Water falling onto a toothed wheel
Two mounted fragments: a waterwheel study (287a) and a blank red-chalk sketch (287b)
The left fragment (287a) shows a paddle-and-tooth wheel driven by falling water, with a note tracing how the stream bears on each part of the wheel. Leonardo marks the water g o pressing on the paddle t, the water n on the tooth S and the channel S t, and cites a proposition to gauge how lightly m weighs on the tooth r. The right fragment (287b) carries a rough red-chalk sketch but is catalogued as devoid of writings.
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How the falling water bears on the wheel
All the water g o rests upon the paddle t, while the water n rests upon the tooth S and partly upon the channel S t. By the sixth proposition of the fifth book, m rests but little upon the tooth r.
Paddle-and-tooth wheel in its channel
The wheel is described through its lettered members — the paddle t, the teeth S and r, and the channel S t — the parts on which the driving water presses.