The spaces between the parts in the mass of trees, and the spaces
between the trees in the air, are, at great distances, invisible to
the eye; for, where it is an effort [even] to see the whole it is
most difficult to discern the parts.--But a confused mixture is the
result, partaking chiefly of the [hue] which predominates. The
spaces between the leaves consist of particles of illuminated air
which are very much smaller than the tree and are lost sight of
sooner than the tree; but it does not therefore follow that they are
not there. Hence, necessarily, a compounded [effect] is produced of
the sky and of the shadows of the tree in shade, which both together
strike the eye which sees them.