Page:Popular Science Monthly Volume 37.djvu/317

Rh, the ice-cap slopes like a shield uniformly toward the interior. Thus, in certain places the explorer should expect to meet elevations of seven thousand or eight thousand feet; but, owing to an optical illusion, he scarcely knows whether he is climbing or descending. The horizon seems to rise on all sides, says Nordenskjöld, "as if he were at the bottom of a basin."

The aspect of these boundless wastes rolling away in scarcely perceptible undulations, and in the distance mingling the gray of their snows with the gray of the skies, at first gave the impression that Greenland was a uniform plateau, a sort of horizontal table. The belief now prevails that the rocky surface of the land is, on the contrary, carved into mountains and hills, valleys and gorges, but that the plastic snows and ice have gradually filled up all the cavities, which now show only in slight sinuosities on the surface. Allowing to the whole mass of the ice-cap an average thickness of five hundred feet, it would represent a total volume of about one hundred and fifty thousand cubic miles. This sermer suak, or "great ice" of the Greenlanders, flows like asphalt or tar with extreme slowness seaward, while the surface is gradually leveled by the snow falling during the course of ages and distributed by the winds. In the interior of the country the surface of the ice and snow is as smooth as if it were polished, looking like "the undisturbed surface of a frozen ocean, the long but not high billows of which rolling from east to west are not easily distinguishable to the eye." Nevertheless, the exterior form of the ice-cap has been greatly diversified, at least on its outer edge, where in many places it is difficult to cross, or even quite impassable. The action of lateral pressure, of heat produced by the tremendous friction, of evaporation and filtration, has often broken the surface into innumerable cones a few yards high, in form and color resembling the tents of an encampment. The depressions of the snowy plateau are filled with meres, lagoons, and lakes; streams and rivulets excavate winding gorges with crystal walls in the snow and ice. Cascades, frozen at night, plunge during the day into profound crevasses; during the expedition of 1870 Nordenskjöld saw intermittent jets of water rising to a great height, which he was unable to study, but which he supposes must be geysers.

Most of the glaciers reaching the coast round the Greenland seaboard present a somewhat regular frontal line, from which blocks of varying size break off with every wave and drift away with the current. But the frozen streams which yield those huge masses large enough to be called icebergs, that is, "mountains of ice," are relatively few in number, their production requiring a combination of favorable circumstances, such as the thickness of