James Stratton
Director
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Lot 116
A very rare mid 19th Century English brass skeleton timepiece with ten-jar mercury pendulum and deadbeat escapement with jewelled pallets The dial later signed for Vulliamy, London
8 July 2015, 14:00 BST
London, New Bond StreetSold for £4,750 inc. premium
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A very rare mid 19th Century English brass skeleton timepiece with ten-jar mercury pendulum and deadbeat escapement with jewelled pallets
The dial later signed for Vulliamy, London
the tapering frame united by three turned pillars and set on four feet and a later mahogany base under a glass dome, the silvered Roman chapter ring with outer minute track later signed 'Vulliamy London' with blued steel moon hands, the single chain fusee movement with maintaining power, skeletonised barrel cap, wheels of six crossings and high count pinions, terminating in a deadbeat escapement with jewelled pallets, the pendulum rod of rectangular-section steel supporting a stirrup of ten glass phials filled with mercury The frame 29cms (11.5ins) high.
the tapering frame united by three turned pillars and set on four feet and a later mahogany base under a glass dome, the silvered Roman chapter ring with outer minute track later signed 'Vulliamy London' with blued steel moon hands, the single chain fusee movement with maintaining power, skeletonised barrel cap, wheels of six crossings and high count pinions, terminating in a deadbeat escapement with jewelled pallets, the pendulum rod of rectangular-section steel supporting a stirrup of ten glass phials filled with mercury The frame 29cms (11.5ins) high.
Footnotes
George Graham conducted his first experiments on the mercury jar pendulum on 18th December 1721. There was some initial fine-tuning, but the experiment lasted over three years, finally coming to a conclusion on 14th October 1725. He found the use of mercury a useful aid in negating any temperature changes. See Roberts, 'Precision Pendulum Clocks', Schiffer 2003 p68. Other methods of compensating against temperature changes in the 18th and 19th centuries were 'gridiron' pendulums of brass and steel, or those using more inert materials such as seasoned wooden rods, or later on, Invar.
The main issue with glass jars of mercury is the weak thermal conductivity of the glass. The use of cast iron jars later in the 19th century overcame this shortfall to some extent. Other methods used included the use of two or more rods (see the fine wall regulator by Frodsham sold in these rooms 10 December 2014, lot 142) and smaller jars with thinner sides. The British Museum has a fine regulator by Sigmund Rentzsch which uses sixteen mercury phials, see Roberts Figs.5-2A,B,C.
As far as we are aware, this is the only known skeleton clock with such a pendulum.