Charles Whitwell Quadrant

Technical characteristics

Date

1595

Type

English quadrant

Maker

Charles Whitwell

Collection

Istituto e Museo di Storia della Scienza, Firenze

Dimensions

176 mm x 176 mm

Provenance

English

Condition note

The alidade is a replacement

Place recorded

England

Maker / attribution

Charles Whitwell

Design

Visible features

• Shadow square engraved along the lower edges • Straight line horary diagrams with 30-minute divisions • Zodiacal calendar with Aries at nearly 11 March • Lunar volvelle with pointers and phase aperture

Signatures and Construction

The instrument is signed on the face: 'Charolus Whitwell fecit 1595'. The quality of the engraving throughout the brass plate is characterized by restrained italic scripts for calendar information and formal roman scripts for compass notations. The documentation notes the survival of light guide lines on both sides of the plate, indicating the preparation methods used by the maker for the alignment of letters and numerals. Charles Whitwell is noted as a significant producer of scientific instruments in the late sixteenth century, particularly those associated with the designs of Robert Dudley. The instrument's physical state includes an alidade that is not original, highlighting the repair history of the object. The item is currently curated in the Istituto e Museo di Storia della Scienza in Florence, providing a primary example of Whitwell's instrument-making style.

Reverse and Astronomical Scales

The reverse side of the quadrant displays an array of concentric astronomical scales intended for complex timekeeping and navigational calculations. Reading from the outer edge toward the center, the instrument includes a zodiacal calendar where the signs are subdivided into degrees and the months into days, with the 0-degree Aries point positioned at approximately March 11. Inside this scale lies a double hour scale calibrated to 15-minute intervals, surrounding a circle of 32 compass directions. At the center is a lunar volvelle, which includes a lower disc with a pointer and a 30-day month scale. The upper disc features a pointer, an aperture for displaying lunar phases, and an integrated lunar aspectarium. The text on this side is executed in a mix of italic script for names and roman script for compass directions, with light guide lines still faintly visible.

Instrument Geometry and Obverse Features

The instrument is square in form, providing a base for multiple distinct computational diagrams. The primary functional engraving on the face consists of a shadow square arranged along the lower edges, which is decimally subdivided into 120 parts. Above this, the instrument features two horary quadrants defined by straight lines rather than the traditional curved arcs. The lower quadrant is numbered from 4 through 12 to 8, while the upper quadrant follows a 12 to 6 to 12 sequence. These hour diagrams are intersected by parallel season arcs, which represent five-degree divisions of the zodiac. A degree scale is provided along the limb of the quadrant. A central diameter line extends from the apex to the 12/120 point of the shadow square, serving as a geometric reference. The maker's signature is engraved below the arc, and the device utilizes an alidade for sighting, though this element is recorded as a later addition.

Identification

Inventory Number

2159

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.