XVI CORRELATION OF TERTIARY BEDS 369 



lines, over a space of i 1 00 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 sedi- 

 ment 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 contem- 

 poraneous 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 coextensive with 

 those of elevation, by which, within the same period oi 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 2is/. — 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 



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