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Lot 124Y
A month going mahogany Graham-style regulator with equation of timeSigned on the backplate, "Peter Lazarus / bürgls Gross Uhrmacher Meister / in Wien / verfertiget Anno 1806"
16 October 2019, 13:00 EDT
New YorkSold for US$52,575 inc. premium
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A month going mahogany Graham-style regulator with equation of time
Signed on the backplate, "Peter Lazarus / bürgls Gross Uhrmacher Meister / in Wien / verfertiget Anno 1806"
Movement: Mounted on a brass bracket on the back board, the substantial tapered plates joined by six latched knopped pillars, Graham-type dead beat escapement with maintaining power activated by a lever on the front plate and engaging an intermediate wheel, end capped train, steel crutch with adjustable pin engaging brass rod pendulum with massive lenticular bob suspended from back board, brass clad weight, day and month calendar work planted on the front plate, the day wheel linked to a subsidiary year wheel with equation cam by a worm gear with rod and a bevel gear
Dial: Within gilt bezel, resilvered , repainted roman chapter ring enclosing subsidiary seconds, date and month rings, blued hands, the concentric equation hour hand with gilt sunburst
Case: Architectural pediment to glazed hood, above trunk with glazed front and side panels, on plain plinth
Size: 80 ½ in (204cm) high
Movement: Mounted on a brass bracket on the back board, the substantial tapered plates joined by six latched knopped pillars, Graham-type dead beat escapement with maintaining power activated by a lever on the front plate and engaging an intermediate wheel, end capped train, steel crutch with adjustable pin engaging brass rod pendulum with massive lenticular bob suspended from back board, brass clad weight, day and month calendar work planted on the front plate, the day wheel linked to a subsidiary year wheel with equation cam by a worm gear with rod and a bevel gear
Dial: Within gilt bezel, resilvered , repainted roman chapter ring enclosing subsidiary seconds, date and month rings, blued hands, the concentric equation hour hand with gilt sunburst
Case: Architectural pediment to glazed hood, above trunk with glazed front and side panels, on plain plinth
Size: 80 ½ in (204cm) high
Footnotes
The present clock is a remarkable document on the state of published clock making technology at the end of the 18th century. It addresses two of the major concerns faced by clock makers: precision time keeping and the measurement of "true time."
Precision pendulum clocks revealed a significant difference between "true time", the apparent time seen in the shadow of a sundial, and "mean time" the average time measured by a clock. The yearly cycle of this variation became known as the "Equation of Time." Needless to say, building a mechanically elegant, self-adjusting Equation clock presented an irresistible challenge to 18th century clock makers.
Lazarus duplicated the movement of the George Graham regulator described and illustrated in the 1745 treatise , De Astronomica Specula Domestica et Organico Apparatu Astronomico published in Vienna by G.J. Marinoni (1676-1755), mathematician and astronomer to the Imperial Court of Austria. This work is a catalogue of the astronomical instruments in his private observatory. He ultimately left these to the Empress Maria Theresa, to whom he had dedicated the work. The shape of the movement plates and pillars, form of the anchor, layout of the train and the placement of the maintaining power on an intermediate wheel are all clearly illustrated in the engravings that accompany the treatise.
For the additional Equation work Lazarus could have turned to articles Julien Le Roy contributed to the Grande Encyclopédie of Diderot. Lazarus chose to plant his equation cam on a small subsidiary calendar wheel driven from the main calendar by a rod and worm gear. This design was described in Le Roy's essay on the Equation of Time.
The incentive to construct an Equation timepiece may have been in response to LeRoy's pronouncement that that any skilled maker could make a mean time [temps moyen] clock, but the true test of a fine clock maker was to construct a clock keeping apparent solar time [temps vrai].