THE ARID ANDES. PUNTA VACAS, ON THE TRANS-ANDEAN RAILWAY. 



The bottom of the valley is 8,000 feet above sea-level ; the sides buried under rubbish. It is 

 especially in this latitude, above a height of 10,600 feet, in the zone where the moisture falls 

 as snow even in summer, that the rock is everywhere buried under its own rubbish. This is 

 Kddels Schuttzone. It extends to the foot of the Alpine peaks, carved by glaciers. 



Photograph by Moody, Buenos Aires. 



OUEBRADA DE IRUYA. 



Eastern slope of the Sierra de Santa Victoria, 65 miles from the Bolivian frontier, in the zone 

 of summer rain. The valleys have been filled with an enormous mass of torrential alluvia. 

 The water afterwards made a course through the mobile deposits. 



Photograph by Keidel, Mines Division. 

 PLATE II. To face p. 22. 



