Purbach, George

, a very eminent mathematician and astronomer, was born at Purbach, a town upon the confines of Bavaria and Austria, in 1423, and educated at Vienna. He afterwards visited the most celebrated universities in Germany, France, and Italy; and found a particular friend and patron in cardinal Cusa, at Rome. Returning to Vienna, he was appointed mathematical | professor, in which office he continued till his death, which happened in 1461, in the 39th year of his age only, to the great loss of the learned world.

Purbach composed a great number of pieces upon mathematical and astronomical subjects, and his fame brought many students to Vienna; and, among them, the celebrated Regiomontanus, between whom and Purbach there subsisted the strictest friendship and union of studies till the death of the latter. These two laboured together to improve every branch of learning, by all the means in their power, though astronomy seems to have been the favourite of both; and had not the immature death of Purbach prevented his further pursuits, there is no doubt but that, by their joint industry, astronomy would have been carried to very great perfection. That this is not merely surmise, may be learnt from those improvements which Purbach actually did make, to render the study of it more easy and practicable. His first essay was, to amend the Latin translation of Ptolemy’s Almagest, which had been made from the Arabic version: this he did, not by the help of the Greek text, for he was unacquainted with that language, but by drawing the most probable conjectures from a strict attention to the sense of the author.

He then proceeded to other works, and among them he wrote a tract, which he entitled “An Introduction to Arithmetic;” then a treatise on “Gnomonics, or Dialling,” with tables suited to the difference of climates or latitudes; likewise a small tract concerning the “Altitudes of the Sun,” with a table also, “Astrolabic Canons,” with a table of the parallels, proportioned to every degree of the equinoctial. After this he constructed Solid Spheres, or Celestial Globes, and composed a new table of fixed stars, adding the longitude by which every star, since the time of Ptolemy, had increased. He likewise invented various other instruments, among which was the gnomon, or geometrical square, with canons and a table for the use of it.

He not only collected the various tables of the primum mobile, but added new ones. He made very great improvements in trigonometry, and by introducing the table of sines, by a decimal division of the radius, he quite changed the appearance of that science; he supposed the radius to be divided into 600,000 equal parts, and computed the sines of the arcs, for every ten minutes, in such equal | parts of the radius, by the decimal notation, instead of the duodecimal one delivered by the Greeks, and preserved even by the Arabians till our author’s time; a project which was completed by his friend Regiomontanus, who computed the sines to every minute of the quadrant, in 1,000,000th parts of the radius.

Having prepared the tables of the fixed stars, he next undertook to reform those of the planets, and constructed some entirely new ones. Having finished his tables, he wrote a kind of perpetual almanack, but chiefly for the moon, answering to the periods of Melon and Calippus; also an almanack for the planets, or, as Regiomontanus afterwards called it, an Ephemeris, for many years. But observing there were some planets in the heavens at a great distance from the places where they were described to be in the tables, particularly the sun and moon (the eclipses of which were observed frequently to happen very different from the times predicted), he applied himself to construct new tables, particularly adapted to eclipses; which were long after famous for their exactness. To the same time may be referred his finishing that celebrated work, entitled “A New Theory of the Planets,” which Regiomontanus afterwards published, the first of all the works executed at his new printing-house. ¹