On the History of Gunter's Scale and the Slide Rule During the Seventeenth Century

In the seventeenth century, a modest wooden ruler became a cornerstone of calculation, linking merchants, engineers, and scholars through a shared language of numbers. This work follows the evolution of that device—known as Gunter’s scale—and its companion, the slide rule, tracing their spread from English workshops to French academies. By examining surviving manuals and surviving instruments, the author reveals how these tools reshaped everyday problem‑solving long before the advent of modern calculators.

The narrative brings to life the rivalry between William Oughtred, who first described a circular and then a straight slide rule, and the opportunistic Richard Delamain, whose pamphlet sparked a heated debate over priority. It also surveys the practical refinements introduced by figures such as Edmund Wingate, Milbourn, and William Leybourn, whose altered graduations made complex root extractions a matter of “inspection only.” Readers gain a vivid picture of the ingenuity, competition, and scholarly exchange that propelled these instruments into the scientific mainstream.