The Sundial Treatise (1640)

In the early seventeenth century, the correct setting out of shadows was considered an important element in perspective drawing, as may be seen, for example, in Stevin’s treatment of the matter in his work on perspective (1605), (see also Sinisgalli, 1978). Indeed, shadows seem to have been recognized as presenting some kind of analogy to perspective representation in general, for Willebrord Snel’s Latin translation of Stevin’s work (1605) has the title De Sciagraphia (literally: On shadow-drawing). Since sundials are designed to take account of the way the shadow of the gnomon moves in the course of the day, it is not surprising to find that a similar title, Sciographia or the Art of Shadowes,was also used by John Wells (1606–1635) for his treatise on the making of sundials (1635). In fact, laying out sundials seems to have been generally accepted as a part of the study of perspective. Jonas Moore (1617–1679) makes the connection between the two in explicit terms in his ‘Epistle to the reader’ at the beginning of Mr De Sargues’ Universal Way of Dyalling... (1659) (which is a translation by Daniel King of Bosse’s expanded version of Desargues’ work, published in Paris in 1643): Dyalling I accompt one kind of Perspective, for that glorious Body the Sun, the Eye of the world, traceth out the lines and hour-points by his Diurnal Course, and upon the resubjected Plane by the laws of Picture, Scenographically delineates the Dyal.