SCIENTIFIC ADVANTAGES. OF AN ANTARCTIC EXPEDITION. 417 



currents, and our knowledge of the tides would be increased by a 

 systematic series of tidal observations on the shores of Antarctica, 

 where we have at present no observations. The series of scientific 

 observations here mentioned, and others that might be indicated, would 

 fill up many gaps in our knowledge of the physical conditions of these 

 high southern latitudes. 



DEPTH OF THE ANTARCTIC OCEAN. 



In regard to the depth of the ocean immediately surrounding the 

 Antarctic continent we have at present very meager information, and 

 one of the objects of an Antarctic expedition would be to supplement 

 our knowledge by an extensive series of soundings in all directions 

 throughout the Antarctic and Southern oceans. It would in this way 

 be possible, after a careful consideration of the depths and marine 

 deposits, to trace out approximately the outlines of the Antarctic con- 

 tinent. At the present time we know that Eoss obtained depths of 100 

 to 500 fathoms all over the great bank extending to the east of Victoria 

 Laud, and somewhat similar depths have been obtained extending for 

 some distance to the east of Joinville Island. Wilkes sounded in 

 depths of 500 and 800 fathoms about 20 or 30 miles off Adelie Land. 

 The depths found by the Challenger in the neighborhood of the Antarctic 

 circle were from 1,300 to 1,800 fathoms, and farther north the Chal- 

 lenger soundings ranged from 1,260 to 2,600 fathoms. To the south- 

 west of South Georgia, Eoss paid out 4,000 fathoms of line without 

 reaching bottom. In the charts of depth which I have constructed I 

 have always placed a deep sea in this jposition; for it appears to me that 

 Eoss, who knew very well how to take soundings, was not likely to have 

 been mistaken in work of this kind. 



The few indications which we thus possess of the depth of the ocean 

 in this part of the world seem to show that there is a gradual shoaling 

 of the ocean from very deep water toward the Antarctic continent, and, 

 so far as we yet know, either from soundings or temperature observa- 

 tions, there are no basins cut off from general oceanic circulation by 

 barriers or ridges, similar to those found toward the Arctic. 



DEPOSITS OE THE ANTARCTIC OCEAN. 



The deposits which have been obtained close to the Antarctic conti- 

 nent consist of blue mud, containing glauconite, made up for the most 

 part of detrital matters brought down from the land, but containing a 

 considerable admixture of the remains of pelagic and other organisms. 

 Farther to the north there is a very pure diatom ooze, containing a con- 

 siderable quantity of detrital matter from icebergs, and a few pelagic 

 foraminifera. This deposit appears to form a zone right round the 

 earth in these latitudes. Still farther to the north the deposits pass in 

 deep water, either into a Globigerina ooze or into a red clay with 

 manganese nodules, sharks' teeth^ ear bones of whales, and the other 

 SM 97- — 27 



