Aneroid barometer having 4½” china clay glazed card dial calibrated in inches of mercury with a range from 24” – 31” divided to 1/50“, blued steel pointer, gilt index, flat glass held within a Vidi trademark knurled or herringbone bezel, gilt reflector ring. The substantial high quality movement driven from an early pattern 3⅛” single capsule and tensioned on a C spring. All contained within a flared drum form case, extension post and suspension ring. The verso with calibration port.

Condition: The subject of full service, conservation, and calibration under laboratory conditions. The movement responding well to pressure change with good sensitivity and progression, see performance chart. A crisp instrument, the dial clean and true, the case retaining a good proportion of its original lacquer, some losses and areas of oxidation, wear and minor impressions to suspension post.

Comments: A scarce instrument, this is an example of the third iteration of Vidi’s barometer movement, made in his own workshop. These instruments are of great interest, incorporating the C spring but retaining much of the original capsule design, the metallurgy of which does exhibit hysteresis on test. This means that the elastic properties of the metals involved fail to resolve accurately extreme cycles in pressure change. For the purposes of general atmospheric observation this is of little consequence as pressure changes are modest and progress over much longer periods of time.

As an example of this important era in barometer making, this is a very good and collectable example.