A Georgian III mahogany thermometer by John Dollond

A Georgian III mahogany thermometer by John Dollond, of slender rectangular form, the top of the frame removable to aid the cleaning of the glass, with a silvered register engraved to the temperature 220 degrees (rather than the usual 110) and  Temperate, Spits, Summer Heat, Blood Heat, Boil and Water Boil, signed Dollond London. English, circa 1790.

Footnote: Peter Dollond (1731-1820), the son of the Huguenot silk weaver John Dollond, set up as an optician at the age of 20 and became the most eminent optical instrument maker of the late 18^th century.  Such was his success that his father gave up the silk industry and joined him in 1752. The Dollonds became notable for the quality of their optical products. John Dollond was appointed optician to King George III and the Duke of York and Albany, who granted him ‘His Majesty’s Royal Letters’for his refracting telescope.  Other customers included Captain Cook, Admiral Lord Nelson, Frederick the Great and Thomas Jefferson. At the Great Exhibition of 1851, the Dollonds were awarded a medal for excellence.  In 1763 Peter invented the apochromat and began the manufacture of bifocal spectacles in 1781.  Dollond & Co merged with Aitchison & Co in 1927 to form Dollond & Aitchison, the well-known British chain of opticians.