A good important brass cased metric aneroid barometer No 1673 by Breguet for Secrétan, Paris c1860
Aneroid barometer having 11cm silvered and engraved screwed down dial calibrated in centimetres of mercury with a range from 50cm – 80cm divided down to 1mm, the upper part struck “Baromètre Anéroïde,” the lower marked “Secrétan À Paris,” and carrying the Breguet logogram with serial no. “1673” under. The same serial number also struck into extreme periphery of dial. Blued steel pointer, gilt index under heavy polished bevelled glass.
Movement driven from a single early pattern nickel alloy 78.5mm capsule tensioned on twin coil springs, each with adjustable tension screws, lightweight sheet steel bridge and primary lever, attached static mass weights in steel and brass at the head, the brass piece engraved with serial no. “1673,” Breguet ‘A’ form cock. Fine square head adjustments gain and angular positioning.
All contained within a substantial high copper content drum form case with flared mouth, internal dial seat, four movement fixing points. Pendant and suspension ring, single calibration port to verso.
Condition: The subject of a full service, conservation, and calibration under laboratory conditions, see performance chart from dynamic test. The movement appears extremely sensitive with good progression and easily acceptable levels of accuracy.
It is unclear if there was an external finish applied to the brass case as no discernible trace – it is likely that along with many of these early instruments any applied finish was most vulnerable to wear and was soon removed. The surface finish is good with a recognisable lustre especially to the verso. The substantial nature of the case has contributed to its clear inherent resistance to dents and deformability – it remains crisp with some light abrasions, areas of discolouration and general wear. The dial appears to retain its original silvered finish, some areas of ageing, the annotations clear.
Comments: This is barometer making of the very highest quality for its time, the movement is, so far as I am aware, unrecorded. The twin spring arrangement is novel and clearly designed to approach shortcomings in the basic Vidie design.
The Vidie coil spring pattern is essentially asymmetric which may, at least in theory, cause some distortion to the capsule in its various states. Uneven loads are also placed upon bearing surfaces leading to asymmetric wear along with an increase in static friction. I am still considering this most interesting and novel design, and there may be other advantages which come to light over time.
It is interesting to note that this was clearly a design that did not endure, probably for the same reason as many of the more complex developments seen on Vidie instruments – an insignificant gain coupled with a significant increase in production costs.
Dimensions: 12.5cm diameter x 5cm deep
Stock No: BA2614
Price: Vavasseur Archive - not currently for sale