Although a river generally has its source in mountainous regions, it must be remembered that all the waters that descend upon the territory of which it forms the lowest level, gradually find their way into its current. Thus, the monarch of all streams, the Amazon River, is the natural drain of a territory thirty times larger than England. Thousands of rivulets and brooks, fed by the waters which descend from the slopes of thousands of glens and valleys, or filter through the vast forest-plains that rise but a few feet above their surface, all contribute to swell the majesty of its current. Its sources are in reality wherever, on that vast extent of land, water descends and drains into any one of its innumerable affluents. When we hear that on an average the river of the Amazons alone restores every minute half a million of tons of water to the ocean, and then consider the countless number of streams all alike active, that are scattered over the globe, we may form a faint idea of the vast quantity of vapours which are constantly rising from the deep, and of the magnitude of these silent operations of nature. Yet such is the immensity of ocean, that supposing all the waters it constantly loses, never to return again into its bosom, it would require thousands of years of evaporation to exhaust the immensity of its reservoirs! It might be supposed that the waters which congeal on the sides of mountains covered with perennial snow, or fill Alpine valleys in the form of glaciers, were eternally fixed on earth--but there also we are deceived by delusive appearances of immobility. Every year the glacier slowly but restlessly makes a step forwards into the valley, and while its lower end dissolves, new supplies of snow constantly feed it from above. It has been calculated by Agassiz that the ice masses of the Aar glacier require 133 years to perform their descent from its summit to its inferior extremity--a distance of ten miles--so that their sojourn in that chilled valley far surpasses that of the oldest patriarch of the mountains. How great must be their delight when they at last are liberated from the spell which so long enchained them, and freely bound along on their way to Ocean! How they must shudder at the idea of once more returning to their desolate prison, and long for the perpetual warmth of spicy groves and tropical gardens!