REPORT ON OCEANIC CIRCULATION. 
11 
the north coast, and the highest, 30 ‘180 inches, over the basin of the Murray Eiver and 
its affluents. From this region the diminution in pressure is uninterrupted to the 
north, even as far as the low-pressure system of Central Asia. Hence, the prevailing 
winds of Australia are essentially an outflow from the high pressure of the interior 
towards the lower pressure of the coasts, particularly the north coast, and these winds 
are S.E. on the north coast, S.W. at Brisbane, W.N.W. at Sydney, N. at Melbourne, 
and N.E. at Adelaide. The high pressure of the south of Australia is continued west- 
wards in the same latitudes through the Indian Ocean. From these latitudes (about 
lat. 30° S.), pressure falls continuously northward to the low pressure of Central Asia, 
and, following inevitably that diminution of pressure, southerly winds sweep across that 
ocean home into Asia. Where they touch the coast after traversing a great extent of 
the ocean, such as the coasts of the Bay of Bengal, they bring with them a heavy 
rainfall, which, from the lowering of the specific gravity thus occasioned, has an 
important retarding effect on the vertical circulation of the ocean there. On the 
other hand, on the northern and western parts of the Arabian Sea, the rainfall is 
exceedingly small, as the winds there have traversed but a small breadth of the ocean, 
and consequently, from the dryness of these winds, the specific gravity is much increased, 
and the vertical circulation becomes thereby accelerated. 
Similarly, as pressure diminishes from about lat. 25° S. in the Pacific uninterruptedly 
to the low pressure of Central Asia, the southerly winds on the south-eastern coasts of 
Asia, after having traversed a wide extent of ocean, pour a heavy rainfall on these 
coasts and outlying islands, thus lowering greatly the specific gravity of the surface 
during the warm months. 
The winds of Europe are determined by the high pressure of the Atlantic in its 
relations to the low-pressure systems of Asia and Africa at this time. On the 
coasts of Spain and North-West Africa the prevailing winds are northerly ; farther to 
the north, on the coasts of France and the British Islands, south-westerly ; and on the 
coast of Norway westerly and north-westerly. The curving of the winds round the 
anti-cyclone of the North Atlantic, from the N.E. off the coast of Africa, to E. and S.E, 
in the region of the West Indies, to S. and finally S.W. off the Eastern States of 
America, has all-important bearings on the circulation of the waters of that ocean. 
The centre of lowest pressure in North America is over the States about Utah, from 
which pressure rises all round, but chiefly to the south-east and west. In accordance 
with this arrangement of the pressure, the winds blow from the Gulf of Mexico home to 
the coasts of the States as southerly winds. On the other hand, the winds on the coasts 
of the Pacific States are N. and N.W. as far north as Vancouver, but over that island, 
and along the coasts to northward, they are S.W. 
From lat. 30° S. to lat. 63° S. pressure, as already explained, diminishes 
uninterruptedly from 30’150 inches to 29 '000 inches, over a broad ring going round the 
