48 THREE CRUISES OF THE “ BLAKE.” 
of the ocean beds, can only be compared to the highest peaks 
in the Andes and in the Himalaya chain. Similar gigantic pre- 
cipices or depressions have been subsequently discovered. by the 
“ Challenger,” and by Commander Bartlett of the “Blake,” in 
the Western Caribbean, and by Lieutenant-Commander Brown- 
son, off Porto Rico (4,561 fathoms). 
Although replaced in part by the trawl which was first used 
in very deep water by the “ Challenger,” the dredge has played 
a most important part in all except the latest explorations. 
It dates back to O. F. Müller (1779) ; it was used by Forbes 
as modified by Ball in 1838, and with slight modifications by 
all the more recent expeditions. It was, however, little in use 
on the great expeditions before 1860, though in 1801, Péron 
is said to have made casts with it. The Wilkes exploring 
expedition in 1841 also used the dredge. Dr. Stimpson (1853) 
seems to have been the first naturalist to handle it systemati- 
cally within moderate depths in oceanic basins, during the North 
Pacific exploring expedition under Ringgold and Rodgers. 
Now, however, the United States Fish Commission use the 
trawl almost exclusively in deep water. The same practice was 
also observed on the “Blake” expedition, and on the “ Talis- 
man.” The United States Fish Commission and the French 
deep-sea expeditions have adopted for dredging the steel-wire 
rope first introduced for that purpose on board the “ Blake,” 
and it was found greatly to accelerate the trawling operations. 
The publications of the “Depths of the Sea," of the “ Voy- 
age of the Challenger," by Sir Wyville Thomson, of the “ Nar- 
rative" since his death, of “Notes” of the expedition, by 
Professor Moseley, and of * Thalassa," by Dr. Wild, have 
made the public familiar with the work of the English in the 
exploration of the depths of the ocean. But little is known 
even in America of the important part taken by the. United 
States Coast Survey in the solution of the problems of the phy- 
sical geography of the sea, or Thalassography. 
The Coast Survey, during the superintendence of Professor 
Bache, instituted a series of investigations (begun as early as 
1846) on the physical problems of the deep-sea, connected with 
the Gulf Stream, which, little by little, were expanded by his 
