HISTORICAL SKETCH OF DEEP-SEA WORK. 47 



The earlier deep-sea soundings were made with the usual 

 lines and leads, only somewhat heavier of course ; as the depths 

 increased, the difficulty of ascertaining when bottom had been 

 reached became greater and greater. Attempts were made to 

 sound with wire as early as 1849, by Lieutenant Walsh, U. S. 

 N., and Captain Barnet, R. N., neither of which were successful. 

 An earlier attempt to sound with copper wire, also unsuccessful, 

 was made in 1842 by the United States exploring expedition 

 under Wilkes. 



In 1850 Captain Piatt of the U. S-. schooner " Albany," with 

 cod-line and a heavy sinker, appHed the method of determining 

 the depth by time-intervals as first suggested by Rear Admiral 

 W. R. Rogers. In doing this the line sent out was left behind 

 and the amount of twine lost was considerable, small vessels 

 going out fitted up with 40,000 fathoms of line. In 1854 

 Passed-Midshipman Brooke invented his detacher, so that the 

 line could be hauled in again, and Commander Sands perfected 

 in 1857 a cup which could bring back specimens of the bottom. 

 In 1868 the Hydra machine was invented ; it was in general use 

 by the English navy for deep-sea work till comparatively lately. 

 In 1872 Sir William Thomson invented his machine for sounding 

 with wire, and a new era for accurate deep-sea work commenced. 



Commander Belknap devised a number of improvements in 

 this machine, and thus modified, it was in constant use during 

 the first season of the " Blake's " work. To Belknap belongs 

 the credit, not only of having first demonstrated the possibility 

 of using Sir William Thomson's machine for taking accurate 

 soundings in great depths, but also of having made the deep- 

 est soundings yet taken (off the coast of Japan in 4,655 fath- 

 oms.^ The result has taught us that there are in the ocean, 

 generally not very far from the shore lines, immense depressions 

 of the sea-bottom, which, in their relations to the topography 



^ The accuracy of the deepest soundhig the moment the wire stops ruimiiig out, 



made by Commauder Belknap has re- and that it is not necessary to bring up a 



peatedly been questioned by naval au- specimen of the bottom to make an ac- 



thorities, because the wire broke while curate sounding. Lieutenant-Commander 



reeling in. Any one experienced in deep- Brownson brought up a bottom specimen 



sea sounding with wire must know that from a depth only 94 fathoms less than 



the depth is accurately recorded on deck that obtained by Commauder Belknap. 



