The iceberg is often of great height above water; some bergs weigh hundreds of millions of tons. The air, sun, and dashing water cut the berg into beautiful and fantastic shapes of domes, pinnacles, and towers, from which the sun flashes back as from molten metal. The iceberg floats about the Polar sea, and finally may be carried by the currents southward into warmer waters and a milder climate. Then the melting process goes on swiftly, and when the lower portion becomes so much lessened as to destroy the equilibrium of the floating mountain, it turns over, or portions of it break away and fall into the sea. Thus the history of the marvellous mountain of ice is: first snow falling upon high lands; then from the melting and freezing of the snow, glaciers or ice-rivers; then the glacier moving beyond its bed, breaks off into a berg, and the vagrant of the Polar seas drifts to its destruction in warmer climes. Now let us go back to the snow mountains and the forming glaciers. As these rivers of ice grind and crowd down their ravines they tear and crush the sides of the mountains and the face of the valley, so that they have beneath them what we may call another stream, and that not of ice, but of broken stones of all sizes. These are frozen to the bottom of the glacier and are dragged along with it as it slides down the ravine. The bottom of the glacier moves a little more slowly[30] than the surface; finally it comes down upon the valleys in something of the shape of a =V=, or the share of a plow. Thus entering the valley it drives a vast amount of débris, as boulders and pebbles, before it, and carries a vast amount more clinging to its upper and lower surfaces. Now it is evident that as the glacier melts rapidly in the warm valley it will drop the load of stone that it carried with it in its descent from the heights. Such a bed of glacier-driven stone is termed a moraine, and when people have once seen a moraine they will not fail to recognize one wherever they find it, even if it is thousands of miles away from any glaciers. They will say: “Here is a moraine; once there must have been a glacier slowly moving here.” However warm the climate may now be, when we see a moraine we may be assured that once it was cold enough for snow mountains and for glaciers. It is as certain as that every peach-stone we see must once have been in a peach. Again in the present glacier-districts we find that when glaciers and icebergs slide over beds of rock or masses of stone, they cut and groove them, chisel them in a peculiar fashion; and when on any rock we find these chisel-marks of the ice, they are unmistakable, and we know that ice heavy and strong enough to cut the rock has been there. When we see a name or initial cut in a tree we know that some person with a knife has been there and cut the letters. We recognize the glacier-work just as clearly on the rock as the human work on the tree.