Warm shadows will support the strongest colours.
I generally observe that Titian, Rubens, and the best colourists, use their reds in the shadows, at once to support and give them brilliance;—for when it happens that the shadows of a picture are wholly made up of warm colours, the effect is sure to be splendid, though the lights are cold;—considering red, perhaps, too strong a colour to interfere with the light, at the risk of destroying its breadth. Their manner was often that of deepening the colour as it lost or absorbed itself in the background.
Every object receiving the light of the sun, receives likewise the general light, producing two shadows, the darkest one being occasioned by the sun.
When the horizon is tinged with red by the rays of the setting sun, the distant shadows, being blue or azure, mingling with the red, produces purple.
The air between the earth and the sun, when it rises or sets, invests all objects with a degree of obscurity, which is whiter on the earth than towards the zenith.
When the vapours descend to the earth at sunset, all objects that the sun's rays do not reach become confused and dark; but those that are tinged with its light will appear of the colour of that light, and distinctly marked in their outlines, though surrounded by obscurity.
The magnificence of the setting sun, gilding with its rays the slopes of mountains and tops of forests, towns, villages, and waters, while all below is lost in deep brown, grey, and purple masses, has ever been a favourite subject with painters of all schools.
The inferior or lower parts of all objects, when the air is thickest on the earth, will appear farther from the eye than the tops.
In looking down from an eminence on a street or town when the air is thick, the tops of the buildings will be darker, more distinct and articulate than the objects placed at the bottom, which, being filled with air, the tops come off it (as a ground) with more decision.
When the sun is veiled by clouds, in a landscape, the trees receiving a general light, the darkest parts will be the lowest.