MOTION OF GLACIERS. 75 
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 ! 
In the colder regions of the earth, in Greenland or Spitz- 
