Scientific, Instrument, Compass, Diptych Dial, Portable Sundial, Antique, Nuremberg, 19th Century (Sold)

Description

When opened, a string gnomon connects the gnomon dials on the inner parts of each leaf. Inside the upper leaf is a printed and colored vertical string gnomon dial, with points marked for 34 to 56 degrees to adjust the angle of this leaf for applicable latitude. A table on the outside of the upper leaf provides an applied printed latitude table of cities in America, England, Spain, France, Italy and Germany. On the inside of the lower leaf is an inset glazed compass above a printed and colored circular North-South-East-West directional card. The compass is surrounded by concentric printed and colored gnomon dials in Arabic numerals marked for 50 and 55 degrees. Both the upper and lower gnomon dials have circular dials with Roman numerals to indicate time, and are decorated with classical and floral motifs. The outside of the lower leaf is a plain wood bottom to be set down on a horizontal surface. The two leaves are hinged at one end with a hook to fasten the upper leaf open and another on the opposite side to fasten both leaves closed shut when not in use.

A nearly identical diptych dial by Negelein is in The History of Science Museum in Oxford. Their website illustrates the one in their collection (see References Below). A separate article explains the history and use of diptych dials in general, accompanied by a short video:

“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 should 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.”

American Cities and Latitudes on Table:

New York, 41
Philadelphia, 40
Boston, 42
Baltimore, 40
Washington, 39
New Orleans, 30
Cincinnati, 39
St. Louis, 38
St. Francisco, 38
Richmond, 37

Dial marked: Negelein at Nuremberg in Bavaria

Condition: Generally very good, complete as issued with paper table and 2 gnomon dials, glazed compass and needle, string, hinges and closures all intact (rare thus), noting the usual light wear, toning, small abrasions and discoloration to applied paper table, and to a lesser extent to the applied paper gnomon dials.

References:

“Diptych Dial, by Negelein, Nuremberg, 19th Century.” Museum of the History of Science, University of Oxford. https://www.mhs.ox.ac.uk/collections/imu-search-page/record-details/?thumbnails=on&irn=3394&TitInventoryNo=55194 (20 May 2021).

Haggard, Robyn. “Diptych Dial.” Museum of the History of Science, University of Oxford. 2016. http://www.mhs.ox.ac.uk/animateit/diptych-dial/ (20 May 2021).