TESSERACT -- Antique Scientific Instruments -- Dialling

Exceptional Silver Pocket Dial

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EXQUISITE SEVENTEENTH CENTURY SILVER DIAL BY AN UNRECORDED MAKER, French, second half 17th century, signed "Morlet à Paris," and indicating the latitude of Paris "Elevat. 49." This all-silver sundial is round, 1-3/4" (45 mm) in diameter and almost 1/2" (12 mm) tall. The glazed compass has the principal directions beautifully labeled (N, S, E, O). The chapter ring is divided every 15 minutes from 4 am to 8 pm, and is engraved with lovely central rose, leaf tips, and scroll ends. The folding gnomon, noting one little nick to the tip, is exquisitely engraved on both sides with flowered and fruited plants. A related pattern of decoration is found in the Louvre, on a 17th century oval dial by Pierre Debombourg of Lyon. A really wonderful dial in fine condition, by a splendid craftsman not otherwise found. (8142) $4950.

Remarkable Pewter Sundial

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	A SPHERICAL POLAR SUNDIAL, French, c. second half 18th century, made of pewter with brass gnomon, standing 14" (35 cm) overall. This intriguing spherical sundial reproduces the sense of earth in space, with armillary rings defining the celestial projection of the earth's equator, axis of rotation, and local meridian plane. The polar axis of the dial is inclined approximately 43° to the horizontal. The equatorial band is finely marked (with Roman numerals in raised relief) every hour from 5 am to 7 pm, and cleverly subdivided to 1/8 hour (7.5 minutes). The Roman numerals include "...IX, X, XI, XII, I..." for "...9, 10, 11, 12, 1,..." as usual, but also "V, IV, IIV, IIIV,..." for "5, 6, 7, 8,...;" in a curious reversed sense, either in error or in some sense of trying to follow the course of the day with the numeral writing. A rotatable sheet brass gnomon is hand cut and pierced with a sort of handle, and with banner and scroll design, reminiscent of some Alsatian patterns and workmanship. Within the band and rings is a 5" (13 cm) diameter glazed compass, with 32-point rose, again in relief, the 16 principal directionals labeled in French (e.g., Sud, E.S.E., S.S.O., N.Ouest). The "N.N.Ouest" pointer (at 15° west of North) is also labeled, curiously, "S.S.E meridiene" (this is a riddle we have not solved, although possibly representing the magnetic declination which in mid-18th century France was 15° - 20° west). The compass has a circumferential scale divided every degree, and is set with a blued steel needle with raised brass hub and faceted (!) pink stone on glass pivot. The compass directionals are reflected in the design of the attractive pewter stand, with its octagonal baluster and knobs, and eight-lobed base. Condition is very fine throughout, noting one screw replaced.

In use the polar dial would be set up with its compass north point fleur-de-lys pointed toward the geographic north point on the horizon (thus taking into account the offset of the needle -- the magnetic declination -- toward magnetic north).

The polar axis would then be parallel to the earth's axis of rotation (when the user is at the correct latitude for this dial -- about 43° North -- corresponding to southernmost France, e.g., Perpignan or Marseilles). One rotates the brass gnomon until it is in line with the sun; the gnomon then casts a crisp shadow line on the equatorial hour band, giving immediately the apparent solar time. The dial thus models the geometry of the earth in space. This is an elaborate openwork form of the relatively rare spherical dial with rotatable gnomon, usually constructed with a solid sphere of turned stone or wood with sheet metal gnomon. We note an 18th century French example in the Stewart Museum, and a c. 1810 design by Thomas Jefferson for Monticello. A rare form, the first we have seen in pewter, and beautifully executed. $11,500. (7128)

Demonstration, Experimentation & Calculation