A parallel case.

Just as a stone flung into the water becomes the centre and cause of
many circles, and as sound diffuses itself in circles in the air: so
any object, placed in the luminous atmosphere, diffuses itself in
circles, and fills the surrounding air with infinite images of
itself. And is repeated, the whole every-where, and the whole in
every smallest part. This can be proved by experiment, since if you
shut a window that faces west and make a hole [Footnote: 6. Here the
text breaks off.] . .

[Footnote: Compare LIBRI, _Histoire des sciences mathematiques en
Italie_. Tome III, p. 43.]

The function of the eye as explained by the camera obscura (70. 71).