Orreries

Orreries

The next major development came from England where Thomas Tompion, the famous London clockmaker, and his colleague, George Graham, made a working model of the earth-moon-sun-system. It is now in view in the Museum of the History of Science, Oxford. Between 1704 and 1709 Graham made a similar machine for Prince Eugene of Savoy, and of this John Rowley, another instrument-maker, made several copies. One of them later went to Charles Boyle, fourth Earl of Orrery, an association which inspired Sir Richard Steel, editor and essayist to christen the machine an “orrery”.

The Rowley-made orrery sent to Boyle is owned by the present Earl of Cork and Orrery, and now is on loan to the Royal United Service Institution, London. The mechanism drives a model moon around an earth which in turn revolves about a model sun and is enclosed in a twelve-sided ebony and gilt case 30 inches in diameter and about nine inches deep.

Orrery made by John Rowley for Charles Boyle, fourth Earl of Orrery. Source of the photo : ScienceMuseum.org

The fame of the orrery soon spread far and wide and encouraged several London instrument makers to construct similar machines. Many were large, complicated and expensive. For example, the “Grand Orrery” made by Thomas Wright in 1733 showed the motions of the moon, earth, and five then-known planets about the sun, and is said to have cost 1,500 pounds. It was housed in the Royal Observatory, Richmond, and is now on loan to the Science Museum. London.

The first American-made orrery appears to have been a simple wooden model built in 1745 by Thomas Clap, president of Yale College. This was followed by a much more elaborate machine, constructed in 1770 by David Rittenhouse, astronomer and horologist. His aim was not to amuse or amaze the layman who, as he bluntly put it, was “ignorant of astronomy,” but to use the machine as a teaching aid for those who wished know more about the structure of the solar system. The model planets, unlike those of most earlier orreries, moved in elliptical orbits, and the entire mechanism and face plate were mounted vertically in a handsome cabinet. The orrery is now in the Library of the University of Pennsylvania while another, similar in design and construction, is in the Library of Princetown.