also describes the high inclination of the obsidian rocks of the Cerro del
Navaja in Mexico in the "Proc. of the Geolog. Soc." June 1838.): on the
other hand, in Hungary, the layers are horizontal; the laminae, also, of
some of the lava-streams above referred to, as far as I can understand the
descriptions given of them, appear to be highly inclined or vertical. I
doubt whether in any of these cases, the laminae have been tilted into
their present position; and in some instances, as in that of the trachyte
described by Mr. Scrope, it is almost certain that they have been
originally formed with a high inclination. In many of these cases, there is
evidence that the mass of liquified rock has moved in the direction of the
laminae. At Ascension, many of the air-cells have a drawn out appearance,
and are crossed by coarse semi-glassy fibres, in the direction of the
laminae; and some of the layers, separating the sphaerulitic globules, have
a scored appearance, as if produced by the grating of the globules. I have
seen a specimen of zoned obsidian from Mexico, in Mr. Stokes' collection,
with the surfaces of the best-defined layers streaked or furrowed with
parallel lines; and these lines or streaks precisely resembled those,
produced on the surface of a mass of artificial glass by its having been
poured out of a vessel. Humboldt, also, has described little cavities,
which he compares to the tails of comets, behind sphaerulites in laminated
obsidian rocks from Mexico, and Mr. Scrope has described other cavities
behind fragments embedded in his laminated trachyte, and which he supposes
to have been produced during the movement of the mass. ("Geological
Transactions" volume 2 second series page 200 etc. These embedded
fragments, in some instances, consist of the laminated trachyte broken off
and "enveloped in those parts, which still remained liquid." Beudant, also,
frequently refers in his great work on "Hungary" tome 3 page 386, to
trachytic rocks, irregularly spotted with fragments of the same varieties,
which in other parts form the parallel ribbons. In these cases, we must
suppose, that after part of the molten mass had assumed a laminated