Diptych Pocket Sundial Compass Early 19th Century (SOLD)

This is a rare piece being offered, it is a small 19th century Diptych Pocket Sundial Compass. It has a folding wooden case measuring 3” x 1 ¾” x ¾” and it houses the compass and the gnomon (string). There are paper labels on each inner surface, showing time and other details that I am unfamiliar with. The cover has a partial label on one side listing cities in the US, England (mostly gone) and France.

The US cities listed are NY, Philadelphia, Boston, Baltimore Washington, Charleston (SC), New Orleans, Cincinnati, St. Louis, and San Francisco. Given this cities list, I would date the piece to c. 1840. The label on the bottom piece of wood is completely gone, and the interior labels are heavily stained. But the compass does work. Original red painted surface (visible on the sides), and original clasp.

A diptych dial gains its name from the two hinged leaves which open like a book. When opened, a cord holding the top leaf of the dial in its upright position allows it to act simultaneously as the gnomon (the shadow-casting part of the dial). To use the dial to tell the time, it would be placed outside on a horizontal surface, and orientated so that the gnomon is pointing toward true north. This is done with the help of a compass which is embedded in the horizontal leaf within the main dial.

Once the dial has been arranged in the correct manner, the shadow of the gnomon, cast by the sun falls onto the main horizontal dial indicating the local time. As the sun travels through the day, the shadow moves across the dial indicating the passing of time. These types of dials were made in Nuremberg [beginning] in the 16th-century by craftsmen from a small number of families who specialized in manufacturing these instruments.

This truly is a rare and unique piece. It is hard to believe that people really used these instruments before watches and clocks took over. It is a great conversational and display piece.