All the images of objects which pass through a window [glass pane]
from the free outer air to the air confined within walls, are seen
on the opposite side; and an object which moves in the outer air
from east to west will seem in its shadow, on the wall which is
lighted by this confined air, to have an opposite motion.

77.

THE PRINCIPLE ON WHICH THE IMAGES OF BODIES PASS IN BETWEEN THE
MARGINS OF THE OPENINGS BY WHICH THEY ENTER.

What difference is there in the way in which images pass through
narrow openings and through large openings, or in those which pass
by the sides of shaded bodies? By moving the edges of the opening
through which the images are admitted, the images of immovable
objects are made to move. And this happens, as is shown in the 9th
which demonstrates: [Footnote 11: _per la 9a che dicie_. When
Leonardo refers thus to a number it serves to indicate marginal
diagrams; this can in some instances be distinctly proved. The ninth
sketch on the page W. L. 145 b corresponds to the middle sketch of
the three reproduced.] the images of any object are all everywhere,
and all in each part of the surrounding air. It follows that if one
of the edges of the hole by which the images are admitted to a dark
chamber is moved it cuts off those rays of the image that were in
contact with it and gets nearer to other rays which previously were
remote from it &c.

OF THE MOVEMENT OF THE EDGE AT THE RIGHT OR LEFT, OR THE UPPER, OR
LOWER EDGE.