THE DEPTHS OF THE OCEAN. 243 



plummet has ceased to do so. Consequently, there is but little 

 reliance to he placed upon deep-sea soundings of former methods, 

 when the depths reported exceeded eight or ten thousand feet. 



678. Attempts to fathom the ocean, both by sound and press- 

 ure, had been made, but out in " blue water" every trial was only a 

 failure repeated. The most ingenious and beautiful contrivances 

 for deep-sea soundings were resorted to. By exploding heavy 

 charges of powder in the deep sea, when the winds were hushed 

 and all was still, the echo or reverberation from the bottom might, 

 it was held, be heard, and the depth determined from the rate at 

 which sound travels through water. But, though the explosion 

 took place many feet below the surface, echo was silent, and no 

 answer was received from the bottom. Ericsson and others con- 

 structed 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 pur- 

 poses, 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. 



679. Mr. Baur, an ingenious mechanician of New York, con- 

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

 sounding apparatus. To the lead was attached, upon the princi- 

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

 ing the number of revolutions made by the little screw during the 

 descent ; and, it having been ascertained by experiment in shoal 

 water 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. 



680. An old sea-captain proposed a torpedo, such as is some- 

 times used in the whale fishery for blowing up the monsters of the 

 deep, only this one was intended to explode on touching the bot- 

 tom. It was proposed first to ascertain by actual experiment the 



