Photo courtesy of Jeff Mills

The Whitelees engine was built in 1842 by John Petrie & Co. of Rochdale and is just as James Watt left the design when his patent (for the separate condenser) ran out in 1800. The engine runs at 34 rpm with steam at 20 pounds per square inch. It has a Porter governor, parallel motion above the working cylinder and a flywheel with peripheral gear teeth (from which the drive is taken). This engine is unchanged since it was first set to work at Whitelees Mill (Littleborough) in 1842. It is not “compounded” (a technology to improve efficiency, applied to almost all other such engines).