Well-made pump with single upright barrel, mounted on a double wooden tripod. The piston is operated by means of a crank and rack. The base of the barrel is fitted with a valve. A pair of Magdeburg hemispheres is screwed onto the plate on the upper part of the machine. A three-way stop-cock allows the reversal of air inlet and delivery to the plate. The instrument could thus be used either as a vacuum pump or a compressor. For the latter purpose, the air was compressed in a special compartment. This innovation was described by John Smeaton in 1753. The pipe connecting the plate to the pump is a modern replacement. Provenance: Lorraine collections.