Dictionary of National Biography, 1885-1900/Machin, John (d.1751)

by Agnes Mary Clerke

MACHIN, JOHN (d. 1751), astronomer, was elected a fellow of the Royal Society on 30 Nov. 1710, acted as its secretary from 1718 to 1747, and sat on the committees appointed by the same body in 1712 to investigate the dispute between Newton and Leibnitz (Weld, History of the Royal Society, i. 410). On 16 May 1713 he succeeded Dr. Torriano [q.v.] as professor of astronomy in Gresham College, and held the post until his death, which occurred in London on 9 June 1751. Machin enjoyed a high mathematical reputation, but his attempt to rectify Newton's lunar theory in his 'The Laws of the Moon's Motion according to Gravity,' appended to Motte's translation of the 'Principia,' London, 1729, was a poor performance. His ingenious quadrature of the circle was investigated by Hutton (Tracts, i. 266), and be computed in 1706 the value of π by Halley's method to one hundred places of decimals (Jones, Synopsis Palmariorum Matheseos, p. 243). A large work on the lunar theory taken in hand by him in 1717 never saw the light, but a mass of his manuscripts is preserved by the Royal Astronomical Society; and, writing to Jones in 1727, he asserted his claim to the parliamentary reward of 10,000l. for amending the lunar tables (Rigaud, Corresponedence of Scientific Men, i. 280).

Machin contributed to the 'Philosophical Transactions:'

1. 'Inventio Curvæ quam corpus descendens brevissimo tempore describerat' (xxx. 860).
2. 'A Case of a Distempered Skin' (xxxvii. 299).
3. 'The Solution of Kepler's Problem' (xl. 205).

His quadrature was reprinted in Maseres's 'Use of the Negative Sign in Algebra' (p. 289).

[London Mag. xx. 284; Nichols's Illstr. of Lit. iv. 23; Rigaud's Corresp. of Scientific Men, vol. i. passim; Watt's Bibl. Brit.]

A. M. C.