Page:Popular Science Monthly Volume 29.djvu/683

Rh of land is this immense mass of ice piled? It is a question not easy to answer definitely, because no one has ever seen it. The idea has generally been that the continent is high land. But it has been urged with justness that, had the glaciers descended from a mountainous country, they would bear upon their surfaces, or in their mass, stones to indicate the sort of rock of which the mountains were made. But such is not the case. It is said that stones are never found on the Antarctic bergs, and Captain Cook states expressly his idea that the bergs are formed at the mouths of rivers or cataracts, "because we never found any of the ice which we took up in the least incorporated or connected with earth." He goes on to say: "The ice-islands. . . must be formed from snow and sleet consolidated, which gather by degrees, and are drifted from the mountains. In the winter, the seas or the ice-cliffs must fill up the bays if they are ever so large. The fall of snow occasions the accumulation of these cliffs, till they can support their weight no longer, and large pieces break off from these ice-islands. We are inclined to believe that these ice-cliffs, where they are sheltered from the violence of the winds, extend a great way into the sea."

The discovery, by Sir James Ross, of the Parry Mountains and Mounts Erebus and Terror, in latitude 78°, tended to confirm the prevailing notion of a high and mountainous land forming the Antarctic Continent. But the Parry Mountains are merely conjectural, having been seen only at a distance, and it is well known that the coasts charted by some navigators have been proved by subsequent ones to have been either clouds merely or else islands of ice. The most recent idea is, that the land about the pole consists of a cluster of low islands, rising but little above the sea-level, but united by masses of ice. The gradual accumulation of snow for centuries has raised a cap, as before stated, seven miles thick, and from this cap the ice flows away in all directions, forced onward by the pressure of the enormous mass behind.

The immense size of the icebergs seen in the Antarctic Ocean is without a parallel elsewhere. Croll in a late essay gives a list of the largest of which there is record, and we find they range from 400 to 1,000 feet above the water. The one 1,000 feet high was observed in latitude 37° 32' south, and was nearly five miles long. When these bergs are first broken off and float away they all have the tabular form, but, as they grow old and drift northward into warmer airs and waters, they become fissured and seamed in all directions; pinnacles and domes and caverns appear, and they become beautiful objects. Wilkes describes one as exhibiting "lofty arches of many-colored tints, leading into deep caverns open to the swell of the sea, which, rushing in, produced loud and distant thunderings. . . . Every noise on board, even our own voices, reverberated from the massive and pure white walls. These tabular bergs are like masses of beautiful