Description

A REAUMUR WATCH-CASE BIMETALLIC THERMOMETER, French, 19th century. The case is made of bright plated metal, 1-3/4″ (44 mm) in diameter, with glazed front and removable back plate. The dial is delicately hand-painted with “Reaumur” and a -35° to +80° scale divided every degree and labeled “Glace” (i.e., “Ice”) at 0°. The mechanism has a long shaped bimetallic spring, amplification linkage, and geared sector driving the pointer which is preloaded by a fine hairspring. Condition is fine and functional throughout, noting light scratches to the dial plate. This handsome pocket thermometer is unusual in being designed solely for the Reaumur temperature scale, as proposed by Rene Antoine Ferchault de Reaumur in 1731. He set the freezing point of water at 0°, and, for the “convenience” of octogesimal division, the boiling point at 80°. It was generally replaced in the late 18th century by the Centigrade system.