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them smaller still, because a smaller part of the pupil
would exercise its function.
    [Footnote: 9. buso in the Lomb. dialect is the same as buco .]
    33.
    When the eye, coming out of darkness suddenly sees a luminous body,
it will appear much larger at first sight than after long looking at
it. The illuminated object will look larger and more brilliant, when
seen with two eyes than with only one. A luminous object will appear
smaller in size, when the eye sees it through a smaller opening. A
luminous body of an oval form will appear rounder in proportion as
it is farther from the eye.
    34.
    Why when the eye has just seen the light, does the half light look
dark to it, and in the same way if it turns from the darkness the
half light look very bright?
    35.
ON PAINTING.
    If the eye, when [out of doors] in the luminous atmosphere, sees a
place in shadow, this will look very much darker than it really is.
This happens only because the eye when out in the air contracts the
pupil in proportion as the atmosphere reflected in it is more
luminous. And the more the pupil contracts, the less luminous do the
objects appear that it sees. But as soon as the eye enters into a
shady place the darkness of the shadow suddenly seems to diminish.
This occurs because the greater the darkness into which the pupil
goes the more its size increases, and this increase makes the
darkness seem less.
    [Footnote 14: La luce entrer� . Luce occurs here in the sense of
pupil of the eye as in no 51: C. A. 84b; 245a; I—5; and in many
other places.]
    36.
ON PERSPECTIVE.
    The eye which turns from a white object in the light of the sun and
goes into a less fully lighted place will see everything as dark.
And this happens either because the pupils of the eyes which have
rested on this brilliantly lighted white object have contracted so
much that, given at first a certain extent of surface, they will
have lost more than 3/4 of their size; and, lacking in size, they
are also deficient in [seeing] power. Though you might say to me: A
little bird (then) coming down would see comparatively little, and
from the smallness of his pupils the white might seem black! To this
I should reply that here we must have regard to the proportion of
the mass of that portion of the brain which is given up to the sense
of sight and to nothing else. Or—to return—this pupil in Man
dilates and contracts according to the brightness or darkness of
(surrounding) objects; and since it takes some time to dilate and
contract, it cannot see immediately on going out of the light and
into the shade, nor, in the same way, out of the shade into the
light, and this very thing has already deceived me in painting an
eye, and from that I learnt it.
    37.
    Experiment [showing] the dilatation and contraction of the pupil,
from the motion of the sun and other luminaries. In proportion as
the sky is darker the stars appear of larger size, and if you were
to light up the medium these stars would look smaller; and this
difference arises solely from the pupil which dilates and contracts
with the amount of light in the medium which is interposed between
the eye and the luminous body. Let the experiment be made, by
placing a candle above your head at the same time that you look at a
star; then gradually lower the candle till it is on a level with the
ray that comes from the star to the eye, and then you will see the
star diminish so much that you will almost lose sight of it.
    [Footnote: No reference is made in the text to the letters on the
accompanying diagram.]
    38.
    The pupil of the eye, in the open air, changes in size with every
degree of motion from the sun; and at every degree of its changes
one and the same object seen by it will appear of a different size;
although most frequently the relative scale of surrounding objects
does not allow us to detect these variations in any single object we
may look at.
    39.
    The eye—which sees all objects reversed—retains the images for
some time. This