agli occhi per quello circuito fino all' occhio, e tutto quello termine è pieno di quella cosa*.
It is worthy of note that Leonardo had made his memorandum refuting this view, at Milan in 1492]
69.
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 mathématiques en
Italie*. Tome III, p. 43.]
The function of the eye as explained by the camera obscura (70. 71).
70.
If the object in front of the eye sends its image to the eye, the eye, on the other hand, sends its image to the object, and no portion whatever of the object is lost in the images it throws off, for any reason either in the eye or the object. Therefore we may rather believe it to be the nature and potency of our luminous atmosphere which absorbs the images of the objects existing in it, than the nature of the objects, to send their images through the air. If the object opposite to the eye were to send its image to the eye, the eye would have to do the same to the object, whence it might seem that these images were an emanation. But, if so, it would