THE ARGENTINE UPLAND. 363 



same normal direction, and all standing on the same pedestal 1,500 feet above the 

 plains. In general these crystalline mountains present, like the Andes, their 

 steep face towards the west, and slope gently eastwards down to the pampas. 



A first ridge, traversed by the sti'cams descending from the central system, 

 generally falls below 3,000 feet except at a few rare points, and culminates in 

 the Cumbre de la Cal (5.150 feet) north-west of Cordoba. But the central chain 

 attains in the Champaqui peak a height of over 7,550 feet. In the north-west 

 the system merges in a plateau crossed by a line of volcanoes running east and 

 west, and terminating abruptly in the trachytic Cerro de Yerba Buena, which 

 rises 5,400 feet above the western plains. It has no apparent crater, nor has it 

 emitted lavas or vapours in the memory of man ; but slight earthquakes are 

 occasionally felt in the neighbourhood, and underground rumblings are also said 

 to be heard at the foot of these mountains. 



The Sierra de San Luiz, or de la Punta, from its south-western spur, may be 

 regarded as forming part of the Central or Cordoba system, which dies out 

 northwards in the saline depressions. On their western and northern sides the 

 San Luis heights present the aspect of bold mountain masses ; but these escarp- 

 ments merely serve to mask a hummocky plateau, which in many places assumes 

 the character of a simple tableland. Amongst the highest peaks of the escarp- 

 ments are Monigote (6,430 feet), and the Gigantillo, "Little Giant," which faces 

 the Gigante, " Giant," of the Andes system on the opposite side of the deep 

 Canada depression. 



The gneiss rocks of this sierra are distinguished from those of the Cordoba 

 system by their extreme richness in quartz and mica. East of Monigote a short 

 chain of volcanic heights, disposed transversely to the longitudinal axis, rises in 

 the Tomolasta to an altitude of 6,850 feet, culminating point of the plateau and 

 of the whole group. From its auriferous deposits this mountain has received the 

 name of Ceri'o de las Minas. 



The Tandil and Yentana Heights. 



Between the Parana and the Uruguay the surface is broken only by slight 

 rising grounds, or by fluvial cliffs ; but in the territory of the Missions, which 

 stretches cistwards into the Brazilian State of Santa Catharina, the campus 

 plains are traversed by a ridge with crests of from 1,000 to 1,300 feet. 



Distinct chains also rise east of the Patagonian Andes in the province of 

 Buenos Ayres and in the southern territories. A first line of crests runs north- 

 west and south-east parallel with the Lower Parana, terminating at the head- 

 land of Cape Corrientes. In the Sierra de Tandil this system rises to a height 

 of 1,100 feet, and farther on in the direction of the south-east the Sierra del 

 Yulcan has an altitude of 930 feet. Like the other heights of the surrounding 

 region the Sierra del Yulcan consists of granites, gneiss, and archaic rocks. But 

 there are no recent lavas, as might be supposed from the name of the range. But 

 this term " Vulcan " is not a Spanish, but a local Indian word, which would 



