What outlines are seen in trees at a distance against the sky which
serves as their background?
The outlines of the ramification of trees, where they lie against
the illuminated sky, display a form which more nearly approaches the
spherical on proportion as they are remote, and the nearer they are
the less they appear in this spherical form; as in the first tree
_a_ which, being near to the eye, displays the true form of its
ramification; but this shows less in _b_ and is altogether lost in
_c_, where not merely the branches of the tree cannot be seen but
the whole tree is distinguished with difficulty. Every object in
shadow, of whatever form it may be, at a great distance appears to
be spherical. And this occurs because, if it is a square body, at a
very short distance it loses its angles, and a little farther off it
loses still more of its smaller sides which remain. And thus before
the whole is lost [to sight] the parts are lost, being smaller than
the whole; as a man, who in such a distant position loses his legs,
arms and head before [the mass of] his body, then the outlines of
length are lost before those of breadth, and where they have become
equal it would be a square if the angles remained; but as they are
lost it is round.
[Footnote: The sketch No. 4, Pl. XXVIII, belongs to this passage.]
The cast shadow of trees (452. 453).
452.
The image of the shadow of any object of uniform breadth can never
be [exactly] the same as that of the body which casts it.
[Footnote: See Pl. XXVIII, No. 5.]
Light and shade on groups of trees (453-457).
453.
All trees seen against the sun are dark towards the middle and this
shadow will be of the shape of the tree when apart from others.
The shadows cast by trees on which the sun shines are as dark as
those of the middle of the tree.
The shadow cast by a tree is never less than the mass of the tree
but becomes taller in proportion as the spot on which it falls,
slopes towards the centre of the world.
The shadow will be densest in the middle of the tree when the tree
has the fewest branches.
[Footnote: The three diagrams which accompany this text are placed,
in the original, before lines 7-11. At the spots marked _B_ Leonardo
wrote _Albero_ (tree). At _A_ is the word _Sole_ (sun), at _C Monte_
(mountain) at _D piano_ (plain) and at _E cima_ (summit).]
Every branch participates of the central shadow of every other
branch and consequently [of that] of the whole tree.
The form of any shadow from a branch or tree is circumscribed by the
light which falls from the side whence the light comes; and this
illumination gives the shape of the shadow, and this may be of the
distance of a mile from the side where the sun is.
If it happens that a cloud should anywhere overshadow some part of a
hill the [shadow of the] trees there will change less than in the
plains; for these trees on the hills have their branches thicker,
because they grow less high each year than in the plains. Therefore
as these branches are dark by nature and being so full of shade, the
shadow of the clouds cannot darken them any more; but the open
spaces between the trees, which have no strong shadow change very
much in tone and particularly those which vary from green; that is
ploughed lands or fallen mountains or barren lands or rocks. Where
the trees are against the atmosphere they appear all the same
colour--if indeed they are not very close together or very thickly
covered with leaves like the fir and similar trees. When you see the
trees from the side from which the sun lights them, you will see
them almost all of the same tone, and the shadows in them will be
hidden by the leaves in the light, which come between your eye and
those shadows.