The whole in every part: circles of sound and light
Wave, voice and illumination arguments, with a water-channel problem under a river
The page pairs columns of mirror-writing with circular diagrams: a circle enclosing a triangle, circles drawn beside a small ear, and concentric circles. The notes develop Leonardo's argument that sound and light are each whole in every part of the space they fill, testing it through a triangle cast on still water, a voice reaching the ear, light filling a room, and mirrors that each hold the whole light. A separate marginal problem at the right, drawn with a conduit and the number 100, asks what weight is needed to hold down the lid of a water channel passing beneath a river.
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Weight to hold down a channel passing under a river
A conduit crossing beneath a river presses upward, trying to lift the lid of its channel. Leonardo asks what counterweight is needed to resist the water that wants to rise, and marks the marginal diagram with the number 100.
Does a triangle cast on still water make a circular wave?
The heading figure is a triangle inscribed in a circle. Leonardo proposes to test whether a triangle thrown onto quiet water produces, at the end, a wave of perfect circularity, treating the spreading wave as a model for propagation.
Why the ear receives the whole spoken word
Beside a small ear he asks: if the whole circle made through the air by a man's voice carries the entire spoken word, why does the part of that circle striking another's ear deliver not merely a part of the word but the whole. The problem sets sound-spreading against the paradox of the part containing the whole.
Light filling a dwelling
Turning to light, he frames the same puzzle: if the whole light illuminates a whole dwelling, why should a part of that dwelling not be illuminated by a part of that light. Light is used to define and explain what was said of the voice.
Mirrors prove the light is whole in every part
To answer the objection that light acts only with its part, he invokes one or two mirrors set in different places: each part of a mirror holds the whole light within itself. He concludes that the light is wholly throughout and wholly in every part of the room, and that the voice behaves likewise within its circle.