River gravel and the force of a paddle wheel
Where water runs strongest the gravel is coarsest; paddle width on a water wheel
Red-chalk studies of a river current. One note observes that where the water runs strongest the gravel lying there is coarsest, and another that flattened pebbles turn their broadest faces obliquely against the flow. A sketch of a paddle wheel, labelled r, b, d, f, o, n and a, accompanies an argument about how the width and position of a paddle affect the force delivered by falling water.
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Coarsest gravel where the current runs strongest
A study of a water course notes that where the water runs strongest, there the gravel will be of the greatest coarseness. A curving line at the top of the sheet sketches the moving stream.
Flat pebbles turn edge-on to the flow
All flattened gravel-stones will turn their broadest faces obliquely against the course of the water, a note observes beside a small group of drawn pebbles.
Paddle width and the force of a water wheel
Beside a spoked paddle wheel labelled r, b, d, f, o, n, a, Leonardo reasons that widening a paddle to receive 12 ounces at a-n is equivalent to narrowing it so the same 12 ounces strike at n-o, and weighs the objection that n-o lies nearer the wheel's pole and so has less force.