The nearly intact mechanical model of the solar system created by astronomer David Rittenhouse in 1770-71 is on the sixth floor of the Van Pelt-Dietrich Library Center.
Penn Libraries curator John Pollack with the 18th-century Rittenhouse Orrery on the sixth floor of the Van Pelt-Dietrich Library Center.
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The Rittenhouse Orrery, a nearly intact 18th-century mechanical model of the solar system, demonstrating the motions of the planets and their satellites around the sun.
“It’s absolutely the most important surviving piece of early American scientific apparatus, period,” says John Pollack, curator of research services at the Penn Libraries. “It is a priceless early American artifact. And it’s a work of art.”
According to Pollack, the Rittenhouse Orrery was built in 1770-71 by astronomer David Rittenhouse for the College of Philadelphia, which became the University of Pennsylvania. The device got its name from instrument maker John Rowley of London who made a planetary model in 1712-13 for the fourth Earl of Orrery in Ireland and named it for his patron.
Rittenhouse built his first orrery sometime between 1767 and 1770, Pollack says, and sold it to John Witherspoon for the College of New Jersey, now Princeton University; that orrery, which is still at Princeton, is only partially intact. William Smith, provost of the College of Philadelphia, convinced Rittenhouse to construct a second orrery, and that is the device at Penn. Visitors in the 18th century came to see the Rittenhouse Orrery, and it became a symbol for many of colonial scientific ingenuity.
Once wound with the clock mechanism, the machine would rotate the planets on mechanical arms into their proper relative positions on any given date, past or future. The central panel is a “grand orrery,” showing the movements of the entire known solar system, with the sun at its center and Jupiter, Saturn, and their satellites on the two arms. The right panel, a lunarium, depicts the movements and eclipses of the moon. A third panel, intended to show Jupiter and Saturn in more detail, was probably never completed. “Rittenhouse was a real craftsman,” Pollack says, a clock maker, a mathematician, as well as astronomy professor, “possessing both the mechanical science and the intellectual science.”
The Rittenhouse Orrery is housed in a large Chippendale-style case built by Philadelphia cabinetmakers John Folwell and Parnell Gibbs. The device was examined and conserved in the 1970s, but its mechanism has not been made to function in modern times. It is likely that the orrery was in the College of Philadelphia building at Fourth and Arch streets and moved to the University’s building at Ninth and Chestnut streets and then to College Hall, the first building on the West Philadelphia campus, completed in 1873. The orrery came to Van Pelt once the building was completed in 1962, placed on the first floor by the windows on the Walnut Street side. On Oct. 20, 2012, the orrery was crated and lifted by a crane through a window to the newly renovated sixth floor and the “Orrery Pavilion,” where it is on view today.
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