cks, their surfaces, being violently heated
by the sun, whose most intense warmth always precedes rain, occasion
sudden and violent evaporation, actually converting the first shower
into steam. Consequently, upon all such hills, on the commencement of
rain, white volumes of vapor are instantaneously and universally formed,
which rise, are absorbed by the atmosphere, and again descend in rain,
to rise in fresh volumes until the surfaces of the hills are cooled.
Where there is grass or vegetation, this effect is diminished; where
there is foliage it scarcely takes place at all. Now this effect has
evidently been especially chosen by Turner for Loch Coriskin, not only
because it enabled him to relieve its jagged forms with veiling vapor,
but to tell the tale which no pencilling could, the story of its utter
absolute barrenness of unlichened, dead, desolated rock:--

"The wildest glen, but this, can show
Some touch of nature's genial glow,
On high Benmore green mosses grow,
And heath-bells bud in deep Glencoe.
And copse on Cruchan Ben;
But here, above, around, below,
On mountain, or in glen,
Nor tree, nor plant, nor shrub, nor flower,
Nor aught of vegetative power,
The wearied eye may ken;
But all its rocks at random thrown,
Black waves, bare crags, and banks of stone."

LORD OF THE ISLES, Canto III

Here, again, we see the absolute necessity of scientific and entire
acquaintance with nature, before this great artist can be understood.
That which, to the ignorant, is little more than an unnatural and
meaningless confusion of steam-like vapor, is to the experienced such a
full and perfect expression of the character of the spot, as no means of
art could have otherwise given.

Sec. 16. The drawing of transparent vapor in the Land's End.

Sec. 17. The individual character of its parts.

In the Long Ships Lighthouse, Land's End, we have clouds without
rain--at twilight--enveloping the cliffs of the coast, but concealing
nothing, every outline being visible through their gloom; and not only
the outline--for it is easy to do this--but the _surface_. The bank of
rocky coast approaches the spectator inch by inch, felt clearer and
clearer as it withdraws from the garment of cloud--not by edges more and
more defined, but by a surfac