64 NOTES ON DEEP SEA SOUNDINGS. 



Polar seas the temperature goes on increasing in depth till it 

 reaches 39° may now be disposed of." He attributes that notion 

 to the effect of pressure on the thermometers used by D'Urville 

 and Sir James Koss. He argues that the warmth of the sub- 

 surface stratum can have no local source. Captain Nares found, 

 between 13th and 25th February, a slightly colder climate in 64° 

 S. latitude than is found in August in the Arctic seas in 74° N. ; 

 and Dr. Carpenter argues from this that, as the atmosphere in the 

 winter tends to keep down the surface warmth, the temperature 

 of from 30° to 34° must have come from a lower latitude, and 

 JNares regards it as " evidently the continuation towards the cold 

 regions of the main oceanic flow of water." Dr. Carpenter sees 

 that, as there is no " G-ulf Stream " in the Antarctic area, the 

 warm water of the underlying stratum shows the tendency of 

 the upper stratum to the Pole, which is the result of indraught 

 produced by the downward movement in the Polar area by the 

 effect of surface cold. Any interruption of this descent is 

 purely local and temporary, being limited to the margin of the 

 ice-region in a brief summer season. 



Dr. Carpenter considers the passage of the " Challenger" from 

 the Antarctic ice to Melbourne peculiarly instructive, especially 

 between 58° 55' S. and 108° 35' E. and Cape Otway, in 38° 50' S. 

 and 143° 37' E. On the 3rd March, at the former position, the 

 surface temperature of 37°'2 was gradually reduced to 36° - 6 at 60 

 fathoms ; then to 33° at 70 fathoms ; the temperature from that 

 to the bottom, in 1,950 fathoms, being 31°, only 2° lower. In the 

 next sounding, on 7th March, in 50° 1' S., and 123° 4' E., the surface 

 being at 45°, the Isotherm of 40° was found to be at 250 fathoms, 

 and that of 35° at about 1,000 fathoms ; the bottom at 1,800 

 fathoms, being 32°5. On 10th March, in 47° 25' S., the 

 isotherm of 45° had sunk to about 450 fathoms, that of 40° to 

 about 600, and that of 35° to 1,350 ; the bottom being, in 2,150 

 fathoms, at 33°3. 



As the Australian coast was neared, the temperature of the 

 surface gradually increased. Comparing this with the sections 

 in the Southern Indian Ocean and the South Atlantic under 

 nearly the same parallels, the thickness above the isotherm of 

 40° is noticeable, but especially so in the stratum between 45° 

 and 50°, which thus corresponds with the stratum between 55° 

 and 60° in the western portion of the North Atlantic under cor- 

 responding parallels. This Dr. Carpenter considers to be due to 

 " an extension of the East Australian current, which is the 

 southward prolongation of the southern portion of the Pacific 

 Equatorial." 



We are thus brought face to face with the effects of the 

 current which sets southwards along our coast, frequently with 

 rapidity, between Moreton Bay and Cape Howe, and by which, 



