HOW THE SEA-DEPTHS ARE EXPLORED. 261 



examination, and it became desirable to devise means of bringing up 

 larger amounts of matter. Many contrivances Lave been made for this 

 purpose. Sir John Ross, in 1818, invented a machine for this purpose, 

 called the " deep-sea clamm." A large pair of forceps were kept asun- 

 der by a bolt, and the instrument was so contrived that, on the bolt 

 striking the ground, a heavy iron weight slipped down a spindle and 

 closed the forceps, which retained within them a considerable quantity 

 of the bottom, whether sand, mud, or small stones. By this arrange- 

 ment Sir John Ross brought up six pounds of soft mud from a depth 

 of 6,300 feet. 



Fig 3. 



Mabset's Sounding-Machine. 



In the year 1854, J. M. Brooke, passed midshipman in the United 

 States Navy, contrived the arrangemeut known as " Brooke's Deep-Sea 

 Sounding- Apparatus," of which all the more recent contrivances have 

 been to a great extent modifications and improvements, his funda- 



