Prepared in connection with his lectures as Professor of Perspective at the Royal Academy, Turner’s diagram is based on part of an illustration from Samuel Cunn’s Euclid’s Elements of Geometry (London 1759, Book 6, Plate 2). It illustrates a portion of Proposition 33: ‘Theorem. In equal circles the angles have the same proportion with the circumferences on which they stand, whether the angles be at the centres, or at the circumferences; and so likewise are the sectors, as being the centres’.1 See Tate D17017; Turner Bequest CXCV 47 for a representation of the other part of Proposition 33. There is a pencil sketch of the entire Proposition in Turner’s lecture notes.2
Blank, save for an inscription by an unknown hand in pencil ‘15’ bottom left.
Supported by The Samuel H. Kress Foundation