§ 564. THE DEPTHS OF THE OCEAN. 307 



the surface, echo was silent, and no answer was received from the 

 bottom. Ericsson and others constructed deep-sea leads having 

 a column of air in them, which, by compression, would show the 

 aqueous pressure to which they might be subjected. This was 

 found to answer well for ordinary purposes, but in the depths of 

 the sea, where the pressure would be equal to several hundred 

 atmospheres, the trial was more than this instrument could stand. 

 Mr. Baur, an ingenious mechanician of Kew York, constructed, 

 according to a plan which I furnished him, a deep-sea sounding 

 apparatus. To the lead was attached, upon the principle of the 

 screw propeller, a small piece of clock-work for registering the 

 number of revolutions made by the little screw during the de- 

 scent ; and, it having been ascertained by experiment in shoal wa- 

 ter that the apparatus, in descending, would cause the propeller 

 to make one revolution for every fathom of perpendicular descent, 

 hands provided with the power of self-registration were attached 

 to a dial, and the instrument was complete. It worked beautifully 

 in moderate depths, but failed in blue water, from the difficulty 

 of hauling it up if the line used were small, and from the difficulty 

 of getting it down if the line used were large enough to give the 

 requisite strength for hauling it up. An old sea-captain proposed 

 a torpedo, such as is sometimes used in the whale fishery for blow- 

 ing up the monsters of the deep, only this one was intended to ex- 

 plode on touching the bottom. It was proposed first to ascertain 

 by actual experiment the rate at which the torpedo would sink, 

 and the rate at which the sound or the gas would ascend, and so, 

 by timing the interval, to determine the depth. This plan would 

 afford no specimens of the bottom, and its adoption was opposed 

 by other obstacles. One gentleman proposed to use the magnetic 

 telegraph. The wire, properly coated, was to be laid up in the 

 sounding-line, and to the plummet was attached machinery, so 

 contrived that at the increase of every 100 fathoms, and by means 

 of the additional pressure, the circuit would be restored, somewhat 

 after the manner of Dr. Locke's electro-chronograph, and a mes- 

 sage would come up to tell how many hundred fathoms up and 

 down the plummet had sunk. As beautiful as this idea was, it 

 was not simple enough in practical application to answer our pur- 

 poses. 



564. Greater difficulties than any presented by the problem of 



