Lot 115

Breguet à Paris, circa 1810
A remarkable, very rare and very fine thermometer ring with original box
Case: 18k pink gold, oval-shaped case, polished, 12 g, 28 x 22 mm. Dial: enamel, scales for indicating different climates: "Chaleur"-"Fièvre"-"Gelée"-Tempéré" ("warmth"-"heat"-"frost"-"moderate"), signed "Thermomètre Breguet", blued Breguet hand. Movm.: brass/steel, double-curb bimetallic strip, double rack, pinion, spring.
Breguet produced two types of thermometers - this ring thermometer is one of the second type pieces. The first models only had a single rack and were slightly less sensitive in operation than their successors; the later thermometers were fitted with two racks that moved in opposite directions and had a tensioning spring. They were much better equipped to distribute the force acting on the pinion that carries the hand.
However, Breguet developed his thermometers even further; for his exhibit at the French Industrial Exhibition of 1819 he used a trimetallic curb made of platinum, gold and silver, which he described in a small catalogue published for this occasion.