The habitable area of the earth everywhere shows its boundaries to be peripheral zones of varying width, now occupied and now deserted, protruding or receding according to external conditions of climate and soil, and subject to seasonal change. The distribution of human life becomes sparser from the temperate regions toward the Arctic Circle, foreshadowing the unpeopled wastes of the ice-fields beyond. The outward movement from the Tropics poleward halts where life conditions disappear, and there finds its boundary; but as life conditions advance or retreat with the seasons, so does that boundary. On the west coast of Greenland the Eskimo village of Etah, at about the seventy-eighth parallel, marks the northern limit of permanent or winter settlement; but in summer the Eskimo, in his kayak, follows the musk-ox and seal much farther north and there leaves his igloo to testify to the wide range of his poleward migration. Numerous relics of the Eskimo and their summer encampments have been found along Lady Franklin Bay in northern Grinnell Land (81 deg. 50' N. L.), but in the interior, on the outlet streams of Lake Hazen, explorers have discovered remains of habitations which had evidently, in previous ages, been permanently occupied.[326] The Murman Coast of the Kola Peninsula has in summer a large population of Russian fishermen and forty or more fishing stations; but when the catch is over at the end of August, and the Arctic winter approaches, the stations are closed, and the three thousand fishermen return to their permanent homes on the shores of the White Sea.[327] Farther east along this polar fringe of Russia, the little village of Charbarova, located on the Jugor Strait, is inhabited in summer by a number of Samoyedes, who pasture their reindeer over on Vaygats Island, and by some Russians and Finns, who come from the White Sea towns to trade with the Samoyedes and incidentally to hunt and fish. But in the fall, when a new ice bridge across the Strait releases the reindeer from their enclosed pasture on the island, the Samoyedes withdraw southward, and the merchants with their wares to Archangel and other points. This has gone on for centuries.[328] On the Briochov Islands at the head of the Yenisei estuary Nordenskiold found a small group of houses which formed a summer fishing post in 1875, but which was deserted by the end of August.[329] [Sidenote: Altitude boundary zones.]