A fine mahogany wall regulator with Buckney’s zinc / steel compensation pendulum'
signed: Dent, Clockmaker to the King, 61 Strand, London, no. 58745, circa 1915
60 in. [152 cm] H
Dent 58745 is fitted with Buckney’s pendulum whose steel rod supports the massive lead weighted cylindrical brass bob. Compensation is by means of zinc and blued steel tubes concentric with the rod. Both the bob and the tubes are pierced to allow air to freely flow around them and rapidly adjust to the ambient temperature.
The clock’s substantial movement is typical of English 19th century regulators. It has massive plates, a high count train and dead beat escapement mounted on the backplate. The stability of the clock is provided by a cast iron mounting bracket to hold both the pendulum and movement. The mahogany case is little more than a protective dust cover that supports none of the weight of the clock. Made originally to generate an electrical time signal, the brass contacts can be seen within and on the side of the case and formerly in an aperture in the dial.
The basic design of Dent wall regulator no. 58745 is derived from the so-called “Sidereal Standard Clock” at Greenwich Observatory. This regulator, devised by George Airy, the Astronomer Royal and built by E. Dent & Co. in 1871 remained the Greenwich Standard Time Clock until 1922.
The Greenwich prototype (Dent, no. 1906), built under the supervision of Thomas Buckney, Jr. originally had a mercurial pendulum. It was replaced by an improved zinc / steel pendulum, ultimately patented by Buckney in 1885.
The design was a success for Dent as the clock remained in production until the 1920's. Some dozen of these clocks, numbered in sequence, 1914-1916 and 2009-2017, were used in the British Transit of Venus Expeditions of 1874 and 1882. The robust case made them suitable for the harsh conditions under which the clocks were used in the field. The Dent historian, Vaudrey Mercer noted that several of these were still in regular use nearly a century later.
The present clock is 58745 of a new numbering series begun in1876, with the introduction of their triangular trademark. The surviving serial number list indicates the clock was completed about 1915. Other examples of this type of clock were purchased by many astronomical observatories around the world. |
