Oxford DNB article: Sharp

Sharp, Abraham (bap. 1653, d. 1742), mathematician and scientific instrument maker, was born at Horton Hall, Little Horton, near Bradford, and baptized at Bradford, Yorkshire, on 1 June 1653, the ninth child and sixth son of John Sharp of Little Horton, and his wife, Mary, the daughter of Robert Clarkson of Bradford. His nineteenth-century biographer, William Cudworth, believed that he was born in 1653 and that the monumental inscription stating that he died in his ninety-first year is incorrect; evidence to support this appears in a letter of November 1715, where Sharp says he is 'now in my grand Clymacterick', or sixty-third year (Royal Greenwich Observatory Archives, CUL, RGO 1/34, fol. 125r).

John Sharp prospered as a farmer, clothier, and merchant; during the civil war period he took the side of parliament and served as financial secretary to General Sir Thomas Fairfax; he later became a collector of Commonwealth taxes. He gave his sons a good education, sending two to university and placing the rest in respectable trades. Abraham went on from a village school to Bradford grammar school and in May 1669 was apprenticed to a York mercer. He probably learned some mathematics as a schoolboy, and as an apprentice must have studied its practical applications. Some accounts assert that he left his master prematurely and moved to Liverpool, where he taught writing and commercial arithmetic; this is not implausible, as a legacy of £160 on his father's death in 1672 may have prompted or assisted the move.

Nothing more is known of Sharp's activities until the spring of 1684, when he was in London, using the Hen and Chickens in the Strand as a correspondence address, and began to assist the astronomer royal, John Flamsteed, at the Royal Observatory at Greenwich. He was employed there for some months during 1684-5 and from August 1688 to the autumn of 1690. In the intervening period he lived in London but remained in close touch with Flamsteed. During his second stay at the observatory he helped complete the great mural arc, 6 feet 9 inches in radius, which was to serve as Flamsteed's principal instrument for three decades and set a new standard for the observatories of Europe. In this connection Flamsteed described Sharp as:

the fittest for my purpose, that could be[,] a curious Mechanick and An excellent Geometrician, who screwd the limbe, wrought the Index and after I had fixed the point for the beginning of the divisions inscribed them and engraved the Numbers both for the diagonalls and revolves so curiously that I thinke I may say ... tis the neatest limbe that ever was made of the same bignesse. (Correspondence of John Flamsteed, 2.449)

On leaving the Greenwich observatory in November 1690, Sharp lodged with William Court at the Mariner and Anchor on Little Tower Hill, where mathematical books and instruments were sold; he possibly succeeded his acquaintance Marmaduke Hodgeson as Court's resident teacher of mathematics. Soon afterwards he was offered a clerkship in the king's shipyard at Portsmouth and overcame a reluctance to accept it: one of his notebooks reveals that he moved to Portsmouth in February 1691 and had some connection with the dockyard, though his presence seems to have left no trace in its official records. He also received occasional sums for teaching and a salary of £10 a year from a Mr Graham, perhaps as an instrument maker. The interlude was a brief one: on the death of his eldest brother in 1693, his widowed sister-in-law asked him to return to Little Horton. He did so early in 1694 and lived there for the rest of his life. His principal importance in the locality was as a promoter and generous patron of the first Presbyterian chapel in Bradford.

Horton Hall was demolished in the 1960s, but is known to have been a stone-built house in a style characteristic of the area; Sharp is believed to have adapted its central tower to create an observing platform. His continuing interest in mathematics, astronomy, and instrument making is reflected in surviving notebooks and in correspondence with local and London friends. He sold an odometer to his distant relative John Sharp, archbishop of York, and corresponded occasionally with the antiquary Ralph Thoresby, who lists 'a declining Dial for the Library Window, by the celebrated Mr. Abr. Sharp' among his collection of 'Rarities' (Thoresby, 475). Sharp was also in touch with the elder and younger Euclid Speidell, Joseph Raphson, Henry Sherwin, Edmond Halley, the optical instrument maker John Yarwell, and the publisher Richard Mount; their letters reflect Sharp's endeavours to obtain books and instruments and to secure publication of mathematical works. His Geometry Improv'd, containing elaborate tables and a treatise on polyhedra, appeared in 1717; Sherwin's Mathematical Tables (1710 and many later editions) also included a substantial contribution from:

the ingenious and unwearied Mr. Abr. Sharp, with his Table of Logarithms to above fifty Figures ... the Construction of the Sines, Tangents and Secants; with the whole Process of the Quadrature of the Circle to 72 Figures: Which Quadrature was invented ... by Mr. Halley. (Sherwin, preface)

From February 1702 until his death at the end of 1719, Flamsteed was Sharp's principal correspondent. Virtually all the letters they exchanged survive, and many of them reveal details of Sharp's activities. By 1702 he had 'made a small Instrument to which I have adapted a Six ft Telescope in the nature of sights; hereby both the altitude and azimuth may be had at the same instant' (Correspondence of John Flamsteed, 2.908), had improved his lathe by devising 'Engines, one for Rose and Crown work, the other for Ovall and Rose work, and likewise ... an Engine for cutting Wheels' (ibid., 2.909), and had 'made a large brasse Sphaere or Armilla of a peculiar contrivance, which with much ease ... represents any sphaericall Triangle that can be proposed' (ibid., 2.932). This last may be the instrument depicted on his tombstone and in a portrait engraving by George Vertue (1744).

Sharp went on to assist his former employer in a variety of ways: he made him a micrometer (1704); calculated places of the moon and planets and extensive subsidiary tables for the planned Historia coelestis; produced tables of the predicted eclipses of Jupiter's satellites annually from 1707 to 1719 (for 1708 to 1720); attempted to observe some of these and other eclipses, rarely with success; and systematically collected barometric observations. After Flamsteed's death he corresponded with the Greenwich assistant Joseph Crosthwait and helped prepare the revised Historia coelestis Britannica (1725) for publication; in particular he produced an updated version of Halley's catalogue of the southern stars. He also worked on star charts for the Atlas coelestis (1729).

Sharp died at Horton Hall on 18 July 1742, and was buried on 21 July in St Peter's, Bradford (now Bradford Cathedral), where a monument was later erected. His instruments and tools were dispersed; those few that survive are at Bolling Hall Museum, Bradford, the National Maritime Museum, and the Science Museum.

Sources
W. Cudworth, The life and correspondence of Abraham Sharp (1889)
W. Yorks. AS, Bradford, Bardsley-Powell family papers
The correspondence of John Flamsteed, the first astronomer royal, ed. E. G. Forbes and others, 3 vols. (1995-2001)
F. Baily, An account of the Revd John Flamsteed, the first astronomer-royal (1835); repr. (1966)
W. T. Lancaster, ed., Letters addressed to Ralph Thoresby FRS, Thoresby Society, 21 (1912), 11-12, 188-9
R. Thoresby, Ducatus Leodiensis, or, The topography of ... Leedes (1715), 475, 497, 548
M. Holbrook, R. G. W. Anderson, and D. J. Bryden, Science preserved: a directory of scientific instruments in collections in the United Kingdom and Eire (1992), 98-9
N. S. Heineken, 'Relics of the mechanical productions of Abraham Sharp, the assistant of Flamsteed', London, Edinburgh, and Dublin Philosophical Magazine, 3rd ser., 30 (1847), 25-7
S. Melmore, 'Abraham Sharp's universal instrument', The Observatory, 61 (1938), 248-50
H. Sherwin, Mathematical tables (1710)
GM, 1st ser., 12 (1742), 387
CUL, Royal Greenwich Observatory papers, RGO 1/34, fol. 125r

Archives
Bolling Hall Museum, Bradford, instruments
CUL, Royal Greenwich Observatory archives, MSS
NMM, instruments
RS, MSS
Sci. Mus., instruments
York Minster Library, York Minster Archives, account and memo books, notes, and tables | W. Yorks. AS, Bradford, Bardsley-Powell MSS, corresp. and papers

Likenesses
G. Vertue, engraving, 1744, AM Oxf., NMM [see illus.]
portrait, priv. coll.; repro. in Cudworth, Life and correspondence, facing p. 157

Wealth at death
over £1250; plus lands: will, Cudworth, Life and correspondence, 201-2