262 ANNUAL REPORT SMITHSONIAN INSTITUTION, 195 7 



of the world" in a great dome. The sun gained daily access to 

 the interior of the dome by way of doors in the east and west. 



There have been many other attempts to depict and explain the 

 motions of the celestial objects. Some have been preserved for 

 their pure artistry, and most are evidence of a rather good com- 

 prehension of the mechanisms of the planets, sun, and moon. The 

 Farnese Globe in the National Museum at Naples is a sculpture 

 in white marble of Atlas supporting the world on his shoulders. 

 Some of the constellation figures are carved in relief on its surface, 

 as is the path of the sun. Dating back to 73 B. C, it is still another 

 early attempt to illustrate and portray the skies. Other globes, 

 with the Equator and the Tropics of Cancer and Capricorn painted 

 on them, can be found to represent nearly every century of the 

 Christian Era. 



Mechanisms showing the relative motions of the sun, moon, and 

 planets have been constructed at various times since the day of 

 Christian Huy gens (1629-1695) and Roemer (1644-1710). Huygens 

 solved many of the mathematical problems involving the relative 

 motions of the planets, which are essentially the same problems 

 that must be solved for the gear trains of the most modem instru- 

 ments. In England, a device of this type was built for Charles 

 Boyle, the fourth Earl of Orrery (1676-1731), and was named for 

 him. The name "orrery" is still used to apply to such pieces of 

 apparatus. These machines usually consisted of a series of globes 

 to represent the various objects in the solar system. Each globe 

 was supported by a metal rod, and interrelated by the gearing at 

 the central pedestal. Some undertook to reproduce the planetary 

 satellites, properly relating their motions to those of the planets. 

 Their complexity can be readily appreciated. 



One of the most elegant of these orreries was on exhibit for several 

 years at the Fels Planetarium of the Franklin Institute in Philadel- 

 phia. Known as the Rittenhouse Orrery, it was built for use at the 

 College of Philadelphia in the early part of the nineteenth century. 

 It was a remarkable device because of its accuracy in representing the 

 Keplerian motion of the planets. Both the Fels Planetarium and the 

 Buhl Planetarium and Institute of Popular Science in Pittsburgh ex- 

 hibit the modern counterpart of these orreries. It is the planetarium 

 built by M. Sendtner of Munich, and in addition to the planet repre- 

 sentation it has the advantage that the observer may look through 

 one glass surface of an enclosing sphere and look on the opposite sur- 

 face to see the stars in their natural formations. 



Still another variation to the orrery or planetarium was constructed 

 in 1913 for the Deutsches Museum in Munich. It is a model of the 

 solar system according to Copernicus. The distinguishing features 

 are its size and its earth orientation. 



