ANNOTATIONS AND ADDITIONS. 57 



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 outpour- 

 ing and elevation of eruptive rocks, as well as to the slow 

 and complicated process of metamorphic action taking place 

 in clefts filled with vapours and favourable to the conduction 

 of heat. 



For a long time past, from ] 830 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 23692 Parisian, or 

 25250 English feet. 



The Nevado de Illimani, west of the Mission of 

 Yrupana (S. lat. 16 38') in the same mountain range 

 as Sorata: elevation 3753 toises, or 22518 Parisian, or 

 24000 English feet. 



The Chimborazo (S. lat. 1 27') in the province of 

 Quito : elevation 3350 toises, or 20100 Parisian, or 

 21 423 English feet. 



The Sorata and Illimani were first measured by a dis- 

 tinguished geologist, Mr. Pentland, in 1827, and also in 

 1838. Since the publication, in June 1848, of his great 

 map of the basin of the lake of Titiaaca, we know that the 

 above-mentioned elevations of these two mountains are 



