Z SUBMARINE CABLE LAYING AND REPAIRING. 



of 301b. to 601b. weight attached. The introduction of this- 

 wire for the purpose is due to Lord Kelvin, who in the year 

 1872 made the first successful deep-sea sounding with wire, 

 recovering all of it from depths of 2,700 fathoms in the Bay of 

 Biscay. These experiments and results were communicated by 

 him to the Society of Telegraph Engineers in 1874 in a Paper 

 entitled " On Deep-Sea Sounding by Pianoforte Wire " {Journal 

 of the Society, Vol. III., 1874). The wire at that time was 

 manufactured only in 100-fathom lengths, and had to be 

 spliced, but is now obtainable in lengths up to 7,000 fathoms 

 without joint. Splices, when required, are made by warming and 

 coating the ends with marine glue, twisting into a long bell- wire 

 joint (about 6ft. long), and then serving over with fine twine. 



The sounding tube (for bringing up samples of the bottom) 

 and sinker are attached to the end of the line, a few fathoms 

 of hemp line being interposed between the sinker and the 

 end of sounding wire to avoid the latter coiling and kinking 

 when the weight strikes bottom. The sinker is either detached 

 by a self-acting trigger on striking bottom, or drawn up 

 again with the wire, according to convenience and the time afr 

 disposal. The quickest way is to use a heavy sinker and 

 release it at the bottom. By adjusting the brake the wire 

 can then be run out at about 100 fathoms per minute,, 

 reaching, say, 2,000 fathoms depth in 20 minutes. The sinker 

 commences to descend at a speed of about 150 fathoms per 

 minute, gradually slackening down to half this speed at 2,000' 

 fathoms. For depths exceeding this the weight of the sinker 

 is usually about 601b. The ship is only hove to during the 

 descent of the wire, and proceeds on her course to the next 

 position immediately bottom is reached, the wire at the same 

 time being reeled in. When it is desired to recover the sinker, 

 as, for instance, when a large number of soundings are being- 

 taken, one of less weight, say 351b., is employed. The speed 

 of descent is then about 70 fathoms per minute, or about 

 half an hour for 2,000 fathoms. The reeling-in with weight 

 attached is done while the ship is under way, slowly for the- 

 first few hundred fathoms. 



If the ship remains hove to while the wire is recovered a 

 complete sounding in 2,000 fathoms, including recovery, can be 

 made in as little time as 40min.; but it saves time to reel in. 



