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Maker, George Jamison, Charing Cross, London, England, c. 1800. Movement net 18"h x 8"diameter, overall with base 22"h x 10.5"diameter. Two plane anchor escapement with divided lift, i.e. the two pallets are in different planes relative to each other. One half second pendulum with engraved silvered Earth globe as the bob. Rack and pinion striking on the hour. Two train chain fusee, with Harrison maintaining power, eight day duration. Silvered chapter rings and fire gilt ormolu decorations and tripod frame.

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The apex clock dial displays Greenwich time with along with a perpetual calendar, moon's phase, and age. Longitude is indicated by two equatorial bands shown against twenty seven locations of the world with Greenwich at zero degrees. Local time is read off the two rotating, silvered rings for minutes and hours and can be set for any location using the starburst indicator. A zenith ring bearing the four compass points encircle the device in a vertical plane. This is one of very few examples of a clock using annular rings to tell the time of English origin. The French had made more use of this device although usually in a simpler format. The use of a classical tripod was favored in tellurian and orrery demonstration models about this time most notably by George Adams, Jr., but this might be the first example of the use of a tripod to support clockwork. Thomas Cole is known for using this as a decorative device in his clocks in the mid 1800's.

Albert Odmark, whose collection this example came from noted: "Whilst English spherical skeleton clocks are extremely rare French examples, sometimes called horloges circle de tournants, were made either at the end of the 18th or very beginning of the 19th Century. They all have the same two-plane escapement with divided lift (obviating the use of a verge escapement) horizontal revolving chapter rings and folding tripod feet. The most complex and there are possibly three examples, are those with calendar work and of those it is thought that this example with perpetual calendar, Halifax moon and Greenwich Mean Time is probably the most complex of all."  Two other simpler examples are depicted here. Anyone with information about other additional examples please do contact me.

The movement in this clock is oriented in a horizontal plane as opposed to the conventional arrangement of most clocks that are in a vertical plane. Before the advent of the pendulum being applied to the anchor escapement in 1666 the verge escapement was the only arrangement for the pendulum. In this application the crown wheel was in the horizontal plane. Given the geometry of this clock's movement the use of the verge would have been a logical choice. However, that escapement has many mechanical disadvantages when it comes to accurate timekeeping. By the time this clock was conceived the verge would have been thought to have been hopelessly outdated. So the maker tried to bring the advantages of an updated escapement to replace the horizontally oriented crown wheel found in the verge escapement. In this clock the two train, two-plane anchor escapement takes the place of the horizontal crown wheel by replacing it with a horizontal anchor wheel. The pallets for the anchor escapement are normally in the same plane as the escape wheel, but given that the escape wheel is horizontally positioned and the pendulum is swinging in the vertical plane this is impossible. Therefore the the escapement anchor is turned 90 degrees to the escape wheel. This is not a simple procedure. Both the escape wheel as well is the anchor escapement must be altered in a custom manner for this arrangement to work, hence the two plane geometry of the escapement anchor. Also the teeth of the escape wheel resemble more those of a turbine fan blade in that they are canted to allow for impulse of the escapement. I have not seen this type of escapement elsewhere although I'm sure it exists (other than in these spherical clock examples).

This clock is illustrated in British Skeleton Clocks, Derek Roberts, pp. 15, 18-19, 22; and Skeleton Clocks, F.B. Royer-Collard, pp. 100, 102-104.

Provenance: Carter-Wright, 2014. Formerly Albert Odmark collection, Christie's, London, March 2005. Formerly Malcom Gardner, October 20, 1965. Formerly Charles Alix collection, Seven Oaks, Kent, England.

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