Near Falkirk in Scotland, the Forth & Clyde Canal meets with the Union Canal, however at their meeting point the two differ in height by approximately 115 feet. Before the 1930s, travel between these canals was provided by a series of eleven conventional locks, but they became disused and were filled in about seventy-five years ago. In more recent history, the United Kingdom's Millennium Commission began an effort to restore the canals of central Scotland in order to reconnect the east and west coasts of the landmass. As part of that effort, a brilliant, one-of-a-kind contraption was engineered which uses gravity and Archimedes' principle to transfer boats between the two canals using very little electricity. It's called the Falkirk Wheel.
The Wheel is essentially two huge, balanced water tanks suspended on arms which rotate around a central axis like a Ferris wheel. Each tank can support up to four twenty-meter-long boats at one time. Boats move into the tanks through the lock gates, which displaces a mass of water from each tank equal to the weight of the vessels. The tanks are thus always equalized in weight, allowing the pull of gravity on the descending tank to do most of the work elevating the rising tank.
This balance allows the wheel to consume very little electricity per turn despite the enormous weight involved. It uses a mere 1.5 kilowatt-hours-- or roughly the equivalent power needed to boil eight kettles of water-- each time if hefts a 600 metric ton load. And it does this in under four minutes per turn.
Due to flooding caused by vandals there was a month's delay before going into operation, but on 24 May 2002 the Falkirk Wheel officially opened as part of Queen Elizabeth's Golden Jubilee celebrations. The Wheel's design is truly revolutionary, as it is the only rotating boat lift in the world. Its beautiful form-- reminiscent of a Celtic double-headed ax-- and its graceful movement have made it a bit of a tourist destination, with a visitor's center, a café, and landscaped grounds nestled in the natural amphitheater.