REPORT ON OCEANIC CIRCULATION. 
33 
temperature of 53° is now liiglier than any observed in the Pacific or South Atlantic, 
but is 10° lower than the highest in the North Atlantic near Bermuda. Again the 
lowest temperature, viz., 45°, is to the north of Australia, being only 0°'3 above the 
general mean. 
At 400 fathoms the highest temperature continues to be found near Cape G-uardafui, 
being, of course, due to the outflowing undercurrent from the Red Sea. The whole 
ocean is above the general mean, the lowest temperature being still to the north of 
Australia, but the highest, 50°, with the large extent of high temperature surrounding 
it, has now moved bodily a considerable distance to the south-west, so that the central 
position which, at 100 fathoms, was al)out lat. 18° S. and long. 90° E., is now in lat. 
34° S. and long. 60° E. 
From 500 to 800 fathoms substantially the same features characterise the 
temperature distribution of this ocean — a relatively high temperature in the Arabian Sea, 
another region of high temperature well to the south-west of the ocean, a region of 
lowest temperature between, extending from the north of Australia westwards, and a 
temperature much higher than is found in the Pacific or South Atlantic, but lower 
than the highest of the North Atlantic. 
The high temperature of the Atlantic is mainly brought about by the large 
accessions of warm currents poured into it by the South Atlantic and the Mediterranean. 
But as regards the Indian Ocean, no such accessions from other oceans are received, with 
the exception of what is contributed by the Red Sea, and by a surface outflow from the 
Persian Gulf. Now these accessions cannot be regarded as influencing in any 
appreciable degree the region of high temperature near the centre of the ocean. This 
high temperature, as compared with the Pacific and South Atlantic, is in all probability 
due to the circumstance that for the heat generated on the surface in this intertropical 
region there is no escape to northward, but it is, on the contrary, all retained within the 
ocean itself. 
At 900 and 1000 fathoms the Indian Ocean and South Atlantic have nearly the 
same temperature, both in this respect being intermediate between the North Atlantic 
on the one hand and the Pacific on the other. 
At 1500 fathoms this is all reversed, the Indian Ocean beino; now the coldest ocean : 
the larger portion is under the average, pointing out that, on account of the low surface 
specific gravity of this ocean taken as a whole, the higher temperature of the upper 
strata is not conveyed to such depths as occurs in the other oceans. Hence, at less 
depths, temperature is higher than would otherwise be the case. The highest temper- 
ature is in the north-west, about the region where, so far down as observations have 
been made, the specific gravity is_ great. 
(I’HYS. CHEM. CHALL. EXP. — PART Vltl. — 1895 .) 
5 
