482 Section by the P or til I Pass. paet n. 



fig. 1, which 1 will now describe in detail, is on a 

 horizontal scale of a third of an inch to a nautical mile, 

 and on a vertical scale of one inch to a mile or 6,000 

 feet. The width of the range (excluding a few out- 

 lying hillocks), from the plain on which St. Jago the 

 capital of Chile stands, to the Pampas, is sixty miles, as 

 far as I can judge from the maps, which differ from each 

 other and are all exceedingly imperfect. The St. Jago 

 plain at the mouth of the Maypu, I estimate from ad- 

 joining known points at 2,300 feet, and the Pampas at 

 3,500 feet, both above the level of the sea. The height 

 of the Peuquenes line, according to Dr. Gillies, 1 is 

 13,210 feet; and that of the Portillo line (both in the 

 gaps where the road crosses them) is 14,345 feet ; the 

 lowest part of the intermediate valley of Tenuyan is 

 7,530 feet — all above the level of the sea. 



The Cordillera here, and indeed I believe throughout 

 Chile, consist of several parallel, anticlinal and uniclinal 

 mountain-lines, ranging north, or north with a little 

 westing, and south. Some exterior and much lower 

 ridges often vary considerably from this course, pro- 

 jecting like oblique spurs from the main ranges : in 

 the district towards the Pacific, the mountains, as be- 

 fore remarked, extend in various directions, even east 

 and west. In the main exterior lines, the strata, as also 

 before remarked, are seldom inclined at a high angle ; 

 but in the central lofty ridges they are almost always 

 highly inclined, broken by many great faults, and often 

 vertical. As far as I could judge, few of the ranges are 

 of great length : and in the central parts of the Cor- 

 dillera, I was frequently able to follow with my eye a 

 ridge gradually becoming higher and higher, as the 

 stratification increased in inclination, from one end 

 where its height was trifling and its strata gently inclined 

 1 ' Journal of Nat. and Geograph. Science,' August, 1830. 



