fore detain a much larger
share; and those dark and sombre forms, which sometimes make the sky so
gloomy, can only result from the abundant absorption of the solar light.
The brilliant whiteness which their edges occasionally exhibit, must
result from the more copious transmission of light, so that the depths of
shade in a cloud may be regarded as comparative measures of the varied
thickness of its mass.

Sometimes the clouds absorb equally all the solar rays, in which case the
sun and moon appear through them perfectly white. Instances are recorded
in which the sun appeared of a pale blue. It has also been observed to
be orange at its upper part, while the lower was of a brilliant red.

The position from which clouds are seen, has much to do with their
colours; and it seems difficult sometimes to believe that the clouds,
which in the evening are seen drenched with crimson and gold, are the
same we beheld absolutely colourless in the middle of the day.

In the immediate neighbourhood of the sun the most brilliant colours may
be disclosed; and their vividness and intensity diminish, and at last
disappear at some distance from it. Parry noticed some white fleecy
clouds, which, at the distance of fifteen or twenty degrees from the sun,
reflected from their edges the most soft and tender tints of yellow,
bluish green, and lake; and as the clouds advanced the colours increased
gradually, until they reached a sort of limit two degrees below the solar
orb. As the current continued to transport them, the vividness of colour
became weakened by almost insensible degrees until the whole assemblage
of tints vanished.

"Who can venture to imitate, by the pencil, the endless varieties of red
and orange and yellow which the setting sun discloses, and the magical
illusions which all the day diversify the vast and varied space the eye
travels over in rising gradually from the horizon to the upper sky?
Those who have paid any attention to colours, must be aware of the
difficulty of describing the various tints and shades that appear, and
which are known to amount to many thousands."

The rapid changes of colour which the clouds undergo, seem to depend on
something more than change of position either in the cloud or in the sun.
Forster mentions an instance of some detached cirro-cumuli being of a
fine golden yellow, but in a single minute becoming deep red. On another
occasion he saw the exact counterpart in a cirro-stratus, by i