A very good scarce Mining Aneroid bulkhead mounting barometer retailed by John Davis & Son, Derby, manufactured by Short & Mason c1920

Mining Aneroid barometer having 7½” silvered and machine engraved dial, the barometric scale calibrated in inches of mercury with a range from 27” – 33” divided down to 1/20”, the upper part marked “Mining Aneroid” and “Compensated,” the lower signed by the retailer “John Davis & Son (Derby) Ltd, Derby.” Silvered reflector ring. Semi circular thermometer calibrated in degrees Fahrenheit, with a range from 20° – 140° divided to 2°. Japanned alloy pointer, lacquered brass index with red marker, bevelled glass.

Conventional grey painted (rust inhibited) Vidie pattern movement driven from a single flux welded 2⅞” capsule, tensioned on a C spring, plated cock and spindle assembly, the chassis stamped with the Short & Mason “S&M” logogram. All contained within a japanned zinc drum form case fitted with three mounting plates, calibration port to verso.

Condition: The subject of a full service, conservation, and calibration under laboratory conditions, see performance chart from dynamic test. The movement working well with good sensitivity and progression. The dial with slight shading, ageing, the reflector ring with minor oxidation, the index with some losses to lacquer, finish to case generally oxidised.

In completely original condition, save the dial from which was removed a substantial coating of coal tar, the silvered finish remaining original.

Comments: John Davis was perhaps the leading supplier of mining instruments in the UK. These instruments are very hard to find – we see perhaps one every two years or so – and condition and originality, as always, is all. This instrument, bearing in mind it has certainly either been located in or very close to mining activity, is a very scarce survivor.

A history of John Davis & Son (Derby) Ltd and its successor, Davis Derby, which still flourishes today, may be found HERE.

Colliery, Mining or Pit Barometers were made specifically for use in mines from early in the 19th century, with a higher reading scale than above ground barometers. In 1872, an Act of Parliament was passed making their use compulsory. Records clearly showed that before an explosion in a coal mine there had been a diminution of atmospheric pressure. The Act required a barometer to be placed above ground in a conspicuous position near the mine entrance but they were always made of solid construction so they could also be used underground. With the scale going up to 33″ the barometer could be used at least 2,000 feet below sea level.