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Double Barometer by Domenico Sala

For a comparatively brief period at the end of the 18th century, there was a short-lived fashion for the so-called ‘double barometer’, the aim of which was to make the domestic instrument more compact.

A small group of makers of Italian extraction, such as Ronchetti, Gatty and Manticha developed a design first proposed by Guillaume Amontons in 1688 and produced instruments where the mercury column was divided between two parallel glass tubes, with oil in the intervening and outer tubes. The size was almost halved, and as an additional benefit, the oil magnified the scale reading by a factor of five.

We currently have a good example by Domenico Sala; like most barometers of this type, the scale, instead of engraved silvered brass, is made of boxwood, which has the scale, numerals and characters punched into its surface and then painted in.

The whole ensemble is mounted on a mahogany frame and fitted behind a mahogany-framed glass door to form an unusual and rather elegant artefact.

 



 
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