An interesting aneroid barometer altimeter by Troughton & Simms, London, No. 1473, presented to Edward Slater McDonald by the Institution of Civil Engineers winning the Miller Prize 1895-96

Aneroid barometer having 4½” silvered and die struck dial, the outer bezel rotated altimetric scale calibrated in feet with a range from 0 – 12,000ft and divided down to 50ft, the inner barometric scale calibrated in inches of mercury with a range from 20” – 31” divided down to 1/20th. The upper part marked “Miller Prize Awarded to Edward Slater McDonald, Stud. Inst. C.E. by The Institution of Civil Engineers, Session 1895-96.” The lower part signed by the maker “Troughton & Simms, London,” serial no. “1473,” and “Compensated.” Fine blued steel pointer, bevelled glass.

Conventional 1st quality finely poised Vidie pattern movement driven from a single 2½” nickel alloy capsule tensioned on a C spring, the spindle mounted on a separate sub chassis. The whole contained within a substantial drum form case, pendant and bow. The verso with calibration port.

Condition: The subject of a full service, conservation, and calibration under laboratory conditions, see performance chart from dynamic test. The movement working exceptionally well across the scale, maximum error noted ¼” at 20”.

The dial with some minor marks to centre, otherwise clean and crisp, the glass damage free. The rolled and soldered case with some wear, traces of original finish.

Comments: Although finding aneroid barometers or altimeters that were presented as prizes is fairly unusual, many having been lost, in the day such awards were fairly common, the barometer being a much valued instrument. It is very unusual, though, to find an instrument such as this presented to a student within the discipline for which the instrument was intended in the first place, and this piece is thus an interesting commentary on the instruments used by civil engineers of the period.

The basic pattern is found quite commonly and was adopted widely in many applications connected with height finding. It is noteworthy though that most are fitted with a barb type index extending from the reflector ring toward the dial centre – this instrument has full rotation of the altitude ring and in that respect is unusual as well as being more convenient in use.

Edward Slater McDonald was born on 29 August 1876, and served in the Royal Naval Air Squadron/Royal Naval Volunteer Reserves during WWI until 1918 when he transferred to the Royal Air Force.