# Mackay, Andrew (DNB00)

**MACKAY,** ANDREW (1760–1809), mathematician, was born in 1760 and lived in Aberdeen. He was in October 1781 appointed keeper (without salary) of the observatory on the Castle hill (see *Aberdeen Journal*, 15 Oct. 1781), and here he made his calculations on the latitude and longitude of his native town (see infra). He was created LL.D. of Aberdeen in 1786, and was also fellow of the Royal Society of Edinburgh, honorary member of the Literary and Philosophical Society of Newcastle-on-Tyne, mathematical examiner to the corporation of Trinity House (1805-9) and to the East India Company. In his later years he took pupils in London at his house in George Street, Trinity Square; he taught mathematics and natural philosophy, navigation, architecture, and engineering. He died on 3 Aug. 1809, leaving a widow and children, and was buried in Allhallows Barking.

He made important contributions to the science of navigation, and was a skilful, accurate, and indefatigable calculator of mathematical tables. His principal works are: 1. 'The Theory and Practice of finding the Longitude at Sea or on Land: to which are added various Methods of Determining the Latitude of a Place by Variation of the Compass: with new Tables,' published by subscription, 1793, 2 vols.; 2nd edit., with author's portrait, 1801, 3rd edit. 1810. In this work is given an account of a new method of finding the longitude and latitude of a ship at sea, together with the apparent time, from the same set of observations; for which the author had received the thanks of the boards of longitude of England and France. 2. 'A Collection of Mathematical Tables,' 1804. 3. 'The Complete Navigator,' 1804; 2nd edit. 1810. The preface contains severe criticism of the books on navigation then in current use.

His minor works are: 1. 'A Comparison of different Methods of Solving Halley's Problem' (Masebes, *Scriptores Logarithmici,* vol. iv.; see also Preface, p. ix). 2. 'Description and Use of the Sliding Rule in Arithmetic and in the Mensuration of Surfaces and Solids,' &c, 1799; 2nd edit. 1806. 3. 'The Commencement of the Nineteenth Century determined upon unerring Principles,' Aberdeen, 1800. The object of this tract was to explain that the century began on 1 Jan. 1800 and not on 1 Jan. 1801. 4. 'Description and Use of the Sliding Gunter in Navigation,' Aberdeen, 1802; 2nd edit. Leith, 1812, edited by Alexander Ingram, with portrait of author prefixed. He also contributed articles to the 'Encyclopædia Britannica,' 3rd edit. 1797 (see Preface, xv), on 'Navigation,' 'Parallax,' 'Pendulum,' 'Projection of the Sphere,' 'Ship-building,' and (naval) 'Tactics,' and he was a contributor to Rees's 'Cyclopædia.' He published a paper on the latitude and longitude of Aberdeen in the 'Philosophical Transactions of the Royal Society of Edinburgh,' vol. iv. For examples of Mackay's skill as a computer reference may be made to Maseres's 'Scriptores Logarithmici,' vol. vi.

[Works; European Mag. 1809, lvi. 157; Fasti Acad. Mariscallanæ, ed. P. J. Anderson, i. 450; Notes and Queries, 3rd ser. iii. 153.]