Astronomical and Calendrical Volvelle or 'Astronomical Rotula', Designed by James Ferguson, Engraved by James Mynde, Adapted and Reissued by Lewis Evans and Thomas Jones, London, 1817

Paper and card instrument consisting of a circular base scale and four concentric volvelles mounted on a square board, the scales printed from engraved plates, hand coloured, and varnished or lacquered. It is a version of James Ferguson's 'Astronomical Rotula' which has been brought up to date by the mathematician Lewis Evans and re-issued by the instrument maker Thomas Jones; the engraver whose signature appears on it, James Mynde, was Ferguson's original engraver (working 1740s-1770s), so the inference is that Jones acquired the original copper printing plates and had them amended with information valid for the 19th century, calculated by Evans. In addition to the phases of the Moon, eclipses, etc indicated by the original title it also shows dominical letters and mean times for new moons for the years 1817-64.

One of a pair with 14576; the two instruments formerly hinged together, the base board of each functioning as the boards of a bound volume or portfolio, part of the leather spine remaining along one edge of each.