In the colder regions of the earth, in Greenland or Spitzbergen, immense glaciers frequently fill the valleys that open on the sea, descend even beyond the water's edge, and, as they move along, their overhanging masses separate from their base and plunge into the deep with a crash louder than thunder. The icebergs that drift about the Arctic seas, and are annually conveyed by the currents into lower latitudes, are formed in this manner. Huge blocks of granite, detached by atmospherical vicissitudes from the higher mountains and precipitated on the surface of the glaciers, frequently float on the broad back of an iceberg far away from the spot where they seemed rooted for eternity. As their crystal support melts away in its progress to warmer climes, these rocky fragments, which have been appropriately named _erratic blocks_, fall to the bottom of the sea hundreds or even thousands of miles from the starting point of their journey. Thus the great bank of Newfoundland is covered with stones from distant Greenland, raised high in the air by volcanic power myriads of years ago, and now condemned to an equally long repose below the surface of ocean. When will they rise again above the waters, and what further changes will they have to undergo ere their compacted atoms resolve themselves into dust and assume new forms? But, however remote their dissolution, it will inevitably come, for Time is all-powerful, and has an eternity to work out his changes.
The large blocks of stone that so wonderfully migrate on the wandering iceberg form but a small and insignificant portion of the terrestrial spoils which are transported to ocean by the returning waters. Every river is more or less laden with earthy particles which its current carries onwards to the sea and deposits at its mouth. In course of time their accumulation, as I have already mentioned, forms large tracts of fertile territory encroaching upon the maritime domains.
I shall end with a few words on the influence of forests in attracting or retaining the atmospherical moisture, as it is a subject of great importance in the economy of nations, and shows us how much it is in the power of man to improve or to defeat the provisions of nature in his favour.