THE DEPTHS OF THE OCEAN. 201 



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 constructed deep- 

 sea leads having a column of air in them, which, by compression, 

 would show the aqueous pressure to which they might be subject- 

 ed. This was found to answer well for ordinary purposes, but in 

 the depths of " blue water," where the pressure would be equal to 

 several hundred atmospheres, the trial was more than this instru- 

 ment could stand. 



Mr. Baur, an ingenious mechanician of New 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 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 

 hauhng 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 re- 

 quisite strength for hauling up. 



424. But, notwithstanding these failures, there was encourage- 

 ment, for greater difficulties had been overcome in other depart- 

 ments of physical research. Astronomers had measured the vol- 

 umes and weighed the masses of the most distant planets, and in- 

 creased thereby the stock of human knowledge. Was it credita- 

 ble to the age that the depths of the sea should remain in the cat- 

 egory of an unsolved problem ? It was a sealed volume, abounding 

 in knowdedge and instruction that might be both useful and profit- 

 able to man. The seal which covered it was of rolling waves 

 many thousand feet in thickness. Could it not be broken ? Cu- 

 riosity had always been great, yet neither the enterprise nor the 



