be somewhat habituated to the climate of these countries to perceive
the extreme improbability of rain falling at such seasons, except as a
consequence of some law quite unconnected with the ordinary course of
the weather. In the cases of great volcanic eruptions, as that of
Coseguina, where torrents of rain fell at a time of the year most
unusual for it, and "almost unprecedented in Central America," it is
not difficult to understand that the volumes of vapour and clouds of
ashes might have disturbed the atmospheric equilibrium. Humboldt
extends this view to the case of earthquakes unaccompanied by
eruptions; but I can hardly conceive it possible, that the small
quantity of aeriform fluids which then escape from the fissured ground,
can produce such remarkable effects. There appears much probability in
the view first proposed by Mr. P. Scrope, that when the barometer is
low, and when rain might naturally be expected to fall, the diminished
pressure of the atmosphere over a wide extent of country, might well
determine the precise day on which the earth, already stretched to the
utmost by the subterranean forces, should yield, crack, and
consequently tremble. It is, however, doubtful how far this idea will
explain the circumstances of torrents of rain falling in the dry season
during several days, after an earthquake unaccompanied by an eruption;
such cases seem to bespeak some more intimate connection between the
atmospheric and subterranean regions.
Finding little of interest in this part of the ravine, we retraced our
steps to the house of Don Benito, where I stayed two days collecting
fossil shells and wood. Great prostrate silicified trunks of trees,
embedded in a conglomerate, were extraordinarily numerous. I measured
one, which was fifteen feet in circumference: how surprising it is that
every atom of the woody matter in this great cylinder should have been
removed and replaced by silex so perfectly, that each vessel and pore
is preserved! These trees flourished at about the period of our lower
chalk; they all belonged to the fir-tribe. It was amusing to hear the
inhabitants discussing the nature of the fossil shells which I
collected, almost in the same terms as were used a century ago in
Europe,--namely, whether or not they had been thus "born by nature." My
geological examination of the country generally created a good deal of
surprise amongst the Chilenos: it was long before they could be
convinced that I was not hunting for mines. This was sometimes
troublesome: I found the most ready way of explaining my employment,
was to ask them how it was that they themselves were not curious
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