Thomas Earnshaw was a pioneer horologist and one of several developers of the marine chronometer. He was born in Mottram, Ashton-under-Lyne, Lancashire, (now in the Metropolitan Borough of Tameside). Though his youth was spent in Lancashire, he spent most of his productive adult life working in premises at 119 High Holborn in London, where he lived and raised his family.
In 1782 he invented the so-called spring detent chronometer escapement, (also known as the chronometer escapement), which was to become the standard for marine chronometers throughout the 19th century and essentially remained unchanged to the present day. It has only been superseded in quite recent times by quartz digital timepieces. Earnshaw's detent escapement revolutionised portable time-telling at sea.
His work paralleled that of his rival, John Arnold, another celebrated London watchmaker. However, it was Earnshaw who had simplified the design of the pocket and marine chronometers into their modern, readily reproducible form. Both Arnold and Earnshaw had produced chronometers for £60 and these had become commonplace by the 1820s.
Initially, Earnshaw did not hold the patent to his invention - this was owned by Thomas Wright because Earnshaw was unable to afford the cost of registration.
Two Earnshaw chronometers can be found at the Royal Observatory, placed there at the request of the Astronomer Royal, Nevil Maskelyne, (another rival). Earnshaw's so-called No.1 chronometer had been delivered for trials at the Royal Greenwich Observatory in February 1792, where it remained for two years until it was finally installed by Earnshaw himself at Armagh in Northern Ireland on the 18th August 1794, (where it remains to this day).
There were rival claims as to the origination of his timepieces, and Earnshaw fought both of his horological rivals for more than a decade, as well as taking on the government in order to secure fair recognition and reward for his endeavours.
His mechanism differed from its predecessors in that it gave impulse to the balance in one direction during a short section of its arc, and had the advantage over Arnold's type in not requiring oil on the escape wheel teeth.
Disillusioned, Earnshaw even published an article, "Appeal to the Public" in 1808, in which he presented the evidence of his invention, but even this failed to gain the recognition he deserved.
Eventually, recognition and remuneration did come, so that in 1853 Thomas Robinson, another celebrated clock maker, wrote of Earnshaw's clock that it was "…probably the best in the world".
Eventually, Earnshaw's spring detent escapement was awarded £3,000 from the Board of Longitude for its contribution towards the solution of the longitude at sea problem, and nowadays Thomas Earnshaw ranks amongst our greatest chronometer inventors and has finally secured his rightful place in the history of marine technology. He died in 1829 in London, and his old premises in High Holborn carries a Blue Plaque to mark his achievement.