One of the most interesting, traditional features of many tallcase clocks is the moon dial, the idea of which originated with the very first clockmakers. This dial indicates each phase of the moon. There are two appropriate scenes, sea and landscape, with a moon on each. Above the scene is an arch. This arch is graduated to the lunar or moon month of 29-1/2 days (not to be confused with the calendar month).
At either end of the arch is a hemisphere, representing the earth. The moon face first appears over the left, or Western Hemisphere. As the disc progresses, the quarters of the new moon come into view until the moon is clear of the Western Hemisphere when it is full. Then the moon disappears back of the right or Eastern Hemisphere. In turn, the sequences register each lunar phase, new moon, first quarter, half moon, full moon, third quarter and old moon.