PHYSICAL GEOGRAPHY 717 



climbs a thousand feet out of the canyon and across a high ridge a half 

 mile north of the stream bed. 



Sierra de Guarui. — About 20 miles west of the southern portion, of the 

 Sierra de Charagua there is a parallel, but much shorter, range, known 

 as the Sierra cle Guarui. Among its unnamed peaks is the highest sum- 

 mit along the eastern front of the Andes, with serrate crest at an altitude 

 of slightly over 6,000 feet. The whole sierra is exceedingly rugged in its 

 Youthful topography; its eastern margin is a bold fault-scarp which rises 

 almost sheer for ten or twelve hundred feet above the floor of the broad 

 lowland belt occupied by the Eio Guarui, which borders the range on the 

 east and intervenes between it and the western back-slope of the Cuestas 

 de Pipi. Ten to 15 miles south of Eio Parapiti there are numerous 

 irregular hills of almost mountainous dimensions which clog this inter- 

 montane depression and connect the Sierra de Guarui with the northwest 

 part of the Sierra de Mandiyuti. 



Sierra de A guar ague. — The Sierra de Aguarague extends from a point 

 in latitude 20° 25' south to latitude 22° 45', a distance of nearly 170 

 miles. It is the front range of the Andes throughout its entire length 

 and overlooks the plain stretching eastward to the Paraguay River. The 

 mountain summits rise abruptly above this plain to altitudes of about 

 4,500 feet. In certain places the mountain front is a sheer cliff, unbroken 

 by erosion, rising almost vertically toward the higher summits. Else- 

 where the eastern front of the mountains is formed by steeply inclined 

 hogbacks, the dip slopes of which are conspicuous features of the topog- 

 raphy. There is a rather striking accordance in summit elevation of the 

 higher ridges and peaks throughout the entire extent of the sierra. At 

 the north its heights decline gradually and blend into the plain near 

 Boyuibi, about 10 miles southwest of the southern end of the Sierra de 

 Charagua. At the south there is a similar descent to the plain which 

 extends southward past Embarcacion. 



Southwest of the Sierra de Aguarague is a narrow intermontane low- 

 land, at an elevation of about 3,000 feet above sealevel, which separates 

 it from the Sierra de Vitiacua. Its topography of undulating bills is 

 similar to that of the plain east of the mountains. The northern part of 

 this lowland in the vicinity of Ibo is shown in figure 6. In this same 

 view the western slopes of the range, with their steeply inclined hogbacks 

 dipping toward the west, may be observed in the distance. I have not 

 observed the western slopes of this sierra south of Rio Vitiacua, but it is 

 my understanding from the local inhabitants that the intermontane low- 

 land continues southward and everywhere separates the Sierra de Agua- 

 rague from the more westerly ranges of the Andes. 



