In Lecture 3 as Professor of Perspective at the Royal Academy, Turner provided a history of techniques for drawing a cube and other rectilinear forms in perspective. Then he gave four different methods for various circular shapes, explaining that ‘the circle has from the earliest time been considered from the various modes of the Old Masters the most difficult to attain’.1 The left side of Diagram 38 illustrates a method by Lorenzo Sirigatti for forming a Tuscan capital, while the right shows a one for a circle ascribed to both Jacques Androuet du Cerceau (1515–1585) and Joseph Moxon (1627–1691). The reasons for including these methods on the same diagram are unclear, as they are not related to each other in the lecture text.
Turner’s description of Sirigatti’s method deviates significantly from the source material. Maurice Davies writes that Turner may have based his knowledge of the method on a single diagram from Sirigatti’s La Pratica di Prospettiva (1625 edition, pl.33), which he copied into his Perspective sketchbook (Tate D07433; Turner Bequest CVIII 46).2 In an early draft of the lecture, Turner copied two versions of Sirigatti’s diagram into the margins and wrote his own interpretation of the method.3 When revising the manuscript for lecturing, Turner wrote a new description of the procedure which seems to correspond to what is illustrated in the diagram.4 Davies further notes that ‘Turner does not explain the method fully and it is not possible to determine whether it works or not’5 while the diagram reveals many errors which ‘all relate to the dual function of the top element of the construction as both geometrical section and perspective representation’.6
The right side of the diagram purports to illustrate a method for drawing a circle by du Cerceau and Moxon. It is unclear how the diagram corresponds to the lecture text, or why the two theorists are linked to the method illustrated. Davies explains that Turner’s description is based on a diagram from Moxon’s Practical Perspective Made Easie (1670, operation XI)7 while the drawing is derived from various diagrams in the same treatise (see for instance diagrams IX and XI). There is no obvious link to du Cerceau.
Turner, ‘Royal Academy Lectures’, circa 1807–38, Department of Western Manuscripts, British Library, London, ADD MS 46151 M folios 12 and verso.
Davies 1994, p.121.
Turner, ‘Royal Academy Lectures’, circa 1807–38, Department of Western Manuscripts, British Library, London, ADD MS 46151 F folio 9.
Turner, ‘Royal Academy Lectures’, circa 1807–38, Department of Western Manuscripts, British Library, London, ADD MS 46151 M folios 12 recto-verso.
Davies 1994, p.123.
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