Giovanni Battista Giusti Quadrant
Record status
Individual type · partial
Period
1568
This brass quadrant, measuring 226 mm in radius, was made by Giovanni Battista Giusti in Florence in 1568. The instrument is designed for the latitude of 43° 40'.
One face contains an Italian hours dial, a zodiacal calendar, a magic square, and a 'Rota medii motus et quantitas diei' for calculating solar motion and day length. The limb is calibrated from 0 to 90 degrees. Two decoratively moulded block sights are positioned on the top edge, and a hole at the apex allows for a suspension thread. The reverse side features an engraved shadow square of 12. The maker, Giovanni Battista Giusti, was active in Florence during the 1560s.
This instrument currently resides in the collection of the Istituto e Museo di Storia della Scienza, Firenze.
Evidence at a glance
- Linked sources
- 1
- Photograph views
- 1
- Catalogue references
- 0
Counts describe this entry’s documentation, not authenticity, rarity or completeness. Photographs may show one specimen; check each caption and licence.
Technical characteristics
- Date
- 1568
- Type
- Italian quadrant
- Maker
- Giovanni Battista Giusti
- Latitude
- 43° 40'
- Material
- Brass
- Inscription
- Quadrans horarium
- Place recorded
- Italy
- Maker / attribution
- Giovanni Battista Giusti
Design
- Visible features
- • Limb calibrated from 0 to 90 degrees • Magic square displaying numbers 4, 9, 2 / 3, 5, 7 / 8, 1, 6 • Two decoratively moulded block sights along the top edge • Circular rotating table in the apex
- Reverse and Inscriptions
- The reverse of the brass instrument contains an engraved shadow square of 12. This scale is divided into segments read to half-points and is numbered in groups of three. The numbered divisions extend as radial lines toward the center of the quadrant to assist in calculations. The front face bears a specific inscription providing the instrument's function and the latitude for which it was calculated. The maker, Giovanni Battista Giusti, is also identified by a signature on the instrument, dating his work to 1568.
- Sighting and Orientation Features
- For the purpose of solar observation, the quadrant is equipped with two decoratively moulded block sights fixed to the top edge. These sights allow the user to align the instrument with the sun. A suspension hole located at the apex of the quadrant serves as an attachment point for a thread cursor and runner. By using a plumb-line suspended from this point, the user could determine the sun's height. The altitude is indicated by reading the degrees on the limb of the quadrant. The morning hours on the Italian hours dial are delineated with smooth lines, while afternoon hours are marked with dotted lines.
- Instrument Layout and Calibrations
- The front face of the quadrant is densely engraved with multiple astronomical and mathematical scales. The limb features a scale of 90 degrees, divided into 1-degree increments indicated by alternating hatched and unhatched markings, with larger divisions marked by dots at five-degree intervals. The instrument is calibrated specifically for the latitude of 43 degrees and 40 minutes, which corresponds to Florence. In addition to the timekeeping scales, the quadrant includes a circular table in the apex labeled 'Rota medii motus solis e quantitatis diei'. This feature consists of six concentric rings used to track solar motion and determine the length of the day. A three-by-three magic square is also present on the face, totaling 15 in all directions, as well as a diagram for an Italian hours dial marked from 9 to 23.
Identification
- Inventory Number
- 2520
- Source note
- Facts transcribed from the linked source listing or collection record. Attribution and specifications are source-reported and have not been independently authenticated.
Catalogue references
No catalogue numbers recorded. Numbers are only published once transcribed from a verified edition of a standard catalogue — they are never inferred.
Research required
- Research required: Originality of the plumb-line cursor not confirmed
- Research required: Exact workshop production location within Florence is based on probability