impressive. Number is always
most felt when it is symmetrical, (vide Burke on "Sublime," Part ii.
sect. 8,) and, therefore, no sea-waves nor fresh leaves make their
number so evident or so impressive as these vapors. Nor is nature
content with an infinity of bars or lines alone--each bar is in its turn
severed into a number of small undulatory masses, more or less connected
according to the violence of the wind. When this division is merely
effected by undulation, the cloud exactly resembles sea-sand ribbed by
the tide; but when the division amounts to real separation we have the
mottled or mackerel skies. Commonly, the greater the division of its
bars, the broader and more shapeless is the rank or field, so that in
the mottled sky it is lost altogether, and we have large irregular
fields of equal size, masses like flocks of sheep; such clouds are three
or four thousand feet below the legitimate cirrus. I have seen them cast
a shadow on the Mont Blanc at sunset, so that they must descend nearly
to within fifteen thousand feet of the earth.

Sec. 7. Causes of their peculiarly delicate coloring.

Fourthly, Purity of Color: The nearest of these clouds--those over the
observer's head, being at least three miles above him, and nearly all
entering the ordinary sphere of vision, farther from him still,--their
dark sides are much grayer and cooler than those of other clouds, owing
to their distance. They are composed of the purest aqueous vapor, free
from all foulness of earthy gases, and of this in the lightest and most
ethereal state in which it can be, to be visible. Farther, they receive
the light of the sun in a state of far greater intensity than lower
objects, the beams being transmitted to them through atmospheric air far
less dense, and wholly unaffected by mist, smoke, or any other impurity.
Hence their colors are more pure and vivid, and their white less sullied
than those of any other clouds.

Sec. 8. Their variety of form.

Lastly, Variety: Variety is never so conspicuous, as when it is united
with symmetry. The perpetual change of form in other clouds, is
monotonous in its very dissimilarity, nor is difference striking where
no connection is implied; but if through a range of barred clouds,
crossing half the heaven, all governed by the same forces and falling
into one general form, there be yet a marked and evident dissimilarity
between each member of the great mass--one more finely drawn, the next
more d