A Victorian mahogany wall regulator with Dennison’s three-legged gravity escapement, signed: Dent, 61 Strand & 34 Royal Exchange London, Clockmaker to the Queen, 1437,
circa 1853
60 in. [152 cm] H
Probably made for astronomical or other scientific use, the substantial four pillar movement is secured to brackets on a cast - iron backplate; the train has Harrison's maintaining power and wheels cut with six crossings. The escapement is pivoted beneath arched cutouts in the plates.
The heavy five-rod zinc and steel gridiron pendulum, is suspended from the backplate. The design, introduced by John Arnold, consists of two zinc and three steel rods and a large brass-clad bob, pierced with rectangular openings and a bridge acting as the point of suspension. In this configuration, the bob’s center of gravity rests on a screw threaded into the lowest cross piece of the pendulum. The screw may be turned for adjustment by means of a pin inserted into small holes along its length. The screw also has a calibrated rating scale and terminates with an index to the silvered beat scale. The original patinated brass-cased weight has integral pulley.
The 15 inch, signed, circular, silvered regulator dial is engraved with outer minutes ring enclosing an hours dial above a seconds dial. The relative positions of the dials was dictated by the placement of the escapement. Each has a fine blued steel hand.
The arched mahogany case with glazed sides and conforming arched lenticle in the trunk is also suspended from the backplate. There is a brass shuttered winding hole set into the glass.
Made while Dent was engaged in the construction of “Big Ben,” the clock employs a very early form of the three - legged gravity escapement, invented by Edmund Beckett Dennison (Lord Grimthorpe) for use in the Westminster clock. An 1852 drawing by Dennison, sent to the Astronomer Royal, G. B. Airy, is virtually identical to the gravity escapement in the present clock. |
