Complex sentence: The wheel raises boats by, but the Union Canal is still higher than the aqueduct which meets the wheel, and boats must pass through a pair of locks to get between the top of the wheel and the Union Canal.
Split into simpler sentences: The wheel raises boats by, but the Union Canal is still higher than the aqueduct which meets the wheel. Boats must also pass through a pair of locks between the top of the wheel and the Union Canal.