COLIN, a most eminent mathematician and philosopher, was the son of a clergyman, and born at Kilmoddan in Scotland in 1698. He was sent to the university of Glasgow in 1709; where he continued five years, and applied himself to study in a most intense manner. His great genius for mathematical learning discovered itself so early as at twelve years of age; when, having accidentally met with an Euclid in a friend's chamber, he became in a few days master of the first six books without any affluence: and it is certain, that in his 16th year he had invented many of the propositions which were afterwards published under the title of Geometria Organica. In his 15th year he took the degree of master of arts; on which occasion he composed and publicly defended a thesis On the power of Gravity, with great applause. After this he quitted the university, and retired to a country-seat of his uncle, who had the care of his education; for his parents had been dead some time. Here he spent two or three years in pursuing his favourite studies; but, in 1717, he offered himself a candidate for the professorship of mathematics in the Marischal college of Aberdeen, and obtained it after a ten days trial with a very able competitor. In 1719, he went to London, where he became acquainted with Dr Hoadly then bishop of Bangor, Dr Clarke, Sir Isaac Newton, and other eminent men; at which time also he was admitted a member of the Royal Society; and in another journey in 1721, he contracted an intimacy with Martin Folkes, Esq. the president of it, which lasted to his death.

In 1722, Lord Polwarth, plenipotentiary of the king of Great Britain at the congress of Cambray, engaged Maclaurin him to go as a tutor and companion to his eldest son, who was then to set out on his travels. After a short stay at Paris, and visiting other towns in France, they fixed in Lorraine; where Maclaurin wrote his piece On the Percussion of Bodies, which gained the prize of the Royal Academy of Sciences for the year 1724. But his pupil dying soon after at Montpellier, he returned immediately to his profession at Aberdeen. He was hardly settled here, when he received an invitation to Edinburgh; the curators of that university being desirous that he should supply the place of Mr James Gregory, whose great age and infirmities had rendered him incapable of teaching. He had some difficulties to encounter, arising from competitors, who had good interest with the patrons of the university, and also from the want of an additional fund for the new professor; which however at length were all surmounted, principally by the means of Sir Isaac Newton. In November 1725, he was introduced into the university. After this, the mathematical classes soon became very numerous, there being generally upwards of 100 young gentlemen attending his lectures every year; who being of different standings and proficiency, he was obliged to divide them into four or five classes, in each of which he employed a full hour every day, from the first of November to the first of June.

He lived a bachelor to the year 1733: but being not less formed for society than for contemplation, he then married Anne, the daughter of Mr Walter Stewart, solicitor-general to his late majesty for Scotland. By this lady he had seven children, of whom two sons and three daughters, together with his wife, survived him. In 1734, Berkeley, bishop of Cloyne, published a piece called "The Analyst;" in which he took occasion, from some disputes that had arisen concerning the grounds of the fluxionary method, to explode the method itself, and also to charge mathematicians in general with infidelity in religion. Maclaurin thought himself included in this charge, and began an answer to Berkeley's book: but, as he proceeded, so many discoveries, so many new theories and problems occurred to him, that instead of a vindictive pamphlet, his work came out, A complete system of fluxions, with their application to the most considerable problems in geometry and natural philosophy. This work was published at Edinburgh in 1742, 2 vols. 4to; and as it cost him infinite pains, so it is the most considerable of all his works, and will do him immortal honour. In the mean time, he was continually obliging the public with some performance or observation of his own; many of which were published in the fifth and sixth volumes of the "Medical Essays" at Edinburgh. Some of them were likewise published in the Philosophical Transactions; as the following: 1. Of the construction and measure of curves, No. 356. 2. A new method of describing all kinds of curves, No. 359. 3. A letter to Martin Folkes, Esq., on equations with impossible roots, May 1726, No. 394. 4. Continuation of the same, March 1729, No. 408. 5. December the 21st, 1732, on the description of curves; with an account of farther improvements, and a paper dated at Nancy, November 27, 1722, No. 439. 6. An account of the treatise of fluxions, January 27, 1742, No. 467. 7. The same continued, March 10, 1742, No. 469. 8. A rule for finding the meridional parts of a spheroid with the same exactness as of a Maclaurin sphere, August 1741, No. 401. 9. Of the basis of the cells wherein the bees deposit their honey; Nov. 3, 1734, No. 471.

In the midst of these studies, he was always ready to lend his assistance in contriving and promoting any scheme which might contribute to the service of his country. When the earl of Morton set out in 1739 for Orkney and Shetland, to visit his estates there, he desired Mr Maclaurin to assist him in settling the geography of those countries, which is very erroneous in all our maps; to examine their natural history, to survey the coasts, and to take the measure of a degree of the meridian. Maclaurin's family affairs, and other connexions, would not permit him to do this; he drew, however, a memorial of what he thought necessary to be observed, furnished the proper instruments, and recommended Mr Short, the famous optician, as a fit operator for the management of them. He had still another scheme for the improvement of geography and navigation, of a more extensive nature; which was the opening a passage from Greenland to the South sea by the north pole. That such a passage might be found, he was so fully persuaded, that he has been heard to say, if his situation could admit of such adventures, he would undertake the voyage, even at his own charge. But when schemes for finding it were laid before the parliament in 1744, and himself consulted by several persons of high rank concerning them, before he could finish the memorials he proposed to send, the premium was limited to the discovery of a north-west passage: and he used to regret, that the word west was inserted, because he thought that passage, if at all to be found, must lie not far from the pole.

In 1745, having been very active in fortifying the city of Edinburgh against the rebel army, he was obliged to fly from thence to the north of England; where he was invited by Herring, then archbishop of York, to reside with him during his stay in this country. In this expedition, however, being exposed to cold and hardships, and naturally of a weak and tender constitution, he laid the foundation of an illness which put an end to his life, in June 1746, at the age of 48.

Mr Maclaurin was a very good as well as a very great man, and worthy of love as well as admiration. His peculiar merit as a philosopher was, that all his studies were accommodated to general utility; and we find, in many places of his works, an application even of the most abstruse theories, to the perfecting of mechanical arts. He had resolved, for the same purpose, to compose a course of practical mathematics, and to rescue several useful branches of the science from the bad treatment they often met with in less skilful hands. But all this his death prevented; unless we should reckon, as a part of his intended work, the translation of Dr David Gregory's "Practical Geometry," which he revised, and published with additions, 1745. In his lifetime, however, he had frequent opportunities of serving his friends and his country by his great skill. Whatever difficulty occurred concerning the constructing or perfecting of machines, the working of mines, the improving of manufactures, the conveying of water, or the execution of any other public work, he was at hand to resolve it. He was likewise employed to terminate some disputes of consequence that had arisen at Glasgow concerning the gauging of vessels; and for that purpose presented to the commissioners of excise two elaborate memorials, with their demonstrations, containing rules for which the officers now act. He made also calculations relating to the provision, now established by law, for the children and widows of the Scots clergy, and of the professors in the universities, entitling them to certain annuities and sums, upon the voluntary annual payment of a certain sum by the incumbent. In contriving and adjusting this wise and useful scheme, he bestowed a great deal of labour, and contributed not a little towards bringing it to perfection. It may be said of such a man, that "he lived to some purpose;" which can hardly be said of those, how uncommon soever their abilities and attainments, who spend their whole time in abstract speculations, and produce nothing to the real use and service of their fellow creatures.

Of his works, we have mentioned his *Geometria Organica*, in which he treats of the description of curve lines by continued motion. We need not repeat what has been said concerning his piece which gained the prize of the Royal Academy of Sciences in 1724. In 1749, the academy adjudged him a prize, which did him still more honour, for solving the motion of the tides from the theory of gravity; a question which had been given out the former year, without receiving any solution. He had only ten days to draw this paper up in, and could not find leisure to transcribe a fair copy; so that the Paris edition of it is incorrect. He afterwards revised the whole, and inserted it in his Treatise of Fluxions; as he did also the substance of the former piece. These, with the Treatise of Fluxions, and the pieces printed in the Philosophical Transactions, of which we have given a list, are all the writings which our author lived to publish. Since his death, two volumes more have appeared; his Algebra, and his Account of Sir Isaac Newton's Philosophical Discoveries. His Algebra, though not finished by himself, is yet allowed to be excellent in its kind; containing, in no large volume, a complete elementary treatise of that science, as far as it has hitherto been carried. His Account of Sir Isaac Newton's Philosophy was occasioned in the following manner: Sir Isaac dying in the beginning of 1728, his nephew, Mr Conduitt, proposed to publish an account of his life, and desired Mr MacLaurin's assistance. The latter, out of gratitude to his great benefactor, cheerfully undertook, and soon finished, the history of the progress which philosophy had made before Sir Isaac's time, and this was the first draught of the work in hand; which not going forward, on account of Mr Conduitt's death, was returned to Mr MacLaurin—To this he afterwards made great additions, and left it in the state in which it now appears. His main design seems to have been, to explain only those parts of Sir Isaac's philosophy which have been, and still are, controverted; and this is supposed to be the reason why his grand discoveries concerning light and colours are but transiently and generally touched upon. For it is known, that ever since the experiments, on which his doctrine of light and colours is founded, have been repeated with due care, this doctrine has not been contested; whereas his accounting for the celestial motions, and the other great appearances of nature, from gravity, is misinterpreted, and even ridiculed by some to this day.