Prepared in connection with his lectures as Professor of Perspective at the Royal Academy, Turner’s diagram of upright lines of various lengths intersected is based on an illustration from Samuel Cunn’s Euclid’s Elements of Geometry (London 1759, Book V). The left portion represents Proposition 1: ‘Theorem. If there be any number of magnitudes equimultiples of a like number of magnitudes, each of each; whatsoever multiple any one of the former magnitudes is of its correspondent one, the same multiple are all the former magnitudes of all the latter’.1 The right represents Proposition 2: ‘Theorem. If the first be the same multiple of the second, as the third is of the fourth; and if the fifth be the same multiple of the second, as the sixth is of the fourth; then shall be the first, added to the fifth, be the same multiple of the second, as the third, added to the sixth, is of the fourth’.2
Blank, save for an inscription by an unknown hand in pencil ‘7’ bottom left.
Supported by The Samuel H. Kress Foundation