An explanation of this may be found in the fact that in southern latitudes the drift of ice is very much further away from the Pole than is the case in the north. In the northern hemisphere massive ice-floes are not encountered until the 70th parallel of latitude has been passed, while it is not until the 75th parallel is passed that the ice becomes so packed as to appear to be stationary. In the southern latitudes, on the other hand, drift ice is encountered in the 50th parallel, and by the time the 60th parallel is reached, the ice is found to be as close set as it is in the 80th parallel in the north. In the islands off Tierra del Fuego the mountains remain covered with snow down to the water's edge through all the summer months, though the latitude is only 54° S. This may be due, in a large measure, to the small quantity of land existing in the south, as compared with the north. The heat of the sun does not radiate from the sea with the same intensity as it does from the earth, whence the ice, drifting from the south into the oceans nearer the equator, melts more slowly, and is consequently enabled to travel longer distances, thus lowering the temperature of the surrounding atmosphere and still further delaying the melting process. At a comparatively recent period, the limit of the floes, in the southern oceans, was much nearer the equator than it is to-day, for the most southerly parts of Africa, Australia, and America all show unmistakable evidences of having, within recent times, been under a great ice covering. It was not until 1600 that the first contact was made with the southern world of ice. Dirk Gerritz, a Dutch navigator, sailing with a squadron for the East Indies, was separated from his other ships while passing through the Straits of Magellan and was driven as far as 64° S. He discovered, in that latitude, a rocky coast line covered with snow. The discovery did not excite any great interest at the time, and, for a period of nearly two centuries, nothing was done to probe further into the mysteries of the South. In 1769 an expedition was sent out under Captain Kerguellen to explore the regions lying to the south of the Cape of Good Hope. He was successful in locating the group of islands, still known as Kerguellen Islands, and sailed thence to Australia, demonstrating that no land, other than these islands, existed between the Cape of Good Hope and Australia.