Priorslee furnaces (SJ 702099) of the Lilleshall Company in Shropshire two vertical compound engines to the design of Edward Allis & Co. of Milwaukee were installed in 1900 and worked until the furnaces were finally blown out in 1959. The barring engine, used to set the flywheel in motion, is preserved at Ironbridge. During the twentieth century electric blowers became standard, just as mechanical charging of raw materials, first employed at Scunthorpe in 1905, replaced the filling of furnaces with hand barrows. By the 1990s the burden charged to furnaces was a semi-fused cake of ore and coke called sinter, the first British sinter plant having been built at Scunthorpe in 1934. All furnaces built in the twentieth century employed hot blast, and their stacks were therefore surrounded by tall cylindrical Cowper stoves, in which refractories, heated by waste gas, raised the temperature of the air being blown into the furnaces.4