410 SOUTH AMEEICA— THE ANDES EEGIONS. 



organisms, such as infusoria, urchins and corals. Above follow shell sandstones^ 

 gypsum, and beds of native salt, succeeded on the surface by sands covered with 

 shell mounds, the remains of mussels and other species resembling those still living 

 in the neighbouring waters. 



The Chilian Andes Proper. 



Juncal (17,530 feet) and towards the south-west Dona Inez (18,245) are the first 

 great summits of the Andean Cordillera within the former limits of Chili. A little 

 farther south is the converging point of the various Atacama, Bolivian and Argen- 

 tine ranges, and here cease the old lacustrine depressions, which occupy vast level 

 spaces between the different sierras. Owing to their moister climate , these 

 uplands have been far more eroded than those farther north ; the cirques, combes 

 and vallej^s have been more deeply excavated, and consequently present, at least 

 on the southern slope facing the Argentine plains, terraced escarpments assuming 

 the aspect of mountain ranges. Thus are formed on the south side such groups 

 of summits as the Cerro Azul, the Cerro Pintado, the Negro Muerto and the 

 Cerro Bravo. 



The narrow territory of Chili proper, excluding the recent northern annexa- 

 tions, is disposed in three parallel zones running from north to south with varying 

 breadth : the Andean Cordillera, the coast range, and between the two a longi- 

 tudinal depression, interrupted at intervals in the northern regions by transverse 

 ridges. In South Chili the intervening valley, although extremely sinuous, and 

 in certain districts narrowed to a sort of gorge between the opposite slopes, still 

 remains an open plain with a gradual incline. Towards the south it is studded 

 with lakes, beyond which it falls to sea-level, developing a vast marine basin half 

 lake, half gulf. Farther on the plain assumes the form of a strait, and here a long 

 line of channels stretches between the insular Magellanic groups (a continuation 

 of the coast range) and the Andean Cordillera, whose southern extremity plunges 

 into deep water. 



The coast range is far less elevated than the inner cordillera, and in some 

 places even falls below the transverse ridges connecting it with the main chain, 

 although on both sides a certain correspondence has been observed between the 

 respective altitudes. East of Quillota, Valparaiso and Santiago, between 32° and 

 34'^ south latitude, rise the culminating peaks of the Chilian Andes, and undei- 

 the same latitudes also occur the loftiest summits of the coast range. 



Of the two Cordilleras the highest is not geographically the oldest. The 

 coast range, formed chiefly of heights with gently-rounded contour lines and 

 undulating crests, consists of granites and other crystalline rocks in the northern 

 and central provinces, and in the south of mica schists, while tertiary strata, locally 

 called cancnguas, abut on the seaward slope against the primitive crystalline 

 nucleus. 



The islands forming a southern continuation of the coast range belong to the 

 same archaean and paleozoic horizons. On the other hand, the more recent 



