I316

There is still another kind of Perspective; called the Aerial One; which by the different Colours of the Air, shows the different Distances of several Objects placed in the same Line. For Instance, if in seeing a Number of Buildings rising behind a Wall, which appear of the same bigness, and ranged in the same Line, you have a Desire to paint them, in such manner, as that one may appear further removed from the Eye, than another; To favour this Design, you must represent the Air, somewhat Grosser than Ordinary; because, in that Case, it will tinge far distant Bodies very sensibly with its Azure, as is observed in Mountains, &c. This, once supposed, you may show the Building which appears first, on the other side the Wall, in its natural Colour; The next, which is to be a little further removed, must have its Profile a little more slight, and must farther show a faint Tincture of Azure; the Third, which is to be still further distant, must appear still more Azure, in proportion; and, if you wou'd represent a Fourth, removed five time the distance of the last, you must distinguish it with an Azure five Degrees more strong and sensible: By this Means, your Buildings, tho' painted all in a Line, and of the same bigness, will nevertheless discover themselves to be all considerably different, both in Bigness and Distance.