# Dictionary of National Biography, 1885-1900/Robertson, John (1712-1776)

**ROBERTSON**, JOHN (1712–1776), mathematician, was born in 1712. Though apprenticed to a trade, he became a teacher in mathematics, and in 1748 was appointed master of the royal mathematical school in Christ's Hospital. In 1755 he became first master of the Royal Naval Academy at Portsmouth. Having lost this appointment in 1766 'through petty cabals of the second master,' he returned to London, and was appointed clerk and librarian to the Royal Society on 7 Jan. 1768. This office he held, with repute, till his death, on 11 Dec. 1776. He was respected by prominent members of the society, and his advice in the council was much respected.

His chief publication was 'The Elements of Navigation,' which appeared in 1754, and went through seven editions in fifty years. His other works were:

- 'A Compleat Treatise of Mensuration,' 1739; 2nd edit. 1748.
- 'Mathematical Instruments,' 1747; 4th edit. 1778 (by W. Mountaine).
- 'A Translation of De La Caille's Elements of Astronomy,' 1750.

He also published nine papers in the 'Philosophical Transactions,' 1750–72, 'On Logarithmic Tangents;' 'On Logarithmic Lines on Gunter's Scale' (cf. Masères, *Script. Log*. vol. v. 1791); 'On Extraordinary Phenomena in Portsmouth Harbour;' 'On the Specific Gravity of Living Men;' 'On the Fall of Water under Bridges;' 'On Circulating Decimals;' 'On the Motion of a Body deflected by Forces from Two Fixed Points;' and 'On Twenty Cases of Compound Interest.' He is said to have been the first to discover the theorem that in stereographic projection the angle between two circles on the sphere equals the angle between two circles on projection (Charles, *Aperçu Hist*. pp. 516–17).

[Hutton's Mathematical Dict.; Allibone; Brit. Mus. Cat.]