PHYSICAL GEOGRAPHY. 



55 



land is about 3405 feet above the sea. On the 

 continent of Europe, the most elevated mountain is 

 Mont Blanc, which forms the highest peak of the 

 Alps, and rises 15,660 feet above the sea. The Py- 

 renees are about 11,000 feet high, and Etna is 

 equally lofty. 



In Africa, the highest mountains are those of 

 Abyssinia, which are about 15,000 feet high. On 

 our own continent, the highest points are those of 

 the Andes; Chimborazo being elevated 21,425 feet, 

 while several other peaks are equally lofty. The 

 volcano of Popocatepetl, in Mexico, is 17,720 feet 

 high ; the^ Rocky Mountains* are stated to be proba- 

 bly still higher. 



The external structure and configuration of hills 

 and mountains forms a curious and interesting, al- 

 though hitherto neglected branch of geological inqui- 

 ry. These elevations have been shown to perform 

 an important function in the economy of nature, 

 by collecting and duly distributing over the earth's 

 surface the waters derived from the atmosphere; 

 and, to fit them for this office, a suitable struc- 

 ture has been given ; a structure which is infinitely 

 varied, according to the nature and composition of 

 the mass. The more perfect representation of the 

 undulations of the surface in modern maps, and, 

 more especially, in those constructed for military 

 purposes, will, however, in time, throw much light 

 upon this subject, and more firmly establish those 

 principles of which, at present, we have only a 

 vague and general idea. As regards the direction 

 of elevated ranges of ground, there is generally one 

 or more extending through every continent and isl- 

 and, and thus determining its general form and con- 

 figuration. The mountains of Great Britain present 

 an example of this kind, and a still more striking one 

 is afforded by the vast chain of mountains which 



* 18,000 feet, according to Prof. Renwick. 



