LA YING. DEEP-SEA CABLES. 425 



Forces concerned in the Submergence of a Cable. 



In a paper published in the Engineer Journal 

 in 1857, the speaker had given the differential 

 equations of the catenary formed by a submarine 

 cable between the ship and the bottom, during the 

 submergence, under the influence of gravity and 

 fluid friction and pressure ; and he had pointed out 

 that the curve becomes a straight line in the case 

 of no tension at the bottom. As this is always the 

 case in deep-sea cable laying, he made no farther 

 reference to the general problem in the present 

 address. 



When a cable is laid at uniform speed, on a level 

 bottom, quite straight, but without tension, it forms 

 an inclined straight line, from the point where it 

 enters the water, to the bottom, and each point of 

 it clearly moves uniformly in a straight line towards 

 the position on the bottom that it ultimately 

 occupies. 1 That is to say, each particle of the 

 cable moves uniformly along the base of an isosceles 



1 Precisely the movement of a battalion in line changing front. 



