marble silence is suddenly broken by the rush of an avalanche, that
tears away the superincumbent masses, rolling them into the sea; and the
ponderous block, laid open to the light, finds itself on the bleak shore
of a desert island of the northern Scottish archipelago, with a wintry
scene of snow-covered peaks behind, and an ice-mottled ocean before. The
winter passes, the cold severe spring comes on, and day after day the
field-ice goes floating by,--now gray in shadow, now bright in the sun.
At length vegetation, long repressed, bursts forth, but in no profuse
luxuriance. A few dwarf birches unfold their leaves amid the rocks; a
few sub-arctic willows hang out their catkins beside the swampy runnels;
the golden potentilla opens its bright flowers on slopes where the
evergreen _Empetrum nigrum_ slowly ripens its glossy crow-berries; and
from where the sea-spray dashes at full tide along the beach, to where
the snow gleams at midsummer on the mountain-summits, the thin short
sward is dotted by the minute cruciform stars of the scurvy-grass, and
the crimson blossoms of the sea-pink. Not a few of the plants of our
existing sea-shores and of our loftier hill-tops are still identical in
species; but wide zones of rich herbage, with many a fertile field and
many a stately tree, intervene between the bare marine belts and the
bleak insulated eminences; and thus the alpine, notwithstanding its
identity with the littoral flora, has been long divorced from it; but in
this early time the divorce had not yet taken place, nor for ages
thereafter; and the same plants that sprang around the sea-margin rose
also along the middle slopes to the mountain-summits. The landscape is
treeless and bare, and a hoary lichen whitens the moors, and waves, as
the years pass by, in pale tufts, from the disinterred stone, now
covered with weather-stains, green and gray, and standing out in bold
and yet bolder relief from the steep hill-side as the pulverizing frosts
and washing rains bear away the lesser masses from around it. The sea is
slowly rising, and the land, in proportion, narrowing its flatter
margins, and yielding up its wider valleys to the tide; the low green
island of one century forms the half-tide skerry, darkened with algae, of
another, and in yet a third exists but as a deep-sea rock. As its summit
disappears, groups of hills, detached from the land, become islands,
skerries, deep-sea rocks, in turn. At length the waves at full wash