Dent barometer with silvered brass 4½” dial annotated “Stormy,” “Much Rain,” “Change,” “Fair,” “Set Fair,” “Very Dry,” calibrated from 27½-31½ inches of mercury, further annotated “Aneroid Barometer” in script. The lower portion bearing the maker’s legend “E.J. Dent, Paris,” “Fahrenheit’s Thermometer” and serial no. “22769,” and having curved spirit thermometer calibrated from 10-114 degrees Fahrenheit. Blued-steel pointer and gilt brass telltale. Flat glass, with fine knurled gilt brass telltale adjustment wheel to centre. Lacquered spun brass case and bezel, the latter with trademark Dent herringbone pattern. Set pillar with suspension ring to top. The reverse with screw calibration port set at 3 o’clock as viewed. The whole contained within its original rare-pattern lacquered oak, flat top case with circular glazed viewing port, having bronzed and laquered brass ring to circumference, internal brass sliding locking catch designed to securely hold the instrument, rear mounted pull out picture stand and extending brass hanging plate. High gloss laquered interior with blue velvet-faced recess. Circular brass escutcheon and hinges set with brass screws, lock and key. The picture stand recess marked with the name “Major Reed, IMS” (Indian Medical Service).
The instrument movement having been cleaned and serviced, the dial re-silvered, the thermometer a later replacement, the brass case retaining much original lacquer, with some wear at contact points with oak display box. The box, having small repair to shrinkage crack at three o’clock, retaining much original lacquer, some wear to finish and minor abrasions consistent with age.
The movement in this Dent barometer is extremely unusual – Collins, Phillip, Aneroid Barometers and Their Restoration, p16, fig 2.10, shows this movement in another Dent barometer of the same period. It is of great interest and, depending upon how one views it, almost contradictory. There are a number of departures from what at the time was normal practice: for example, the use of levers bearing in cones to transmit a mechanical signal, a much shortened fusee made to a long brass lever and advanced by 90 degrees to 270 degrees, but possibly most interesting of all, what appears to be a counter-weight set on a short steel shaft located at the fulcrum of the “C” spring, passing through it and lying in the same plane as the capsule. It was clearly thought this innovation most desirable since a channel had to be cut in the “C” spring and a bespoke cast-iron weight manufactured. The exact purpose of this innovation may be unclear – for example, it will certainly affect the reading given by the instrument depending upon the plane in which it is located, i.e. with the instrument lying horizontally it will cause it to under-read, the extra moments of force applied to the “C” spring fulcrum effectively mimicking an expansion of the capsule indicating falling pressure. There is one explanation, though, that bears greater examination: the cast-iron weight has mass, and any vibration or tiny movement imparted to the instrument will cause an acceleration of this mass passing a small impulse into the movement, thus causing any residual deflection brought about by a barometric change to be translated into movement of the pointer. These innovations are clearly designed to effect more instant registration.
Dimensions: 6½” wide x 6¾” deep x 3″ high
Stock No: BA0228
E.J. Dent (1790-1853) was a famous English watchmaker noted for his highly accurate clocks and marine chronometers, and is recorded in Banfield, Edwin, Barometer Makers and Retailers, 1660-1900 as working from 1844-1851. Dent was the first to sell the Vidie aneroid barometer in England in 1847, and in 1849, he published A Treatise on the Aneroid, a Newly Invented Portable Barometer. He exhibited at the Great Exhibition at the Crystal Palace in 1851 when the Vidie barometer was awarded a Council Medal.
Surgeon-Major Augustus Keppel Reed
Indian Medical Service
The Indian Medical Service (IMS) was a military medical service in British India, which also had some civilian functions. It served during the two World Wars, and remained in existence until the independence of India in 1947. Many of its officers, who were both British and Indian, served in civilian hospitals.
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