The Calcutta Earnshaw | Circa 1792
A highly important George III month-going mahogany regulator with Maskelyne’s proposed hermetically sealed case and jewelled deadbeat escapement by Thomas Earnshaw, London.
Height: 6 feet 2 inches (1880 mm).
Case: The very substantial flat top solid mahogany case with bombe-shaped trunk and conventional base. The hood with concave main top moulding above the canted and fluted hood sides, the sides with blind aperture mouldings, and the whole hood extended top and sides to seal with the massive 2-inch-thick backboard, also extended to match the hood, which is sealed with longer hood sealing screws, each knurled and number stamped 2, to correspond with the inlaid brass numbered hood holes. The hinged and glazed hood door, similarly screw sealed, the glass with a sealed gilt-brass winding shutter or ‘valve’. The trunk with concave throat moulding, and further conforming sealing screws up into the hood, above the trunk with sides shaped to take pendulum swing and rectangular screw sealed trunk door, the conforming concave lower moulding leading to the base with panelled front and double skirted hood, the underside with a thick wooden floor to keep it airtight, while each screw-tightened surface is fitted with strips of cloth to ensure a perfect seal.
Dial: 10 inch (254 mm) square silvered brass regulator dial with Arabic minutes, marked 5to 60, outside the division ring, the subsidiary Arabic hour ring below centre reverse numbered 1-24, and signed within Earnshaw London. The upper subsidiary Arabic seconds ring supplemented with bold observatory marks every 5 seconds, the lower subsidiary Arabic hour ring reverse numbered 24 to 1. Both subsidiary dials have counter balanced hands, the hour hand rotating contraclockwise.
Duration: One month.
Movement: The very substantial five pillar (Betts ref. Type 1) movement is of the very highest quality, with an extension to the right side of the plates taking the stop work, jewelled to the escape and pallet arbors with Harrison’s maintaining power, exceedingly fine train wheels and high-count pinions. The top with dust plate and knurled fixing screws, similar to the case screws but smaller, the movement located onto the massive 2 inch seatboard with two brass edge strips, stepped at either end to guide the plates, and conventionally screw-fixed to the base pillars. Massive cast-brass pendulum support with suspension for the 5-rod zinc/steel gridiron compensated pendulum with massive bob, engraved regulation nut, and secondary fine rating ball below.
Escapement: Jewelled deadbeat.
Provenance:
• First reported in Calcutta (Kolkata) in 1999, sold by Bobinet in 2006 for £100,000.
Literature:
• Derek Roberts, English Precision Pendulum Clocks, 2003, Chapter 4, Thomas Earnshaw by Jonathan Betts, p.55-67, illus. fig. 14-4.
In his Marine Chronometers at Greenwich, 2018, Jonathan Betts states that Earnshaw’s famous 8-day Armagh Transit Regulator (No.1) is one of the finest regulators in horological history, amazing the astronomers at Armagh with its good going. It still keeps excellent time today, over 200 years later, still in its original home at that observatory. The regulator presented here is the only surviving example of essentially the same format, suggesting perhaps a near concurrent manufacture, however it is not jewelled below the escapement, and the extra jewelling in the Transit clock No.1 gives it the edge, but the Calcutta regulator must come in a very close second and its additional month duration, with no interference to the pendulum for 30 days, must also be considered in its favour.
Thomas Earnshaw was one of England’s most important and famous chronometer makers. He was born on 4 February 1749 at Ashton-under-Lyne, Lancashire and appears to have been apprenticed at the age of fourteen, to William Hughes of High Holborn, from 1763 to 1770. In 1769 Earnshaw married Lydia Theakston at St James’s church, Piccadilly and was still only 20 years old. The Earnshaw family grew quickly and within five years he had three sons, keeping his family on a journeyman’s wages proved impossible and finances became critical. In 1774, he fled to Dublin, returning later that year to surrender himself to debtor’s prison; from here he was able to come to terms with his creditors and was soon back in business. He taught himself the highly specialised trades of watch jewelling and ruby-cylinder making and, by 1780, he turned his attention to making chronometers with detached, pivoted-detent escapements.
For further information about Dr John C Taylor, please visit his website at www.johnctaylor.com