This fold-out diagram from 1626 was an inclusion in the Henrion Book in this collection.1 It shows the graphical construction methods by which the various scales on the Gunter rule were constructed.
In 1606 Edmund Gunter, Professor of Astronomy at Gresham College, Cambridge, published in Latin a description of his Sector. In 1620 he published his Canon triangulorum, and in 1624 a collection of his mathematical works entitled “The description and use of sector, the cross-staffe, and other instruments for such as are studious of mathematical practise” containing amongst other things the detail of “Gunter’s scale” (or “Gunter’s rule”) which was a logarithmically divided scale able to be used for multiplication and division by measuring off lengths and was thus the predecessor to the slide rule.2
This book by Henrion in 1626 includes details of the design of the logarithmic proportional rule (derived from Gunter’s 1624 publication), along with additional explanations, charts and other elaborations. The proportional rule could be used directly by means of a pair of compasses to measure off lengths corresponding to logarithms and thus to evaluate multiplications and divisions. It is significant however in itself since it was by positioning two Gunter Rules together and sliding them that William Oughtred (1575–1660), a friend of both Edmund Gunter and his colleague Professor Briggs (Professor of Geometry at Gresham College), in 1622 first developed his concept of the slide rule (which was not however published until 1632).3
1 Dennis Henrion, Traicté de logarithmes, règle à calcul (“Treatise on logarithms, calculating rule”), Paris, l’Isle du Palais, 1626. (↑)
2 http://en.wikipedia.org/wiki/Edmund_Gunter - see also http://www.livres-rares.com/livres/HENRION_Denis-_Traicte_des_Logarithmes-95656.asp (↑)
3 Georgi Dalakov, “The Logarithms and Rules”, in History of Computers, http://history-computer.com/CalculatingTools/logarythms.html (viewed 2 Jan 2012) (↑)
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