ate
very many times, and are quite conformable one to the other. During two
days of careful examination I said to myself at least fifty times, how
exactly like (only rather harder) these beds are to those of the
upper Tertiary strata of Patagonia, Chiloe and Concepcion, without
the possible identity ever having occurred to me. At last there was
no resisting the conclusion. I could not expect shells, for they never
occur in this formation; but lignite or carbonaceous shale ought to
be found. I had previously been exceedingly puzzled by meeting in
the sandstone, thin layers (few inches to feet thick) of a brecciated
pitchstone. I strongly suspect the underlying granite has altered
such beds into this pitchstone. The silicified wood (particularly
characteristic) was yet absent. The conviction that I was on the
Tertiary strata was so strong by this time in my mind, that on the
third day in the midst of lavas and [? masses] of granite I began my
apparently forlorn hunt. How do you think I succeeded? In an escarpement
of compact greenish sandstone, I found a small wood of petrified trees
in a vertical position, or rather the strata were inclined about 20-30
deg to one point and the trees 70 deg to the opposite one. That is,
they were before the tilt truly vertical. The sandstone consists of
many layers, and is marked by the concentric lines of the bark (I have
specimens); 11 are perfectly silicified and resemble the dicotyledonous
wood which I have found at Chiloe and Concepcion (6/2. "Geol. Obs." page
202. Specimens of the silicified wood were examined by Robert Brown,
and determined by him as coniferous, "partaking of the characters of the
Araucarian tribe, with some curious points of affinity with the yew.");
the others (30-40) I only know to be trees from the analogy of form
and position; they consist of snow-white columns (like Lot's wife) of
coarsely crystalline carb. of lime. The largest shaft is 7 feet. They
are all close together, within 100 yards, and about the same level:
nowhere else could I find any. It cannot be doubted that the layers
of fine sandstone have quietly been deposited between a clump of trees
which were fixed by their roots. The sandstone rests on lava, is covered
by a great bed apparently about 1,000 feet thick of black augitic lava,
and over this there are at least 5 grand alternations of such rocks and
aqueous sedimentary deposits, amounting in thickness to several thousand
feet. I am quite afraid