Everards Sliding Rule, 1739.

UNITED KINGDOM - JULY 15: Uses of the slide rule, improved by Charles Leadbetter (active 1728), included 'finding all manner of Proportions: for Gauging Malt, measuring all manner of Square and Round Bodies, eg Timber, Stone etc; extracting the Square and Cube Roots, Gauging all sorts of Vessels and Casks; Ullaging of Vessels or Casks, ie for finding exactly what quantity of Ale, Beer, Wine etc remains, after any Part has been drawn off; reducing to a Cylinder all Vessels or Casks which are of the form of a Spheroid, Parabolic Spindle, or a Parabolic Conoid; to shew the Area in Ale-Gallons of all Diameters from 13 to 36 inches; Reducing Casks in the Form of the Frustum of a Cone to a Cylinder'. Frontispiece from Leadbetter�s �The royal gauger; or, Gauging made perfectly easy�, published in London in 1750. (Photo by SSPL/Getty Images)