Space is more clearly indicated by the drawing of objects than by their hue.

In the first chapter of this section, I noticed the distinction between real aërial perspective, and that overcharged contrast of light and shade by which the old masters obtained their deceptive effect; and I showed that, though inferior to them in the precise quality or tone of aërial colour, our great modern master is altogether more truthful in the expression of the proportionate relation of all his distances to one another. I am now about to examine those modes of expressing space, both in nature and art by far the most important, which are dependent, not on the relative hues of objects, but on the drawing of them: by far the most important, I say, because the most constant and certain; for nature herself is not always aërial. Local effects are frequent which interrupt and violate the laws of aërial tone, and induce strange deception in our ideas of distance. I have often seen the summit of a snowy mountain look nearer than its base, owing to the perfect clearness of the upper air.