Concave versus convex canals; a spoked hydraulic wheel
Water keeps even depth in a concave bed but not a convex one, with a drawing of a hydraulic wheel
Two short propositions contrast the flow in a concave and a convex canal, illustrated by channel sketches at the upper right: water can run at even depth through a canal hollowed along its length, but cannot keep an even depth through a convex one even if the width stays constant. Below, a carefully drawn spoked wheel is labelled simply as a hydraulic wheel. The transcription supplies the two propositions and the wheel's caption only.
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In a concave canal water can run at equal depth
Leonardo states that it is possible for water to run with equal depth through a canal that is concave along its length. The point is paired with its opposite in the convex case.
In a convex canal water cannot keep equal depth
It will be impossible, he writes, for water to run at equal thickness through a convex canal, even though the canal be equal in width along its course. The convex bed necessarily disturbs the depth of the current.
A spoked hydraulic wheel
At the right is a drawing of a wheel with many radiating spokes or vanes on an axle, labelled in the manuscript as a hydraulic wheel. The transcription gives only this caption; no explanatory text accompanies it.