Narrative of the surveying voyages of his majesty's ships Adventure and Beagle (vol.2): between the years 1826 and 1836 : describing their examination of the southern shores of South America, and the Beagles's circumnavigation of the globe

ON THE DELUGE. 667 tliat tidal oscillations,* combined with immense pressure, spread and smoothed it, while in a rapidly cooling though viscous state, over the surface of the land. The vast quantity of shingle, or rounded stones of all sizes, may be accounted for in a manner unconnected with that of water acting upon a shore ; though doubtless a great propor- tion of the shingle we see has been rounded in that manner. Melted stone, thrown out of a volcano, and propelled through water with great velocity, might be rounded and cooled as shot are when dropped into water from a tower. In modern volca- noes we observe that some matter is thrown into the air, while other, and the greater quantity, runs over the edges of a crater, overflowing the adjacent tracts of land. Proceeding to the west coast of South America, we find that near Concepcion there are beds of marine shells at a great height above the level of the sea. These, say geologists, were once under the ocean, but, in consequence of the gradual upheaval of the land, are now far above it. They are closely com- pressed together, and some are broken, though of a very solid and durable nature ; and being near the surface of the land are covered with only a thin stratum of earth. They are massed together in a manner totally different from any in. which they could have grown, therefore the argument used in Patagonia is again applicable here. But in addition to this, there is another fact deserving attention : namely, that there are similar beds of similar shells, (identical with living species) about, or rather below the level of the present ocean, and at some distance from it.-f- In crossing the Cordillera of the Andes Mr. Darwin found petrified trees, embedded in sandstone, six or seven thousand feet above the level of the sea : and at twelve or thirteen thou- sand feet above the sea-level he found fossil sea-shells, lime- stone, sandstone, and a conglomerate in which were pebbles of the " rock with shells."" Above the sandstone in which the petri- fied trees were found, is " a great bed, apparently about one thousand feet thick, of black augitic lava; and over this there * Sec remarks on tides in the Appendix. t Pafjes 421, 2, 3.