descend vertically in a float chamber, the boat contained within a timber caisson; this had been unsuccessful. In 1809 a vertical lift had been installed at Tardebigge, Worcestershire, where boats in a wooden caisson were winched up by manpower; it was not successful and was replaced in 1815. Finally, the Morris Canal was built between 1825 and 1831 in spectacularly hilly country from coal mines down to estuarial rivers in New Jersey, US. Its builders installed 23 inclined planes carrying boats of 18 tons payload: the boats were hauled dry on rail-borne carriages. (Other systems were adopted on the canal later). However, after consideration of the technical alternatives, it was "resolved to rebuild the two old upper locks and to build two new lower ones, so as to give an entire double set, which was done in 1841". An inclined plane for canal boats With the lock system duplicated, the trade was amply accommodated until July 1849, when the supply of water ran short, notwithstanding that storage is provided exceeding and the canal was shut in consequence for six weeks. It then became evident that some effectual means must be adopted for preventing any such interruption in future. The storage capacity in reservoirs already exceeded the catchment, so that larger reservoirs were no solution; back-pumping water from the lower reach to the upper at Blackhill was considered too expensive, and Leslie and a colleague recommended the construction of an inclined plane, in which the empty boats would be hauled up "wet"—floating in a caisson on a rail-borne carriage. The dominant traffic was loaded down to Glasgow and empty back up; the intention was to haul the empty boats up the plane, and to let the loaded boats continue to use the locks. The "wet" system was preferred because boats long were in use; "dry" haulage required the carriage to traverse a brow, over which the carriage and boat descended into the upper reach, and with a long boat this was impractical. (Hauliers were also said to object to supposed damage to their vessels in this system.) In October 1849 the Committee of Management of the Forth and Clyde Canal (which had by now taken over the Monkland Canal) gave instructions to James Leslie to proceed, and the work was completed by July 1850. The caissons for the boats were made of malleable iron; they were 70 feet long by 13