Edinburgh, where at one time he taught mathematics in the college, although he appears to have resided at Leith, and is described as schoolmaster there. He occupied himself in making and recording experiments in physics. He was one of the first in Scotland to utilise the barometer, which he styled the baroscope, as a means of measuring altitudes and also the depth of mines, although he based his calculations on erroneous principles. He appears also to have been employed by coalowners in the Lothians to report on the extent and dip of the various beds of coal in their neighbourhood, and his report was published in 1672 in his ‘Hydrostaticks,’ where he suggested the best methods of draining off water from the coal seams. In this work he shows a knowledge of English collieries as well as of Scottish. The book, perhaps owing to the author's self-complacency, provoked a severe attack by James Gregory [q. v.], professor of mathematics in St. Andrews, under the pseudonym of ‘Patrick Mathers, arch bedal to the university of St. Andrews.’ Sinclar wrote, but never published, a retort, entitled ‘Cacus pulled out of his Den by the Heels’ (manuscript in Glasgow University Library). Gregory's satire was so severe that it injured for a time the sale of Sinclar's book; but in 1673 and 1674 he superintended, at the request of the magistrates, the laying of pipes to bring water into the city of Edinburgh. It was in 1685 that he published the work by which he is best known, ‘Satans Invisible World discovered’ (Edinburgh, 12mo), written to ‘prove the existence of devils, spirits, witches, and apparitions,’ and to vindicate this belief against those who would assault ‘one of the outworks of religion.’ It was dedicated to the Earl of Wintoun. Sinclar supplies many marvellous narratives, which are declared to be authentic. The writer obtained from the privy council the sole right of publication for eleven years. The book has been frequently reprinted.
After the revolution or early in 1689, Sinclar resumed his chair of philosophy in the college of Glasgow, and two years later he demitted that charge on being appointed professor of mathematics (3 March 1691), a post which he held till his death. The last notice of him in the records of the college is on 18 April 1696, and he appears to have died in that year. The college treasurer records that he died poor, but he ‘was ane honest man.’
Sinclar also published: 1. ‘Tyrocinia Mathematica, in iv. Tractatus, viz., Arithmeticum, Sphæricum, Geographicum et Echometricum divisa,’ Glasgow, 1661, 12mo, which was reissued with a new title-page as ‘Principia Mathematica, Editio secunda priore correctior,’ London, 1672, 12mo. 2. ‘Ars Nova et Magna Gravitatis et Levitatis, sive Dialogorum Philosophicorum libri sex de aeris vera et reale gravitate,’ Rotterdam, 1669, 4to. 3. ‘The Hydrostaticks, or the Weight Force and Pressure of Fluid Bodies made evident by Physical and Sensible Experiments,’ Edinburgh, 1672, 4to, containing also a ‘Short History of Coal.’ This work was reissued, with some additions, under the new title of ‘Natural Philosophy improven by New Experiments,’ Edinburgh, 1683, 4to. 4. ‘The Principles of Astronomy and Navigation, or a clear, short, yet full Explanation of all Circles of the Celestial and Terrestrial Globes,’ Edinburgh, 1688, 4to.
Besides these, Sinclar published in 1684, as his own composition, a work styled ‘Truth's Victory over Error,’ with an elaborate preface enumerating his other books. This work was a translation of the Latin lectures on the confession of faith delivered by David Dickson [q. v.], professor of divinity in Glasgow. Sinclar's version reached a second edition in 1688. The first edition to bear Dickson's name was issued at Glasgow in 1726.
[Munimenta Universitatis Glasguensis (Maitland Club), 4 vols.; the prefaces and personal references contained in Sinclar's own works; Satans Invisible World, reprinted by T. S. Stevenson, Edinburgh, 1871, with biographical notice; Wodrow's Life of David Dickson; Ray's Three Discourses, 1713, p. 263; Chambers's Eminent Scotsmen, iv. 263–4.]
SINCLAIR, GEORGE (1786–1834), botanical writer, was born in 1786 at Mellerstain in Berwickshire, and was descended from a Scots family which had long been devoted to gardening. His father, George Sinclair (1750–1833), gardener to the Hon. G. Baillie of Jerviswood, was in his earlier years considered one of the best horticulturists in the south of Scotland, and his uncle was superintendent of the grounds, gardens, and farms at Bonnington, near Lanark. The son was himself originally in the service of the Gordon family, and became, upon the duke's marriage with Lady Georgiana Gordon in 1803, gardener to John Russell, sixth duke of Bedford [see under Russell, Lord John, first Earl Russell], at Woburn Abbey. By the instructions of the duke, and under the direction of Sir Humphry Davy [q. v.], he conducted an extensive series of experiments, the results of which were embodied in the costly folio, ‘Hortus Gramineus Woburnensis, or an account of the results of Experiments on the Produce and Nutritive
