Longcase regulator by Thomas Earnshaw / Joseph Catherwood

London, England, around AD 1795

One of the more important regulators made at this time

From the middle of the eighteenth century a growing number of private observatories were set up in Britain. King George III had one built at Kew where he personally tested John Harrison's timekeeper H5. Less well known was the astronomer William Larkin's private observatory at Blackheath. A sale catalogue of 23 June 1800 lists the contents of Larkins' observatory, including the following entry: 'an excellent transit clock, compound pendulum, barometer and thermometer within, in a handsome mahogany case, Earnshaw.' There is no conclusive proof that this clock is the one referred to in the sale catalogue. However, the whole design of the movement and case point to Earnshaw as the maker, rather than Joseph Catherwood, who is known to have been a retailer and whose signature appears on the clock. Indeed, Earnshaw, in his Longitude. An Appeal to the Public (1808) says, 'The best clock I ever made, was for Mr. Larkins of Blackheath'. It may be that it is this clock to which Earnshaw refers. The clock is also the only regulator with a thermometer and barometer in the dial known to survive from that period.

The case is of exceptional quality with reeded pilasters on the hood and trunk corners. The plinth has an extra door which allows access to the pendulum for rating. The composite dial has a middle section of gilt-brass with floral ornament surrounding two white enamel dials. The upper of these two dials shows seconds and the lower dial shows hours and minutes. To the left is a silvered plate carrying a thermometer calibrated in degrees Fahrenheit and to the right is a barometer with a vernier scale calibrated in inches of mercury. The weight-driven movement of two week duration is also of fine quality with an Earnshaw-made example of Thomas Mudge's detached gravity escapement (the earliest known example), controlled by a nine-bar Harrison gridiron compensation pendulum.