I835-] PASSAGE OF THE CORDILLERA. 227 



upraised, and their injection by fluidified rock. This rending and 

 injection would, if repeated often enough (and we know that earth- 

 quakes repeatedly affect the same areas in the same manner), form a 

 chain of hills ; and the linear island of St. Mary, which was upraised 

 thrice the height of the neighbouring country, seems to be undergoing 

 this process. I believe that the solid axis of a mountain, differs in 

 its manner of formation from a volcanic hill, only in the molten stone 

 having been repeatedly injected, instead of having been repeatedly 

 ejected. Moreover, I believe that it is impossible to explain the 

 structure of great mountain-chains, such as that of the Cordillera, 

 where the strata, capping the injected axis of plutonic rock, have been 

 thrown on their edges along several parallel and neighbouring lines 

 of elevation, except on this view of the rock of the axis having been 

 repeatedly injected, after intervals sufficiently long to allow the upper 

 parts or wedges to cool and become solid ; for if the strata had been 

 thrown into their present highly-inclined, vertical, and even inverted 

 positions, by a single blow, the very bowels of the earth would have 

 gushed out ; and instead of beholding abrupt mountain-axes of rock 

 solidified under great pressure, deluges of lava would have flowed out 

 at innumerable points on every line of elevation.* 



CHAPTER XV. 



PASSAGE OF THE CORDILLERA^ 



Valparaiso Portillo Pass Sagacity of Mules Mountain-torrents Mines, 

 how discovered Proofs of the Gradual Elevation of the Cordillera Effect 

 of Snow on Rocks Geological Structure of the Two Main Ranges, their 

 Distinct Origin and Upheaval Great Subsidence Red Snow Winds 

 Pinnacles of Snow Dry and Clear Atmosphere Electricity Pampas 

 Zoology of the Opposite Sides of the Andes Locusts Great Bugs 

 Mendoza Uspallata Pass Silicified Trees buried as they grew Incas 

 Bridge Badness of the Passes Exaggerated Cumbre Casuchas Val- 

 paraiso. 



March 7th, 1835. WE stayed three days at Concepcion, and then 

 sailed for Valparaiso. The wind being northerly, we only reached the 

 mouth of the harbour of Concepcion before it was dark. Being very 

 near the land, and a fog coming on, the anchor was dropped. Presently 

 a large American whaler appeared close alongside of us ; and we heard 

 the Yankee swearing at liis men to keep quiet, whilst he listened for 

 the breakers. Captain Fitz Roy hailed him, in a loud clear voice, to 

 anchor where lie then was. The poor man must have thought the 

 * For a full account of the volcanic phenomena which accompanied the 

 earthquake of the 2Oth, and for the conclusions deducible from them, I must 

 refer to Volume V. of the Geological Transactions. 



B 



