# Rheticus, George Joachim

, a celebrated German astronomer and mathematician, was born at Feldkirk in Tyrol, February 15, 1514. After imbibing the elements of the mathematics at Zurick with Oswald Mycone, he went to Wittemberg, where he diligently cultivated that science, and was made master of philosophy in 1535, and professor in 1537. He quitted this situation, however, two years after, and went to Fruenburg to profit by the instructions of the celebrated Copernicus, who had then acquired great fame. 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, atNorimberg, together with an illustration of the same, 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 figures, 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 folio 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 Dr. Button’s Logarithms.

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 4, 1576, near sixty-three years of age.

His “Narratio de Libris Revolutionum Copernici,” was
first published at Dantzick in 1540, 4to; and afterwards
added to the editions of Copernicus’s work. He composed
and published “Ephemerides,” according to the doctrine
of Copernicus, till 1551, and projected other works, and
partly executed them, though they were never published,
of various kinds, astronomical, astrological, geographical,
chemical, &c. All these are 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. ^{1}

^{1}

Hutton’s Dict.-^-—Vossius do Scient. Mathemat. —Melchior Adam.—Moreri.