II. fig. 1. 2. 3.]

Considered as a porphyry, this specimen is no less singular than as a
granite. For, instead of a siliceous ground, maculated with the rhombic
feld-spar, which is the common state of porphyry, the ground is
uniformly crystallised, or a homogeneous regular feld-spar, maculated
with the transparent siliceous substance. But as, besides the feld-spar
and quartz, which are the constituent parts of the stone, there is also
mica, in some places, it may, with propriety, be termed a granite.

The singularity of this specimen consists, not in the nature or
proportions of its constituent parts, but in the uniformity of the
sparry ground, and the regular shape of the quartz mixture. This
siliceous substance, viewed in one direction, or longitudinally, may
be considered as columnar, prismatical, or continued in lines running
nearly parallel. These columnar bodies of quartz are beautifully
impressed with a figure on the sides, where they are in contact with the
spar. This figure is that of furrows or channels, which are perfectly
parallel, and run across the longitudinal direction of the quartz. This
is represented in fig. 4. This striated figure is only seen when, by
fracture, the quartz is separated from the contiguous spar.

But what I would here more particularly represent is, the transverse
section of those longitudinal siliceous bodies These are seen in fig. 1.
2. and 3. They have not only separately the forms of certain typographic
characters, but collectively give the regular lineal appearance of types
set in writing.

It is evident from the inspection of this fossil, that the sparry and
siliceous substances had been mixed together in a fluid state; and that
the crystallization of the sparry substance, which is rhombic, had
determined the regular structure of the quartz, at least in some
directions.

Thus, the siliceous substance is to be considered as included in the
spar, and as figured, according to the laws of crystallization proper
to the sparry ground; but the spar is also to be found included in the
quartz. It is not, indeed, always perfectly included or inclosed on all
sides; but this is sometimes the case, or it appears so in the section.
Fig. 5. 6. 7. 8. 9. and 10. are those cases magnified, and represent the
different figured quartz inclosing the feld-spar. In one of them, the
feld-spar, which is contained within the quartz, contains also a small
triangle of quartz, which it incloses. Now,