Quadrant, late 15th century
Record status
Individual type · partial
Period
late 15th century
This late 15th-century brass quadrant, measuring 228 mm in radius, functions as both an observational and astrological instrument. The object is composed of two brass plates held by small rivets.
The front side features a sinecal quadrant with edges graduated 0 to 60 and a limb marked 0 to 360, alongside indicators for zodiacal signs and astrological houses. A ring near the apex was intended for a plumb bob, which is now missing. The reverse side houses a rotating volvelle with a brass arm. The plate beneath the volvelle is engraved with 15 concentric circles containing various astronomical and calendar scales.
The brass arm features inscriptions corresponding to these scales, relating to planetary movements such as trepidation, medius motus, and medium argumentum. John's College, Oxford.
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
- Quadrant
- Dating
- Late 15th century
- Radius
- 228 mm
- Material
- Brass
- Components
- Two brass plates
- Provenance
- St. John's College, Oxford
Design
- Visible features
- • Missing plumb bob • Missing one sight • Initials 'T [N]' engraved on back
- Provenance and Markings
- Engraved on the back of the instrument are the initials 'T [N]', which are attributed to a former owner. Additionally, the name 'Pointer' appears faintly on this side. This refers to the collector who ultimately bequeathed the quadrant to St. John's College, Oxford. The instrument is currently held by the Museum of the History of Science in Oxford, and it has been documented in the research of R. T. Gunther regarding early science in Oxford.
- Construction and Front Face
- The quadrant is constructed from two brass plates secured by small rivets. The front face is designed for observational and calculations purposes, featuring a sinecal quadrant. The square edges are marked from 0 to 60, while the limb is graduated between 0 and 360 across two sectors. Between these sectors are two additional sections inscribed with the names of the zodiacal signs and numbered from 1 to 12 in Gothic numbers, which identify the astrological houses. A small ring is located near the apex for mounting a plumb bob, though the bob itself is missing, and one of the instrument's sights is also absent.
- Volvelle and Astronomical Scales
- The reverse side of the instrument consists of a rotating volvelle equipped with a brass arm. The main plate beneath the arm displays two concentric circles divided into 12 parts for calendar use, as well as 15 concentric circles engraved with various mathematical and astronomical data, including numerical sequences and the days of the months. The brass arm contains inscriptions that identify the purpose of the underlying scales, including references to precession, trepidation, and the medius motus and medium argumentum of various planets, including the sun, moon, and visible planets like Saturn and Jupiter. These values provided the necessary data for astrological predictions.
Identification
- Inventory number
- 16856
- 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: Late 15th-century dating is tentative
- Research required: Origin is unknown