Daniel Gabriel Fahrenheit (1686-1736)
signed on the reverse Fahrenheit Amst, the graduated scale from [-4°] to 132°, numbered by 4° on alternating sides of the tube and divided to 2°, the later mercury tube secured with brackets at both ends to the shaped brass plate.
4½in. (11.5cm)
Private collection formed in the 1970s.
cf. de Clerq, P. The Leiden cabinet of physics; A descriptive catalogue (Leiden, 1997) no.224 on p.139.

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Lot Essay

Born into a family of Polish Merchants who died when he was 15, Fahrenheit was sent by his guardian to Amsterdam. There he entered into the scientific instrument trade and was settled by 1717. He produced areometers, barometers and thermometers, supplementing his incoming by teaching physics and chemistry. He was known by all the leading Dutch natural philosophers of the time, and was made a Fellow of the Royal Society in 1724. "He may have been the first to use mercury as a thermometric fluid" (PMM).

In his Experimenta circa gradum caloris liquorum nonnullorum ebullientium instituta (London, 1724) Fahrenheit published the basis for the modern instrument, his "most significant achievement [being] the development of the standard thermometric scale that bears his name" (DSB). His principal innovation being a 'fixed point' of departure, namely the temperature to which water can be cooled when mixed with ice and salt. This he called zero. At the ends of his scale were normal human blood-heat--which he took at 96°--and the normal freezing point of water, 32°. When this scale was later extended upwards, the boiling point of water fell at 212°.

His instruments today are extremely scarce: a handful of signed barometers survive, and only two other scientific thermometers, both at the Museum Boerhaave. One of unknown provenance is dated 1727 (inv. no. 10232) and another that was acquired by the university from Willem 's Gravesande in 1741 (inv. no. 10229). The latter bears a signature in the same hand as the current example and also has a replaced glass tube. It is dated to 1718 when Fahrenheit was presenting thermometers as gifts in order to establish his name.

Along with the Celsius scale, Fahrenheit's is the only temperature scale to survive from the many that were proposed in the 17th and 18th centuries. It is still used in the United States of America and was used by the Met Office up until 1970.

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