Nor had those antagonistic forces been dormant, which are always at work wearing down the surface of the land; the great piles of strata had been intersected by many wide valleys, and the trees, now changed into silex, were exposed projecting from the volcanic soil, now changed into rock, whence formerly, in a green and budding state, they had raised their lofty heads.

Now, all is utterly irreclaimable and desert; even the lichen cannot adhere to the stony casts of former trees.

Vast, and scarcely comprehensible as such changes must ever appear, yet they have all occurred within a period, recent when compared with the history of the Cordillera; and the Cordillera itself is absolutely modern as compared with many of the fossiliferous strata of Europe and America.
APRIL 1, 1835.
We crossed the Uspallata range, and at night slept at the custom-house--the only inhabited spot on the plain.

Shortly before leaving the mountains, there was a very extraordinary view; red, purple, green, and quite white sedimentary rocks, alternating with black lavas, were broken up and thrown into all kinds of disorder by masses of porphyry of every shade of colour, from dark brown to the brightest lilac.

It was the first view I ever saw, which really resembled those pretty sections which geologists make of the inside of the earth.
The next day we crossed the plain, and followed the course of the same great mountain stream which flows by Luxan.