A caisson lock is a type of canal lock in which a narrowboat is enclosed in a sealed box and raised or lowered between two water levels. It was intended primarily as a water-saving measure, but also to save construction costs when compared with other engineering solutions. It was capable of replacing up to seven conventional locks. Other design benefits were speed of boat decent /ascent, and only a little loss of water when operating compared with a conventional boat lock, which required a volume of water equal to a boat and its cargo weight for each lock used in a flight between levels.
It was first demonstrated at Oakengates on the now lost Shropshire Canal in 1792, where its inventor, Robert Weldon (b:?1754 to d:1810) built a half-scale model. He claimed that his design would solve the problem of water supply in dry seasons or at greater elevations, be cheaper than building aqueducts or tunnels, and be quicker to operate than the number of surface locks his design could replace. would probably have displaced about 270 tonnes and weighed about 170 tonnes, including the water in it, so about 100 tonnes of ballast would have been needed to give neutral buoyancy. The box would have needed to be strong... Read More