474 Messrs. Carpenter, Jeffreys, awe? Thomson [Nov. 18, 



perature of the deepest parts of the great Southern Ocean even below that 

 of the North-Atlantic Sea-bed. Now so far as our present knowledge 

 extends, both these inferences are in accordance with fact ; for it is well 

 known to Navigators that in all the Southern Oceans there is a perceptible 

 "set" of warm surface-water towards the Antarctic Pole (this "set" being 

 so decided in one part of the Southern Indian Ocean as to be compared 

 by Capt. Maury to the Gulf-stream of the North Atlantic) ; and it is ob- 

 vious that such a constant flow of surface-water cannot be maintained 

 without an equivalent flow of deeper water in the opposite direction. Of 

 the great depression of temperature which would be produced by such an 

 unrestricted spread of frigid water over the deeper parts of the Southern 

 Oceanic basins, indications are afforded by the deep Temperature-soundings 

 taken in Sir James C. Ross's Antarctic Expedition, the Voyage of the 

 * Venus,' &c. ; for when, as in several of these observations, the indicated 

 Temperature was from 39° to 36° at depths greater than 1500 fathoms, the 

 probable correction for pressure would reduce these to actual temperatures 

 of from 32° to 29°, or even lower. 



122. It would appear from the foregoing considerations that the Tem- 

 perature of the Deep Ocean will everywhere depend upon the amount of 

 Frigid water which can find its way from the Polar towards the Equatorial 

 area ; and that this will be mainly regulated by the Distribution of Land 

 and Water, any considerable alteration in which may produce a wide- 

 spread general change of submarine climate over vast areas, besides modify- 

 ing, in the manner already pointed out (§ 105), the distribution of sub- 

 marine climate over the parts of the Sea-bed traversed by special Polar or 

 Equatorial Polar currents. And thus great additional force is added to the 

 remark made in the 'Lightning' Report (p. 194) that a considerable 

 modification of Submarine Climate might depend upon alterations in 

 the contour of the land, or on the level of the sea-bottom, at a great 

 distance. For when the South Polar basin was in great part shut in by 

 the Antarctic Continent which (as appears from Dr. Hooker's Botanical 

 researches) must have formerly united South America, New Zealand, and 

 Australia, the Deep-sea temperature of the Southern Oceanic area generally 

 must have been higher by some degrees than we have reason to believe it to 

 be at present ; whilst, on the other hand, if there ever was a time when the 

 present North Pacific Area had a more free communication with the Arctic 

 Basin than the present narrow and shallow channel of Behring's Straits 

 affords, its Deep-sea temperature must have been lower by some degrees 

 than it is likely to be found at present. 



123. It is obvious that the distribution of Submarine Climate must 

 exert a most important influence on the distribution of Animal Life ; and 

 of such influence the Deep-sea Dredgings carried on in this Expedition 

 through a wide Geographical range have afforded most convincing evidence ; 

 as will be fully set forth in the Second Part of this Report. For many 

 species of Mollusca, Crustacea, and Echinodermata previously supposed to 



