Canal-lock gates and safe mooring in the lock chamber
A self-lowering sill (S–K) that ponds water so laden boats can climb against the current
Three studies of canal locks and their gates. At the top a sill stands raised one braccio and is pushed down by boats as they pass, letting them travel in shallow water; a small lettered figure gives loads a b of 100 libbre and b c of 110 libbre over 1 braccio. A middle drawing of a lock being filled warns that opening the gates can swamp and sink a boat, so it must be moored back at m. The lower figure, lettered S K a n m, is a self-acting water-support: when a boat touches S, S drops and K rises to dam the water, which ponds up so the loaded boat mounts against the current.
On this page
Sill raised one braccio, pressed down by boats
This sill stands raised one braccio in front, and the boats, in rising and descending, push it down; by this method the boats travel in shallow water.
Danger of swamping; moor the boat at m
It is dangerous to founder boats within and outside the lock when the gates are opened. Tie the boats back so they cannot run toward the low place where the gate-water falls, for that water would fall into the boat, fill it and sink it. Therefore tie it at m.
Self-acting water-support S K a n m
This instrument below is a water-support of great use for boats going loaded against the current: when the boat touches at S, S lowers and K rises and shuts off the water above S. That water is dammed and rises at once, so the boat easily mounts against the open mouth of the water.
Loads on the members (a b, b c)
The lettered figure gives a b c as 1 braccio, with a b weighing 100 libbre and b c weighing 110 libbre.