General Section of Wanlockhead Engine

Hand-coloured ink and watercolour drawing showing a general cross-section of an atmospheric condensing beam pumping engine designed by James Watt and supplied by the firm Bolton & Watt, of Birmingham, to the Margaret Mine, at Wanlockhead, Dumfries, Scotland, in 1785-86. Scale: 1/3 inch to 1 foot.

The drawing is part of a set of technical drawings supplied by the manufacturers showing general arrangements, details of foundations and key components for a 55-inch (1397 mm) bore x 8 foot (2438 mm) stroke single-acting single-cylinder steam pumping engine ordered for the Margaret Mine by Gilbert Meason, general manager of the Wanlockhead Mining Company, in June 1785. Labelled as sheet No.1, it shows a longitudinal cross-sectional elevation through the three-storey engine house and key components of the engine including the steam cylinder and condenser.

The drawing is believed to have been executed by James Watt, or an assistant working under his direction, and includes a number of annotations written in blue ink in what appears to be Watt’s hand, giving selected dimensions of the general assembly and other notes to the erectors.