DEEP-SEA SOUNDING 23 



the sounding is taken. As the drum revolves it works 

 an arrangement of cog-wheels, by which the exact 

 amount of wire paid out is registered in units, tens, 

 and hundreds of fathoms, on a series of dial plates. 

 When not in use, the whole machine with its reel 

 of sounding-wire occupies about as much space as 

 an ordinary travelling trunk, exclusive of the pipes 

 which, when it is in action, convey the motive steam- 

 power from the engine-room. 



The sounding-rod is a metal cylinder, about 2J 

 feet long, and about as stout as an old gentleman's 

 Malacca walking-cane. Its lower part is hollow, for 

 sticking in and bringing away a sample of the ocean 

 bottom, after the manner of a cheese-taster s gouge ; 

 its upper part is solid and ends in a ring, through 

 which the sounding-line is rove. 



The sounding-rod must be light, otherwise a wire- 

 line would never be strong enough to haul it in from 

 a great depth ; but it is equally essential that it should 

 be heavy, otherwise it would never reach the bottom. 



These two conflicting requirements are reconciled 

 by weighting the sounding-tube with heavy sinkers, 

 which carry it to the bottom quickly, and then auto- 

 matically disengage themselves and leave it free to be 

 hauled up alone. Simple as it is, I shall not attempt 

 to describe the mechanism by which the sinkers detach 

 themselves when the sounding-tube strikes the bottom. 

 However, the ordinary reader will understand the 



