CHAP. V. | DEEP-SEA SOUNDING. 931 
have been prosecuting a most careful and elaborate 
survey of their coast-line; and latterly the Coast 
Survey, under the late Professor Bache and the pre- 
sent energetic head of the Bureau, Professor Pierce, 
has pushed its operations into deep water, particu- 
larly in the Gulfstream region north-westwards of 
the Strait of Florida. Dredging operations have 
been conducted most successfully under Count . Pour- 
tales, and it will be seen hereafter that his results 
are a valuable complement and corroboration of our 
own. The Swedish Government has twice executed 
careful soundings in the sea between Spitzbergen and 
Greenland and to the south-west of Spitzbergen ; in 
1860 under the direction of Otto Thorell, and in 
1868 through the Swedish Arctic Exploring Expe- 
dition under Captain Count von Otter of the Royal 
Swedish steamer ‘Sophia.’ In 1869 the Swedish 
corvette ‘Josephine’ sounded and dredged in the 
North Atlantic, taking soundings to the depth of 
upwards of 3,000 fathoms, and discovered the ‘ Jose- 
phine Bank,’ with a minimum depth of 102 fathoms, 
in lat. 36° 45’ N., long. 14° 10’ W. to the north-west 
of the Strait of Gibraltar. The North-German Polar 
expeditions greatly increased our knowledge of the 
Spitzbergen and the Greenland Seas; and finally, 
on December 20th, 1870, the American nautical 
- school-ship ‘ Mercury,’ Captain P. Giraud, crossed the 
Tropical Atlantic to Sierra Leone, which she reached 
on the 14th of February, 1871. She left Sierra 
Leone on February 21st, and soundings and other 
observations were continued till she reached Havan- 
nah on the 13th of April. The object of this ex- 
pedition and the character’ of the observers are 
