Bloud-type magnetic azimuth, ivory diptych sundial
Date: 1653
Inventory Number: 7800
Classification: Sundial
Dimensions:closed: 2.7 x 18.2 x 21.7 cm (1 1/16 x 7 3/16 x 8 9/16 in.)
Accessories: Stored in briefcase (not with sundial in its present location).
DescriptionFor full description, see Steven A. Lloyd, Ivory Diptych Sundials, 1570-1750 (Cambridge: Collection of Historical Scientific Instruments, 1992), cat. no. 56.
lack coloring. Elaborate decoration along the outer edges. Two silver ornate scythe clasps on I, one clasp on II. Silver hinges. Silver arm in right side of Ha to set upper tablet to proper angle. Silver clasp on left side to hold gnomon rod (missing). Compass needle, glass, and ring missing.
la Double-lined border with typical Dieppe "pecked" ornamentation along edges and surrounding circular equinoctial dial (labeled I-XII twice). Latitudes of24 cities worldwide arranged in a circular fashion. At the center is the coat ofarms of Henri d'Orleans, the Duke of Longueville. Elaborate engraving in corners of monstrous beasts.
lb Double-lined border with typical Dieppe "pecked" ornamentation along edges and surrounding the type 2 French lunar vol- velle. Highly decorated silver volvelle (refinished), with scales labeled 1-29 1⁄2 (inner), I-XII twice (middle), 10-20-30 twelve times for each house of the zodiac (depicted by engravings of the zodiacal animals), and 10-20-28, 30 or 31 for each month (outermost) fromja1111ier through Dece111bre. Elaborate engravings of mon- strous beasts in corners. Latitude scale along right side from 0° to 90° to set angle of upper tablet.
Ila Silvered moveable elliptical scale (labeled IIII-XII-VIII) for magnetic azimuth dial. Writing on parchment compass bowl insert is extremely faint. Cardinal directions labeled Septe11trio11, Orie11s, Myd}\ and Occidet1s. Outer scale on parchment cali- brated 0°-90° four times, beginning at north and south. Parchment and elliptical hour scale rotated to an angle of5° east of north. Double-lined border with typical
Dieppe "pecked" ornamentation along
edges. More mythical, monstrous animals and fanciful foliage engraved in the corners. Compass bowl is slightly elliptical, 17.4 cm in diameter from top to bottom, 17.0 cm in diameter from side to side.
llb Double-lined border with ornamenta- tion along edges and surrounding the vol- velle. Silver volvelle with perpetual calendar square and calendar scale by which to set the date for the magnetic azimuth elliptical hour scale inside. Index for setting the cal- endar scale is the pointing finger of the winged man in the upper left quadrant. The index pointer is 5° west of north to com- pensate for the magnetic dedinatioμ of5° east o f north. Also included are scales o f the epacts, dominical letters, and the dates for Easter and Pentecost from 1653 to 1700. Inscribed "Faict & Inuente par Charles
Bloud A Dieppe ANNO MDCLIII." More fanciful engraving.
This dial is perhaps the largest ivory diptych ever made. It weighs 3.5 pounds (1.6 kilos)! Note that each tablet is actually made from two smaller tablets spliced together.
This is an exceptional diptych sundial for many reasons. It is one of the few French ivory diptychs that does not include a string gnomon; in other words, it has no horizontal or vertical dial, typically the hallmark ofa diptych sundial. Technically, it is a relatively simple dial: it inclndes a mag- netic azimuth dial, an equinoctial dial, and a lunar volvelle. Its elaborate decoration and its sheer size are what make this diptych so distinctive. It is also the only Dieppe mag- netic azimuth dial in the collection which compensates for magnetic declination.
One technical error is apparent on the epact and liturgical calendar scale. The epact for the final year, 1700, should be 9
rather than 10, according to the Gregorian reform; apparently the maker neglected to consider the shift in the epact sequence each one or two centuries. The dominical letter underwent a similar shift at the turn of the century.
The coat ofarms on Ia indicates that this dial was made for Henri d'Orleans, the Duke ofLongueville (1595-1663). This illustrious personage made a name for himself in politics, but was jailed in 1650 for his activities in the Fronde. He then retired from political life to Normandy, the region in France where Dieppe is located and where Charles Bloud had his work- shop. The family est2.te of Longueville is located just south of Dieppe.