From the website Thomas-earnshaw.com:
“THOMAS EARNSHAW (1749-1829) was born on the 4th of February at Ashton under Lyne, Lancashire near Manchester, England.
Thomas Earnshaw is revered as a legend and pioneer in the field of Horology, and celebrated for his work in refining, and improving upon the Marine Chronometers of the era. It was those Marine Chronometers, crucial to the journeys taken by the boats in the Royal Navy as they circled the globe during a golden era in English history of science and exploration…Lauded for his work with marine chronometers, Earnshaw also embraced the challenge of developing clocks for use in Observatories such as those in Greenwich and Armagh and examples of his exquisite work can be seen in museums and auction houses around the world…
He devised a modification to the detached chronometer escapement, and the compensation balance which would be used in the standard marine chronometer thereafter.
Earnshaw was introduced to Nevil Maskelyne, the Astronomer Royal, who tested an Earnshaw chronometer for six weeks and encouraged Earnshaw to continue making them. As a result, Earnshaw received orders to repair clocks at the Greenwich Observatory and was commissioned to make a regulator for the new observatory at Armagh.
Captain William Bligh purchased, on behalf of the Admiralty, Earnshaw’s chronometer no. 1503 at a price of 40 Guineas for an expedition he was to command in HMS Providence to the West Indies.
After the passing of his mentor William Hughes in November 1792, Earnshaw succeeded to the business at *119 High Holborn. Earnshaw then signed his work with his own name. He built chronometers to a standard plan, which led to batch production of movements by outside workers
Matthew Flinders’ ship, HMS Investigator, carried two boxed Timekeepers by Earnshaw E520 and E543, at a cost of 100 Guineas each. The Investigator carried out the first circumnavigation and mapping of the coastline of Australia. The chronometer E520 was mounted in a wooden box with gimbals to compensate for the motion of the ship. Flinders went to shore regularly to check the settings of the chronometers against the stars. The Earnshaw chronometer Flinders refers to in his book A Voyage to Terra Australis as “this excellent timekeeper”.
Earnshaw was granted an award of £2500 by the Board of Longitude for his improvements to chronometers. The bimetallic compensation balance and the spring detent escapement in the forms designed by Earnshaw have been used essentially universally in marine chronometers since then, and for this reason Earnshaw is generally regarded as one of the pioneers of chronometer development.
Thomas Earnshaw retired from running the business, which he handed over to his son (who continued until 1854). He died at home in Chenies Street on the 1st of March, 1829, and was buried at St Giles-in-the-Fields, Bloomsbury. A plaque in the memory of Thomas Earnshaw has been since mounted at St. Giles in the Fields.
Chronometer no. 506 was carried on HMS Beagle on a voyage to circumnavigate the globe and establish, for the first time, a chain of points around the world of accurately known longitude. The ship was commanded by Captain Robert FitzRoy, a future Vice-Admiral and founder of the Meteorological Office. This was also the voyage that carried Charles Darwin who was afterwards inspired to write his book about the theory of evolution, On the Origin of Species.”