nomy. The manner of placing the two specula upon the same axis, appearing to Sir Isaac Newton, to be attended with the disadvantage of losing the central rays of the larger speculum, he proposed an improvement on the instrument, by giving an oblique position to the smaller speculum, and placing the eye-glass in the side of the tube. But it is worth remarking, that the Newtonian construction of that instrument, was long abandoned for the original, er Gregorian, which is, at this day, universally employed, where the instrument is of moderate size; though Mr. Herschell has preferred the Newtonian, for the construction of those immense telescopes, which he has, of late years, so sucessfully employed, in observing the heavens.

Soon after the appearance of his first work, Mr. Gregory went to the university of Padua, where he continued for several years, and in 1667, published, in Latin, his "Quadrature of the Circle and Hyperbole," in which he propounded another discovery of bis own, the invention of an infinitely converging series for the areas of the circle and hyperbole. To this treatise, when re-published, in 1688, he added a new work, entitled "Geometriæ pars Universalis, in which he is allowed to have shewn, for the first time, a method for the transmutation of curves. These works, naturally recommended Mr. Gregory to the notice of the greatest mathematicians of the age, in consequence of which, he was chosen a member of the Royal Society of London; and by many excellent papers, greatly enriched the philosophical transactions of that respectable body.

In 1668, he was elected professor of mathematics, in the university of St. Andrews, which office he held till the year 1674, when he was called to Edinburgh, to fill the mathematical chair in that university. This place, however, he had held for little more than a year, when, in October, 1675, being employed in shewing the satellites of Jupiter, through a telescope,

to some of his pupils, he was suddenly struck with total blindness, and died a few days after, at the early age of thirty-seven.

GREGORY, (DAVID) Savilian professor of astronomy at Oxford, nephew of the above mentioned James Gregory, was born at Aberdeen, in 1661, in which city he received the earlier parts of his educa tion. He completed his studies at Edinburgh, and being possessed of the mathematical papers of his uncle, soon distinguished himself, likewise, as the heir of his genius. In the 23d year of his age, he was elected professor of mathematics in the university of Edinburgh, and published, in the same year, a geometrical treatise, exhibiting a general method of measuring figures of any kind. He saw, very early, the excellence of the Newtonian philosophy, and had the merit of being the first, who introduced it into the schools, by his public lectures, at Edinburgh.

In 1691, he was appointed Savilian professor of astronomy, at Oxford. In 1693, he published in the Philosophical Transactions, a solution of the Florentine problem," De Testudine Veliformi Quadribili," and he continued to communicate to the public, from time to time, many ingenious mathematical papers, through the same channel.

In 1702, our author published, at Oxford, “ Astronomie Physica, et Geometrica elementa." a work, which is accounted his master piece. It is founded on the Newtonian docrines, and was esteemed by Sir Isaac Newton himself, as a most excellent explanation and defence of his philosophy. In the following year, he gave to the world, an edition in folio, of the works of Euclid, in Greek and Latin; in which, although it contains all the treatises attributed to Euclid, Dr. Gregory, has been careful to point out such, as he had reason to believe, were the productions of some other inferior geometrician. He had, likewise, soon after, began the publication of the Conics of

Apollonius in the same year; but had made but small progress in that undertaking, when he died, in the 49th year of his age, A. D. 1710.

To the genius and abilities of David Gregory, the most celebrated mathematicians of the age, Sir Isaac Newton, Dr. Halley, and Dr. Keill, have given ample testimonies. Besides those works, which he published in his life time, he left in manuscript "A short Treatise of the Nature and Arithmetic of Logarithms," which was printed at the end of Dr Commandine's Euclid, and a "Treatise of Practical Geometry", which was afterwards translated, and published in 1745 by Mr. M'Laurin.

Mathematical genius appears, for some time to have been hereditary in the family of the Gregorys; for besides those we have already mentioned, there was James the brother of David, who for 33 years viz. from 1691 to 1725, filled the mathematical chair at Edinburgh, with great abilities. There was, likewise, another brother, named Charles, who was appointed professor of mathematics, at St. Andrews, in 1707. This office he held with great credit, for thirty-two years; and, resigning in 1739, was succeeded by his son, who eminently inherited the talents of the family, and died in 1763.

GREGORY, (DR. JOHN) professor of medicine in the university of Edinburgh-the son of Dr. James Gregory, professor of medicine, in King's College, Aberdeen, and grandson of James, the inventor of the Gregorian telescope, was born, June 3d, 1724. Losing his father, when only in the 7th year of his age, the care of his education devolved on his grandfather, Principal Chalmers, under whose eye, he completed in King's College, his studies in the Latin and Greek languages, and in the science of ethics, mathematics, and natural philosophy. His preceptor in philosophy and mathematics was, Dr. Thomas Gordon,

who is still a professor in King's College, and who has filled an academical chair, with great reputation, for above half a century.

In the year 1742, Mr. Gregory went to Edinburgh, where the school of medicine was rising to that celebrity, which has since so remarkably distinguished it. After having attended the lectures of the different professors, for three years, he set out for Leyden, in order that he might make himself still more perfect in the knowledge of his profession, under the very able teachers, who then filled the different medical chairs of that university. While at this place, he had the honour of receiving from King's College, of Aberdeen, his alma mater, who regarded him as a favourite son, an unsolicited degree of Doctor of Medicine and, soon after, on his return thither, from Holland, he was elected professor of philosophy, in the same university. In this capacity, he read lectures, during the years 1747, '48, and '49, on mathematics, natural and moral philosophy. In the end of 1749, however, he chose to resign his professorship of philosophy, his views being turned chiefly to the practice of physic, with which, he apprehended the duties of this professorship too much interfered.

After continuing for some time, as a physician in his native city, finding that the field of medical practice was, in a great measure, pre-occupied by his elder brother, Dr. James Gregory and others of some note in their profession, our author determined to try his fortune in London. Thither he accordingly went in 1754; and, being already known by reputation as a man of genius, he found an easy introduction to many persons of distinction, both in the literary and polite world. The late lord George Lyttleton, in particular, was his friend and patron. An attachment which was founded on a striking similarity of manners, of tastes and of dispositions, grew up into a firm and permanent friendship; and to that nobleman, to whom Dr. Gregory was wont to communicate all his literary

productions, the world is indebted for the publication of the "Comparative View of the State and Faculties of Man, with those of the Animal World," which made him first known as an author.

In 1754, Dr. Gregory was chosen Fellow of the Royal Society of London, and as he was daily advancing in the public esteem, it is not to be doubted, that, had he continued his residence in that metropolis, his professional talents would have found their reward in a very extensive practice. But the death of his brother Dr. James Gregory, in November 1755, occasioning a vacancy in the professorship of physic, in King's college, Aberdeen, which he was solicited to fill, he returned to his native country, in the beginning of the following year, and took upon him the duties of that office.

Here our author remained till the end of the year 1764, when, urged by a very laudable ambition, he changed his place of residence for Edinburgh, as being a more extensive field of practice. His friends in that metropolis had represented to him the situa tion of the college of medicine, as favourable to his views of filling a professional chair in that university, which accordingly he obtained in 1766, on the resig nation of Dr. Rutherford, professor of the practice of physic. In the same year he had the honor of being appointed first physician to his majesty for Scotland.

On his first establishment in the university of Edin burgh, Dr. Gregory gave lectures on the practice of physic, during the years 1767, 1768 and 1769. Afterwards by agreement with Dr. Cullen, professor of the theory of physic, these two eminent men gave alternate courses of the theory and of the practice. As a public speaker, Dr. Gregory's manner was simple and animated; and he expressed his ideas with uncommon perspicuity. By the assistance of a few notes he lectured with great facility and elegance: The only lectures which he fully committed to writing, were those introductory discourses, which he read at