Submarine Telegraphy . 



117 



this fashion, I quote literally : — " Three hundred and fifty- 

 nautical miles of cable were payed out at 12 - 50 p.m. to-day, 

 and 350 miles were run at 4'50 p.m." Again : " Five hundred 

 nautical miles of cable were payed out at 10*50 a.m. to-day. 

 The distance run was 460 miles." In reading these two tele- 

 grams, it will be observed that, in the first case, 350 miles of 

 cable were payed out soon after mid-day, but that it took four 

 hours longer before the ship had made the same distance from, 

 land. In the second case, we see that at one and the same 

 instant of time, the length of cable payed out was forty miles 

 greater than the distance the ship had traversed — the difference 

 being due to the irregularities of the ocean bed, together with 

 some other deflections from a right line, caused by submarine 

 currents, and the divergence of the ship itself from a perfectly 

 straight course. Moreover, there may be chasms in the sea- 

 bottom not detected by the sounding line, across which the 

 cable would be stretched, in which case the tension of the 

 wires would be such as to render it amenable to many untoward 

 influences. 



Supposing, however, that the bed of the ocean is tolerably 

 even, it may yet lie so far below the level of the surface as to 

 offer very serious obstacles to the successful laying down of a 

 telegraph cable. The new Atlantic cable was constructed with 

 special reference to this source of danger. The deepest water to 

 be encountered in its course between Yalentia Island and New- 

 foundland was 2424 fathoms, or little less than 2-i- miles. Now, the 

 weight of the cable in water is about 14 cwt. per mile. Hence, 



Fig. 1. 



if the cable were delivered freely, and fell nearly perpendicular 

 from the stern of the vessel, there would never be a strain of 

 more than about two tons upon the cable during immersion ; 

 while the breaking strain which it is calculated to bear is 7-f- tons. 

 But it is not likely that the cable would be paid out so easily 



