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Signed by Giovanni Battista Giusti
Dated 1565; Florence
Brass; 203 mm in radius

On the face the limb is divided with a 90? scale marked in two concentric arcs; that along the edge of the limb being the unnumbered single degrees with dotted half degree sub-divisions, the inner arc carrying the numeration in groups of five degrees. Between the two arcs is a third concentric arc marked with the relative positions of the tropics and the equator. Above this, the left and centre of the instrument are filled with the diagram for an Italian hours dial (9 to 23 without subdivisions) for 43? 40', the morning hours being indicated by smooth lines, the afternoon hours by dotted lines. On each side of the diagram the two halves of a zodiacal calendar are marked, and the remaining space at the right of the instrument carries the inscription 'QVADRANS HORARIVM AD LATITVDINEM GRADVVM XLIII XL MINVTORV{M)} LINEA PVMTOR{UM} POS{T} MERIDIES' ('horary quadrant for latitude 43? 40', dotted line afternoon') and the signature. Above the hour diagram is a shadow square of 12 numbered in undivided divisions of three, surrounding a circular solar table giving the Italian hour of Noon for each month which is also provided with its corresponding sign of the zodiac. The back of the instrument is engraved with an eight point wind-rose with the directions named as 'Ostro', 'Tramon{tano}', 'Libecc{io}', 'Crecho', 'Pone{nte}', 'Levante', 'Maestr{o}', 'Syrocc{o}'. Each sector is divided to 45 by numbered groups of 5. A compass was perhaps originally set at the centre of this diagram (or intended to be), but the space is now filled by a lead plug. Two shaped moulded sights with a fore pinnule are set on the longer side of the instrument.

Anthony J. Turner

Istituto e Museo di Storia della Scienza, Firenze
Inventory no. 2524

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