astronomical regulator, no. 394
Date: circa 1867
Inventory Number: 2503a
Classification: Clock
Dimensions:case: 245 x 61.5 x 74.5 cm (96 7/16 x 24 3/16 x 29 5/16 in.)
DescriptionThis astronomical regulator has a silvered brass dial, with a matte, white finish, which is signed by the maker, William Bond and Son, Boston, and engraved, "Escapement invented by R. F. Bond."
The seconds-beating pendulum is temperature-compensated through the use of a steel cylinder filled with mercury. The steel rod has a threaded weight for fine adjustments to the timekeeping.
The movement is powered by two weights. The original weights, which were lead-filled brass spheres, were replaced by lead-filled brass cylinders with compound pulleys during an earlier reconstruction of the case. The two winding barrels are fitted with Harrison's maintaining power.
The pendulum is impulsed by a single gravity arm, which is reset by the remontoire mechanism that is controlled by the conical pendulum at the top of the clock. The conical pendulum has a red-brass bob on a wooden rod.
This clock has break-circuitry work for use at the Observatory. The electrical contacts are for 1, 2, and 5 minute intervals.
This clock originally had a glass dome (called a shade by horologists) over the conical pendulum. It is now missing. The movement was in a glass box below the dome. The current wooden case is a late replacement to the original clock housing. This replacement was necessitated by the clock's removal from its original Observatory location.
More details about the movement and other parts are to be found in the captions to the photos.
Signedon the dial: WM. BOND & SON, BOSTON.
on the dial: Escapement invented by R. F. Bond.
Inscribedon the dial: WM. BOND & SON, BOSTON. / Escapement invented by R. F. Bond. / No. 394.
FunctionTo see and hear this clock in motion go to the following Vimeo link. The video was made by Don Saff in 2012.
Historical AttributesThis clock has the ingenious conical pendulum devised by Richard F. Bond in the 1860s. It was set up at the the Harvard College Observatory around 1867. The trial of the clock is recorded in the HCO Annals (1876). However, the clock was not officially purchased by the Observatory until 17 August 1876 for $500. It was supported by one of the marble piers in the East Transit Room, where astronomical observations were no longer made.
This clock distributed standard time signals to New England from 1872 until late in the 19th century.
According to the Day Book of William Bond & Son:
August 21, 1876: Astronomical Clock 394 sold to [the Harvard College] Observatory for $500.00 William Bond & Son retaining the right to receive time signals, paying only for batteries.
May 8, 1878: The time ball on top of the building of the Equitable Life Insurance Co., corner of Milk & Devonshire St. was dropped for the first time today by the clock at the Cambridge Observatory.
Primary SourcesAnnals fo the Astronomical Observatory of Harvard College, 8 (1876): 16-17.