MARCH 30, 1835.
The solitary hovel which bears the imposing name of Villa Vicencio
has been mentioned by every traveller who has crossed the Andes. I
stayed here and at some neighbouring mines during the two
succeeding days. The geology of the surrounding country is very
curious. The Uspallata range is separated from the main Cordillera
by a long narrow plain or basin, like those so often mentioned in
Chile, but higher, being six thousand feet above the sea. This
range has nearly the same geographical position with respect to the
Cordillera, which the gigantic Portillo line has, but it is of a
totally different origin: it consists of various kinds of submarine
lava, alternating with volcanic sandstones and other remarkable
sedimentary deposits; the whole having a very close resemblance to
some of the tertiary beds on the shores of the Pacific. From this
resemblance I expected to find silicified wood, which is generally
characteristic of those formations. I was gratified in a very
extraordinary manner. In the central part of the range, at an
elevation of about seven thousand feet, I observed on a bare slope
some snow-white projecting columns. These were petrified trees,
eleven being silicified, and from thirty to forty converted into
coarsely-crystallised white calcareous spar.
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