ch is lighter or darker, in proportion as the air is more or
less mixed with damp vapours.'

Shadows produced by the redness of the setting sun, will be blue; from
the reflexes of that part of the air not illumined by its rays.

If the sun is overcast, the lights will be general; so will the shadows.
If the sunbeams burst out, and strike the objects in a landscape, the
shadows will then be dark in _proportion_ to the lights. The brilliant
edges of the clouds all assist the general illumination; and all objects
in the light, will participate of _their_ colour from reflexion. On the
contrary, those parts not included in the range of rays, remain the
colour of the _air_.

The air partakes less of the azure of the sky as it approaches the
horizon, being more remote from the sun than that part of it above our
heads, which receives a larger portion of its rays. The horizon will be
light, while, in ascending to the meridian, it becomes, from this cause,
deeper and bluer. So the nature of all colours diminish in proportion as
density of air is interposed between them and the eye.

Reflected colours, thrown from, and upon, equal angles, will be the
strongest: the most distinct, being produced by the shortest ray.

No reflected colour will have the brilliance of a direct one. For, if a
reflected light from a blue object be thrown on a yellow one, the result
would be green:--green being composed of blue and yellow. This
circumstance refers to most mixtures.

It only happens to those colours which are on a _level_ with the eye,
that their gradation is in proportion to their distance. As to those of
elevation, they are influenced by the quality of the air they are seen
through.

Colours, whose nearest approach is to black, as they retire into
distance, partake most of the azure of the air:--and those colours most
dissimilar to black, preserve their proper colour as they recede. The
golden lights on distant mountains or fields will best explain this.
'The green, therefore, of the fields will change sooner into blue, than
yellow or white, which will preserve their natural colour at a greater
distance than that, or even red.'

'It may happen that a colour does not alter, though placed at different
distances, when the thickness of the air and the distance are in the
same inverse proportion.'

_Masses_ of shadow carry the strongest part of their colour to the
greatest distance; as when trees appear thick together, accumulating