Mack Improved Mannheim Simplex Slide Rule by Dietzgen

This wooden ten-inch Mannheim slide rule is faced with white celluloid. The top edge is beveled and has a scale of inches divided to sixteenths of an inch. The bottom edge is flat and has a scale of centimeters divided to millimeters. The base has A and D scales, with B and C scales on one side of the slide and S, L, and T scales on the other side of the slide. The L scale is not lettered. The base underneath the slide is marked: EUGENE DIETZGEN CO. CHICAGO–NEW YORK (/) W. F. M. It is also marked: PAT. JUNE 28 1898. The indicator is glass in a metal frame. A paper glued to the back of the rule gives the properties of various substances and equivalents of various weights and measures. Carved into the back is: W.F.M. 1907.

The base of the rule is cut lengthwise into two sections that are joined together by invisible springs. This was intended to create more uniform resistance to the motion of the rule (even if it is fully extended) and to make it possible to straighten the parts of the rule by scraping, should it become warped. A cardboard box covered with burgundy leather is marked: The Mack Improved Slide Rule (/) NO. 1765 (/) EUGENE DIETZGEN CO. (/) CHICAGO. NEW YORK.

This rule is named for John Givan Davis Mack (1867–1924), an early member of the engineering faculty at the University of Wisconsin who taught from 1893 to 1915. On June 28, 1898, he received U.S. Patent 606388 for dividing the base of a slide rule and rejoining the pieces with springs. He assigned the patent to the Eugene Dietzgen Company of Chicago, which first sold a slide rule built on Mack's patent in 1898 and offered this version from 1902 to 1912 for $4.50.

The carved initials are those of the owner, the spectroscopist William F. Meggers (1888–1966), who was long associated with the U.S. National Bureau of Standards. He received his B.A. in physics from Ripon College in 1910, his M.A. in physics from the University of Wisconsin in 1916, and his Ph.D. in physics, mathematics, and astronomy from Johns Hopkins University in 1917. It seems likely that he acquired this rule as a student. For a less precise slide rule associated with Meggers, see 293320.2820. For later slide rule instructions distributed by Dietzgen, see 1981.0933.07.

References: Catalogue & Price List of Eugene Dietzgen Co., 7th ed. (Chicago, 1904), 171; Rodger Shepherd, "Some Distinctive Features of Dietzgen Slide Rules," Journal of the Oughtred Society 5, no. 2 (1996): 42–45; Peter M. Hopp, Slide Rules: Their History, Models, and Makers (Mendham, N.J.: Astragal Press, 1999), 159–160, 276; J. G. D. Mack Papers, University of Wisconsin Archives: U. S. Patent 606388.

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