MACLAURIN, COLIN Scottish mathema tician, was the son of a clergyman, and born at Kilmodan, Argyll shire. He was educated at the University of Glasgow.
At nineteen he was elected professor of mathematics in Mari schal college, Aberdeen, two years later he was admitted F.R.S. and made the acquaintance of Sir Isaac Newton. In 1719 he pub lished his Geometria organica, sive descriptio linearum curvarum universalis. In it Maclaurin developed several theorems due to Newton, and introduced the method of generating conics which bears his name, and showed that many curves of the third and fourth degrees can be described by the intersection of two mov able angles. In 1721 he wrote a supplement to the Geometria organica, which he afterwards published, with extensions, in the Philosophical Transactions for 1735. This paper is principally based on the following general theorem, which is a remarkable extension of Pascal's hexagram: "If a polygon move so that each of its sides passes through a fixed point, and if all its summits except one describe curves of the degrees m, 71, p, etc., respec tively, then the free summit moves on a curve of the degree 2mnp . . . which reduces to mnp . . . when the fixed points all lie on a right line." In 1722 Maclaurin travelled as tutor and companion to the eldest son of Lord Polwarth, and of ter a short stay in Paris resided for some time in Lorraine, where he wrote an essay on the percussion of bodies, which obtained the prize of the French Academy of Sciences for the year 1724. In 1725 he was made professor of mathematics in the university. of Edinburgh on the recommendation of Newton.
In 1740 Maclaurin divided with Leonhard Euler and Daniel Bernoulli the prize offered by the French Academy of Sciences for an essay on tides. His Treatise on Fluxions (1742), written
in reply to George Berkeley contains his essay on the tides. In this he showed that figures of equilibrium for a homogeneous rotating fluid mass are the ellipsoids of revolution, now known as Maclaurin's ellipsoids. Maclaurin was the first to introduce into mechanics, in this discussion, the important conception of level surfaces. He also gave in his Fluxions, for the first time, the correct theory for distinguishing between maxima and minima in general, and pointed out the importance of the distinction in the theory of the multiple points of curves. As a result of Maclaurin's suggestion, the newly formed (1731) Medical Society of Edinburgh was enlarged into the Philosophical Society (1739), and later (in 1783) into the Royal Society of Edinburgh. Of Newton's British successors, Maclaurin alone ranked equal with continental mathematicians of his day.
In 1745, when the rebels were marching on Edinburgh, Mac laurin took a prominent part in preparing trenches and barricades for its defence. As soon as the rebel army got possession of Edinburgh Maclaurin fled to England, to avoid making submission to the Pretender. He died on June 14, 1746, at Edinburgh.