Lot 216

Francois Ducommun à la Chauxdefonds, 159 mm, 356 g, circa 1825 A rare equinoctial sunring dial Meridian-ring: brass, suspension ring is attached to bracket by means of a hook and moves in grooved rim, engraved degree scale divided clockwise from 0°-90°, signature. Equatorial ring: brass, signed, engraved, observe side with 24 hour division with inlaid Roman numerals. Bridge: one side has an engraved scale with zodiacal symbols, the other side with engraved French months, pinhole gnomon has indexes that move over the bridge scales. Francois Ducommun (1763-1839) François Ducommun-dit-Boudry was born in 1763 as son of officer and master clockmaker Abraham Ducommun-dit-Boudry and Marie Anne Robert. He was a grandson of Josué Robert, clockmaker to the King of Prussia. Ducommun-dit-Boudry was a descendant of the famous watch- and clockmaking dynasty Ducommun and married Julie Dubois on April 1, 1786 in Les Planchettes. Their son Nestor Ducommun-dit-Boudry (1787-1843) would become the grandfather of watch factory owner Paul-Louis Ducommun-dit-Boudry. Francois Ducommun specialized in making orreries; the Museum Beyer in Zurich exhibits a clock designed by him which goes by the name of Copernic. In 1998 Michel Parmigiani restored an orrery by François Ducommun-dit-Boudry for the Museum Castello Sforzesco Milan. François Ducommun-dit-Boudry died on June 13, 1839 in La-Chaux-de-Fonds. The equinoctial ring The equinoctial ring dial is the mariner’s watch and an integral part of all navigation inventories. It can be used to determine time for all lines of latitude as well as for solving various navigational problems. The ring dial was invented in the first half of the 17th century and soon became very popular because it was robust and folding, which make it easy to transport. In this case the usual hand aligned to the pole is replaced by a rectangular bar with a central slit; this is mounted diagonally in the vertically suspended ring. The inclination of the slider corresponds to the position of the celestial pole, so that when the ring is in the meridian, the bar is parallel to the Earth’s axis. A perforated slider sits in the central slit and is adjusted along a scale according to the height of the sun at the time of the measurement. A second ring that is vertical to the first ring and thus parallel to the equatorial plane has the hour markings. When the instrument is set, a sunray falls through the slit in the slider onto the inner ring and shows the time. Vice versa the fact that the light falls on the inner ring proves that the instrument is adjusted correctly, thus eliminating the need of a compass. Source: "Uhren- und Messinstrumente des 15. bis 19. Jahrhunderts" by Samuel Guye / Henri Michel, p. 251. "Nautische Antiquitaeten" by Jean Randier, Bielefeld 1973, p. 103. Case: very good.