The Peterborough Lift Lock, number 21 on the Trent Severn Waterway, is impressive, probably even more so to the grandees who opened it on July 9, 1904. It operates virtually unchanged from when opened, much like the locks in another waterway built about the same time, the Panama Canal.

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Hydraulic gravity moves two big bathtub trays, one going up and the other going down, at the same time. Kind of like a huge seesaw. The trays are 140 by 33 feet and 7 feet deep, enough to hold 20 L.T. Loopers if packed in tight! Each tray goes up and down on its own 7½ foot diameter ram filled with water and connected by a valve underneath the structure. The cycle starts when the valve is opened and the upper tray, filled with a foot more water making it 144 tons heavier, pushes down to start the bottom tray up. Once they get going, the trays move eerily fast, taking about 2½ minutes to go up/down 65 feet.

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Unfortunately, it takes a lot longer than that to corral the boats in and out of the treys. That’s OK. It gives more time to admire the structure, its builders and how well such a simple concept works.

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