Declinatory Quadrant
Record status
Individual type · partial
Period
16th century
This brass declinatory quadrant, measuring 170 x 170 mm, is attributed to the Florentine maker Giovanni Battista Giusti. The device consists of a square brass plate engraved with cardinal directions and a quadrant scale divided into 90 degrees.
A modelled alidade is pivoted at the vertex, allowing for rotational movement across the scale. Integrated into the lower portion of this alidade is a small compass with an intact glass cover and magnetic needle, having a diameter of 23 mm. The instrument functions as a specialized tool for sundial makers, enabling the design of vertical declining sundials by determining specific angles relative to the meridian. Its construction reflects the practices of 16th-century Florentine mathematical instrument workshops.
The underside of the plate remains unadorned and lacks any inscriptions. The object is held in the collection of the Istituto e Museo di Storia della Scienza in Florence.
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
- Type
- Italian quadrant
- Maker
- Attributed to Giovanni Battista Giusti
- Dating
- 16th century
- Dimensions
- 170 x 170 mm
- Inscriptions
- Italian cardinal directions
- Place recorded
- Italy
- Compass diameter
- 23 mm
- Maker / attribution
- Giovanni Battista Giusti
Design
- Visible features
- • The quadrant features a central pivoted alidade with an integrated compass box. • Engraved degree scales are positioned along the lower curved edge. • Cardinal points are inscribed in Italian along the four outer edges of the square plate. • The instrument includes a suspension hole at the top vertex.
- Functionality and Use
- This device serves as a declinatory, an essential tool for the design and construction of vertical declining sundials. When in use for vertical walls, the edge of the plate is held horizontally against the wall surface. The alidade is adjusted until the compass needle aligns with the meridian, allowing the designer to read the specific angle from the scale. Beyond its primary role for vertical surfaces, the instrument is suited for the layout of inclining dials. By holding the plate vertically, the compass box acts as a weight, causing the pivoted alidade to hang in a vertical plane, which permits the measurement of the dial's inclination.
- Construction and Design
- The instrument is fabricated from brass as a 170 x 170 mm square plate. At its vertex, a pivoted radial arm, or alidade, is secured, allowing it to traverse the arc of the quadrant. This arc is engraved with a numerical scale divided into 90 degrees, measured in both directions from the center point. A small, circular compass, measuring 23 mm in diameter, is fixed to the lower portion of the alidade. The compass retains its original glass cover and magnetic needle. The four edges of the square plate are engraved with Italian inscriptions identifying the cardinal directions, providing the necessary orientation for its function as a surveying tool.
- Attribution and Provenance
- The instrument does not carry a maker's mark or signature. The attribution to the workshop of Giovanni Battista Giusti is based on the technical characteristics observed in its construction and the specific style of its engravings. This identification aligns the object with the production of 16th-century Florentine instrument makers. The object is currently part of the collection at the Istituto e Museo di Storia della Scienza in Florence. The provenance is documented under the inventory number 3822, which remains the primary reference for its identification within the museum's holdings.
Identification
- Inventory Number
- 3822
- 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: The attribution to Giovanni Battista Giusti is based on stylistic construction and engraving rather than a signature.
- Research required: The intended use for inclining dials is a functional possibility suggested by the source.