An eight-day duration mahogany longcase sidereal regulator, by William Hardy, London, circa 1825

Catalogue description — Royal Museums Greenwich

This longcase regulator, though not historically related to the Observatory, plays an important role in the display as it is representative as to how the original regulator, supplied by Hardy, would have looked before Dent’s alterations. The first of Hardy’s regulators used a mercurial temperature compensated pendulum suspended from the stone pier to which the case was affixed. This sidereal timekeeper retains its original spring pallet escapement which was carefully restored circa 1900 by London based horologist, Alphonse Lecluse. Scottish by birth, Hardy was already working in London by the early 1800s and had evidently had a first rate apprenticeship as he was producing fine chronometers at that time. His comments on Arnold’s and Earnshaw’s specifications for chronometers, submitted to the Board of Longitude in 1804, reveal him to be a careful and intelligent observer of the behaviour and structure of chronometers and regulators. Between 1804 and 1820 he was awarded a succession of prizes by the Society of Arts for improvements in horology. He was the first to have the wheels of his regulators made with accurately formed cycloidal-shaped teeth as is theoretically correct. Protected from dust by a sliding mahogany dust cover protecting the robustly built movement has thick (7mm) arched brass plates which are united by five stout pillars fixed to the front and backplates by large brass screws. The lightly constructed six-wheel train is driven by a cylindrical brass cased weight with integral pulley suspended from a double line to the going barrel with sprung stop iron and chamfered nib passing through the barrel flange lying across the nineteenth turn. The barrel also carries Harrison’s maintaining power, the greatwheel and a second wheel driving the large hour wheel. All wheelwork on this clock has six tapered crossings and is triple screwed to brass collets (with the exception of the hour wheel which has seven crossings). The rear pivots all have brass end caps mounted to the backplate. Hardy’s fully jewelled spring pallet escapement is fixed separately to the backplate. The clock has a mercurial temperature compensated pendulum running against a silvered beat scale reading 0 to 3.5 degrees. The signed silvered twelve inch circular dial of typical regulator layout inscribed ‘Willm. Hardy Invt. et Fecit, London’ in cursive script between the seconds subsidiary dial with engraved observatory marks and the twenty four-hour dial; both subsidiaries are enclosed by an outer minutes chapter with arabic five-minute markings. The mahogany case has an arched hood with locking front door decorated with raised stringing below the circular glazed aperture with gilt brass bezel. The tapered trunk has canted corners, trapezoidal glazed brass moulded door which closes into a felt-lined rebate. The crossbanded base has a stepped upper moulding, moulded front panel and plinth.