THE EARTH. 123 



nels to the sea, after the performance of a tedious 

 and fruitless circulation. * 



However this be, certain it is that almost all 

 our great rivers find their source among moun- 

 tains ; and, in general, the more extensive the 

 mountain, the greater the river : Thus the river 

 Amazons, the greatest in the world, has its source 

 among the Andes, which are the highest moun- 

 tains on the globe ; the river Niger travels a long 

 course of several hundred miles from the moun- 

 tains of the Moon, the highest in all Africa ; and 

 the Danube and the Rhine proceed from the 

 Alps, which are probably the highest mountains 

 of Europe. 



It need scarcely be said, that, with respect to 

 height, there are many sizes of mountains, from 

 the gently rising upland, to the tall craggy pre- 

 cipice. The appearance is in general different in 

 those of different magnitudes. The first are 

 clothed with verdure to the very tops, and only 

 seem to ascend to improve our prospects, or sup- 

 ply us with a purer air : but the lofty mountains 

 of the other class have a very different aspect. 

 At a distance their tops are seen, in wavy ridges, 

 of the very colour of the clouds, and only to be 

 distinguished from them by their figure, which, 

 as I have said, resembles the billows of the sea.t 

 As we approach, the mountain assumes a deeper 

 colour; it gathers upon the sky, and seems to 

 hide half the horizon behind it. Its summits also 



* Nature Displayed, vol. iii. p. 88. 



f Lettres Philosophiques sur la Formation, &c. p. 196. 



