Mining aneroid barometer having 8″ silvered and engraved dial with a barometric range of 27 – 33 inches of mercury, the upper portion marked “Mining Aneroid,” the lower portion signed by the maker “John Davis & Son (Derby) Ltd,” and carrying a curved Fahrenheit thermometer with a range from 20 – 150 degrees. Blued steel pointer and gilt brass telltale under heavy bevelled glass retained by polished brass bezel. Conventional good quality 2½” capsule-driven C-spring tensioned movement with bronze hairspring and bimetallic compensation. The whole raised on three columns within drum form copper case, verso with fixing point at 12 o’clock, compensation screw port at 4 o’clock.
Overall condition is excellent though it should be noted that the case would originally have been japanned, the finish having been removed at some time to reveal the aesthetically pleasing copper and brass. Some slight discolouration to the dial, case remarkably dent-free, movement having been serviced and calibrated in good working order.
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.
A rare, very attractive and functional instrument.
Dimensions: 9½” diameter x 2¾” deep
Stock No: BA0729