We must date the origin of a floe like this back to a very remote period. Probably it was cradled, at the outset, in some deep recess of the land, where it remained until it had accumulated to a thickness which defied the summer’s sun and the winter’s winds. Then it would grow, as the glacier grows, from above; for, like the glacier, it is wholly composed of fresh ice--that is, of frozen snow. Thus it will be seen, to quote Dr. Hayes once more, that the accumulation of ice upon the mountain-tops is in nowise different from the accumulation which takes place upon these floating fields, where every recurring year marks an addition to their depth. Vast as they are to the sight, and pigmies as they are compared with the inland Mer de Glace, yet, in all that concerns their growth, they are truly glaciers, dwarf floating glaciers. That only in this manner can they grow to so great a depth will at once be conceded by the reader, if he recollects that ice soon reaches a maximum thickness by direct freezing, and that its growth is arrested by a natural law. Necessarily, this maximum thickness varies according to the temperature of the locality: but the ice is in itself the sea’s protection. The cold air cannot absorb the warmth of the water through more than a certain thickness of ice, and that thickness attains a final limit long before the winter has reached its close. The depth of ice formed on the first night is greater than that formed on the second; on the second is greater than on the third; on the third greater than on the fourth; and so it continues, until the increase no longer takes place. In other words, the ratio of increase of the thickness of ice is in inverse proportion to the duration of the period of freezing. There comes a time when the water beneath the ice no longer congeals, because the ice-crust above it protects it from the action of the atmosphere. Dr. Hayes asserts that he never saw an Arctic ice-table _formed by direct freezing_ that exceeded eighteen feet; and he justly adds, that were it not for this all-wise provision of the Deity,--this natural law, as our men of science term it,--the Arctic waters would, ages ago, have been solid seas of ice to their profoundest depths. Having said thus much about the various forms which the ice assumes in the Polar seas,--about their icebergs and ice-fields, pack-ice and drift-ice, and the thick belt of ice which surrounds their shores,--we may now direct the reader’s attention to their Animal Life; to the creatures which inhabit them, walrus and seal and whale, the fishes, the molluscs, and even minuter organisms. And first we shall begin with the Walrus, which finds a congenial home in the Arctic wildernesses.