by Thomas Whittaker, rev. Adrian Rice
© Oxford University Press 2004 All rights reserved
Bonnycastle, John (c.1760-1821), mathematician, was born at Whitchurch, in Buckinghamshire. His parents, though not affluent, managed to provide him with a reasonable basic education. At an early age he went to London 'to seek his fortune' (GM), and afterwards kept an academy at Hackney. On the title-pages of the earlier editions of his first work (The Scholar's Guide to Arithmetic) he is described as a 'private teacher of mathematics', and was at one time private tutor to the sons of the earl of Pomfret, during which time he lived at Easton Neston in Northamptonshire. In October 1782 he became a mathematics master at the Royal Military Academy, Woolwich, and in July 1807 succeeded Charles Hutton as professor of mathematics.
Bonnycastle was a prolific and successful writer of textbooks. Of his chief works, The Scholar's Guide to Arithmetic first appeared in 1780 and ran to an eighteenth edition in 1851. An Introduction to Algebra followed in 1782. (A thirteenth edition appeared in 1824, 'with addenda by Charles Bonnycastle', the author's son.) His Introduction to Astronomy (1786), intended as a popular introduction to astronomy rather than as an elementary treatise, was one of the best-selling books on the subject for many years. An edition of Euclid's Elements, with notes (1789), and An Introduction to Mensuration and Practical Geometry (1782; 18th edn, 1840) were both translated into Turkish. Other works included A Treatise on Plane and Spherical Trigonometry (1806) and A Treatise on Algebra (2 vols., 1813). Besides elementary mathematical books, Bonnycastle was in early life a frequent contributor to the London Magazine. He also wrote the introduction to a translation (by T. O. Churchill) of Bossut's Histoire des mathématiques (1803) and a 'chronological table of the most eminent mathematicians from the earliest times' for the end of the book.
Bonnycastle married twice. His first wife, a Miss Rolt, whom he married when he was nineteen, died young. His second wife, Bridget Johnstone, survived him, as did three sons, including Sir Richard Henry Bonnycastle, army officer, and one daughter. He seems to have been a man of considerable classical and general literary culture. He was strongly associated with the military, since many of the artillery officers had been his students, and he also seems to have been a popular tutor for children of the aristocracy. Leigh Hunt, who used to meet him in company with the Swiss painter Fuseli, of whom Bonnycastle was a great friend, left a description of him in his book Lord Byron and Some of his Contemporaries. He describes him as 'a good fellow ... passionately fond of quoting Shakespeare and of telling stories'; he suggests that Bonnycastle may have 'thought a little more highly of his talents than the amount of them strictly warranted', but that 'the delusion was not only pardonable but desirable' in this case, given his strong sense of duty and his common humanity. Bonnycastle died at Woolwich Common, after a 'long and tedious illness' (GM), on 15 May 1821, and was interred, during a semi-military funeral, in a purpose-built vault at Charlton, Kent.
THOMAS WHITTAKER, rev. ADRIAN RICE
Sources
GM, 1st ser., 91/1 (1821), 471-2, 482
L. Hunt, Lord Byron and some of his contemporaries, 2 (1828), 203-7
[J. Watkins and F. Shoberl], A biographical dictionary of the living authors of Great Britain and Ireland (1816)
A. De Morgan, Arithmetical books from the invention of printing to the present time (1847), 76
H. D. Buchanan-Dunlop, ed., Records of the Royal Military Academy, 1741-1892 (1895)
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