W. P. Trowbridge on Deep Sea Soundings, 159 
Where the time required for the weight and line to sink to the depth 
4 of 3000 fathoms is now one hour and a half, by the method proposed 
: the apparatus might be made to sink to the same depth in fifteen or 
twenty minutes, and to smaller depths in proportionally less time. 
Yours, very respectfully, 
W, P. TROWBRIDGE, 
" Asst. U.S. Coast Survey. 
Coast Survey Office, Washington, D, C., May 31st, 1858. 
ee Lieut. Commanding Joseph Dayman, R. N., have shown that to 
i = - the bottom of the sea is not beyond the power of human ~ 
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equally penetrable at all depths, the laws of which are well 
: known, wend seem to offer aroun hopes of our being able ulti- 
~ mately to determine the depressions of the bottom of the ocean, 
greater number of observations and with greater accuracy, 
than the elevations of continents. * : 
The solution of the question requires that the difficulties 
: wh e been : the present methods of sound- 
| ing, should be clearly determined and overcome, and where 
these methods fail, that they should be improved if possible, or 
W Ones substitutee’ e least reflection that the difficulties are of 
a mechanical nature; not simply practical, for all that skill and 
experience can accomplish has been effected in overcoming the 
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