The Eye, Light Through a Window, and Recipes for the Hair
Optics of light entering a darkened room, the seat of vision in the eye, and cosmetic distillations.
The left leaf and its diagrams treat the passage of light into a confined space: the thicker the wall, the less the light, and images entering through a window appear reversed on the far, lit wall. Leonardo argues that the receptive faculty (imprensiva) must lie within the eye, and describes the optic nerve running to the brain and the common sense like perforated cords. The facing leaf turns to household recipes, one distilled in an alembic to remove freckles and lighten the hair, another a boiled lead-and-vinegar wash for colouring hair. Further faint, untranscribed notes run across both leaves.
On this page
The thicker the wall, the less the light
A brief maxim on how the passage of light through an aperture depends on the depth of the wall it crosses. The thicker the intervening wall, the less light is admitted.
Images reversed passing through a window into confined air
All the images of things passing through a window from the open air into air confined by walls are seen in a reversed position. A thing moving in the open air from east to west appears by its shadow, on the lit walls, to move the contrary way. Light-cone and eye diagrams accompany the note.
The receptive faculty and the optic nerve to the brain
Leonardo reasons that the imprensiva must lie within the eye, since although b comes by a straight line to the eye f and thence to d, the line to the imprensiva stays straight and oblique. The nerve leaving the eye for the brain is likened to perforated cords that with infinite branches weave the skin, carrying to the common sense.
Recipes to remove freckles and colour the hair
A distillation of tartar with sugar and honey in an alembic yields a first liquor that drives off freckles and a second that turns hair from black to golden. A second recipe boils litharge of lead, quicklime, gall and walnut husks in strong vinegar as a hair wash.