It's all about displacement

After a meeting in Falkirk today, I dropped in at the Falkirk Wheel for a coffee. We were at the royal opening a few years back - a memorable occasion for the incessant rain and the sight of hundreds of people sitting patiently in plastic ponchos, awaiting the queen's arrival.

It is a remarkable object and a remarkable piece of engineering, using Archimedes' principle of displacement to allow the giant gondolas to rotate using very little input of energy, carrying boats between the two levels of the Forth & Clyde and Union canals.

I was entertained afterwards by the sight of a family trying to steer their hired narrow boat along the canal in reverse. I guess their brief instruction session at the start of the hire didn't deal with the fact that rudders don't really work in reverse. The groans from the lockkeeper as they bumped their boat along the canal banks said it all.