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Signed by Charles Whitwell
Dated 1595; English
Brass; 176 mm x 176 mm

The face of the instrument is engraved along the lower edges with a shadow square of twelve decimally sub-divided to 120 parts. Above this is the maker's signature below the arc of a quadrant of 90? reading to 30' and numbered by groups of ten. Above this are two straight line horary quadrants, the lower one numbered 4 to 12 to 8; the upper 12 to 6 to 12. Both diagrams are divided to 30 minutes by dashes on the parallel season arcs corresponding to 5? divisions of the zodiac, which are drawn across the hour diagram, the signs being marked to the right. A diameter is drawn from the apex of the instrument to the 12 / 120 point of the shadow square. An alidade with two sights pivoted from the apex is not original.

The reverse of the instrument is engraved with concentric scales which (reading from the outside towards the centre) are a zodiacal calendar (with 0? Aries at nearly 11 March) the signs being divided to degrees and the month to days. Within this is a double hour scale reading to 15 minutes and within this a circle of 32 compass directions, alternate directions being indicated by their initials. Within this a lunar volvelle, the lower disc with pointer and 30 day month scale reading to quarters, the upper with pointer, aperture for the lunar phase read from the disc below and a lunar aspectarium. The month and zodiac names are in restrained italic script, the compass points in roman. On both sides of the instrument the remains of light guide lines for the height of the letters and numerals can be seen.

Anthony J. Turner

Istituto e Museo di Storia della Scienza, Firenze
Inventory no. 2159

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