1835.] OF THE TERTIARY FORMATIONS. 345 
tinent, yet that at this ancient tertiary epoch, sedimentary matter 
containing fossil remains, should have been deposited and pre- 
served 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 mode- 
rately 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 move- 
ments have been coextensive 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 thick- 
ness; 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 Co- 
quimbo. 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 
