LA YING DEEP-SEA CABLES. 429 



cable slipping down through the water, on which 

 the longitudinal friction operates, to reduce the 

 egress strain to the very safe limit formed in the 

 recent expedition. In estimating its amount, even 

 if the slope were as much as I in 5, we should 

 commit only an insignificant error, if we supposed 

 it to be simply equal to the weight of the cable in 

 water, or about 14 cwt. per mile for the 1865 

 Atlantic cable. The transverse component velocity 

 to which this is due may be estimated with but 

 insignificant error, by taking it as the velocity of a 

 body moving directly to the bottom in the time 

 occupied in laying a length of cable equal to the 17 

 miles of oblique line from the ship to the bottom. 

 Therefore, it must have been about 2 miles in 

 17 -v- 6J = 2*6 1 hours, or *8 of a mile per hour. It is 

 not probable that the actual motion of the cable 

 lengthwise through the water can affect this result 

 much. Thus, the velocity of settling of a horizontal 

 piece of the cable (or velocity of sinking through 

 the water, with weight, just borne by fluid friction) 

 would appear to be about '8 of a mile per hour. 

 This may be contrasted with longitudinal friction 



