[Illustration: Fig. 67. Globe of Christian Heyden, 1560.]
Doppelmayr likewise gives us a brief biographical note referring to one Johannes Praetorius, a globe maker, born at Joachimsthal in the year 1537.[311] After a considerable period of study, chiefly at Wittenberg, where he turned his attention to the philosophical and mathematical sciences, he took up a residence in Nürnberg in the year 1562. Here he became interested in the construction of mechanical and astronomical instruments, and soon won the favor of the Emperor Maximilian II, which favor he enjoyed to the end of that Emperor's reign. It was about the year 1576 that he became a professor of mathematics at Altdorf, where he died in the year 1616. Doppelmayr refers to a number of the mathematical and astronomical instruments constructed by him, noting that in the year 1566 he completed two globes of metal richly gilded, each having a diameter of 11¼ inches, that each was furnished with an hour circle, a movable quadrant and semicircles, and that a compass was set in the base of each. We learn also from the same biographer that in the year 1568 he completed a brass astrolabe having a diameter of "one schuh" (foot?), three and one half inches, and that it was supplied with all parts essential to a complete apparatus of its character. We are further informed that shortly after the beginning of his career in Altdorf he undertook the construction of a large celestial globe of wood and paper, having a diameter of four Nürnberg feet, that he was assisted in this work by the artist and draughtsman, Christopher Heinrichs, and that on the surface of the sphere one thousand six hundred and fifty stars were indicated with appropriate accompanying inscriptions.
Two pairs of Praetorius' globes are now known, one pair in the Mathematical Salon of Dresden (Fig. 68),[312] and the other in the Germanisches National Museum of Nürnberg. These globes are of brass, each having a diameter of 28 cm.; each is supplied with meridian, horizon, and hour circles and rests on a tripod base. They are richly engraved pieces, the terrestrial example being remarkably well preserved, the celestial being slightly injured, through rubbing which has removed parts of certain figures of the constellations.