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action), I was astonished to find perfectly rounded masses
of the black calcareous clay-slate with organic remains,—the
same rock which I had just crossed in silu on the Peuquenes.
These phenomena compel us to arrive at the following conclusion
:—that the Peuquenes existed as dry land for a long
period anterior to the formation of the second range, and
that, during this period, immense quantities of shingle were
accumulated at its submarine flank. The action of a disturbing
force then commenced : these more modern deposits
were injected by dikes, altered by heat, and tilted towards
the line whence, in the form of sediment and pebbles, they
had originally proceeded,—thus making the offspring at first
appear older than its parent. This second, grand, and subsequent
line of elevation is parallel to the first and more
ancient one.
I will only make one other geological observation: the
Portillo chain in the neighbourhood of the pass is rather
more elevated than the Peuquenes, yet the waters of the
intermediate district have burst a passage through it. On
the supposition of a subsequent and gradual elevation of the
second line, this can be understood; for a chain of islets
would at first appear, and as these were lifted up, the tides
would always be working out deeper and broader channels
between them. At the present day, even in the most retired
sounds on the southern coast, the currents in the transverse
breaks which connect the longitudinal channels, is so strong,
that I have heard of one instance where a small vessel under
sail was whirled round and round.
Mr. Pentland,* when describing an hydrographical phenomenon
of a nearly similar kind, but on an infinitely
grander scale, which occurs in Bolivia, says, “ This very
curious fact, of rivers escaping through such an immense
mountain-mass as the Bolivian Cordillera, is perhaps one of
the most important points connected with the physical
geography of this portion of the Andes, and deserves to be
J o u rn a l o f th e R o y a l G e o g ra p h . So c ie ty for 1835.
noticed at greater length.” It would be extremely rash to
affirm that the eastern chain in Bolivia, like that of central
Chile, must be of subsequent origin to the western one, or
that nearer to the Pacific : but excepting through the explanation
above offered, the circumstance that rivers flowing from
a less elevated chain, should penetrate one far more lofty,
appears to me quite inexplicable.
About noon we began the tedious ascent of the Peuquenes,
and then for the first time experienced some little difficulty in
our respiration. The mules would halt every fifty yards, and
then the poor willing animals after a few seconds started of
their own accord again. The short breathing from the rarefied
atmosphere is called by the Chilenos “ puna and they have
most ridiculous notions concerning its origin. Some say,
“ all the waters here have puna others that “ where there
is snow there is puna ;”—and this no doubt is true. It is
considered a kind of disease, and I was shown the crosses
over the graves of some who had died “ puñado.” Excepting
perhaps in the case of a person suffering from some organic
disease of the heart or chest, I should think this must be an
erroneous conclusion. A person near death, would probably
at this elevation experience a more unusual difficulty in
breathing than others ; and hence the effect might be assumed
as the cause. The only sensation I felt was a slight tightness
over the head and chest ; a feeling which may be experienced
by leaving a warm room and running violently on
a frosty day. Tliere was much fancy even in this; for
upon finding fossil shells on the highest ridge, I entirely
forgot the puna in my delight. Certainly the exertion of
walking was extreme, and the respiration became deep and
laborious. It is incomprehensible to me, how Humboldt
and others were able to ascend to the elevation of 19,000
feet. No doubt a residence of some months in the lofty
region of Quito would prepare the constitution for such an
exertion ; yet I am told that in Potosi (about 13,000 feet),
strangers do not become quite accustomed to the atmosphere
for an entire year. The inhabitants all recommend onions
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