It May Naturally Be Asked, How It Comes That,
Although No Extensive Fossiliferous Deposits Of The Recent
Period, Nor Of
Any period intermediate between it and the
ancient tertiary epoch, have been preserved on either side of
the continent, yet
That at this ancient tertiary epoch,
sedimentary matter containing fossil remains, should have been
deposited and preserved at different points in north and
south lines, over a space of 1100 miles on the shores of the
Pacific, and of at least 1350 miles on the shores of the
Atlantic, and in an east and west line of 700 miles across the
widest part of the continent? I believe the explanation is
not difficult, and that it is perhaps applicable to nearly
analogous facts observed in other quarters of the world.
Considering the enormous power of denudation which the sea
possesses, as shown by numberless facts, it is not probable
that a sedimentary deposit, when being upraised, could pass
through the ordeal of the beach, so as to be preserved in
sufficient masses to last to a distant period, without it were
originally of wide extent and of considerable thickness: now
it is impossible on a moderately shallow bottom, which
alone is favourable to most living creatures, that a thick
and widely extended covering of sediment could be spread
out, without the bottom sank down to receive the successive
layers. This seems to have actually taken place at about
the same period in southern Patagonia and Chile, though
these places are a thousand miles apart. Hence, if prolonged
movements of approximately contemporaneous subsidence
are generally widely extensive, as I am strongly
inclined to believe from my examination of the Coral Reefs
of the great oceans - or if, confining our view to South
America, the subsiding movements have been co-extensive
with those of elevation, by which, within the same period
of existing shells, the shores of Peru, Chile, Tierra del
Fuego, Patagonia, and La Plata have been upraised - then
we can see that at the same time, at far distant points,
circumstances would have been favourable to the formation of
fossiliferous deposits of wide extent and of considerable
thickness; and such deposits, consequently, would have a
good chance of resisting the wear and tear of successive
beach-lines, and of lasting to a future epoch.
May 21st. - I set out in company with Don Jose Edwards
to the silver-mine of Arqueros, and thence up the valley of
Coquimbo. Passing through a mountainous country, we
reached by nightfall the mines belonging to Mr. Edwards.
I enjoyed my night's rest here from a reason which will not
be fully appreciated in England, namely, the absence of
fleas! The rooms in Coquimbo swarm with them; but they
will not live here at the height of only three or four
thousand feet: it can scarcely be the trifling diminution
of temperature, but some other cause which destroys these
troublesome insects at this place. The mines are now in a
bad state, though they formerly yielded about 2000 pounds
in weight of silver a year.
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