j:8 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 0. F. MUller (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 expeditious before 1860, though in 1801, Peron 

 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 mthin 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 Httle^ were expanded by his 



