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British Library, London — Arundel MS 263

On the light that appears in the eye when it is rubbed.

Figure with letters.

In the column of text on the right of the sheet:

The rays that seem to depart from the luminous body and come to the eye are caused by the eyelids of these eyes; and the lower ones make the upper rays, and the upper ones make the lower. And if, closing one eye, you move the eyelids of the other, you will see the experiment.

In the column of text on the left of the sheet:

The eye that is pushed with the finger from below upward will make a contrary movement of the posterior parts where the visual faculty [inprensiva] is formed, and it will seem to that faculty that, as the front of the eye rises, the things seen lower themselves. And this will appear when one of the eyes stays still and the other is moved with the finger.

That eye which gazes upon a lit candle will seem to see, around its light, a round splendor, although the flame be long.

The reason for this is that, the surface of the eye receiving the image of the light, that image lights up and illuminates the hole of the eye that is full of transparent humor; the image of the light being in the middle of the surface of that hole, the power of the visual faculty that sees this light sees it surrounded by the roundness of that illuminated hole. And if it sees other circles around that light, they will arise from the more distant circular parts of that hole, which hold something of the transparent and which incorporate themselves with that light.

Figure with letters.

Beneath the figure, at the left:

If you place a shadowed body before the eyes at a distance of 4 fingers, and it is smaller than the distance from one light [eye] to the other, it will not obstruct the sight of anything that is behind it.

Beneath the figure, at the right:

No thing placed behind the near object of the eye can be obstructed by that object, if it is smaller than the space that lies between the lights [eyes].

In the left margin of the sheet, at the top:

Test whether the square body behaves, toward the sun's rays, like the square aperture, which loses its corners.

Figures with letters.

On the light seen in the eye and how the eye sees light

Phosphenes from rubbing and pressing the eye, the halo around a candle flame, and binocular vision

Optics & Light

Under the heading 'On the light that appears in the eye when it is rubbed,' Leonardo studies subjective effects of vision: rays that seem to leave a bright body are ascribed to the eyelids, pressing the eye with a finger makes seen objects appear to shift downward, and a lit candle shows a round halo because the pupil, full of transparent humor, is illuminated by the image of the flame. Two lower notes argue that a small object held before the eyes, if narrower than the gap between the two 'lights' (the eyes), hides nothing behind it. A marginal note on folio 112r asks whether a square body loses its corners in sunlight as a square aperture does. The facing pages carry many ray diagrams and a small perspectival object, several of them captioned but not transcribed.

Gazing at a lit candle, the eye seems to see a round splendor about the flame even though the flame is long. The pupil's surface receives the image of the light, which illuminates the hole full of transparent humor, so the faculty sees the light ringed by the roundness of that lit opening; outer circles arise from more distant transparent parts of the hole.

A small object between the two eyes hides nothing behind it

A shadowed body set before the eyes at four fingers' distance, if smaller than the gap from one eye ('light') to the other, does not block the sight of anything behind it; nothing behind the near object can be hidden if it is narrower than the space between the two eyes.

Does a square body lose its corners in sunlight, like a square aperture?

A marginal note asks whether a square body behaves toward the sun's rays as a square aperture does, which loses its corners (a reference to the rounding of light passed through a square hole).

Reader's Edition — described with AI from the e-Leo transcription.

0115 v

Figura con lettere.

Nella colonna di testo a destra del foglio:

Nella colonna di testo a sinistra del foglio:

Figura con lettere.

Sotto la figura a sinistra:

Sotto la figura a destra:

0112 r

Nel margine sinistro del foglio, in alto:

Figure con lettere.

Figure with letters.

In the column of text on the right of the sheet:

In the column of text on the left of the sheet:

Figure with letters.

Beneath the figure, at the left:

Beneath the figure, at the right:

In the left margin of the sheet, at the top:

Figures with letters.

On the light seen in the eye and how the eye sees light

On this page

Rays from a bright body traced to the eyelids

Pressing the eye makes seen objects appear to lower

A round halo of light around a candle flame

A small object between the two eyes hides nothing behind it

Does a square body lose its corners in sunlight, like a square aperture?