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. 8. 
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 Platt of the U. 8. schooner “ Albany,” with 
cod-line and a heavy sinker, applied 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 eup 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 
1 The accuracy of the deepest sounding 
made by Commander Belknap has re- 
peatedly been questioned by naval au- 
thorities, because the wire broke while 
reeling in, Any one experienced in deep- 
sea sounding with wire must know that 
the depth is accurately recorded on deck 
the moment the wire stops running out, 
and that it is not necessary to bring up a 
specimen of the bottom to make an ac- 
curate sounding. Lieutenant-Commander 
Brownson brought up a bottom specimen 
from a depth only 94 fathoms less than 
that obtained by Commander Belknap. 
