428 POPULAR LECTURES AND ADDRESSES. 



the motion of this length of cable through it, is 

 therefore about '81 of a cwt. per mile. The longi- 

 tudinal component velocity of the cable through 

 the water, to which this resistance was due, may be 

 taken, with but very small error, as simply the 

 excess of the speed of paying out above the 

 speed of the ship, or about I mile an hour. Hence, 

 to haul up a piece of the cable vertically through the 

 water, at the rate of I mile an hour, would require 

 less than I cwt. for overcoming fluid friction, per 

 mile length of the cable, over and above its weight 

 in water. Thus fluid friction, which for the laying 

 of a cable performs so valuable a part in easing the 

 strain with which it is paid out, offers no serious 

 obstruction, indeed, scarcely any sensible obstruc- 

 tion, to the reverse process of hauling back, if done 

 at only I mile an hour, or any slower speed. 



As to the transverse component of the fluid 

 friction, it is to be remarked that, although not 

 directly assisting to reduce the egress strain, it 

 indirectly contributes to this result; for it is the 

 transverse friction that causes the gentleness of the 

 slope, giving the sufficient length of 17 miles of 



