It will readily be understood that when destruction such as this follows from landslips along the borders of insignificant rivers, those occurring on the banks of the mighty rivers which drain whole continents are still more terrible. The following account from the pen of Mr. Bates the naturalist, indicates the nature of the landslips which occur on the banks of the Amazon. “I was awoke before sunrise, one morning,” he says, “by an unusual sound resembling the roar of artillery; the noise came from a considerable distance, one crash succeeding another. I supposed it to be an earthquake, for, although the night was breathlessly calm, the broad river was much agitated, and the vessel rolled heavily. Soon afterwards another loud explosion took place, followed by others which lasted for an hour till the day dawned, and we then saw the work of destruction going forward on the other side of the river, about three miles off. Large masses of forest, including trees of colossal size, probably 200 feet in height, were rocking to and fro, and falling headlong one after another into the water. After each avalanche the wave which it caused returned on the crumbly bank with tremendous force, and caused the fall of other masses by undermining. The line of coast over which the landslip extended was a mile or two in length; the end of it, however, was hid from our view by an intervening island. It was a grand sight; each downfall created a cloud of spray; the concussion in one place causing other masses to give way a long distance from it, and thus the crashes continued, swaying to and fro, with little prospect of termination. When we glided out of sight two hours after sunrise the destruction was still going on.” We might consider here the action of glaciers in gradually grinding down the mountain slopes, the destructive action of avalanches, and a number of other forms in which snow and ice break down by slow degrees the upraised portions of the earth. For in reality all these forms of destructive action take their origin in the same process whence running waters and heavy rainfalls derive their power. All these destructive agencies are derived from the vapour of water in the air. But it seems better to limit the reader’s attention in this place to the action of water in the liquid form; and therefore we proceed to consider the other ways in which rain wears down the land. Hitherto we have considered effects which are produced chiefly along the courses of rivers, or in their neighbourhood. But heavy rainfall acts, and perhaps in the long run as effectively (when we remember the far wider region affected) over wide tracts of nearly level ground, as along the banks of torrents and rivers.