THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



JULY 1858. 



I. On the Mechanical Conditions of the Deposit of a Submarine 

 Cable. By G. B. Airy, Esq., Astronomer Roijal. 



To the Editors of the Philosophical Magazine and Journal. 



Royal Observatory, Greenwich, 

 Gentlemen, June 16, 1858. 



IN the present state of the enterprise for laying down the 

 Atlantic Submarine Telegraph Cable, and after the failure 

 of last year, it appears desirable to investigate, with the utmost 

 practicable accuracj^, the circumstances of such a cable in the 

 act of deposit ; especially with reference to the tension which its 

 different parts sustain. The problem is by no means simple, as 

 will appear from the following considerations : — 



First, if there were no frictional resistance of water (its in- 

 fluence in diminishing the sensible weight of the cable being 

 always recognized), still the circumstances of what may be called 

 a travelling curve are totally different from those of a fixed 

 catenary, and require an investigation of totally different form. 

 This, however, is not difficult; and the result, as will be seen 

 in the first investigation below, is remarkably simple. 



Secondly, the frictional resistance of the water to the move- 

 ment of the cable is so great as entirely to modify the circum- 

 stances of its deposit. Some time since, I had prepared an 

 investigation of approximate character, on the supposition that 

 the friction is small, when I learnt from good authority that, 

 in consequence of the slcnderness of the Atlantic Cable and the 

 lightness of its materials, its terminal velocity in falling through 

 water would not much exceed three feet per second ; and that 

 the ship's velocity would probably be more than double the 

 terminal velocity of the falling cable. It was impossible after 



Phil. May, S. 4. Vol. 16. No. 104. July 1858. B 



