116 Mr. Pentland's Observations on the Peruvian Andes, 



letter, in which I shall confine myself to the correction of 

 some of the errors into which Mons. de Montbret has fallen, 

 and to rebutting the conclusions drawn by this writer and 

 Mons. Brue against the accuracy of my measurements. 



The principal objection raised against the great elevation 

 which I have attributed to certain peaks of the Peruvian Andes, 

 situated between the 14th and 17th parallels of south latitude, 

 consists in an assumption, that if the geographical position in 

 which my astronomical observations have placed these moun- 

 tains be correct, they must be easily seen from the coasts of 

 the Pacific Ocean, and could not have hitherto escaped the 

 attention of the navigators frequenting the ports of Peru situ- 

 ated in or near the same latitude. , 



To meet this inference, I take the liberty of annexing an 

 extract from a letter, which, in my own justification, I have 

 judged it necessary to address to Mons. Coquebert de Mont- 

 bret, in reply to his observations : — 



" The great chain of the Andes, between the 14th and 20th 

 parallels of southern latitude, is divided into two longitudinal 

 and parallel ridges, or Cordilleras (the name by which they 

 are designated by the Creole population of Peru). These two 

 Cordilleras are separated by a very extensive interalpine valley, 

 the mean elevation of which is 12,600 feet; its southern por- 

 tion is traversed by the river Desaguadero, whilst its northern 

 is occupied by the celebrated lake of Titicaca, on the shores 

 and in the islands of which Peruvian civilization and the Em- 

 pire of the Ingas had their origin. 



" The western cordillera, or, as it is called, the Cordillera 

 of the Coast, separates the valley of the Desaguadero (the 

 Thibet of the new world), and the basin of the lake of Titicaca, 

 from the shores of the Pacific. Many of its peaks exceed 

 20,000 feet in elevation, and in it are situated several active 

 volcanoes; whilst the eastern cordillera, composed chiefly of 

 transition and secondary rocks (grauwacke-slate and new- 

 red-sandstone), separates the same valley from the extensive 

 plains of Chiquitos and Moxos, and the confluents of the rivers 

 Beni, Mamore and Paraguay, from those streams which 

 empty themselves into the lake of Titicaca, and into the river 

 Desaguadero. 



" The eastern cordillera of the Peruvian Andes is situated 

 within the political limits of the Republic of Bolivia ; and it 

 presents, between the 14th and 17th degrees of latitude, an 

 almost continuous ridge of snow-capped mountains, the mean 

 elevation of which exceeds 19,000 feet It is upon this snowy 

 range of the eastern cordillera that rise the most elevated 

 mountains hitherto determined throughout the entire extent 



of 



