If you mention the name David Rittenhouse in Philadelphia, your listeners will likely think first of the tree-lined streets of Rittenhouse Square, the neighborhood named in his honor. Born in 1732 and raised in Norritown, Rittenhouse developed an interest in astronomy and mathematics early in life and later became a major contributor to science and innovation in revolutionary America. He is most widely recognized as a Philadelphia inventor, surveyor, astronomer, friend to Benjamin Franklin, president of the American Philosophical Society, and the first director of the United States Mint.

But in the minds of collectors and enthusiasts of antique clocks, David Rittenhouse was first and foremost a clockmaker. Specifically, he was the designer and creator of two antique clocks which, in terms of innovation and complexity, are considered the most important clocks in the United States and among the most important in the world. Both clocks still exist and are still in Philadelphia– One of the two is owned by Penn Hospital, and the other belongs to Drexel University and is kept on display in a University picture gallery.

What makes these Rittenhouse clocks so valuable? A brief history of antique clocks and clock-making can provide a bit of context. Before the industrial revolution, when most Europeans and Americans lived an agrarian lifestyle, clocks were not a common personal possession. When it came to dividing and marking the hours of the day, a single clock in a town square could provide all that most people required. Between about 1663 and the mid 1800’s—prior to the rise of regular working hours and train schedules– household clocks in America were owned by the wealthy few. And before David Rittenhouse, most household clocks required weekly winding, had only an hour hand, and ran on relatively simple mechanisms driven by long counterweights that hung down below the clock face. Long pendulums required a distance between the clock face and the floor, and cases were often built around the mechanisms in order to hide them. These early antique clocks were called case clocks, long case clocks, or wags-on-the-wall. (The term “grandfather clock” didn’t come along until the 1800’s.) This was the general state of the household clock around 1742 when David Rittenhouse began turning his fascination with astronomy and mathematics to the purpose of clock-making.

A close look at the famous Drexel clock reveals some of the fascinating features unprecedented among the antique clocks of its time. For example, the main face contains not only an hour hand, but also minute and second hands, as well as a hand pointing to the month of the year. In addition, Rittenhouse designed the central face with a lunarium, a device that tracks the phases of the moon. To the left of the primary dial, a smaller face shows the location of the sun and moon at any given point the zodiac. The little moon in this dial actually rotates on its axis from a darker to a lighter side, in keeping with the phases of the real moon. Within the lunarium, a dial reveals the day of the month. The clock can play ten different chimes as well, according to its setting.

Most significantly, a miniature model of the solar system is set above the clock face—six planets orbiting a tiny sun in a circle about eight inches wide. This is called an orrery, and before the construction of the Drexel clock, Rittenhouse had already created two large and astonishingly accurate orreries, one of which had been donated to Rutgers University.

By the time he built the Drexel clock around 1773, his orreries had launched Rittenhouse’s reputation as a scientist. With his ingenious contributions to clock making, Rittenhouse established himself as a representative of the strong intellectual and innovative capacity of the colonies.

Both famous orreries and several antique clocks designed by Rittenhouse survive to this day, and some of them—like the Drexel clock—still work. With careful conservation, they may continue keeping accurate time well into the future.

Erin Sweeney

8/20/2010