356 AMAZONIA AND LA PLATA. 



accompanied by blinding snowstorms. In this region of the puna, the tracks 

 followed by the muleteers across the plateau, between the upland valleys of the 

 Rioja and Copiapo, take the name oî pircas. 



In that part of the plateau which bears the lofty peak of Bonete, the eastern 

 Cordillera is carved into four distinct sections by the streams belonging to the 

 Argentine drainage area. The first section, with some crests exceeding 1,600 

 feet, is separated from the Argento-Chilian Cordillera by the deep valley of the 

 Kio Blanco, one of the main branches of the Rio de Jachal. The second, lying 

 nearer to the frontier, develops the pico del Salto, and numerous other summits 

 over 18,000 feet high. The third fragtnent of the eastern Cordillera broadens out 

 into a huge mountain mass with peaks, such as Mainrique and Totora, also 

 exceeding 18,000 feet, lower limit of the snowline. Lastly the fourth section, 

 known as the Cordillera del Tigre (16,400 feet), is connected with mighty Acon- 

 cagua, towering above the valley traversed by the main route, which leads over 

 the Cumbre pass fiom Buenos Ayres to Santiago de Chili. 



All the tracks crossing the Andes between the Cumbre and the pircas of 

 Copiapo, follow the course of the river valleys to turn the transverse barriers of 

 the eastern Cordillera. But these tracks are little used, except for the importation 

 of Argentine mules into Chili. But in 1817 a whole army of San Martin's 

 republican forces advanced against the Spaniards over the pass of los Patos or 

 Valle Hermoso, which stands at an altitude of 12,700 feet between Aconcagua 

 and Ramada. Other breaches in the range followed by the muleteers exceed 

 14,750 feet, amongst others that of Agua Negra, or la Laguna (15,190), on the 

 direct route between Jachal and Coauimbo. 



The Little Cokdim.eka — Overo and other Yolcanoes. 



Besides the eastern and western Cordilleras with their snowy peaks, Argentina, 

 like Chili, has its chain of foothills, its "little Cordillera," running parallel with 

 the axis of the Andes proper, and interrupted at intervals by deep river valleys. 

 West of the plain occupied by the two cities of San Juan and Mendoza, these 

 foothills develop the imposing Paramillo group, which in the Cerro Pelado attains 

 a height of 11,280 feet. Although now free from snow, these mountains had at 

 one time their glaciers, traces of which are still seen on the plain in the neigh- 

 bourhood of Mendoza. Here the so-called cerriUos, little knolls with rounded 

 crests, are evidently the remains of frontal and other moraines. They are disposed 

 in ridges ranging from 150 to 300 feet in height, and consisting of trachytic 

 blocks, angular or slightly rounded boulders brought down by the glaciers to the 

 base of the foothills. 



The depression in the Cordillera followed by the Cumbre route, and by the line 

 of the future trans- Andean railway, coincides very closely with a natural division 

 of the orographic system. A little south of the snowy Tupungato giant (20,286 

 feet), itself of eruptive origin, rise the craters of numerous volcanoes, some extinct, 

 some still active. Here also the Arjrentino-Chilian Cordillera breaks into two 



