183:;.] OF THE TERTIyVRY FORMATIONS. 345 



tinent, yet that at this ancient tertiary epoch, sedimentaiy 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 

 ( ould be spread out, without the bottom sank down to receive 

 tlie successive layers. This seems to have actually taken place 

 at about the same period in soutliern 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, 

 wiihin 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 favourablato 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 2\st, — 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 wliich will not be fully 



