LEYDEN, John, a man of singularly varied genius and accomplishment, was born on the 8th of September, 1775, at Denholm, a village on the banks of the Teviot, in the parish of Cavers and county of Roxburgh. His parents were John Leyden and Isabella Scott, who had three sons and two daughters younger than himself. His ancestors in both lines had been farmers on the estate of Cavers for several generations ; but his father, though skilful in rural affairs, declined to engage on his own account in the same occupation, thinking even the fortunate pursuit of gain a poor compensation for the anxiety that attends it. About a year after the birth of their first child, he removed to Henlawshiel on the farm of Nether Tofts, which was then occupied by Andrew Blythe, his wife's uncle, whom he first served as shepherd, and subsequently as overseer, his master having had the misfortune to lose his sight. The cottage in which the family resided was of an humble construction; its internal accommodations were equally simple; but it was situated at the foot of the majestic hill of Ruberslaw, and there, among the "dun heathy slopes and valleys green," did Leyden imbibe that enthusiasm and manliness of character which afterwards displayed
branches of knowledge, he had few rivals. But it was for mathematical science and its kindred studies, that he discovered, at a very early period, a decided predilection; and it is in the successful illustration of scientific truth and of all the complicated phenomena of physics, that his great reputation has been acquired. In these pursuits he was eminently qualified to excel by the great original powers of his mind, which were further stimulated by an ardent enthusiasm, and an early desire of distinction among the illustrious names of his day. Along with a profound knowledge of his subject, he possessed great inventive powers, which not only enabled him to sound the depths of science, but to expound its important problems with a simplicity and elegance rarely equalled. In making his way through the intricacies of physical research, his severe judgment guided him in the right path; and hence his demonstrations always afford a striking and beautiful display of pure reason, without any tendency to that spirit of metaphysical subtlety which occasionally perplexes the speculations of Laplace, Legendre, with others of the continental philosophers; and it is worthy of remark that, along with the penetrating force of his judgment, he carried into those studies that taste and fancy—that predilection for the beautiful, which may be recognised in all his speculations, whether in literature or in science. His taste in geometry was founded on the purest models of Grecian philosophy; he delighted to expound to his pupils the simplicity and elegance of the demonstrations by the great masters of antiquity; he commended them to their imitation, and expatiated on the subject in a manner well fitted to inspire a kindred enthusiasm; so that we might have fancied that he was dilating, not on the merits of a mathematical problem, but on some of those beautiful forms and classic models of ancient art which have been the wonder of all succeeding times. Nor was this admiration of ancient geometry a mere pedantic or barren speculation. The great philosopher of whom we are speaking carried his principles into practice, and applied the abstract properties of figures with the happiest success to experimental philosophy; many branches of which he greatly extended by his discoveries; and in all of them he developed the most original views, which may yet be traced to important results. The range of his studies was amazingly extensive; and he had accumulated vast stores of knowledge, especially on scientific subjects. He was deeply versed in the history of science, which he had traced from its earliest dawnings in the times of Greece and Rome, through all the subsequent vicissitudes which it experienced during the dark ages of barbarism, till it was revived by the Arabians in the east, and was afterwards improved and perfected fay the more brilliant discoveries of modern times. We speak literally when we say, that we doubt if there is a single publication relating to this subject, either in the ancient or the modern languages, which he had not diligently perused; and his knowledge, minute and accurate on every point, and, once acquired, never forgotten, overflowed in his conversation and in his writings. The date of any great discovery was familiar to him; he could give anecdotes or biographical sketches of all the great promoters of science in every age; and the prodigality of his information was not more surprising than the ease with which he preserved its disposition and arrangement, under certain great leading principles, which were the land-marks of his mind, by which the store of facts which he had been treasuring up for years was reduced into order, and each distributed into its proper place in the great system of which it formed a part. For the truth of this remark we may refer to the History of the Barometer,' in the Edinburgh Review, and to his papers on Meteorology, and other subjects in the Encyclopædia Britannica, to his continuation of Playfair's Introductory Discourses prefixed to that work, as well as to many of his other productions, which display the great extent of his researches. On other subjects, also, not connected with his peculiar studies, his information was minute and extensive. He was deeply read in Scottish history and antiquities; and on all modern questions of politics or political economy, he had his own original ideas, which he was always ready to express and expound in a fair and temperate strain."
