Parallelogrammum Prosopographicum

Abstract

This paper investigates the 'parallelogrammum prosopographicum' (prosopographical parallelogram), a little-known device for drawing from life using parallel lines. The instrument, described in an article published in 1673 in thePhilosophical Transactions, was adapted from Christoph Scheiner's stereograph and designed as a practical method to bypass the visual effects of perspectival foreshortening. The present paper examines the geometrical and mechanical principles of the parallelogram and the rationale deployed by its inventor. It then locates the implications of the device within a history of orthographic projection through mathematical instruments in late seventeenth-century London. The paper ultimately argues that the programmatic aim of the parallelogram constitutes a relevant case study for a history of early modern architectural representation, a permeable field of research laying on the threshold between projectivity, mathematical practice and instrumentation. (© 2020 Kim Williams Books).