The clocks — several styles exist — consist of a round or octagonal wooden base that rises in a tapered column, which is itself surmounted by clockworks that are covered by a glass dome, giving the effect of a standing lighthouse. The clocks are generally 24 to 30 inches tall. The notion of a clock under a dome may hark back to the imported, glass-domed, French Empire clocks fashionable at the time. Or, they might have been influenced by English and French skeletonized clocks; that is, clocks whose plates have been cut and exposed in such a way as to show the internal workings of the clock. Willard's clockworks were not skeletonized, but they often had an alarm mechanism and were known as patented alarm clocks. The alarm bell was mounted atop the clock movement. Clock mechanisms are driven by a weight concealed in the body of the lighthouse, though the alarm mechanism is sometimes driven by a separate weight raised by a pullcord.