More than £5,000 for old scientific instrument is measure of lot’s rarity

Iam calling again at Hutchinson Scott, the Yorkshire auctioneers, this time for a rare late-georgian “signpost” barometer by Louis Bellatti, a noted Italian immigrant barometermaker who operated a jewellery and optician’s shop in High Street, Grantham, from 1824-52.

In figured mahogany with a moulded edge frame and hinged glazed door, its long mercury tube had a silvered calibrated dial and adjusting brass marker.

The first barometers were recorded about 1642, the credit for their invention going to Evangelista Torricelli (1608-47), an Italian scientist who had been secretary to the great Galileo, and who had improved on his master’s notes on measuring atmospheric pressure by using mercury rather than tubes of water.

Indeed, barometers were scientific instruments for almost a century before they became affordable to the wealthier classes.

Torricelli’s barometer was stick shaped, and this set the pattern for most 17th and early 18th Century examples.

These were superseded by wheel barometers and their derivatives, the ‘“banjo” barometers, most common in Victorian and Edwardian homes.

Diagonal or angle barometers reached their peak of popularity between 1720 and 1740, by which time, of course, mahogany was used quite widely.

The angle, in which the upper part of the tube is turned nearly to horizontal, allowed the movement of mercury to be measured over a larger scale than a straight tube.

The lower end (the bulbous shape on today’s illustration) concealed its cistern of mercury.

Signpost barometers like this, being rather unwieldy and quirky, were never very popular compared with the highly elegant stick variety.

Rare nonetheless, and very seldom seen at auction, this example took a mid-estimate £5,400.

Picture shows: “Signpost” barometer, £5,400 (Hutchinson Scott Auctioneers).