dentity, in their mineral components, of the pumice and
obsidian of the recent volcanoes; and that pitchstone, the obsidian of
the trap-rocks, is resolvable into a pumice by the art of the chemist.
If pumice was to be found anywhere in Scotland, we might _a priori_
expect to find it in connection with by far the largest mass of
pitchstone in the kingdom. It is just possible, however, that Mr.
Greig's two specimens may not date farther back, in at least their
existing state, than the days of the hill-fort. Powerful fires would
have been required to render the exposed summit of the Scuir at all
comfortable; there is a deep peat-moss in its immediate neighborhood,
that would have furnished the necessary fuel; the wind must have been
sufficiently high on the summit to fan the embers into an intense white
heat; and if it was heat but half as intense as that which was employed
in fusing into one mass the thick vitrified ramparts of Craig Phadrig
and Knock Farril, on the east coast, it could scarce have failed to
anticipate the experiment of the Hon. Mr. Knox, of Dublin, by converting
some of the numerous pitchstone fragments that lie scattered about,
"into a light substance in every respect resembling pumice."

It was now evening, and rarely have I witnessed a finer. The sun had
declined half-way adown the western sky, and for many yards the shadow
of the gigantic Scuir lay dark beneath us along the descending slope.
All the rest of the island, spread out at our feet as in a map, was
basking in yellow sunshine; and with its one dark shadow thrown from its
one mountain-elevated wall of rock, it seemed some immense fantastical
dial, with its gnomon rising tall in the midst. Far below, perched on
the apex of the shadow, and half lost in the line of the penumbra, we
could see two indistinct specks of black, with a dim halo around
each,--specks that elongated as we arose, and contracted as we sat, and
went gliding along the line as we walked. The shadows of two gnats
disporting on the edge of an ordinary gnomon would have seemed vastly
more important, in proportion, on the figured plane of the dial, than
these, our ghostly representatives, did here. The sea, spangled in the
wake of the sun with quick glancing light, stretched out its blue plain
around us; and we could see included in the wide prospect, on the one
hand, at once the hill-chains of Morven and Kintail, with the many
intervening lochs and bold jutting headlands that giv