Cooper 100-Inch Slide Rule

This instrument consists of a wooden base to which a flat rectangular scale printed on white celluloid is attached. The scale is divided logarithmically and arranged in 20 parallel lines. Each line is about five inches long. A wooden frame slides backward and forward over the base. Within this frame is a second frame, which has a clear celluloid window. Four index marks are drawn on the window. A loose metal wedge with a pin attached serves as a pointer, and it may be placed at any point on the window. The scales are marked: THE COOPER 100 INCH SLIDE RULE (/) PATENTED.

The feet of the base are lined with green felt. The instrument fits in a leather-covered cardboard box that is lined with white felt. A sticker inside the lid reads: WILLIAM DUBILIER (/) 72 Esplanade (/) NEW ROCHELLE, N. Y. There is also a note that reads: TELEPHONE, PARK 1081. (/) WIRELESS CALL, 5AU. (/) 94, ADDISON ROAD (/) KENSINGTON, W. 14. (/) 24/12/22 (/) To W. D. (/) With very best wishes for (/) Xmas and the New Year. (/) W.v.P.

William Dubilier (1888–1969), the donor of this instrument, was an American electrical engineer and inventor who received this instrument from a friend in Great Britain in 1922. By 1923, W. F. Stanley & Co. made this rule and stamped the outer frame with its mark. Although the rule worked well for multiplication and percentage problems, it was difficult to set the rule accurately for more complex calculations. At the relatively high price of £4, the instrument probably never sold widely. No patents for the device have been found. For the instruction manual, see MA.259739.01.

References: Werner H. Rudowski, "The Cooper 100-inch Slide Rule: An Update," Slide Rule Gazette 8 (Autumn 2007): 25–27; Peter M. Hopp, Slide Rules: Their History, Models, and Makers (Mendham, N.J.: Astragal Press, 1999), 116; "William Dubilier, Inventor, Is Dead," New York Times (July 27, 1969), 65; accession file.

Currently not on view