A very good scarce aneroid pocket mining barometer manufactured by Short & Mason for John Davis & Son (Derby) Ltd., Derby c1914

Larger sized mining pocket barometer having 2½” silvered and die struck dial, the outer bezel turned altitude ring with ascending and descending scales calibrated in feet, divided to 10ft with ranges 0 to 6,000ft and 0 to -2,000ft respectively. The inner barometric scale calibrated in inches of mercury with a range from 25” – 33½” divided down to 1/50”, the upper part marked “Compensated,” the lower signed by the retailer “John Davis & Son (Derby) Ltd.” Blued steel pointer, bevelled glass set with convex bonded loupe (magnifier).

The movement, finely constructed in brass and steel, raised over a circular chassis principally finished in frosted gilt lacquer and driven from a single nickel alloy soldered 1½” capsule tensioned on a C spring, the bridge extension dated “19/5/14” and initialled by the finisher “HY.” All contained within a semi-barrel form, gilt and lacquered brass case, concentric decoration to circumference, engine turned grip ring to bezel, pendant and bow, calibration port to verso.

Presented in its original oxblood leather over timber, red silk and velvet lined travel case, snap closure on a button release.

Condition: The subject of a full service, conservation, and calibration under laboratory conditions, see performance chart from dynamic test. The movement working exceptionally well, accurate to within .03” across the range – an exceptional performance. Sensitive with stepless progression. 

The dial crisp and clear, very minor marks only, some slight ageing to altitude ring. The glass clear. The brass case retaining virtually all its original gilt and lacquered finish, minor age related losses and marks to verso. The travel case structurally sound, externally in good condition, some wear to edges and base, minor losses. The fabric interior vibrant, clean, and sound, with little sign of wear.

Comments: Mining in the early C20th was widespread as a vital source of energy and raw materials, including copper and tin. Most mines had barometers installed at the mine head on the surface, the importance of fluctuations in barometric pressure understood to be directly related to mining accidents caused principally by the egress of noxious and explosive gases from the surrounding rock strata at times of low barometric pressure. Mines also operated special barographs enabling predictions to be made for critical conditions.

The use of pocket barometers was probably quite restricted, a properly checked and calibrated instrument a useful piece of very portable equipment that may have been used by the inspectors of mines when checking mine and pit head barometers for accuracy and function.

This instrument, unsigned but by Short & Mason, was retailed by the principal supplier of mining related instruments, John Davis & Son (Derby) Ltd. Unlike a good proportion of pocket barometers that were really more gadgets than practical propositions as critical equipment, this instrument, by its larger size and more open scales, along with its superb quality and attested accuracy, was clearly intended as a proper professional instrument. The barometric scale extends a full 2½” higher (to 33½”) than standard barometric instruments, suggesting potential use of the instrument to depths of around 2,000ft below ground at standard pressure.

Just another application of the Aneroid Barometer, and a fascinating commentary on mining and industry in the first part of the twentieth century. These instruments are certainly very scarce. A collector’s piece.