Sluice-gate construction with quadrature-of-the-circle notes
Water-gate, basin and stone trough details beside studies squaring the circle
The right side details a sluice for a lock-basin: the water is to drain through the plug of a stone trough, the upper gate made in one piece, and the trough's slab given a casing of hard sarizzo stone so that gravel cannot lodge on its lips and keep it from closing. A note on a circular apparatus sets a proportion 'from current to current as from slope to slope.' The left side turns to geometry, arguing that a pyramid (triangle) can be made equal to a semicircle and that a curved figure can be reduced to an equal square. Sketches of gates, boxes and a hatched wheel fill the leaf.
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Draining the lock-basin through the trough's plug
The water is to be drained from the basin (conca) through the stopper of a stone trough (avello), while the upper gate of the basin is to be made in a single piece. Marginal notes ('Good') mark approved details of the sluice.
Stone casing to keep the sluice trough sealed
The slab of the trough is to be surrounded by a casing of sarizzo, a hard granite-like stone, so that gravel cannot remain on the lips of the trough and prevent it from closing tight. Related notes tell the maker to set the frame or support lying flat against the oncoming water.
Proportion of current to slope
Beside a circular apparatus at the top left, Leonardo notes that the proportion holds from one current to another as it does from one obliquity (slope) to another.
Squaring a semicircle by an equal triangle
In a lettered semicircle (b, a, d, c, S), if the pyramid a b S is made equal to the semicircle c a d, then the portion a b is worth exactly all the like portions contained in the semicircle.
A curved figure made equal to a square
In two overlapping semicircles, a e b f is set equal to f c g d; removing f from each leaves a e b equal to c g d, and removing the four equal portions leaves the square g equal to the curved figure e.