In the central part of a range of the Andes, at an elevation of about seven thousand feet, on a bare slope, may be observed some snow-white projecting columns. These are petrified trees, eleven being silicified, and from thirty to forty converted into coarsely crystallized white calcaraeous spar. They are abruptly broken off, the upright stumps projecting a few feet above the ground. The trunks measured from three to five feet each in circumference. They stood a little way apart from each other, but the whole formed one group. The volcanic sandstone in which the trees were imbedded, and from the lower part of which they must have sprung, had accumulated in successive thin layers around their trunks, and the stone yet retained the impression of the bark. "It required," says the eminent scientific man who visited the spot in 1835, "little geological practice to interpret the marvelous story which this scene at once unfolded. I saw the spot where a cluster of fine trees once reared their branches on the shores of the Atlantic, when that ocean, now driven back seven hundred miles, came to the foot of the Andes. I saw that they had sprung from a volcanic soil which had been raised above the level of the sea, and that subsequently this dry land, with its upright trees, had been let down into the depths of the ocean. In these depths, the formerly dry land was covered by sedimentary beds, and these again by enormous streams of submarine lava--one such mass attaining the thickness of a thousand feet; and these deluges of molten stone and aqueous deposits five times alternately had been spread out. The ocean which received such thick masses must have been profoundly deep; but again the subterranean forces exerted themselves, and I now beheld the bed of that ocean, forming a chain of mountains more than seven thousand feet in height. Nor had those antagonist forces been dormant which are always at work, wearing down the surface of the land; the great piles of strata had been intersected by many wide valleys, and the trees, now changed into silex, were exposed projecting from the volcanic soil, now changed into rocks, whence formerly, in a green and budding state, they had raised their lofty heads."