Dalby, Isaac (DNB00)

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DALBY, ISAAC (1744–1824), mathematician, was born in Gloucestershire in 1744. He received a very imperfect education. His friends wished him to be a clothworker, but he, ambitious of a more intellectual career, secured the post of usher in a country school. In 1772 he arrived in London, and obtained an appointment as teacher of arithmetic in Archbishop Tenison's grammar school, near Charing Cross. Afterwards he was employed by Topham Beauclerk in making astronomical observations in a building which the latter had erected for the purpose. This establishment was broken up by the death of Beauclerk in 1780, and in the year following Dalby was appointed mathematical master in the naval school at Chelsea. About this time he was recommended by Ramsden, the philosophical instrument maker, to General Roy, whom he assisted from 1787 to 1790 in making a trigonometrical survey for the purpose of connecting the meridians of Greenwich and Paris. He was engaged at a later period with Colonel Williams and Captain Mudge to carry on the trigonometrical survey of England and Wales. In 1799 he was appointed professor of mathematics in the Royal Military College, High Wycombe, which was subsequently removed to Farnham in Surrey, and is better known as Sandhurst College. This post he held for twenty-one years, resigning it in 1820, when old age and infirmity had overtaken him. He published: 1. ‘Account of the late Reuben Burrow's Measurement of a Degree of Longitude and another of Latitude in Bengal,’ London, 1796, 4to. 2. ‘Account of the Operations for accomplishing a Trigonometrical Survey of England and Wales, from the commencement in 1784 to the end in 1796,’ 3 vols. London, 1799, 4to. 3. ‘A Course of Mathematics designed for the use of the Officers and Cadets of the Royal Military College,’ 2 vols. London, 1805, 8vo. 4. ‘The Longitude of Dunkirk and Paris from Greenwich, deduced from the Triangular Measurement in 1787–1788, supposing the Earth to be an Ellipsis,’ Phil. Trans. abr. xvii. 67, 1791. He was besides a contributor to the ‘Ladies' Diary.’ Dalby died at Farnham in Surrey, on 3 Feb. 1824, in the eightieth year of his age. He was an original member of the Linnean Society (Nichols, Illustr. vi. 834.)

[Imperial Dict. of Universal Biog. ed. Waller, ii. 4; Watt's Bibl. Brit. i. 280 f.]

R. H.