​CLARKE, HENRY (1743–1818), mathematician, was born at Salford in 1743, and baptised 17 April. He was educated at the Manchester grammar school; was very precocious, and at the age of thirteen became assistant in the academy of Aaron Grimshaw, a quaker at Leeds. Here he made the acquaintance of Priestley. After a brief partnership with Robert Pulman, a schoolmaster at Sedbergh, he travelled on the continent, and returned to settle as a land surveyor at Manchester. On 2 April 1766 he married Martha Randle of the same place. He again became a schoolmaster, and the rest of his life was spent in various educational posts. He first had a ‘commercial and mathematical’ school in Salford, giving lectures on astronomy and other scientific subjects. In 1783 he became ‘prælector in mathematics and experimental philosophy’ in the ‘College of Arts and Sciences’ at Manchester, a body anticipating the Royal Institution, which only lasted a few years. Clarke's school was not profitable, and in 1788 he was an unsuccessful candidate for the mastership of a school at Stretford, worth 60l. a year. Some time before 1793 Clarke moved to Liverpool, and, after returning to Manchester, was at Bristol from 1799 till 1802. ​He was in that year appointed professor of history, geography, and experimental philosophy at the military college at Great Marlow (removed in 1812 to Sandhurst). In the same year he was made LL.D. by the university of Edinburgh. He retired on a pension in 1817, and died at Islington, 30 April 1818.

Clarke was a frequent contributor to mathematical journals, especially to the ‘Ladies' Diary,’ then edited by Hutton, from 1772 to 1782. He was a candidate for a fellowship of the Royal Society in 1783, but rejected by the influence of Sir Joseph Banks, then president. Horsley (afterwards bishop), in a speech directed against Banks, complains especially of this case, and speaks of Clarke as an ‘inventor’ in mathematics. Clarke's works are: 1. ‘Practical Perspective,’ 1776 (for the use of schools). 2. ‘The Rationale of Circulating Numbers,’ 1777. 3. ‘Dissertation on the Summation of Infinite Converging Series with Algebraic Divisors’ (translated from Lorgna), 1779, with appendix. John Landen [q. v.] attacked this in a pamphlet, on the ground that the method was contained in Simpson's ‘Mathematical Dissertations.’ Clarke replied in a ‘Supplement’ (1782), and to a further attack in ‘Additional Remarks,’ 1783. The controversy is noticed in Hutton's ‘Mathematical Dictionary’ (under ‘Landen’). Clarke was attacked in the ‘Monthly Review’ for 1783, and defended by Horsley (see above). 4. ‘The School Candidates,’ a prosaic burlesque, 1788. This is a squib upon the election to the Stretford school. Clarke appears also to have published two pieces, ‘The Pedagogue’ and ‘The College,’ of similar character, about the same time. 5. ‘Tabula Linguarum,’ 1793 (tables of declension and conjugation in forty languages, a book of antiquated philology). 6. ‘Tachygraphy, or Shorthand improved’ (founded on Byrom's system), before 1800. 7. ‘The Seaman's Desiderata,’ 1800 (tables for calculating longitude, &c.). 8. ‘Animadversions on Dr. Dickson's translation of Carnot's reflections on the Theory of the Infinitissimal [sic] Calculus,’ 1802. 9. ‘Abstract of Geography,’ 1807 (only published number of a projected series of school-books for the Marlow College). 10. ‘Virgil revindicated,’ 1809, an answer to a tract by Horsley on Virgil's ‘Two Seasons of Honey.’

Clarke projected many other books, noticed by Mr. Bailey. He drew some plates for Whitaker's ‘History of Manchester.’ He was a man of wide knowledge, versatile talents, and great industry. He left a widow, and was survived by two sons and four daughters out of seventeen children.

L. S.