8 
THE VOYAGE OF H.M.S. CHALLENGER. 
this ocean, temperatures have been observed at fifty-five stations, the mean of these 
being 36 0, 4, or 1 0, 2 above the average, thus showing a strikingly marked difference 
between the deep-sea temperature of the Indian Ocean and the South Atlantic on the 
one hand, and the North Atlantic on the other. The two sections of the Pacific Ocean 
where the temperature is above the average do not show any such excess as appears in 
the North Atlantic, the excess above the average being, roughly speaking, about half a 
degree. The mean of the two stations in the China Sea is 36 0, 5, or 1 0, 3 above the 
average. 
In connection with deep-sea temperatures the following facts are interesting. In 
the Arctic Ocean, at a depth of 2005 fathoms, Professor Mohn observed a temperature 
of 29°‘6 in lat. 68’ 21' N. and long. 2 C 5' AV. This position, however, is in a “closed 
area,” shut off from the general oceanic circulation by the Wyville-Thomson Ridge. A 
little to the south of Greenland, at 1860 fathoms, 33 - 4 has been observed ; and ten 
degrees to westwards, at 1750 fathoms, 34 o, 0. To the east of Ceylon, at 2020 fathoms, 
33 0, 9 was observed, lat. 9° N. and long. 85° E., and to north-west of Madagascar, at 
1877 fathoms, a temperature of 33°'5 has been noted. On the other hand, to the east 
of Australia, lat. 19° S. and long. 165° E., at a depth of 2525 fathoms, the temperature 
was found to be 36° - 4. It will be seen, when the bottom temperatures are dealt with, 
that the Atlantic stands alone among the oceans for relatively high temperatures at 
great depths. 
It is remarkable that at the depth of 2200 fathoms the water of the sea falls to its 
lowest temperature off the east of the Argentine Coast of South America, and is nearly, 
if not quite, at its highest off the east coast of North America, thus pointing to very 
diverse conditions in the oceanic circulation off the east coasts of these two continents. 
The striking fact is that deep-sea temperatures in all latitudes, equatorial as well as 
polar, are uniformly low, and, except in a few restricted regions, do not differ from each 
other more than about two degrees. The exceptional regions are where the Sea of 
Okhotsk meets the ocean ; the whole of the deep water immediately to the east of South 
America from Cape St Roque to Grahame’s Land, in Antarctica; and, in a less degree, 
the southern portion of the Indian Ocean. It is also to be noted that the lowest deep- 
sea temperatures are found in those parts of the ocean which lie in the Southern 
hemisphere, and that, on the whole, higher temperatures are encountered as we recede 
from the Antarctic region. It may also be pointed out that the lower deep-sea 
temperatures extend farther to the north from the Southern Ocean, just over those 
depths of the sea which appear to have, and probably do have, a direct communication 
wdth the south ; that is, are not cut off by any intervening submarine ridge separating 
them from the cold waters of Antarctica. 
There can be no doubt that these very low deep-sea temperatures have their origin 
in the Southern or Antarctic Ocean, the icy-cold waters of which are propagated north- 
