William Wallace's chorograph (1839): a rare mathematical instrument

Abstract

In 1839, William Wallace, Edinburgh University's newly retired professor of mathematics, invented the chorograph, a mathematical instrument for use in cartography and navigation. This instrument, owned by a descendant of Wallace, has recently come to light. As it failed to replace the station pointer, no other copies are known to have survived. Its mode of operation and its merits and demerits are here described.

Acknowledgments

This paper was prompted by the unexpected approach by Mr Michael C G Cox, whose subsequent comments and whose photograph reproduced in Figure 1 are gratefully acknowledged. I also thank Dr Alison Morrison-Low, Principal Curator of Scientific Instruments at National Museums Scotland, both for her interest and comments, and for drawing my attention to the very relevant articles by her former colleague, Dr Allan D C Simpson, and by Suzanna Fisher. The images for the other figures were supplied by St Andrews University Library Special Collections and were further processed by Mr Peter Lindsay, to whom I am grateful.

I dedicate this paper to the memory of the late Maria Panteki, who would surely have been interested.