THREE CRUISES OF THE “ BLAKE.” 
2 
fathoms and “no bottom,” or to find, as was found by the 
* Blake" in the Old Bahama Channel, where the current was 
running at the rate of four knots an hour, a depth.of only four 
hundred and fifty fathoms when sounding with wire, on the very 
spot where previous rope soundings indicated eight hundred 
fathoms and “no bottom.” 
This problem of deep-sea sounding was attacked from many 
sides by American, English, and French naval officers, and the 
most successful results were obtained by increasing the weight 
of the sinker in proportion to the size of the line. The line was 
thus gradually diminished in size in order to reduce both its 
weight and the friction, and comparatively accurate soundings 
were made with a stout cod-line and a heavy sinker (one hun- 
dred pounds). This method of sounding had, however, its own 
objections, for it involved the loss of the line, which was not 
strong enough to bring back the sinker, and thus also no speci- 
men of the bottom could be obtained. 
Unsuccessful attempts to sound with wire as a substitute for 
rope were made as far back as 1849, both by English and Amer- 
ican naval officers. Their failures led to ever-renewed efforts to 
improve the methods of sounding with line, and all the recent 
more accurate deep-sea soundings taken with rope or line have 
been made with comparatively small lines weighted with heavy 
sinkers, which caused the line to run out with great velocity. 
This velocity, of course, decreased as the depth increased, and 
the time of reaching the bottom was indicated theoretically by 
an abrupt change, — one practically, however, very difficult to 
observe with great accuracy. Consequently, a good deal of line 
would run out before the certainty of having reached bottom 
became apparent. 
It is to the need of submarine cables that Thalassography ' 
owes its great development. While a knowledge of the depth 
of the sea is one of the first requisites for the laying of cables, 
the character of the bottom is also an important element, and 
an instrument which would bring up a good sample of the bot- 
tom became therefore an absolute necessity. Professor John 
1 The need of some single word to ex- basins has led to the construction of this 
press the science which treats of oceanic term. 
