ANTARCTIC GEOGRAPHY.

New Zealand Times, Volume XXIX, Issue 4205, 11 September 1874, Page 3

ANTARCTIC GEOGRAPHY.

(From the New York Herald, June 15.) From the latest notes of the Challenger expedition, now in the Southern Hemisphere, it appears that the thermal observations have settled another great problem of Antarctic geography. The outflow of a great ocean current from the South Indian Ocean has long been asserted and even recently as stoutly denied by the physical geographers of Europe. The most recent data forwarded by the Challenger put this matter at rest as definitely as' the much-talked-of Wilkes Antarctic Continent, discussed in Lieutenant Hyue’s letter. The Challenger explorers state in their latest reports, published in the London Times, that, after leaving the Cape of Good Hope they entered the Agulhas current, and add: —“The breadth of this stream was about two hundred and fifty miles, and it was found to affect the temperature of the sea to the depth of four hundred fathoms.” We have here the discovered dimensions of a mighty “liver in the ocean,” compared with which the Gulf Stream of the Atlantic is but a rill. The sectional measurements of the Gulf Stream at the Florida Pass do not exceed thirty miles in breadth and three hundred fathoms in depth, so that the Agulhas current, as now gauged by the Challenger, is nearly ten times as large. The temperature of the two oceanic streams is about the same; and the velocity of the Agulhas current is not less than that of the mighty outflow from the Mexican Gulf. As the former passes the port of Natal, it tears violently at the shore—as the Mississippi when in flood—cutting through headlands, carrying away small islands and creating others with the mud it deposits. This broad and sweeping band of superheated water represents the collective force of the South-east trade winds and North-east monsoons, which blow the steaming water of the tropical Indian Ocean upon the East African coast, whence its only outlet is southward, along the Mozambique channel. In bringing to light the thermometric agency of this powerful and immense current which projects itself into the icy basin of the Antarctic, the Challenger has unmasked the main secrets of Antarctic meteorology and of the future penetrative exploration in the South Polar seas. Released from the pressure of the easterly winds after passing Cape Agulhas, the great equatorial flow soon enters the realm of westerly and north-westerly winds, 1 The power and regularity with which these latter winds blow, especially in the middle latitudes, or “roaring forties,” of the Southern hemisphere, are familiar to every Australian seagoer. They drive the hot streaks of Indian water before them towards the south-east, and necessarily gave it an enormous thermal energy,, on a course extending far into the South Polar Basin. The track of the Challenger, from the Cape of Good Hope to its highest southern latitude, near sixty-seven degrees south and eighty degrees east, took her outside of the warm water. Doubtless, too, the surface of'.the sea within the Antarctic circle, especially during the summer, when the icc is rapidly melting, is coated with a thin stratum of glacier water, serving to disguise the equatorial stream. But the potential presence of the latter, in the high Austral latitudes, remains a physical necessity. The Challenger’s observations, though partial, have/' it would seem, settled the question of the thermal phenomena of the southern hemisphere. Whatever may be said (and, no doubt, much may be said) of the advantage of land exploration in the far South, the pathway of the Agulhas current when fully traced by the deep sea thermometer, will, as Sir James Boss found, be the best path for the nautical survey of the South Pole.