ing from Mealfourvonny, on the
northern shores of Loch Ness, to the Maiden Paps of Caithness.

The more ancient boulder-clays of Scotland seem to have been formed when
the land was undergoing a slow process of subsidence, or, as I should
perhaps rather say, when a very considerable area of the earth's
surface, including the sea-bottom, as well as the eminences that rose
over it, was the subject of a gradual depression; for little or no
alteration appears to have taken place at the time in the _relative_
levels of the higher and lower portions of the sinking area: the
features of the land in the northern part of the kingdom, from the
southern flanks of the Grampians to the Pentland Frith, seemed to have
been fixed in nearly the existing forms many ages before, at the close,
apparently, of the Oolitic period, and at a still earlier age in the
Lammermuir district, to the south. And so the sea around our shores must
have deepened in the ratio in which the hills sank. The evidence of this
process of subsidence is of a character tolerably satisfactory. The
dressed surfaces occur in Scotland, most certainly, as I have already
stated on the authority of Dr. Fleming, at the height of fourteen
hundred feet over the present sea-level; it has been even said, at
fully twice that height, on the lofty flanks of Schehallion,--a
statement, however, which I have had hitherto no opportunity of
verifying. They may be found, too, equally well marked, under the
existing high-water line; and it is obviously impossible that the
dressing process could have been going on at the higher and lower levels
at the same time. When the icebergs were grating along the more elevated
rocks, the low-lying ones must have been buried under from three to
seven hundred fathoms of water,--a depth from three to seven times
greater, be it remembered, than that at which the most ponderous iceberg
could possibly have grounded, or have in any degree affected the bottom.
The dressing process, then, must have been a bit-and-bit process,
carried on during either a period of elevation, in which the rising land
was subjected, zone after zone, to the sweep of the armed ice from its
higher levels _downwards_, or during a period of subsidence, in which it
was subjected to the ice, zone after zone, from its lower levels
_upwards_. And that it was the lower, not the higher levels, that were
first dressed, appears evident from the circumstance, that though on
these lower levels