Answer To Question #8

Answer To Question #8. . , How A Lock Works , Instead of following the slope of the land, a canal periodically takes a vertical step between levels of flat water. This is accomplished at a series of locks, which on the C&O averaged a drop of 8 feet. The locks' hand-operated mitre gates were simple, virtually unchanged from Leonardo da Vinci's original 1485 design (right). The operation, though, demanded experience and close attention. As a boatman approached a lock, he would sound his horn a half to a quarter mile away, alerting the lockkeeper. Entering the lock was the most demanding part of canalling. The boat fit the lock with only 3 inches to spare on both sides, and if the helmsman allowed a loaded boat to hit the lock walls, he could damage or even sink the boat. Such a blow could also damage the masonry. Once in the lock, the 93-foot boat-only 7 feet shorter than the lock-had to have enough momentum to go all the way in, but had to be stopped before it crashed into the gate at the other end. A crew member jumped ashore and turned a heavy rope around the snubbing post to brake the boat. This was an art in itself: too tight and the momentum of the boat would break the post. Now the locking-through operation could begin. One crew set a record of 3 minutes, but 8 to 10 minutes was a good time., Locking Through , Upper sluice valves are opened and water in lock is raised to level of upstream canal. Upper gates are opened and boat enters lock 1. Upper gates and their sluice valves are closed. Sluice valves in lower gates are opened, allowing water to empty from lock 2. The boat is lowered slowly as the water in the lock drops to level of downstream canal. Lower gate is opened and boat proceeds on lower level of canal 3.