gravity of the carriages to be below the upper surface of the rail'. The vehicles straddled the rail, rather like a pair of pannier baskets on a mule. Propulsion was by horse. A line was built in 1824 in the Deptford Dockyard in London, and in 1825, another line was built in Cheshunt, Hertfordshire. Dubbed the "Cheshunt Railway", this line made history as it was the world's first passenger-carrying monorail, and the first railway line to open in Hertfordshire. In 1826 a company was formed to construct a line between Barmen and Elberfeld in Germany, but construction never started.