of the stars. The whole interior was lighted by two small lamps. At the center of the sphere, the inner surface of which, as stated above, represented the starry heavens, was placed a small ball, about 15 cm. in diameter, representing the earth. The great globe, driven by water power, was therefore made to appear to revolve around this central terrestrial globe. A representation of the sun, made of glass, had its own proper motion along the circle of the ecliptic, and a representation of the moon likewise was made to move in its own proper course. This globe, in the year 1713, was presented by the grandson of Duke Frederick to Czar Peter the Great of Russia. A note in the Royal Geographical Journal refers to this as a seventeenth-century globe, adding in substance that the St. Petersburg Academy of Sciences has lately installed at Tsarskoe Selo this large globe, weighing some three and one half tons, constructed in the seventeenth century for Duke Frederick of Holstein, under the superintendence of Olearius, the astronomer and traveler. On its completion it was placed in the castle of Gottorp, from which fact it became known as the Gottorp globe. It was presented to the Academy in the year 1725 and up to the present has remained in the Zoölogical Museum.[64] Information has been kindly given by the director of the National Museum of Copenhagen that an exceedingly fine armillary sphere (Fig. 104) may be found in the Museum of National History in the Friedricksborg Castle. From the catalogue of this institution we learn that it was constructed in the year 1657 by Andreas Busch, under the guidance of Adam Olearius, for Frederick III of Holstein-Gottorp. As will be noted from the illustration it is an elaborately constructed piece of mechanism. What we may term the globe proper is composed of six great circles on which are the fixed constellations, having the several stars represented in silver. Through the mechanism passes a steel bar which carries a ball of brass representing the sun, which is at the center of the complicated system of circles. Around the sun are six circles of brass representing the orbits of the planets each carrying a small silver angel. That part of the mechanism which represents the equator and the zodiac is calculated to make one revolution in 25,000 years. In the base of the globe has been placed the clockwork by which the several movements of circles and planets are effected, and time is told by the striking of hours and quarters. Topping the piece is a small armillary sphere representing the Ptolemaic system. [Illustration: Fig. 104. The Gottorp Armillary Sphere, 1657.]