Bird, John

(b. Bishop Auckland, England, 1709; d. London, England, 31 March 1776)

mathematics, optics.

Bird was an eminent maker of mathematical instruments; the precision of his products made possible considerable advancement of practical astronomy. Almost nothing is known of his early life, which was spent in northeast England. He worked as a weaver and developed an interest and a proficiency in metal engraving. He also divided and engraved clock dial plates, demonstrating considerable skill in this work. About 1740 Bird moved to London, where he was employed by the well-known maker of astronomical and navigational instruments, Jonathan Sisson. Shortly after his arrival in London, Bird devised an instrument for finding the latitude at sea. He soon came to the attention of George Graham, another maker of astronomical instruments and clocks. Graham, impressed with the accuracy and quality of his work, assisted Bird in establishing his own shop for the making of mathematical instruments in 1745.

The nature of the instruments first produced by Bird at his own shop is not precisely known, but among them were portable quadrants with radii ranging from ten to twenty-four inches, as well as transit instruments ranging in length from one foot to five feet.

Bird received his first major order in 1749. The astronomer royal, James Bradley, had applied to and received from George II a grant of £1,000 for the construction of new instruments for the Royal Observatory at Greenwich. Bradley thereupon commissioned Bird to produce a movable forty-inch-radius quadrant cast in brass. He labored three years over the production of this instrument, which required 2,000 screws and weighed nearly 800 kilograms. Bird provided against error due to temperature change, and when the instrument was completed in June 1750 it was found to be a mere.05 greater than 90°.

This achievement brought Bird considerable fame, and by means of the instrument Bradley was able to achieve numerous important astronomical observations. When the Imperial Academy of Science at St. Petersburg remodeled its observatory within the next several years, Bird was employed to provide the instruments, including an eight-foot quadrant. He produced similar instruments for the Royal Observatory at Paris and for the Naval Observatory at Ca’diz. In 1754 Bird constructed a six-foot mural quadrant that was presented by the king to Tobias Mayer at the University of Göttingen. Other important instruments made by Bird were two eight-foot quadrants for Radcliffe Observatory at Oxford. In 1758 and 1759 he was commissioned to produce a standard yard measure for the committees of the House of Commons and an apparatus for determining capacity measures.

During this same period Bird was engaged in commercial production of reflecting telescopes, barometers, thermometers, octants, and drafting instruments. He produced the reflecting circles, designed by Tobias Mayer, that were tested by Captain John Campbell for the Admiralty in 1757–1759, and in 1773 he was called upon by the Board of Longitude to examine the sextant scale divided by Jesse Ramsden’s new dividing engine.

Bird’s methods for the accurate division of scientific instruments were made available to others in two published works in which he described his methods and tools.

Not only were Bird’s instruments the most accurately graduated prior to the invention of the dividing engine, but by his example and his publications others were enabled to achieve greater precision in scientific instrumentation.

BIBLIOGRAPHY

I. Original Works. Bird’s published writings are The Method of Dividing Astronomical Instruments (London, 1767) and The Method of Constructing Mural Quadrants (London, 1768).

II. Secondary Literature. Writings on Bird or his work are Jean Bernoulli, Lettres astronomiques (Berlin, 1771), pp. 107–108, 126–129; C. Doris Hellman, “John Bird (1709–1776) Mathematical Instrument-Maker in the Strand,” in Isis, 17 (1932), 127–153; Thomas Hornsby, ed., Astronomical Observations Made at the Royal Observatory at Greenwich, From the Year MDCCL, to the Year MDCCLXII, by the Rev. James Bradley, I (Oxford, 1798), Preface, ii-iii, vii, xiv, xv; Henry C. King, The History of the Telescope (London, 1955), pp. 115–118; Pierre-Charles Le Monnier, “Description et usage des principaux instruments d‘astronomie où l’on traite de leur stabilite, de leur fabrique, et de l‘art de les diviser,” in Description des arts et métiers, 42 (1774), 1–60, plates I-XIV; and W. Ludlam, An Introduction and Notes, on Mr. Bird’s Method of Dividing Astronomical Instruments, to Which Is Added a Vocabulary of English and French Astronomical Terms (London, 1786).

Silvio A. Bedini