How Locks Work:
| Step One: Boat casts off towlines from the horses or mules. Lower gates of lock are open while upper gates are closed. Boat on lower stretch of canal enters lock. |
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| Step Two: Lower gates close behind boat. Water is pumped into lock through small tunnels in its walls. Water then fills the lock, lifting the canal boat to the upper level. |
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| Step Three: After water level inside lock is the same as the water level on the upper leg of the canal, the upper gates open. The canal boat can now pick up its towline and continue on its journey up the canal. |
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If the canal boat is going in the opposite direction, the steps are reversed. In Step 2, the upper gates close behind the barge and water is drained from the lock through the same tunnels in the walls of the lock. When the boat is lowered to the level of the lower stretch, the lower gates are opened and the canal boat continues on its journey.
How Were Cargos Weighed to Collect Tolls?
Boats entered a special lock called a weighlock. As water drained from the lock, the boat gradually came to rest on a wooden cradle connected to a scale. The unloaded weight of the boat would then be subtracted from the total, leaving the weight of the cargo.