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Nocturnal And Sundial
Attributed to Girolamo della Volpaia
16th century; Florence
Brass; 136 mm in diameter

The nocturnal is composed of a central circular disc divided with a zodiacal calendar scale (with 0? Aries at 11 March) reading to 1 day and 1?. Within this is a volvelle composed of two discs, the lower carrying a 24 hour scale reading to 10 minutes; the upper with its edge notched with 24 teeth. A sequence of these is numbered 1 to 8 as in their appropriate places are those for 22 (mis-marked 23 and corrected), 23 and 24. Concentric with the teeth are three scales, that closest to the edge reading from January '7 7 6 6 6 5 5 5 4 4 4 4 4 4 5 5 5 6 6 6 7 7 7 7'. Within this a further scale reading from January '20 5 46 25 4 43 22 2 48 34 29 28 35 52 10 30 51 12 34 54 12 25 32 31'. Within this is a month scale. An index on the first disc at the 0 point between 1 and 24 is marked 'MEDIA NOX' ('Middle of the night'); the solar motion disc has an index set on the division of January and December, and a large rule is mounted so as to rotate round the central sighting hole marked 'HOROLGIVM NOCTVRNVM'.

The second face of the instrument carries at the centre the hour diagram for an Italian hours dial (9 to 23), flanked on each side by the two halves of a calendar scale. Beneath the diagram is a scale of 90? reading to one degree and beneath this an empty scroll as there are also to the left and right of the diagram. Above the hour diagram is a shadow square divided to 12 by six cumulatively numbered groups of 2. Two pinhole sights are set on the top line of the instrument and above them is a suspension mount/handle similar in form to the 'throne' of an astrolabe made in one piece with the centre plate of the instrument and decoratively engraved.

Provenance: Vincenzo Viviani

Anthony J. Turner

Istituto e Museo di Storia della Scienza, Firenze
Inventory no. 1286

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