Close up showing the mechanism that raised
the rear gate after the water level has fallen nearly to that of the next lower
part of the canal. The forward gate that can open above water when the level in
the lock has lowered to that of the lower section of the canal can swing open.
But the gate that must be closed on the upper end, when there is high water in
both the lock and the upper side of the canal cannot swing due to water
pressure, it must be raised vertically by means of this chain hoist over the
large drums on each side.. Note also that the water level has now fallen even
below the bottom level of the gate itself.