ANNOTATIONS AND ADDITIONS. 63 



Geology and Natural History of the Countries visited in 1832-1836 

 by the Ships Adventure and Beagle, p. 266) to the North Polar 

 Sea, the Cordilleras extend in length more than 8000 geographical 

 miles. They are the longest though not the loftiest chain on our 

 planet ; being raised from a cleft running in the direction of a meri- 

 dian from pole to pole, and exceeding in linear distance the interval 

 which in the Old Continent separates the Pillars of Hercules from 

 the Icy Cape of the Tchuktches in the north-east of Asia. Where 

 the Andes divide into several parallel chains, it is remarked that the 

 ranges nearest the sea are usually those which exhibit most volcanic 

 activity; but it has also been observed repeatedly, that, when the 

 phenomena of still active subterranean fire disappear in one chain, 

 they break out in another chain running parallel to it. G-enerally 

 speaking, the volcanic cones are found in a direction corresponding 

 with that of the axis of direction of the entire chain ; but in the 

 elevated highlands of Mexico the active volcanoes are placed along 

 a transverse cleft running from sea to sea in the east and west direc- 

 tion, (Humboldt, Essai Politique, t. ii. p. 173.) Where, by the 

 elevation of mountain masses in the ancient corrugation or folding 

 of the crust of the earth, access has been opened to the molten inte- 

 rior, that interior continues to act, through the medium of the cleft, 

 upon the upheaved wall-like mass. That which we now call a 

 mountain chain has not arrived at once at its present state : rocks, 

 very different in the order of succession in reference to age, are found 

 superimposed upon each other, and have penetrated to the surface 

 by early formed channels. The various nature of the formations is 

 due to the outpouring and elevation of eruptive rocks, as well as to 

 the slow and complicated process of metamorphic action taking place 

 in clefts filled with vapors and favorable to the conduction of heat. 



For a long time past, from 1830 to 1848, the following have been 

 regarded as the culminating or highest points of the Cordilleras of 

 the New Continent. 



The Nevado de Sorata, also called Ancohuma or Tusubaya 

 (S. lat. 15 52'), a little to the south of the village of Sorata 

 or Esquibel, in the eastern Bolivia Range: elevation 3949 

 toises, or 23,692 Parisian, or 25,250 English feet. 



The Nevado de Illimani, west of the Mission of Yrupana 



