of the ocean, not less than from twenty years 

 to thirty years. Several short lengths of this cable are now being 

 tried, under various circumstances, and the results, so far as they 

 go, promise to be very successful upon a larger scale. 



In conclusion, the author wishes to acknowledge the valuable 

 assistance he has received, in preparing the statistical portion of 

 this paper, from Messrs. Loeffler and Deede, electricians in the 

 employ of Messrs. Siemens, Halske, and Co. 



The paper is illustrated by a series of diagrams, from which 

 Plates 6 and 7 have been compiled. 



In the discussion of the paper, 



MR. C. "W; SIEMENS, after exhibiting the instruments used in 

 testing the cable, which had been described in his paper, said, that 

 no doubt a much higher rate of working through the Malta and 

 Alexandria line could have been obtained, if the object had simply 

 been to transmit the greatest number of words per minute, irre- 

 spective of other considerations ; but the principal object had been 

 to produce a safe instrument, which, in the hands of an ordinary 

 working clerk, would transmit without failure the greatest number 

 of messages, with the least amount of battery power. The high 

 temperature of the Mediterranean near the African coast, also- 



