Design for a Lock at San Marco
Among the vast array of Leonardo's papers in Milan that
are assembled together in the Codex Atlanticus is a remarkable
drawing of a new canal lock. It is recognized as the first to show the
best form for a water gate, and how another gate within the larger gate
could serve to control the flow of water. Nearly all modern gates follow
this principle, including the massive gates at Panama.
The design is for the lock at San Marco in Milan that was
completed in 1497. The deceptively simple drawing is full of details for
the miter gate, which superseded the portcullis type of gate previously
used. It shows the miter and quoin posts, vertical wooden planks with
horizontal and diagonal braces, iron sheathing for the joints, a brick
floor underneath the gates, and a recess in the wall into which each gate
folds. A detail of the wicket for letting water into the lock from the
upper level is shown below the gate.