Equal Motions from Unequal Force; the Sound of Flies
A note on producing equal effects with different forces, and on air over wings and the hum of insects.
The left folio states an aim to produce two equal 'causal' and 'effective' motions using different quantities of force, adding that the slower device is the easier one; beside it are drawn wheeled linkage mechanisms. The right folio observes that air slips more freely over the smooth solid surface of a wing than over hairy or feathered surfaces, so it resists less, and reasons that a fly could not make its flight-hum with its mouth because that would demand a great bellows and long silences. Radiating star diagrams, a perspective block and jotted fractions fill the remaining space.
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Equal effects from varied force
Leonardo sets himself to produce two equal causal motions, yielding two equal effective motions, from different quantities of power, noting that the slower arrangement is by that much the easier.
Air over wings and the hum of flies
Air flees much more over the smooth solid surface of a wing than over hairy or feathered ones, so it resists less. He argues a fly cannot make its flight-sound with its mouth, since so long and continuous a note would need a great bellows for a lung and long silences to draw breath.
Wheeled linkage mechanisms
The left folio is sketched with mechanisms mounted on paired wheels, joined by rods and cranked linkages, apparently illustrating the motion argument in the adjoining note.
Jotted fractions and sums
Between the diagrams on the right folio Leonardo has set down small columns of fractions and additions, calculations tied to the surrounding radiating and perspective figures.