# Dictionary of National Biography, 1885-1900/Bonnycastle, John

**BONNYCASTLE,** JOHN (1750?–1821), author of several works on elementary mathematics, was born (probably about 1750) at Whitchurch, in Buckinghamshire. At an early age he went to London ‘to seek his fortune,' 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 ‘private teacher of mathematics.' He was at one time private tutor to the sons of the Earl of Pomfret. Between 1782 and 1785 he became professor of mathematics at the Royal Military Academy, Woolwich. He died on 15 May 1821. His chief works are: 1. ‘The Scholar’s Guide to Arithmetic.' The first edition of this book appeared in 1780. In 1851 appeared an eighteenth edition, ‘edited by J. Rowbotham, corrected with additions hy S. Maynard] 2. ‘Introduction to Algebra,' 1782. A thirteenth edition appeared in 1824, ‘with addenda by Charles Bonnycastle,' the author’s son. 3. ‘Introduction to Astronomy,’ 1786. This book is intended as a popular introduction to astronomy rather than as an elementary treatise. An eighth edition appeared in 1822. 4. An edition of Euclid’s ‘Elements,’ with notes, 1789. 5. ‘Introduction to Mensuration and Practical Geometry,' 1782 (thirteenth edition 1823). This book and the last were translated into Turkish. 6. ‘A Treatise on Algebra,' 2 vols., 1813. 7. ‘A Treatise on Plane and Spherical Trigonometry,’ 1806. Besides elementary mathematical books, Bonnycastle was in early life a frequent contributor to the ‘London Magazine.' He wrote also the introduction to a translation (by T. O. Churchill) of Bossut’s ‘Histoire des Mathématiques,’ and a ‘chronological table of the most eminent mathematicians from the earliest times’ at the end of the book (1803). He seems to have been a man of considerable classical and general literary culture. Leigh Hunt, who used to meet him in company with Fuseli, of whom Bonnycastle was a great friend, has left a description of him in his book on ‘Lord Byron and his Contemporaries.' He describes him as ‘a good fellow,' and as ‘passionately fond of quoting Shakespeare and of telling stories.' In conclusion, he suggests that, in common with scientific men in general, Bonnycastle ‘thought a little more highly of his talents than the amount of them strictly warranted;' but, he adds, ‘the delusion was not only pardonable but desirable in a man so zealous in the performance of his duties, and so much of a human being to all about him, as Mr. Bonnycastle was.’

[Gent. Mag. 1821, i. 472, 482; Leigh Hunt's Lord Byron and his Contemporaries, ii. 32-6; Brit. Mus. Cat.; De Morgan’s Arithmetical Books, p. 76; Dict. of Living Authors, 1816.]