Antique barometer having 4¼” jewelled, silvered and engraved dial, the upper portion marked “Stormy, Much Rain, Rain, Change, Fair, Set Fair, Very Dry.” Barometric scale calibrated in inches of mercury with a range from 28 – 31, the lower part with semi-circular thermometer marked “Fahrenheit’s Thermometer” with a range from 0 – 120 degrees, and carrying serial no. “2575.” Blued steel pointer, gilt brass tell tale and reflector ring, bevelled glass retained by a Dent/Vidi pattern bezel. The early coil spring tensioned 2½” capsule driven movement with modified cast primary lever, having added brass extension with adjustable bimetallic strip.

Characteristic pattern copper alloy case with extension piece and suspension loop, the verso with compensation port at 7 o’clock, the centre engraved “Compensated, Elliott, 30 Strand, London,” the upper part engraved freehand “Compensated for Temperature.”  Contemporary carved oak stand.

A very early Vidi-made instrument for the market outside the control of Dent, modified within 10 years of its original manufacture with highly significant developments aimed at reducing the effects of temperature. An extension from the cast primary lever immediately adjacent to the coil spring has clearly been removed. Originally, this would have transferred the impulse from pressure changes to the movement via a vertically set connector – it has been replaced with a later pattern brass rod fixed to the front part of this casting and just above the capsule. The bimetallic strip is mounted upon this two piece brass rod with an adjustable clamp or bridge piece which enables its length to be varied, a way of tuning the effect this addition will have upon temperature changes to the instrument.

This very interesting and almost certainly unique movement was undoubtedly a prototype, probably not intended for sale, something that might be evidenced to the jewelling to the dial, an embellishment setting this aside from standard production pieces. The introduction of temperature compensation was hugely significant in the evolution of these devices and marks one of the very few substantive developments made to the original design.

The dial with later jewelling, the case with some light dents and losses, the index knob damaged. The instrument serviced and re-calibrated with very good progression and sensitivity.

A highly significant instrument, probably unique. A real collector’s lot.

Dimensions: 12″ wide x 8″ high x 3″ deep

Stock No: BA0573

Price: Vavasseur Archive