The wheel is a boat lift, a phenomenally clever piece of kit that links two canals - the Union Canal and the Forth and Clyde - that are at different heights. In just one roatation, the wheel can lift 300 tons of water and boat 115ft into the air. And it works by balance, gravity and a little electric push that uses no more energy than is needed to boil 15 kettles. As one boat is hoisted up, another is going down on the opposite side. The whole process takes around 15 minutes and, once lifted, a boat then continues its journey along a 100 metre long aqueduct, through a tunnel under the Roman Antonine Wall (built in 140AD), under the main Glasgow to Edinburgh railway and finally through a series of traditional locks to join the Union Canal. I climbed a hill behind the wheel to take a few shots and the sun, obligingly, came out.