332 USPALLATA PASS. (citar. xv. 
six thousand feet above the sea. This range has nearly the 
same geographical position with respect to the Cordillera, which 
the gigantic Portillo line has, but it is of a totally different 
origin: it consists of various kinds of submarine lava, alternat- 
ing with volcanic sandstones and other remarkable sedimentary 
deposits; the whole having a very close resemblance to some 
of the tertiary beds on the shores of the Pacific. From this 
resemblance I expected to find silicified wood, which is generally 
characteristic of those formations. I was gratified in a very ex- 
traordinary manner. In the central part of the range, at an 
elevation of about seven thousand feet, I observed on a bare slope 
some snow-white projecting columns. These were petrified 
trees, eleven being silicified, and from thirty to forty converted 
into coarsely-crystallized white calcareous spar: They were 
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. Mr. Robert Brown has 
been kind enough to examine the wood: he says it belongs to the 
fir tribe, partaking of the character of the Araucarian family, 
but with some curious points of affinity with the yew. The 
volcanic sandstone in which the trees were embedded, 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 little geological practice to interpret the marvel- 
lous story which this scene at once unfolded; though I confess 
I was at first so much astonished, that I could scarcely believe 
the plainest evidence. I saw the spot where a cluster of fine 
trees once waved their branches on the shores of the Atlantic, 
when that ocean (now driven back 700 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 sub- 
sequently 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 
