Large Eighteenth Century Mahogany Wall Thermometer by Polti of Exon

For sale, a late Eighteenth Century mahogany cased wall thermometer by Charles Polti of Exon.

This large and early example measures 57cms in height and has a silvered scale with Fahrenheit readings to the left, measuring from -40 to 210 degrees. The right hand side is engraved with simple guidance for the observer marking various points including “Freezing, Temperate, Summer Heat, Bath Water, Spirit Wine boils and Water boils”. The thermometer is fixed to the scale by two brass clasps and has a protective grill over the thermometer bulb at the base. It is completed with the makers name engraved to the top, (Charles) “Polti Exon.”

The scale is enclosed within a mahogany case with glazed front and graduated mahogany pagoda syle top with back board of the case extending further behind to form an eyelet for wall hanging.

Thermometers of this age are extraordinarily rare and most extant examples were produced by the more famous London makers of the period. Although a regional maker, Charles Polti was well situated in the City of Exeter which had a thriving wool industry and port which managed large scale wine importation. The term “Exon” engraved on the thermometer was simply a Latin derivative which was primarily used by the clergy and in academic circles. The use of it was probably well suited to Polti’s clientele.

Sadly, little has been written about Charles Polti, he is considered to have traded in Exeter between 1780 and 1810 and by reference to his surname, I suspect that he was one of the numerous Northern Italian immigrant instrument makers that blessed the UK’s shores around this time. His extant work is largely comprised of barometers and more complex examples such as perpetual calendars and angle barometers, all of which are of superior quality.

Other Polti’s are recorded as trading in Bristol and as far as Leeds during the first half of the Nineteenth Century so it may also be presumed that his sons set up businesses in other areas of the UK.

Circa 1790