MUEKAY— DEPTH AND MARINE DEPOSITS. 365 



200 fathoms. — At a depth of 200 fathoms the distribution of temperature in the Indian 

 Ocean is most interesting, nearly the whole of the ocean north of lat. 40° S. being above 

 the mean for the whole ocean, viz. 50°'l F. The region of highest temperature (61° F.) 

 remains at the same place as at 100 fathoms, and the lowest temperature (50° F.) is 

 situated to the north-west of Australia, where also occurs at 100 fathoms a secondary 

 minimum. The temperature is also high in the west of the Arabian Sea. 



ZOO fathoms. — At a depth of 300 fathoms the entire Indian Ocean north of lat. 40° S. 

 is again above the mean for that depth for tbe whole ocean, viz. 44° •? F., the absolute 

 highest temperature (55° F.) being near Cape Guardafui. But thehigliest temperature in 

 the ocean proper is 53° F., the position of which is now fully ten degrees of longitude to the 

 westward of its position at 100 and 200 fathoms. The lowest temperature (45° F.) is 

 again to the north of Australia. 



4<00 fathoms. — At a depth of 400 fathoms the highest temperature continues to be found 

 near Cape Guardafui, being of course due to the overflowing undercurrent from the Red 

 Sea. The whole ocean is above the general mean, viz. 41° '8 F., the lowest temperature 

 being still to the north of Australia, but the highest temperature (60° F.), 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 about lat. 18° S. 

 and long. 90° E., is now in lat. 34° S. and long. 60° E. 



500 to 800 fathoms. — From 500 to 800 fathoms substantially the same features 

 characterise the temperature distribution of the Indian Ocean — a relatively higli 

 temperature in the Arabian Sea, another region of high temperature well to the 

 south-west of the ocean, and a region of lowest temperature between, extending from 

 the north of Australia westwards. 



The Indian Ocean receives no accessions from other oceans except what is contributed 

 by the Red Sea and by a surface outflow from the Persian Gulf. 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 is in all probability 

 due to the circumstance that for tlie heat generated on the surface in this intertropical 

 region there is no escape to northwrard, bat it is, on the contrary, all retained w ithin the 

 ocean itself. 



900 and 1000 fathoms. — At 900 and 1000 fathoms the Indian Ocean and the South 

 Atlantic Ocean have nearly the same temperature, both in this respect being intermediate 

 between the North Atlantic Ocean on the one hand and the Pacific Ocean on the other. 



1^00 fathoms. — At 1500 fathoms this is all reversed, the Indian Ocean being at this depth 

 the coldest ocean ; the larger portion is under the general mean, viz. 35° 3 F., 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 the temperature is higher than would otherwise be the 

 case. The highest temperature is in the north-west, about the region where, so far down 

 as observations have been made, the specific gravity is great. 



2200 fathoms. — Everywhere over the Indian Ocean at a depth of 2200 fathoms the 

 temperatures are under the general mean for this depth, viz. 36° '2 F. There are twenty 



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