MOUNTAINS AND MOUNTAIN RANGES. 



51 



the strata by which they were once covered : this constitutes what is 

 called a denudation. Instances of such denudations are of frequent 

 occurrence. 



Mountains, except those formed by volcanoes, are seldom, isola- 

 ted masses rising from a plain, but they form groups, or are arranged 

 together in a certain direction, and compose long and lofty ridges, de- 

 nominated .mountain chains. Lower ranges of mountains, running 

 in the same direction as the principal range, and separated by valleys 

 of greater or less width, may be observed accompanying almost all 

 very lofty mountain chains. This fact appears to indicate the opera- 

 tion of a powerful elevating force, acting in one direction along a cer- 

 tain line, and decreasing in intensity as the distance from each side 

 of this line increases ; but, this action does not appear to extend with 

 equal force on both sides of the line, for the smaller chains parallel 

 to the great chain are seldom so numerous on one side of it as on the 

 other. The principal mountain chain, if very large, has its sides fur- 

 rowed by small lateral valleys, and has been, not unaptly, compared 

 to a back bone or spine, with diverging ribs. 



The shape of many countries and islands is, evidently determined 

 by the direction of the grand mountain chains that run through them. 



The principal mountains in Europe and Asia, when viewed on a 

 large scale, may be considered as forming a mountain chain compo- 

 sed of numerous mountain groups, and extending, in an easterly di- 

 rection, from Cape Finisterre in Spain, to the most eastern extremi- 

 ty of Asia. Various parts of this chain receive different denomina- 

 tions in the different countries through which they pass. The Py- 

 renees, the Alps, Mount Taurus, Mount Caucasus, the Altaic and 

 the Himmaleh mountains, and the Yabblonnoy mountains of Tartary, 

 which extend nearly to Behring's Straits, maybe regarded as form- 

 ing, together, one immense mountain chain, and dividing the north- 

 ern from the southern dryland, both in Europe and Asia. 



In North and South America, one unbroken chain of mountains, runs 

 in a northerly and southerly direction, for eight thousand miles, near 

 the western side of that vast continent, and with some minor diverg- 

 ing chains, has evidently determined the general outline of both coun- 

 tries. 



A remarkable similarity occurs in the position of the escarpments, 

 or steep sides of mountains, in the same mountain range. Various 

 opinions have been formed respecting the law which the position of 

 the escarpments appears to follow, but, I believe the rule I submitted 

 to the attention of geologists in the first edition of this work, will be 

 found to approximate to the truth. 



Mountain chains or ranges present the steepest declivities on the 

 sides nearest to the sea. This is remarkably the case in the long 

 chain of the Alleghany mountains on the eastern side of America, 

 which are steep towards the Atlantic. On the contrary, the Rocky 

 Mountains, which run near the northwest coast, and the Andes, near 



