Keuffel & Esser 1741 Thacher Cylindrical Slide Rule

In 1881, Edwin Thacher, a "computing engineer" for the Keystone Bridge Company in Pittsburgh, Pennsylvania, received a patent for an improvement in slide rules. Thacher, a graduate of Rennselaer Polytechnic Institute, spent much of his career designing railway bridges. To assist in his calculations, he designed a cylindrical slide rule. Thacher's rule, though it fit on a desk, was equivalent to a conventional slide rule over 59 feet long. The rule had scales for multiplication and division and another scale, with divisions twice as large, for use in finding squares and square roots. There were no trigonometric scales.
To produce his "calculating instrument," Thacher turned to the London firm of W. F. Stanley. The company even designed a special dividing engine for preparing the scales for the instrument. These were printed on paper sheets, which were pasted to the drum and the slats. In this example, the paper is also printed in italics on the right side: Patented by Edwin Thatcher [sic], C.E. Nov. 1st 1881. Divided by W. F. Stanley, London, 1882. Made by Keuffel & Esser Co. N.Y. Wayne Feely has suggested that K&E began manufacturing (as opposed to simply distributing) Thacher cylindrical slide rules in 1887, indicating 1887 is the earliest date for this example of the instrument.
The drum is rotated with wooden handles. The cylinder of slats is held in place with a brass frame, which is affixed to a wooden base. A paper of DIRECTIONS AND RULES FOR OPERATING is glued to the front of the base. A small silver metal tag affixed to the front right of the base is engraved: KEUFFEL & ESSER CO. (/) NEW-YORK (/) 589. A metal extension on the front, screwed to both sides of the frame, bears a fixed holder and thumbscrew that once held a magnifying glass.
A paper K&E label on the inside lid of the instrument's mahogany case is marked in ink: 1741/589 (/) Thacher's (/) Calculating (/) Instr. The inside of the lid and the bottom of the base are both painted: M59. The back of the base is missing a chip 5 cm in length. The left and right sides of the case both bear labels marked in ink: INSTRUMENT (/) CALCULATING (/) THATCHER. A diagonal line is drawn through the second T in "Thatcher" on the right side.
Keuffel & Esser Company of New York sold versions of the Thacher cylindrical slide rule from at least 1883 until about 1950. There were two models, one with a magnifying glass (K&E model 1741, K&E model 4013 after 1900), and one without (K&E model 1740, later K&E 4012). This is a model 1741. In 1892, the model 1741 sold for $40.00. The Physics Department of the United States Military Academy transferred this example to the Smithsonian in 1958.
References: Edwin Thacher, "Slide-Rule" (U.S. Patent 249,117 issued November 1, 1881); Wayne E. Feely, "Thacher Cylindrical Slide Rules," The Chronicle of the Early American Industries Association 50 (1997): 125–127; Peggy Aldrich Kidwell, Amy Ackerberg-Hastings, and David Lindsay Roberts, Tools of American Mathematics Teaching, 1800–2000 (Baltimore: The Johns Hopkins University Press, 2008), 113–114; Wilfred Scott Downs, ed., "Nickel, Frank F.," Who's Who in Engineering, (New York, 1931), iii:957; Catalogue of Keuffel & Esser (New York, 1892), 131. This was the first K&E catalog to list the model 1741.
Currently not on view
Object Name
calculating rule
slide rule
date made
Stanley, William Ford
Keuffel & Esser Co.
Physical Description
metal (core, endposts material)
paper (scales material)
wood (base, handles, case material)
overall: 18.4 cm x 61 cm x 21.6 cm; 7 1/4 in x 24 in x 8 1/2 in
place made
United States: New York, New York
ID Number
accession number
catalog number
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Slide Rules
Data Source
National Museum of American History, Kenneth E. Behring Center


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