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Astronomical Compendium
16th century; Florence
Brass; 233 mm along side

Hinged to one edge of a rectangular box with double bun feet is a plain lid with a double stepped frame surrounding four decorative bosses in the corners and at the centre the Medici arms engraved on an applied plaque with their six spheres in relief. At the lower centre is a wing nut holding a slotted strip of metal with shaped and engraved ends in place on the inside of the lid. The strip, which has three steady pins, has a cursor, pierced with three holes of different sizes, adjustable in the slot. The three holes are the attachment point for a string gnomon which passes through a hole in the centre plate of the instrument and is attached at its lower end to a similarly mounted cursor on the bottom plate. The inner face of the lid is engraved with two tables giving the length of a half day throughout the year for the latitudes of Pisa (43? 25') and Florence (43? 45'). The corresponding signs of the zodiac are also indicated in these tables (with 0? Aries at 21 March).

Attached by the same hinge as the lid, the centre plate of the instrument is engraved with a circular twenty four hour scale (0 to XII ? 2) reading to 5'. Within this a second 24 hour scale, also reading to 5' (1 to 24), is drawn on a separate plate which may be rotated within the first thus allowing the two scales to be juxtaposed for the conversion of standard equal hours as shown on the outer scale into Italian hours. An index is set on the inner scale at the 9.30 position. The reverse of this plate is similarly engraved, but in mirror image of the first, and thus acts as a vertical string-gnomon dial. The base of the box is engraved with an unfinished wind-rose, only the Latin names of the four cardinal points having been engraved, although 32 points are indicated. The centre of the wind-rose and the compass are both missing, the recessed space and central hole for them being now filled by a disc of metal, plain except for three radial lined and the letters 'F L' and 'd' lightly incised on it. The plate is fixed in position by a heavy nut and screw, the interior of the screw cylinder also being threaded for attachment to a staff head. The wing nut for the cursor strip mounted at the lower centre of the plate is missing and has been replaced by a recent nut. The bottom of the box is plain and unpolished.

Anthony J. Turner

Istituto e Museo di Storia della Scienza, Firenze
Inventory no. 2497

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