09-038. American, patent dated July 2, 1901, signed 'THE ENGINEER'S SLIDE RULE. From E.M . Scofield, Bridge Engineer. Sta. A. Youngstown, - Ohio. rule sent prepaid on receipt of price. Factory. - Youngstown, Ohio." Made of mahogany, 24" long x 2 1/8" wide x 9/16" thick overall, with two slides and varnished paper scales on both sides, plus detailed instructions along one edge and conversion units on the other edge. The scales on the front side are labeled B, A, A, and C, and marked 'ROOTS' and 'RECIPROCALS;" on the back side the scales are labeled F, E, E, and F. The slide rule has obviously been well used, but is still in very good overall condition.
Conrad Schure's article, "The Scofield-Thacher Slide Rule" in the "Journal of the Oughtred Society," Vol. 3, No. 1, pp. 20-25 illustrates and fully describes this rare American slide rule. Edson M. Scofield was assistant to Edwin Thacher from 1889-94 during which time Scofield made a prototype of this slide rule; a modified rule was patented by Thacher in 1901, and later the instrument retailer, Dietzgen of Chicago, offered the rule in their catalogs. The present early production example has Scofield's offering statement from Youngstown, Ohio, with no mention of a patent, Thacher, or Dietzgen. Perhaps these rules were made for and sold by Scofield before the 1901 patent date was added.
