[_The winged vapours_. l. 14. See additional note No. XXV. on
evaporation.]

[_On each broad cloud_. l. 15. The clouds consist of condensed vapour,
the particles of which are too small separately to overcome the tenacity
of the air, and which therefore do not descend. They are in such small
spheres as to repel each other, that is, they are applied to each other
by such very small surfaces, that the attraction of the particles of
each drop to its own centre is greater than its attraction to the
surface of the drop in its vicinity; every one has observed with what
difficulty small spherules of quicksilver can be made to unite, owing to
the same cause; and it is common to see on riding through shallow water
on a clear day, numbers of very small spheres of water as they are
thrown from the horses feet run along the surface for many yards before
they again unite with it. In many cases these spherules of water, which
compose clouds, are kept from uniting by a surplus of electric fluid;
and fall in violent showers as soon as that is withdrawn from them, as
in thunder storms. See note on Canto I. l. 553.

If in this state a cloud becomes frozen, it is torn to pieces in its
descent by the friction of the air, and falls in white flakes of snow.
Or these flakes are rounded by being rubbed together by the winds, and
by having their angles thawed off by the warmer air beneath as they
descend; and part of the water produced by these angles thus dissolved
is absorbed into the body of the hailstone, as may be seen by holding a
lump of snow over a candle, and there becomes frozen into ice by the
quantity of cold which the hailstone possesses beneath the freezing
point, or which is produced by its quick evaporation in falling; and
thus hailstones are often found of greater or less density according as