26 BROOKE'S APPARATUS. 



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-registering 

 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." One eccentric old sea captain 

 proposed to sound the sea with a torpedo, or shell, 

 which should explode the instant it touched the 

 bottom. Another gentleman proposed to try it by 

 the magnetic telegraph, and designed an instrument 

 which should telegraph to the expectant measurers 

 above how it was getting on in the depths below. But 

 all these ingenious devices failed, and it is probable 

 that the deepest parts of the ocean-bed still remained 

 untouched by man. 



.At last an extremely simple and remarkably 

 successful deep-sea sounding apparatus was invented 

 by Mr. Brooke, an American officer. It consisted 

 of nothing more than thin twine for a sounding- 

 line, and a cannon ball for a sinker. The twine 

 was made for the purpose, fine but very strong, and 

 was wound on a reel to the extent of ten thousand 

 fathoms. The cannon ball, which was from thirty- 

 two to sixty-eight pounds' weight, had a hole quite 



