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Longitude Essays

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John Bird

John Bird was one of the most famed mathematical instrument makers in eighteenth-century Europe. He was especially revered for the precision with which he engraved the lines on instrument scales - like the lines on a ruler or protractor - by geometrical means which he had devised. He was baptised in 1709 in Bishop Auckland in County Durham in northeast England and originally worked as a weaver or clothier. However, even then he was sometimes engraving divisions on the faces of clocks as well. He moved to London in 1740 and learned instrument making from Jonathan Sisson of the Strand. Sisson was an optical and mathematical instrument maker who was widely respected for the skill of his scale engraving. Bird soon set up his own shop in the Strand, 'The Sea Quadrant', with the assistance of the esteemed clock and instrument maker George Graham. (Graham, with whom Bird had worked, was Sisson's former master as well as a mentor of John Harrison.) Bird became particularly known for producing high-quality observatory instruments, starting with a mural quadrant made for the Astronomer Royal James Bradley in 1749. This Greenwich Observatory quadrant spawned similar commissions from institutions in Cadiz, Paris and St. Petersburg. Bird also produced portable observational instruments, and divided rods for setting the standard length of the yard. He was constantly busy with such orders until his death in 1776 and often could not keep up, making some customers wait for many years before they received their instruments.

Bird was involved with the Board of Longitude many times during the 1750s and 1760s. He made, repaired and adjusted [RGO 14/5:49], and judged instruments for it - in addition to having made many of the instruments used at Greenwich during the production of the Nautical Almanac . For example, he was responsible [RGO 14/5:18] for some of the portable astronomical instruments used during the trials of John Harrison's marine timekeepers. He was also one of the experts chosen [RGO 14/5:50] in 1765 to be present at the directed 'discovery' of these clocks. Perhaps most importantly, Bird was involved with the Board in the creation of the sextant. This was a vital development for navigation, the search for the longitude at sea, and the improvement of the lunar-distance method. Bird originally made [RGO 14/5:11] a brass version of the circular instrument (or repeating circle) which Tobias Mayer suggested to the Board in 1755 for taking lunar distances. Captain John Campbell tried it at sea and found it lacking, so Bird produced a new instrument of a sixth of a circle with which Campbell had more success in 1758 and 1759. (It was also Bird to whom the Commissioners turned in 1767 [RGO 14/5:77] when they wanted to present an 18-inch quadrant to Campbell in recognition of his years of assistance.)

Bird went on to publish two treatises as a result of having suggested [RGO 14/5:65] on 26 April 1766 that the Board pay him £500 to fund the building of a new and improved workshop in return for explaining his methods and teaching them to an apprentice and another person. The Commissioners agreed as long as he also taught William Ludlam and John Michell and produced a detailed written explanation with illustrations and if necessary models. (At the Board meeting of 21 March 1767 [RGO 14/5:75], the Commissioners declined to give a similar reward to the well-known instrument maker Jeremiah Sisson. He had argued that he possessed the same skills as Bird since they had both learned them from his father, Jonathan.) It appears that Bird never built a new workshop, and it is unknown whether he truly took on the apprentice. At the meeting of 24 May 1766 [RGO 14/5:68], the Board approved of an unnamed boy whom the instrument maker said he intended to bind to him - but of whom we never hear again. The instrument maker produced one model of the mural arc at Greenwich and the accompanying text and engraved illustration plates. The plates went into his two famous books, The method of dividing astronomical instruments in 1767 and a year later The Method of constructing Mural Quadrants . There were a number of publication delays due to business demands and ill health.

The roles which John Bird and his instruments played in the activities of the Board, especially during the 1750s, are not fully represented in the surviving archives. This is largely because it was from the 1760s on that the Commissioners of Longitude really became a standing body and hired secretaries, which resulted in the making and saving of far more records. The surviving minutes [RGO 14/5:1] of group meetings of the Commissioners show that the instrument maker was mentioned on a number of dates, often having attended a meeting in person or having sent a written message to it. Other RGO volumes contain records related to his two Board-sponsored publications, including RGO 14/15 [RGO 14/15:1] and RGO 14/16 [RGO 14/16:1] containing publication records, and RGO 14/19 containing vouchers and printer accounts [RGO 14/19:108r]. There was a sworn and signed copy of The method of dividing astronomical instruments itself in RGO 4/107 [RGO 4/107], but it is currently missing. Other volumes discuss the use of some of the instruments made by Bird without directly discussing the maker. An example is the account of William Bayly on the HMS Adventure from 1772 to 1774, when the astronomer used a Bird transit instrument, in MS RGO 14/57 [RGO 14/57]. In addition, MS Harrison sometimes gives John and William Harrison's views of what happened during related Board meetings and activities. This sometimes differs from the descriptions in the official minutes. An example is the discussion or debate [HARRISON:97] over the accuracy of the instruments sent on trials of the Harrison timekeepers, including comparisons made between the models of Bird and of James Short.

Outside of the volumes digitised here, there are many bits and pieces relevant to John Bird including receipts and letters and legal documents spread across a variety of institutions. For example, the instrument maker's will proved on 6 April 1776 is now at the National Archives in Kew as document PROB 11/1018/146 [link] . In it, he named the frequent Board collaborator John Campbell as one of his two executors, leaving the Captain a gold watch and half the remainder of his estate. (Campbell was also directed, if Bird's female servant were then no longer alive, to transfer £1000 of stock to the Vice Chancellor of the University of Oxford for the support of the Assistant Astronomer of the Radcliffe Observatory in Oxford - which Bird had kitted out.) Finally, the instrument maker left £30 pounds to George Witchell, the master of the Royal Naval Academy at Portsmouth since 1767, who was another Board collaborator. Some images of Bird survive, for example this print [RMG icon] from the year of his death now at the National Maritime Museum. Many of his instruments survive around the world as well. Those at Greenwich include what is most likely the first marine sextant [RMG icon] made, and the mural quadrant [RMG icon] from 1750.

Alexi Baker
History and Philosophy of Science
University of Cambridge