of the loch, we
find the immense escarpment composed from top to bottom exclusively of
trap; but then the Oolite again begins to appear, and about two miles
further on the section becomes truly magnificent,--one of the finest
sections of this formation exhibited anywhere in Britain, perhaps in the
world. In a ravine furrowed in the face of the declivity by the headlong
descent of a small stream, we may trace all the beds of the system in
succession, from the Cornbrash, an upper deposit of the Lower Oolite,
down to the Lias, the formation on which the Oolite rests. The only
modifying circumstance to the geologist is, that though the sandstone
beds run continuously along the cliff for miles together, distinct as
the white bands in a piece of onyx, the intervening beds of shale are
swarded over, save where we here and there see them laid bare in some
abrupter acclivity or deeper water-course. In the shale we find numerous
minute Ammonites, sorely weathered; in the sandstone, Belemnites, some
of them of great size; and dark carbonaceous markings, passing not
unfrequently into a glossy cubical coal. At the foot of the cliff I
picked up an ammonite of considerable size and well-marked
character,--the _Ammonites Murchisonae_, first discovered on this coast
by Sir R. Murchison about fifteen years ago. It measures, when full
grown, from six to seven inches in diameter; the inner whorls, which are
broadly visible, are ribbed; whereas the two, and sometimes the three
outer ones, are smooth,--a marked characteristic of the species. My
specimen merely enabled me to examine the peculiarities of the shell
just a little more minutely than I could have done in the pages of
Sowerby; for such was its state of decay, that it fell to pieces in my
hands. I had now come full in view of the rocky island of Holm, when the
altered appearance of the heavens led me to deliberate, just as I was
warming in the work of exploration, whether, after all, it might not be
well to scale the cliffs, and strike directly on the inn. It was nearly
three o'clock; the sky had been gradually darkening since noon, as if
one thin covering of gauze after another had been drawn over it; hill
and island had first dimmed and then disappeared in the landscape; and
now the sun stood up right over the fast-contracting vista of the Sound,
round and lightless as the moon in a haze; and the downward
cataract-like streaming of the gray vapor on the horizon showed that
there th