Claire Tole-Moir
Head of Department
Lot 41
A fine and rare George Adams Senior pyrometer, English, Mid-18th century,
18 May 2016, 13:00 BST
London, KnightsbridgeSold for £27,500 inc. premium
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Jon Baddeley
Specialist Consultant Collectors, Science & Marine
A fine and rare George Adams Senior pyrometer, English, Mid-18th century,
Signed on the dial, 'Made by George Adams Instruments maker to His Majesty's Office of Ordnance at Tycho Brahe's Head in Fleet Street London', the steel platform supported by two brass brackets mounted with one of five metal bars; silver, copper, brass, iron and lead and engraved on each bar, one end resting against adjustable screw, the other against a blued steel lever attached by a chord, pulley and weight to indicate changes in length against circular dial with pointer, on mahogany base, 12 1/2 ins (32cm)
Footnotes
The pyrometer was originally invented by Wedgwood for use in his kilns and was first referred to as any instrument associated with a measure of heat. Subsequently it came to refer to a means of measuring the different degree of thermal expansion of various metals in the range where thermometers could not be used. Consisting of a brass clamp to hold metal rods, a burner to heat them, and a dial on a pillar, the instrument would demonstrate any changes in the bar's temperature, meaning any alteration in length would cause the steelyard to rotate, and the change registered on a scale. There is no other George Adams Senior pyrometer known to exist.
See: Sally Newcomb's The World in a Crucible, 2009, p. 46.
G.N. Cantor's Optics after Newton: Theories Of Light In Britain & Ireland 1704-1840, 1983
Literature: This instrument is almost identical with the form of the instrument invented by the clock-maker John Ellicott and described by him in the 'Philosophical Transactions', xxxix 1736, pp. 297-99