Remains of a Hoffman Continuous Kiln at Craven Lime Works, a former limestone quarry in Langcliffe, North Yorkshire. Built in 1873 according to designs patented by German inventor Friedrich Hoffman, the kiln is made up of 22 interconnecting stone walled chambers built in an oval circuit around a central furnace. Efficient and economical, heat cycles progressively from chamber to chamber, with the firing of one preheating the next. As heat moves further round the loop, the chamber cools, its content ready to be unloaded in a continuous production line.