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 1st.--We crossed the Upsallata 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. Here it was a furious
torrent, quite impassable, and appeared larger than in the low country,
as was the case with the rivulet of Villa Vicencio. On the evening of
the succeeding day, we reached the Rio de las Vacas, which is
considered the worst stream in the Cordillera to cross. As all these
rivers have a rapid and short course, and are formed by the melting of
the snow, the hour of the day makes a considerable difference in their
volume. In the evening the stream is muddy and full, but about
daybreak it becomes clearer, and much less impetuous. This we found to
be the case with the Rio Vacas, and in the morning we crossed it with
little difficulty.
The scenery thus far was very uninteresting, compared with that of the
Portillo pass. Little can be seen beyond the bare walls of the one
grand flat-bottomed valley, which the road follows up to the highest
crest. The valley and the huge rocky mountains are extremely barren:
during the two previous nights the poor mules had absolutely nothing to
eat, for excepting a few low resinous bushes, scarcely a plant can be
seen. In the course of this day we crossed some of the worst passes in
the Cordillera, but their danger has been much exaggerated. I was told
that if I attempted to pass on foot, my head would turn giddy, and that
there was no room to dismount; but I did not see a place where any one
might not have walked over backwards, or got off his mule on either
side. One of the bad passes, called _las Animas_ (the souls), I had
crossed, and did not find out till a day afterwards, that it was one of
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