Lecture Diagram 21: Representation of a Globe in Perspective (after Thomas Malton Senior)

Maurice Davies cites Diagram 21 and its corresponding lecture text as one of the many examples of Turner adapting a passage from the elder Thomas Malton (1726–1801) for his own teaching as Professor of Perspective at the Royal Academy. For instance, in an early version of his discussion devoted to curvilinear perspective, Turner quotes a theorem found in Malton’s A Compleat Treatise on Perspective in Theory and Practice on the True Principles of Dr Brook Taylor (1775): ‘The representation of a globe in perspective is an ellipsis, excepting when the centre coincides with the centre of the picture, then it is a circle’.1 Turner copied Malton’s diagram (pl.VII, fig.32), but, according to Davies, ‘realised that he was considering spheres (globes) before he had finished with circles and without a second thought simply amended the passage’ to suit his meaning. In the manuscript used for lecturing in 1811, Turner rewrote the passage thus: ‘The representation of a circle in perspective is an ellipsis, excepting when the centre coincides with the centre of the picture, then only it is a true circle’.2 Because of this alteration, the accompanying diagram is no longer relevant to his lecture discussion. There is a sketch possibly after Malton’s diagram in Turner’s lecture notes.3

Technical notes:

Peter Bower states that the sheet is Super Royal size Whatman paper made by William Balston and Finch and Thomas Robert Hollingworth, at Turkey Mill, Maidstone, Kent. He writes that all ‘the sheets in this batch have some streaking across the sheet, probably from a fault in the sizing’.1

Verso:

Blank, save for an inscription by an unknown hand in pencil ‘66’ bottom left.