cHAP. v.] DEEP-SEA SOUNDING. 207 
is required, as in coast-surveying, it is necessary to 
sound from a boat, which can be kept in position by 
the oars and reference to some fixed objects on shore. 
This ordinary system of sounding answers perfectly 
well for comparatively shallow water, but it breaks 
down for depths much over 1,000 fathoms. The 
weight is not sufficient to carry the line rapidly and 
vertically to the bottom; and if a heavier weight be 
used, ordinary sounding line is unable to draw up its 
own weight along with that of the lead from great 
depths, and gives way. No impulse is felt when the 
lead reaches the bottom, and the line goes on running 
out, and if any attempt be made to stop it it breaks. 
In some eases bights of the line seem to be carried 
along by submarine currents, and in others it is 
found that the line has been running out by its own 
weight only, and coiling itself in a tangled mass 
directly over the lead. All these sources of error 
vitiate very deep soundings. In many of the older 
observations made by officers of our own navy and 
of that of the United States, the depth returned 
for many points in the Atlantic we now know to 
have been greatly exaggerated; thus Lieutenant 
Walsh, of the U.S. schooner ‘ Taney,’ reported a 
cast with the deep-sea lead at 34,000 feet without 
bottom ;* Lieutenant Berryman, of the U.S. brig 
‘Dolphin,’ attempted unsuccessfully to sound mid- 
ocean with a line 39,000 feet long;* Captain 
Denham, of H.M.S. ‘ Herald,’ reported bottom in the 
1 Maury’s Sailing Directions, 5th edition, p. 165, and 6th edition 
(1854), p. 213. 
2 Maury, Physical Geography of the Sea. Eleventh Edition, 
p. 309. 
