often waved and bent by the wind, or
twisted, sometimes even swept upwards from the cloud. The velocity of
these vapors, though not necessarily in reality greater than that of the
central clouds, appears greater, owing to their proximity, and, of
course, also to the usual presence of a more violent wind. They are also
apparently much more in the power of the wind, having less elastic force
in themselves; but they are precisely subject to the same great laws of
form which regulate the upper clouds. They are not solid bodies borne
about with the wind, but they carry the wind with them, and cause it.
Every one knows, who has ever been out in a storm, that the time when it
rains heaviest is precisely the time when he cannot hold up his
umbrella; that the wind is carried with the cloud, and lulls when it has
passed. Every one who has ever seen rain in a hill country, knows that
a rain-cloud, like any other, may have all its parts in rapid motion,
and yet, as a whole, remain in one spot. I remember once, when in
crossing the Tete Noire, I had turned up the valley towards Trient, I
noticed a rain-cloud forming on the Glacier de Trient. With a west wind,
it proceeded towards the Col de Balme, being followed by a prolonged
wreath of vapor, always forming exactly at the same spot over the
glacier. This long, serpent-like line of cloud went on at a great rate
till it reached the valley leading down from the Col de Balme, under the
slate rocks of the Croix de Fer. There it turned sharp round, and came
down this valley, at right angles to its former progress, and finally
directly contrary to it, till it came down within five hundred feet of
the village, where it disappeared; the line behind always advancing, and
always disappearing, at the same spot. This continued for half an hour,
the long line describing the curve of a horseshoe; always coming into
existence, and always vanishing at exactly the same places; traversing
the space between with enormous swiftness. This cloud, ten miles off,
would have looked like a perfectly motionless wreath, in the form of a
horseshoe, hanging over the hills.

Sec. 5. Value, to the painter, of the rain-cloud.

Sec. 6. The old masters have not left a single instance of the painting of
the rain-cloud, and very few efforts at it. Gaspar Poussin's
storms.

To the region of the rain-cloud belong also all those phenomena of
drifted smoke, heat-haze, local mists in the morning or evenin