VIII. Botany for Painters and Elements of Landscape Painting: 447.
447.
OF THE SHADOWS IN TREES.
The sun being in the East [to the right], the trees to the West [or left] of the eye will show in small relief and almost imperceptible
gradations, because the atmosphere which lies between the eye and those trees is very dense 220 , see the 7th of this--and they have no shade; for though a shadow exists in every detail of the ramification, it results that the images of the shade and light that reach the eye are confused and mingled together and cannot be perceived on account of their minuteness. And the principal lights are in the middle of the trees, and the shadows to wards the edges; and their separation is shown by the shadows of the intervals between the trees; but when the forests are thick with trees the thin edges are but little seen.