The Antarctic continent is covered with an ice-cap, which along some coasts is buttressed by ice cliffs terminating in the sea, and on coasts facing east is bordered with lofty mountains through which glaciers have forced their way. Throughout the Antarctic regions there is evidence of much more extensive glaciation in former ages. The glaciers are for the most part receding, although there are proofs that some are still moving down to the sea. But there are fixed masses of ice on the sea coast, in the form of cliffs: tongues which could not have been deposited or fed by existing glaciers. At the period of maximum glaciation the climate was much milder, and as the severity of the temperature, due to less precipitation, increased, there must have been sterile ice conditions, and consequent retirement of glaciers and ice-fields. These receding glaciers do not supply bergs; and as the Antarctic icebergs are by far the largest in the world, their origin must be from some other source. The great ice barrier of Ross fills a vast bay 400 miles across, and at least 300 miles deep, with soundings of about 600 ft. There is no reason why other such barriers should not exist in other parts of the Antarctic regions as yet unknown. These barriers must be the sources of the enormous tabular icebergs which float northward in such vast numbers. Their height is about 200 ft., and their length from one or two to as much as twenty miles. Large floes are not very common, but there is a great deal of drifting ice, broken off from fixed land ice, which forms closely packed or sailing ice according to the winds. In December this pack ice is usually 300 miles across from 66° to 71° S. in front of the Ross Sea, but it lies further south in the King George IV Sea of Weddell. In February the Ross Sea is navigable, and the pack is scattered. CHAPTER III TRIBES AROUND THE POLE Before we begin to follow the achievements of the great Polar worthies, it seems desirable to take a brief survey of the dwellers on the threshold of the Arctic regions; for here are races who have for ages found homes along the European, Siberian, and American coasts of the Polar Ocean and in Greenland.