430 POPULAR LECTURES AND ADDRESSES. 



by remembering that, according to the previous 

 result, a longitudinal motion through the water at 

 the rate of I mile per hour is resisted by only T Vth 

 of the weight of the portion of cable so moving. 



These conclusions justify remarkably the choice 

 that was made of materials and dimensions for the 

 1865 cable. A more compact cable (one for 

 instance with less gutta percha, less or no tow 

 round the iron wires, and somewhat more iron), 

 even if of equal strength and equal weight per mile 

 in water, would have experienced less transverse 

 resistance to motion through the water, and there- 

 fore would have run down a much steeper slope 

 to the bottom. Thus, even with the same longi- 

 tudinal friction per mile, it would have been less 

 resisted on .the shorter length ; but even on the 

 same length it would have experienced much less 

 longitudinal friction, because of its smaller circum- 

 ference. Also, it is important to remark that the 

 roughness of the outer tow covering undoubtedly 

 did very much to ease the egress strain, as it must 

 have increased the fluid friction greatly beyond 

 what would have acted on a smooth gutta percha 



