In this location ocean-currents from the great Pacific, warmer than the normal temperature of this latitude, trending up from southward, ebb and flow around the islands as they pass, giving rise during the summer and early autumn to constant, dense, humid fog and drizzling mists, which hang in heavy banks over the ground and the sea-line, seldom dissolving away to indicate a pleasant day. By the middle or end of October strong, cold winds, refrigerated on the Siberian steppes, sweep down over the islands, carrying off the moisture and clearing up the air. By the end of January, or early in February, they usually bring, by their steady pressure, from the north and northwest, great fields of broken ice, sludgy floes, with nothing in them approximating or approaching glacial ice. They are not very heavy or thick, but as the wind blows they compactly cover the whole surface of the sea, completely shutting in the land, and for months at a time hush the wonted roar of the surf. In the exceptionally cold seasons that succeed each other up there every four or five years, for periods of three and even four months—from December to May, and sometimes into June—the islands will be completely environed and ice-bound. On the other hand, in about the same rotation, occur exceptionally mild winters. Not even the sight of an ice-blink is recorded then during the whole winter, and there is very little skating on the shallow lakes and lagoons peculiar to St. Paul and St. George. This, however, is not often the case. The breaking up of winter-weather and the precipitation of summer (for there is no real spring or autumn in these latitudes), usually commences about the first week in April. The ice begins to leave or dissolve at that time, or a little later, so that by the 1st or 5th of May, the beaches and rocky sea-margin beneath the mural precipices are generally clear and free from ice and snow, although the latter occasionally lies, until the end of July or the middle of August, in gullies and on leeward hill-slopes, where it has drifted during the winter. Fog, thick and heavy, rolls up from the sea, and closes over the land about the end of May. This, the habitual sign of summer, holds on steadily to the middle or end of October again. The periods of change in climate are exceedingly irregular during the autumn and spring, so-called, but in summer a cool, moist, shady gray fog is constantly present. To this certainty of favored climate, coupled with the perfect isolation and an exceeding fitness of the ground, is due, without doubt, that preference manifested by the warm-blooded animals which come here every year, in thousands and hundreds of thousands to breed, to the practical exclusion of all other ground.[88]