The grasses and plants will be paler in proportion as the soil which nourishes them is leaner and devoid of moisture; the earth is leaner and less rich in moisture on the rocks of which the mountains are formed. And the trees will be smaller and thinner in proportion as they are nearer to the summit of the mountain; and the soil is leaner in proportion as it is nearer to the said summit, and it is richer in proportion as it is nearer the hollow valleys. Therefore, O painter, {126} thou shalt represent rocks on the summits of the mountains--for they are composed of rocks--for the greater part devoid of soil, and the plants which grow there are small and lean and for the greater part withered and dry from lack of moisture, and the sandy and lean earth is seen through the faded plants; and the small plants are stunted and aged, exiguous in size, with short and thick boughs and few leaves; they cover for the greater part the rust-coloured and dry roots, and are interwoven in the strata and the fissures of the rugged rocks, and issue from trunks maimed by men or by the winds; and in many places you see the rocks surmounting the summits of the high mountains, covered with a thin and faded moss; and in some places their true colour is laid bare and made visible owing to the percussion of the lightnings of Heaven, whose course is often obstructed to the damage of these rocks. And in proportion as you descend towards the base of the mountains the plants are more vigorous and their boughs and foliage are denser; and their vegetation varied according to the various species of the plants of which such woods are composed, and their boughs are of diverse arrangement and diverse amplitude of foliage, various in shape and size; and some have straight boughs like the cypress, and some have widely scattered and spreading boughs like the oak and the chestnut tree, and the like; some have very {127} small leaves, others have a spare foliage like the juniper and the plane tree, and others; some plants born at the same time are divided by wide spaces, and others are united with no division of space between them. [Sidenote: How to represent Night] 83.