APPLICATIONS OF THE MICROSCOPE. 123 



from the disturbing effects of currents or ice- 

 bergs. But the number of soundings is not yet 

 sufficient to warrant this deduction"* 



4. More recent investigations, however, set 

 the question finally at rest. In the new edition 

 (the sixth, issued December 1856) of his re- 

 markable work, the Physical Geography of the 

 Sea, Lieutenant Maury informs us that the so- 

 lution of the question has been obtained, mainly 

 through the use of Brooke's Sounding Apparatus 

 and the Microscope. Former modes of sounding 

 the depths of the sea, and of bringing up spe- 

 cimens from the bottom, having proved uncer- 

 tain and unsatisfactory, the idea of a small but 

 strong twine for a sounding-line, and of a cannon 

 ball of 32 or 68 Ibs. for a sinker, was suggested. 

 The idea was improved by Mr. J. M. Brooke of 

 the United States Navy, who proposed a con- 

 trivance, by which the shot, on reaching the 

 sea-bottom, detaches itself from the line, and 

 sends up a specimen of the bottom ; for the 

 shot, having a hole through its centre, is made 

 to run easily on a rod (fixed to the end of the 

 line), which passes through the centre of the 



1 Physical Atlas, note, p. 43. 



