A very good unusual 3½” aluminium Watkin Patent tri-concentric scaled aneroid barometer altimeter by James Hicks No 853 c1890

Watkin Hicks barometer having 3⅜” silvered and die struck dial, the tri concentric baro-altimetric scale calibrated in inches of mercury and feet with corresponding ranges 25” – 31” divided to 1/50” and 0 – 6,000ft divided to 10ft, the tri scales broken with scale change prompts, scale indicator port with moving flag below marker I and II, corresponding reference outer and middle scale. The centre marked “Watkin Patent,” “Compensated,” and serial no. “853” with maker’s details below. Fine blued steel pointer and spring tensioned, bezel operated wire index. Bevelled glass.

Conventional Vidie pattern movement constructed principally in aluminium and driven from a single 1¾” nickel alloy soldered pattern capsule tensioned on a C spring. The arbor with axially mounted return spring, the chain with worm take-up and aluminium range-indicating flag marked I and II. The movement retained with threaded top hat rivets. All contained within a drum form aluminium case, calibration port to verso, pendant and bow.

Presented in its original leather over timber, plum velvet and cream silk lined 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 well across the range with easily acceptable levels of accuracy.

The dial clean with minor signs of ageing but without damage. The Aluminium case with traces of original polish, relatively bright and clean. The travel case with obvious signs of age and some external losses, though remaining structurally sound. The fabric interior with wear to top edge of velvet, having good colour; the lid silk later.

Comments: Very infrequently seen, far less in good condition, a fascinating commentary on the quest for ever greater resolution and intended accuracy, the open scales affording closer inspection. The inclusion of scale indicator typical and vital for the correct identification of the values to be read.

Aluminium examples of this instrument are in a minority, the material being supplied as special order only.

Major (later Colonel) Henry Samuel Spiller Watkin of the Royal Artillery was granted a British patent no. 3425 for a rotary indicator and dial scale on 11 March 1886.