204 I. Bowman — Physiography of the Central Andes. 



in other parts of the system. It is a common experience to 

 find these conceptions of the early books generally held to-day. 



Two specific examples from reasonably authoritative sources 

 will be accepted as the standard conceptions current among 

 students of the subject. These will form points of departure 

 for the new considerations which follow. The first deals with 

 both the eastern and western " mountain " (plateau) systems, 

 the second with the western only. The one is a compilation 

 by Herbertson from various original sources, and is taken from 

 Mills's International Geography, a superior and strictly mod- 

 ern reference work ; the other from Sievers, the best general 

 German work on South America. Herbertson describes the 

 Central Andes as follows : 



" From 40° S. to 4° S. the Western and Eastern regions of 

 the Cordillera differ both in composition and age. The East- 

 ern ranges were folded earlier than the Western ranges, 

 where the folds are more marked. A series of young volcanic 

 rocks comes between the Eastern and Western regions ; and 

 along a line which clings to the Eastern foot of the Western 

 or main range, there are numerous active volcanoes. The 

 Western range remains uniform in structure though out its 

 vast length" (p. 817). 



The second reference is to Sievers' Siid und Mittel-Amerika, 

 published in 1903. " Diese Vuleane sind der Westcordillera 

 aufgesetzt, erheben sich iiber das 4000 bis 4500 ffi hohe Grund- 

 gebirge zu hohen von mehr als 6000 in und geben dem Gebirge 

 seine characteristische Erscheinung " ( p. 390 ). It cannot be 

 denied that from the purely scenic standpoint the volcanoes 

 are the principal features of the western Cordillera, but from 

 the morphologic standpoint they are of far lesser importance 

 than the platform (the "Grundgebirge" of Sievers) upon 

 which they rest. 



The best corrective to the notion that the central portion of 

 the Maritime Andes owe their height chiefly or even largely 

 to volcanic accumulation, or that they consist in the main of 

 a series of meridional ranges, is to be found in the appearance 

 they present from any point on the Lagunas nitrate railway 

 back of Iquique, Chile, from Pintados southward. It is hard 

 to conceal one's astonishment on first catching sight of the 

 great highland which there lies on the eastern horizon, pre- 

 senting as it does for at least forty miles in a north-south 

 direction an unbroken summit so nearly absolutely level as to 

 give an appearance of pronounced artificiality. It is this fact, 

 supported by a score of similar ones from widely separated 

 points, that supplies the organizing principle in the physi- 

 ography of this whole region. It will be shown that we have 

 here an uplifted peneplain, whose position 14,000 ft. above 



