Well-executed pocket barometer having engraved and silvered dial scaled in inches of mercury with a range from 27–31, divided into 1/50ths of an inch, outer rotating altitude scale calibrated in feet with a range from 0–3,000ft and divided into 10ft increments. The upper dial marked “Compensated,” the lower portion signed by the maker “Negretti & Zambra, London,” with serial no. “20869” and “NZ” logogram. Fine blued-steel pointer set beneath a bevelled glass. 1¾” capsule driven first quality movement. Substantial spun drum form case, the verso inscribed “The Institution of Water Engineers – Institution Premium – Presented to R. Stevenson Henshaw – June 1914.” Compensation port set at 8 o’clock. Pillar with suspension ring.
The whole contained within its original black and oxblood moroccan leather over wood green silk and velvet lined case. Snap closure on a button release.
This is a wonderful instrument, constructed at a time when Negretti & Zambra were at the height of excellence. These larger sized barometers, whilst not rare, may be described as less common than their smaller counterparts. Specifically the larger diameter dial affords greater accuracy in reading since the scale may be larger. They were commensurately more expensive!
The lacquered brass case with some very minor abrasions and wear though retaining virtually all its original lustrous gold-coloured lacquered finish. The dial extremely clean and crisp. Mechanically excellent with good sensitivity and near stepless progression. Dismantled, serviced and calibrated.
The leather case has been the subject of some restoration, externally re-coloured, the lid silk and button release replaced. Otherwise this most interesting instrument remains entirely original.
Without doubt, in this condition a collector’s piece.
Richard Stevenson Henshaw (b1873) was a civil and water engineer responsible for many municipal works in Wellingborough and Portland, including the Grade II-listed Clock Tower in the Easton Gardens, Portland. He was awarded this barometer as an Institution Premium prize for reading a paper at the Annual General Meeting of the Institute of Water Engineers in December 1913
Dimensions: 3½” diameter x 1½” deep
Stock No: PB0438