Let us now see what was the work of water in its forms of ice and snow in the Ice age. Here we do not wander in uncertainties; for what we see to be now the work and changes of ice and snow in the High Alps and the frozen oceans of the north, we may accurately account to have been the work of the same agents in the Ice period. Let us therefore reason from the present to the past. A vast region such as Greenland or Spitzbergen or the high Alpine country is covered deep with snow, which falls upon it nearly every month in the year. For a little time in the summer the sun partially melts the snow even on the heights, so that floods of snow-water begin to run into the valleys. But freezing generally takes place in the night, and the melting period is short, so that the higher plains and valleys become filled with beds of ice; yet from beneath some of these ice-beds water runs out and descends to the lower plains and valleys, becoming in their warmer temperature broad rivers to water the land. As you look from the distance upon the snow-covered Alps, you see broad spaces flashing and shining like silver. These are the glaciers or ice-rivers between the snowy peaks. These glaciers seem as you observe them to be stationary, but when they are measured they are found to have a steady motion. Thus, you set a post in the glacier and a post in line with it upon the rocks on each side of the glacier. Even in a day or two you will see that instead of three posts in line, thus [Illustration] they stand in this fashion [Illustration], and in a few weeks the central post will seem to have travelled some distance down the glacier. But no; the glacier has been sliding along in its bed and carrying the post with it. As the glacier of the Alps moves down, down, down, it comes into warmer levels, melts and crumbles away, and feeds rivers. But the glacier of the Polar circle when it reaches the limit of its bed has not found a warmer level; it breaks off by its own weight, with a tremendous crash, and falls into the Polar sea, among floes of moving ice. The fallen fragment of glacier settles into the water for about eight-ninths of its entire height, and now takes a new name,--it is an iceberg.