Of the celestial globes constructed by George Roll and Joannes Reinhold three examples are known.[352] One of these may be found in the collection of the Mathematical Salon of Dresden (Fig. 74) one in the Osservatorio di Capodimonte of Naples and one in the K. K. Hofbibliothek in Vienna. The Roll and Reinhold globe of the Dresden collection, bearing the inscription “Georg Roll et Joannes Reinhold elaborabant Augustae 1586,” is an exceedingly interesting instrument, unique in the manner of its construction and remarkably well preserved. It is of brass, having a diameter of 36 cm., and is furnished with numerous movable circles, a large meridian circle surmounted with an armillary sphere, and a brass horizon circle on which are marked the old and the new calendars, the names of the twelve months and of the important holy days. The globe base, very artistically wrought, rests upon four griffin’s feet, between which a small terrestrial globe 10 cm. in diameter has been placed, this having been furnished with its own independent support. The large celestial sphere is furnished with a clocklike mechanism by means of which it is made to revolve in representation of the diurnal motion of the heavens. According to existing records it was purchased in the year 1593 by order of the Elector Christian II, and by him was presented to the Academy of Arts of Dresden. Zeiller tells us that this and the Heyden globe were those “with which the Prince Elector Augustus was accustomed to amuse himself.” [Illustration: Fig. 74. Globe of George Roll and Johannes Reinhold, 1586.] It has not been possible to obtain a description of the Vienna globe. It appears that it was constructed in the year 1588, and that, like the Dresden example, the celestial sphere is made to revolve by means of clockwork.