OF CLOUDS, SMOKE AND DUST AND THE FLAMES OF A FURNACE OR OF A
BURNING KILN.

The clouds do not show their rounded forms excepting on the sides
which face the sun; on the others the roundness is imperceptible
because they are in the shade. [Footnote: The text of this chapter
is given in facsimile on Pls. XXXVI and XXXVII. The two halves of
the leaf form but one in the original. On the margin close to lines
4 and 5 is the note: _rossore d'aria inverso l'orizonte_--(of the
redness of the atmosphere near the horizon). The sketches on the
lower portion of the page will be spoken of in No. 668.]

If the sun is in the East and the clouds in the West, the eye placed
between the sun and the clouds sees the edges of the rounded forms
composing these clouds as dark, and the portions which are
surrounded by this dark [edge] are light. And this occurs because
the edges of the rounded forms of these clouds are turned towards
the upper or lateral sky, which is reflected in them.

Both the cloud and the tree display no roundness at all on their
shaded side.

On images reflected in water.