Chapter Three - History of the Slide Rule 13Oughtred’s circularslide rule, plate, TheCircles ofProportion and theHorizontalInstrument,W. Oughtred,Oxford, England, 1660In 1677, two years after Newton invents the cursor, Henry Coggeshallperfects the timber and carpenter’s rule. Newton’s cursor fails to catch on atthe time. The Coggeshall rule remains in common use 200 years later. Hisdesign and its standardization move the slide rule from a tool of mathematicalinquiry to specialized applications.Beginning in 1683, Thomas Everard popularizes the gauging rule, used todetermine the content of ale, wine and spirits barrels and to calculate theexcise tax thereon. This design, first created by William Oughtred in 1633,sees widespread use well into the 19 th Century.Throughout the 18 th Century, slide rule production and use is mostlyEnglish, with limited penetration into other capitalist economies, includingFrance and the Netherlands. Interesting to note is the lack of slide rules andmakers in Germany, Switzerland, and Italy ... countries which at this timeare producing cutting edge mathematics.The slide rule delivers the mathematical framework for advances in theindustrial arts and for ways of thinking about numbers and their applicationsin engineering. These discoveries are in turn applied to improvements in theCoggeshall timber andcarpenter’s rule,boxwood, England, firstdescribedin 1677
14All About Slide Rulesslide rule’s accuracy, precision, and mass production.In 1722 John Warner, a London instrument dealer, uses square and cubescales. By 1790 James Boulton and James Watt are modifying slide rules toimprove their accuracy and usefulness. By 1799 their Soho slide rule helps tousher in the lndustrial Revolution. It facilitates the design and manufactureof their seminal machine, the steam engine.Soho Slide Rule, JamesWatt and James Boulton,boxwood, England, Ca.1800In the l9 th Century the engineer learns that precision to the thirddecimal place suffices to create superb structures. The slide rule allows suchcalculation, while its portability encourages design verification and standardizationon the job.Modern engineering is invented through the use of the slide rule, itself adesign that could only create this impact through modern engineering.In 1815 Peter Roget, an English physician (and the author of Roget’sThesaurus), invents a log log scale, which he uses to calculate roots andpowers to any number or fraction thereof. It is regarded at the time as amathematical curiosity.Fifty years later, advances in electrical engineering, thermodynamics,dynamics and statics, and industrial chemistry make these scales so necessarythey are rediscovered. In the next fifty years they increase from three, to six,to eight scales on the slide rule, as engineering extends its grip on moderncomputation.During the first half of the 19th Century slide rule use broadens with theextension of education, democracy and free trade. Britain sees tremendousexpansion of slide rule types and manufacturers. France’s revolution of 1795ushers in a period of extreme mathematical rationality. Results includeinvention of the metric system, advanced knowledge of the movements ofthe heavens and earth, and the first requirement that all civil servantsdemonstrate slide rule proficiency as a part of qualifying exams.In 1851 a French artillery officer named Amedeé Mannheim standardizesa set of four scales for the most common calculation problems. The fourscales include two double length, named A & B, for squares and square roots... and two single length, C & D, for multiplication and division. This scaleset becomes the basis of slide rule design for the next 100 years and bears hisname today. His design and use of a cursor hastens the eventual widespreadacceptance of this feature.Tavernier & Gravet of Paris quickly develops an international reputationfor accuracy in production of the Mannheim design. An inverted Cscale (CI) andaK scale (for cubes and cube roots) were added later to theface of the rule by others, along with two trigonometry scales (S & T) anda
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