- Museum number
Quadrant for latitude 51 32'; ivory; circular disc; a) quadrant with hour-scales of Gunter type without azimuth scales; b) circular scales in two groups with rotating index; rotating brass index; equinoxes set at 10 March and 13 September.
- Production date
Diameter: 126 millimetres
Thickness: 9 millimetres
- Curator's comments
A similar quadrant in ivory is in the British Museum, reg. no. 1923,0206.2 and another was in the collection of the Time Museum formerly in Rockford, IL. A very similar quadrant in wood in the Greenwich Maritime Museum, AST0195, is signed with the initials ‘JB’ (‘Londini’) and is also attributed to John Brown; see H. Higton, Sundials at Greenwich, Oxford 2002, no. 328, pp. 342-3.
a. Quadrant with hour-scales of Gunter type but without azimuth scales. Central hole and one hole near edge for sights (now missing). Small hole near edge for plumb-line (line and bob now missing). Scales near lower edge, centred on plumb-line hole, reading 0°-62½° for altitude; scale 0-50 (the latter at 45°) and thrence down past 40 entitled 'Quadrant'; scale of cotangents 4, 3, 2, 1 divided into tenths, entitled 'shadowes' and giving shadow length corresponding to the scale of degrees, with 1 at 45° and 2 at 26½° . Near top of disc a table entitled 'An Allmanack for euer' listing 'Dayess', Months', 'Do. Lett', 'Le Year' and 'Epacte', the last three giving Dominical letters and epacts for a succession of leap years from 44 (i.e. 1644) to 68 (i.e. 1688). This face a. also inscribed: J X B; 'Latitude 51-32 Londini fecit'; 'Lege et intelige'; and 'Perpetuus Solis destinguet tempora motus'.
b. Circular scales in two groups, with rotating index. The inner group of scales is a calendar in four rings for spring, summer, autumn and winter respectively, the outer rings showing the corresponding times of sunrise, sun's 'amplitude' (i. e. sunrise azimuth), declination, true place (in the zodiac), 'longest day', this scale starting at zero at 20 May, 4 July, 20 November or 1 January, and with divisions crowed to a climax between 21 and 24; finally a scale 'Right ascension'. There is a rotating brass index lettered correspondingly. The equinoxes are at 10 March and 13 September.
- Not on display
Latest: 3 (Mar 2017)
3 (Jan 1996) Sticky deposit.
- Acquisition date
- Britain, Europe and Prehistory
- Registration number