Sight Spread Through the Pupil; Air Bubbles Rising in Water

The visual power is spread through the whole pupil

Leonardo states the proof that the seeing power is diffused across the entire pupil of the eye, not concentrated at a point. Schematic figures of the pupil and its visual rays accompany the claim, one of them lettered with the luminous source S and the pupil traced through a b c d e f g h i.

Heavy sinks by the shortest line, light rises by a whirling path

In the fluid or 'flexible' elements, the descent of a heavy body through a lighter one is made along the shortest line, while the rising of a light element out of a heavier one is made along a long and whirling line. This principle underlies the water and air studies that follow.

Air blown under water rises and thins into changing shapes

Air a rising from the bottom of the deep would go by the shortest line to the surface, but the water above it presses down and the lateral water rushes to fill its place. Because the highest water over the centre of the bubble weighs most, the enclosed air keeps thinning into various shapes as it flees the heavier water; in a related figure the air at c f g is pressed hardest by the water c e g f and moves toward c f.

Air under water contended over by contrary powers

The air n is fought over by opposing forces: one part (e c n m) drives it upward and another part (c d a b) drives it downward. Leonardo adds that flames of fire behave the same way within the air.

Nel margine superiore, a sinistra numero del foglio, aggiunta di:

Sotto, colonna principale:

Margine destro. Prima figura schematica di pupilla e raggi visivi, con:

Figura analoga, con:

Figura analoga.

Colonna principale.

Figura d'aria soffiata da un mantice sott'acqua, con:

Figura d'aria sott'acqua, con:

Sotto la precedente figura.

Figura analoga, con:

In the upper margin, at the left, the folio number, added:

Below, main column:

Right margin. First schematic figure of the pupil and visual rays, with:

Analogous figure, with:

Analogous figure.

Main column.

Figure of air blown from a bellows under water, with:

Figure of air under water, with:

Below the preceding figure.