skip to primary navigation skip to content

Cambridge Digital Library

Department A-Z

Longitude Essays

Board of Longitude > Longitude Essays

Edward Troughton

Edward Troughton was a famed mathematical instrument maker and optician of London who was adept at using the dividing engine as well as hand-dividing to precisely engrave the scales on instruments. He assisted the Board of Longitude a number of times by supplying, repairing, and judging instruments as well as marine timekeepers. Troughton was born at Corney in Cumberland, likely in October 1753. He worked with his farmer, a property-owning farmer, until a brother who was assisting his uncle in London died. This uncle, a mathematical instrument maker, took Edward apprentice in place of the deceased in late 1773.

In the meantime, Edward's brother John Troughton went into the instrument business in London and built a dividing engine according to the instructions of Jesse Ramsden between 1775 and 1778. He bought the large retail business of Benjamin Cole on Fleet Street in 1782. Edward was freed from the Grocers' Company two years later and partnered with his brother from about 1788 on. He followed his brother's example in skillfully dividing instruments and producing an improved engine in 1793, and also studied astronomy in order to better himself, for which the siblings built an observatory atop their shop.

The two Troughtons sold diverse instruments, partially subcontracted from within the London instrument trade, and also large observatory instruments beginning in the 1780s. Many people considered them only second in skill to Ramsden. John died in 1807, and Edward started providing some important new instruments to the Greenwich Observatory. He also began improving the designs of many small instruments, which were tested in his home observatory. Troughton's interest in timekeeping led him to be consulted by the Board in 1805 over the comparison of John Arnold's and Thomas Earnshaw's marine timekeepers.

The instrument maker gave Nevil Maskelyne a description of how he hand-divided circular instruments which were too large for a dividing engine, like the mural circle that he was making for Greenwich. As a result, the Royal Society awarded him the Copley medal in 1809 and elected him a Fellow the next year. He earned many other honours as well and was one of the first members of the Astronomical Society. In 1826, he partnered with William Simms, producing large instruments for the trigonometrical survey of India by George Everest and an equatorial telescope for James South. Troughton's disagreements with South over the problematic telescope landed the instrument maker in court up to his death in 1835.

Edward Troughton appears in the digitised volumes in a number of places. These include the later surviving minutes of communal meetings of the Commissioners in RGO 14/6 [RGO 14/6], RGO 14/7 [RGO 14/7] and RGO 14/8 [RGO 14/8]. Other examples are the records of payments made to the craftsmen by the Board in volume RGO 14/18 [RGO 14/18] and RGO 14/19 [RGO 14/19]. Troughton's expert remarks on John Arnold's and Thomas Earnshaw's explanations of their marine timekeepers from 1805 are in RGO 14/26 [RGO 14/26] and RGO 14/27 [RGO 14/27] respectively. The observatory correspondence in volume RGO 14/48 includes bills and receipts for his helping to outfit [RGO 14/48:192a(r)] the new Royal Observatory at the Cape of Good Hope - the first European scientific institution in Africa.

There is a letter in RGO 14/52 in which Friedrich Bessel thanked [RGO 14/52:28] Edward, among others, for assistance with producing and subscribing out his publication Fundamenta Astronomae of 1818. In the Maskelyne correspondence in RGO 4/187, it is revealed that the Astronomer Royal helped the rare female 'computer' of the Nautical Almanac Mary Edwards to settle [RGO 4/187:10:1r] the accounts of her husband (who died in 1784) with London instrument makers including Troughton. The instrument maker makes appearances in the collections of individuals' papers as well, such as those of the astronomer William Gooch in Mm.6.48 [Mm.6.48].

Many of the instruments divided by Troughton survive around the world and at the National Maritime Museum. Examples include Greenwich Observatory's first mural circle [RMG icon] which was installed in 1812, an octant [RMG icon] from circa 1770, and a reflecting circle [RMG icon] from circa 1800.

Alexi Baker
History and Philosophy of Science
University of Cambridge