RHETICUS (George Joachim)

, a noted German astronomer and mathematician, who was the colleague of Reinhold in the university of Wittemberg, being joint professors of mathematics there toge- ther. He was born at Feldkirk in Tyrol the 15th of February 1514. After imbibing the elements of the mathematics at Tiguri with Oswald Mycone, he went to Wittemberg, where he diligently cultivated that science. Here he was made master of philosophy in 1535, and professor in 1537. He quitted this situation however two years after, and went to Fruenburg to put him under the assistance of the celebrated Copernicus, being induced to this step by his zeal for astronomical pursuits, and the great fame which Copernicus had then acquired. Rheticus assisted this astronomer for some years, and constantly exhorted him to perfect his work, De Revolutionibus, which he published after the death of Copernicus, viz, in 1543, folio, at Norimberg, together with an illustration of the same in a narration, dedicated to Schoner. Here too, to render astronomical calculations more accurate, he began his very elaborate canon of sines, tangents and secants, to 15 places of sigures, and to every 10 seconds of the quadrant, a design which he did not live quite to complete. The canon of sines however to that radius, for every 10 seconds, and for every single second in the first and last degree of the quadrant, computed by him, was published in fulio at Francfort 1613 by Pitiscus, who himself added a few of the first sines computed to 22 places of figures. But the larger work, or canon of sines, tangents and secants, to every 10 seconds, was perfected and published after his death, viz, in 1596, by his disciple Valentine Otho, mathematician to the Electoral Prince Palatine; a particular account and analysis of which work may be seen in the Historical Introduction to my Logarithms, pa. 9.

After the death of Copernicus, Rheticus returned to Wittemberg, viz, in 1541 or 1542, and was again admitted to his office of professor of mathematics. The same year, by the recommendation of Melancthon, he went to Norimberg, where he found certain manuscripts of Werner and Regiomontanus. He afterwards taught mathematics at Leipsic. From Saxony he departed a second time, for what reason is not known, and went to Poland; and from thence to Cassovia in Hungary, where he died December the 4th, 1576, near 63 years of age.

His Narratio de Libris Revolutionum Copernici, was first published at Gedunum in 4to, 1540; and afterwards added to the editions of Copernicus's work. He also composed and published Ephemerides, according to the doctrine of Copernicus, till the year 1551.

Rheticus also projected other works, and partly executed them, though they were never published, of various kinds, astronomical, astrological, geographical, chemical, &c; as they are more particularly mentioned in his letter to Peter Ramus in the year 1568, which Adrian Romanus inserted in the preface to the first part of his Idea of Mathematics.