Inventory no. 40847 - Former Display Label
English MATHEMATICAL INSTRUMENT which includes William Oughtred's CIRCLES OF PROPORTION
c.1634
Brass. Signed, on the back, "Elias Allen fecit"; undated. This instrument was given in 1635, by George Barkham, to St. John's College. It is inscribed on the back, "GEORGIVS BARKHAM, COMMENSALIS; FILIVS D. IOANNIS BARKHAM S.T.P. DONO DEDIT A° 1635"; Barkham's arms are engraved below.
This instrument was suitable for many mathematical, astronomical and navigational calculations, and was especially of use in dialling.
On the front are a series of circular trigonometric and logarithmic scales known as Oughtred's CIRCLES of PROPORTION, one of the earliest forms of slide-rule. Within these scales is an astrolabe, with a planispheric projection of the heavens of the type invented in the 16th century by Juan de Roias.
On the back is Oughtred's HORIZONTAL DYALL, an unusual form of astrolabe, mainly used in dialling.
The rule shown probably belonged to this instrument; cursors and another rule are missing.
It is likely that the instrument was made to Oughtred's own specification. The maker, Elias Allen, published and sold the 1632 edition of Oughtred's book, The Circles of Proportion and the Horizontall Instrument. Both invented and the uses of both written in Latine by Mr. W.O. ..., London 1632.
Lent by St. John's College.
Other narratives:
- Inventory No. 40847 & 35515 - Exhibition Label Text 'The Double Horizontal Dial: Then and Now' 13 January to 10 March 2009
- Bennett, J. and Johnston, S., The Geometry of War, 1500-1750 (Oxford, 1996)
- Movable parts
- Circles of proportion
- Special Exhibition Label: 'Geek is Good' (15 May - 2 November 2014)
- Special Exhibition Label: 'Geek is Good' (15 May - 2 November 2014) - Slide rules general introduction
- Reverse prints taken from this instrument