thickness to several thousand feet. I am quite afraid of the only
conclusion which I can draw from this fact, namely that there must have
been a depression in the surface of the land to that amount. But
neglecting this consideration, it was a most satisfactory support of my
presumption of the Tertiary (I mean by Tertiary, that the shells of the
period were closely allied, or some identical, to those which now live, as
in the lower beds of Patagonia) age of this eastern chain. A great part of
the proof must remain upon my ipse dixit of a mineralogical resemblance
with those beds whose age is known, and the character of which resemblance
is to be subject to infinite variation, passing from one variety to another
by a concretionary structure. I hardly expect you to believe me, when it
is a consequence of this view that granite, which forms peaks of a height
probably of 14,000 feet, has been fluid in the Tertiary period; that strata
of that period are altered by its heat, and are traversed by dykes from the
mass. That these strata have also probably undergone an immense
depression, that they are now inclined at high angles and form regular or
complicated anticlinal lines. To complete the climax and seal your
disbelief, these same sedimentary strata and lavas are traversed by VERY
NUMEROUS, true metallic veins of iron, copper, arsenic, silver and gold,
and these can be traced to the underlying granite. A gold mine has been
worked close to the clump of silicified trees. If when you see my
specimens, sections and account, you should think that there is pretty
strong presumptive evidence of the above facts, it appears very important;
for the structure, and size of this chain will bear comparison with any in
the world, and that this all should have been produced in so very recent a
period is indeed wonderful. In my own mind I am quite convinced of the
reality of this. I can anyhow most conscientiously say that no previously
formed conjecture warped my judgment. As I have described so did I
actually observe the facts. But I will have some mercy and end this most
lengthy account of my geological trip.