There rise
on the western side of the boss two hills, one of which attains to the
elevation of nearly seven hundred, and the other of nearly eight hundred
feet over it; and yet both hills to their summits are mottled over with
granite boulders, furnished by the comparatively low-lying boss. One of
these travelled masses, fully two tons in weight, lies not sixty feet
from the summit of the loftier hill, at an altitude of nearly fifteen
hundred feet over the sea. Now, it seems extremely difficult to conceive
of any other agency than that of a rising sea or of a subsiding land,
through which these masses could have been rolled up the steep slopes of
the hills. Had the boulder period been a period of elevation, or merely
a stationary period, during which the land neither rose nor sank, the
travelled boulders would not now be found resting at higher levels than
that of the parent rock whence they were derived. We occasionally meet
on our shores, after violent storms from the sea, stones that have been
rolled from their place at low ebb to nearly the line of flood; but we
always find that it was by the waves of the rising, not of the falling
tide, that their transport was effected. For whatever removals of the
kind take place during an ebbing sea are invariably in an opposite
direction;--they are removals, not from lower to higher levels, but from
higher to lower.

The upper subsoils of Scotland bear frequent mark of the elevatory
period which succeeded this period of depression. The boulder-clay has
its numerous intercalated arenaceous and gravelly beds, which belong
evidently to its own era; but the numerous surface-beds of stratified
sand and gravel by which in so many localities it is overlaid belong
evidently to a later time. When, after possibly a long protracted
period, the land again began to rise, or the sea to fall, the superior
portions of the boulder-clay must have been exposed to the action of the
tides and waves; and the same process of separation of parts must have
taken place on a large scale, which one occasionally sees taking place
in the present time on a comparatively small one, in ravines of the same
clay swept by a streamlet. After every shower, the stream comes down
red and turbid with the finer and more argillaceous portions of the
deposit; minute accumulations of sand are swept to the gorge of the
ravine, or cast down in ripple-marked patches in its deeper pools; beds
of pebbles and gravel are heaped