"And realize that this canal cannot be excavated for less than 4 dinars per braccio, giving each worker 4 soldi per day. And this canal should be built between mid-March and mid-June, because then the peasants
are not involved in their usual work and can be had for a good price, and the days are long and the heat will not tire them."
This canal bridge, drawn by Leonardo in the
years after his return to Florence, allows
a watercraft to pass over another watercourse
by means of a lock. The lock is constituted of
a basin closed upstream and downstream by
two pairs of flap gates, allowing watercraft to
pass over the height difference of the water.
Once the craft enters into the lock, the gates
upstream close, and in the downstream gate,
a small, secondary door opens allowing
discharge of the water until the water level
in the lock reaches the same height as the
downstream canal. After this, the gates open
to allow the watercraft to continue along its
course. In this manner the opening of the gates
would be facilitated, since they did not have
to overcome the resistance of the water
pressure in order to open. In his note beside the drawing, Leonardo describes how to construct the canal banks in order to avoid the water erode the gravel of the banks. In consideration of problems connected with the possibility of spates, he indicates how to construct the bottom of the canal and the best periods for performing works for greatest economic savings.
The model is based on the drawing:
- Codex Atlanticus f. 126 v. (1503-1506)
Milano, Biblioteca Ambrosiana