This engine was probably built around 1840. It is of the type developed by James Watt, although much smaller than those he originally devised for pumping mines, and was developed to provide power for a workshop or possibly a small factory. It is a typical double-acting engine, with slide valve worked by eccentric, suited to taking steam at moderate pressure. Its speed is controlled by a Watt governor acting on a throttle valve.

Until nearly the middle of the nineteenth century the vast majority of engines still followed the configuration developed by Boulton and Watt (the beam engine with vertical cylinder under one end of the beam and crank under the other). These worked in the same way as low-pressure condensing engines, although they were being overtaken by new engine layouts from designers such as Henry Maudslay. Nevertheless, this example gave more than half a century of steady service.

Although the engine is of excellent quality the maker is unknown. The fashion for designing the framing of machinery to imitate architecture has been seen as an attempt to give it an acceptable familiarity. However it is equally probable that this reflects the absence of method and data for the rational design of machine parts in metal.

Inv. 1915-128