John and Edward Troughton, mathematical instrument makers

During the first quarter of the nineteenth century Edward Troughton (c. 1753-1835, F.R.S. 1810) was the foremost mathematical instrument maker in England, and in the last ten or fifteen years of the eighteenth century he and his older brother John Troughton (c. 1739-1807), then in partnership, ranked second only to the celebrated Jesse Ramsden (c. 1735-1800, F.R.S. 1786). Many examples of their work exist in the collections at Greenwich, South Kensington, Cambridge and Oxford. Edward’s method of ‘original division’, or scale graduation, was a most important contribution, for which he received the Copley Medal, and his major instruments hold an honoured place in the history of astronomy, geodetic surveying and metrology. The modern literature incorporates what seems to have become a traditional version of the Troughton story (Note A), but this is inaccurate in some respects and misleading in others. A more reliable account is therefore desirable and we present here, for the first time, biographical memoirs of John and Edward Troughton based on primary sources and contemporary published information. A brief account of their uncle, John Troughton senior, is also included. Some notes on the dating of Troughton instruments are given in an Appendix.