sundial / horary quadrant / altitude dial
The FRONT of this brass horary quadrant is marked with lines for unequal hours, superimposed with a shadow square to the base 12, numbered by 4 and divided to 1. Along the curved edge is an altitude scale 0 to 90, numbered by 10 and divided to 5 and to 1.
The scale of months and corresponding zodiacal signs slides along the altitude scale in a groove. It is marked with the usual Latin names of the months and the Latin names of the signs, all abbreviated. Each month has the corresponding number of days (February apparently with 30 days), divided to 10 and 2. Each sign has 30°, divided to 10° and 2°. The equinoxes are at 12 March and 15 September.
The plumb bob appears to be a later replacement.
The REVERSE has two circular scales (from the outside):
1) marked with the usual Latin names of the zodiac (some abbreviated), divided to 10° and 2°;
2) an eccentric scale with the usual Latin names of the months (abbreviated) with the corresponding number of days, divided to 10 and 2. The equinoxes are at 12 March and 18 September.
A central disc has been engraved at a later date with a shadow scale to the base numbered 1 to 1, divided to 1/3. Over this disc rotates an alidade with two sighting vanes, engraved with the words, 'LINEA FIDUTIA', at a later date.
- Made in: England
- (Europe,United Kingdom,England)
- Length: 106 millimetres (radius)
- Length: 116 millimetres (radius incl. sight)
- Thickness: 2.5 millimetres (plate)
This undated and unsigned instrument is a rare example of a quadrans vetus with markings for unequal hours and a movable scale with months and zodiacal signs so that the quadrant can be used at a wide range of latitudes.
The quadrant's design is very similar to the instrument described in a manuscript by John of Montpellier written before 1350. The Gothic letters and numerals of the original inscriptions make it likely that the quadrant was made in the 14th century. The letter forms resemble those found on a number of early English instruments.
Prehistory and Europe
Horary-quadrant; brass; quadrans vetus/old quadrant of John of Montpellier, showing unequal hours; range of latitudes 25-65 degrees; superposed shadow scales on the hour-lines; plumb-line has bob and slider; reverse: two circular scales showing months and zodiac signs; central raised disc engraved at later date with shadow scale and superimposed short-rotating alidade.
If you’ve noticed a mistake or have any further information about this object, please email: firstname.lastname@example.org
Object reference number: MCC3475
British Museum collection data is also available in the W3C open data standard, RDF, allowing it to join and relate to a growing body of linked data published by organisations around the world.
The Museum makes its collection database available to be used by scholars around the world. Donations will help support curatorial, documentation and digitisation projects.