Prepared in connection with his lectures as Professor of Perspective at the Royal Academy, Turner’s diagram of figures within circles is based on illustrations from Samuel Cunn’s Euclid’s Elements of Geometry (London 1759, Book 4). The top centre diagram shows Proposition 10: ‘Problem. To make an isosceles triangle, having each of the angles at the base double to the other angle’.1 The centre right diagram represents Proposition 15: ‘Problem. To inscribe an equilateral and equiangular hexagon in a given circle’.2 The bottom centre diagram represents Proposition 16: ‘Problem. To describe an equilateral and equiangular quindecagon in a given circle’.3 The centre left diagram is again based on Proposition 15, which is also referred to on another sheet from this series (Tate D16992; Turner Bequest CXCV 23). There are pencil sketches of each figure in Turner’s lecture notes.4
Blank, save for an inscription by an unknown hand in pencil ‘18’ bottom left.
Supported by The Samuel H. Kress Foundation