ON DEEP-SEA SOUNDING. 387 



KNOWN WITH SUFFICIENT CERTAINTY, THE 

 SOUNDING MACHINE SHOULD BE KEPT GOING. 

 TWO MEN SUFFICE TO WORK IT WHATEVER BE 

 THE SPEED OF THE SHIP. It takes from a few 

 seconds to a minute for the sinker to reach the 

 bottom from the time it is let go, and from a 

 quarter of a minute to four minutes for two men 

 to haul it in, if the depth is from 10 fathoms to 100 

 fathoms. (One man can haul it in though the ship 

 be running at 16 knots, but not quite so quickly 

 nor so uniformly as two.) Thus, it is easy to take 

 a sounding every ten minutes, with an extra hand 

 or two to relieve. Two men can with ease take a 

 sounding every quarter of an hour, and this should 

 be the rule whenever in keeping the machine thus 

 going useful information as to the ship's place can 

 be had. It is not necessary to use a tube every 

 time. The reading shown on the counter at the 

 moment the sinker strikes the bottom allows you to 

 judge the depth surely and accurately enough if you 

 use a tube occasionally. The reading on the counter 

 shows approximately the number of fathoms of 

 wire run out. 1 This may be something nearly 



1 Two turns of the wheel give about a fathom of wire ; but this 

 differs a little according to the quantity of wire on the wheel, and 

 therefore if for any purpose, as for instance taking an up-and-down 

 cast, which may be done in 300 fathoms water or anything less, 

 with the wire ordinarily supplied on the wheel, the counter reading 

 must be corrected according to actual measurements of the circum- 

 ference of the wire-wheel when the sinker is at the bottom and 

 when the wire is wound on again. 



C C 2 



