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Bascule bridges tilt upwards on a hinge, with a counter-weight keeping the bridge raised. A single leaf bridge has only one part that raises upwards, spanning the entire waterway beneath. Double leafs have two sections that raise -- one on either side -- that meet in the middle when lowered.
This is the side of the Ship Channel Bridge that raises, with the counterweight area on the far side. According to the Toronto Archives, the bridge cost $149,000 to build.
Of course, that was in 1916.
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