overall: .3 cm x 26.5 cm x 11.8 cm; 1/8 in x 10 7/16 in x 4 21/32 in
United States: Ohio, Akron
This yellow, red, black, and white slide rule has a cardboard front and back, held together with metal grommets along the top and bottom. A paper slide and a clear plastic cover fit inside the cardboard. Three red hairline indicators are on the plastic. The front of the rule bears A, D, and K scales, with B, CI, and C scales on the front of the slide. The scales are 8-1/2 inches long. The front also has a vertical window for reading off four-place logarithms. There are tables for decimal equivalents and slide rule settings.
The back of the rule has A and D scales, with S, L, and T scales on the back of the slide. There are tables for trigonometric formulae and mathematical formulae, and a vertical window for reading off natural trigonometric functions.
The front of the rule is marked: SLIDE RULE & MATHEMATICAL TABLES (/) MIGHTY MITE (/) THERMAL CONTROLS; MECHANICAL INDUSTRIES (/) PRODUCTION COMPANY (/) 217 ASH ST. • AKRON 2, OHIO. The back of the rule is marked: Copyright 1945, Multi Slide Instrument Corp., Chicago, Ill.—Pat. Pending (/) Reproduction in whole or part will be prosecuted.
The rule is housed in an envelope that also contains a sheet of instructions and two samples of Mighty Mite Thermal Controls. The front of the envelope bears the same information about the distributor, Mighty Mite, which appears on the front of the rule. However, the address for Mechanical Industries is given as 217-233 Ash St. The front is also marked: Multi (/) SLIDE (/) RULE. The back of the envelope describes the company's single- and dual-action thermal controls.
The larger silver dual-action sample of a thermal control is marked: M.I.P.CO.AKRON.O. (/) PAT.PEND. The smaller copper single-action sample is marked on one side: M.I.P.CO. (/) AKRON O. (/) SUICOL. On the other side, it is marked: 40 H.P. (/) 15 V.A.C.
According to the magazines <i>Popular Science</i> and <i>Professional Engineer</i>, the Multi Slide Rule sold (without company logos) for $1.00. The company distributed its products from Chicago. Mighty Mite Controls began to manufacture bimetal thermostats for appliances in 1946. Thermtrol Corporation of North Canton, Ohio, purchased Mighty Mite in 1996. The patent mentioned on the slide rule may refer to Norman F. Dewar's 1946 application, which was assigned to the Graphic Calculator Company of Chicago (see 2000.3029.13). The patent for the thermal control is not known.
References: Advertisement, Multi-Slide Instrument Corp., <i>Popular Science</i> 147, no. 3 (October 1945): 294; <i>Professional Engineer</i> (1948): 64; Mechanical Industries Production Company, "Mighty Mite" (U.S. Trademark 71,617,720 issued March 24, 1953); Norman F. Dewar, "Slide Rule" (U.S. Patent 2,530,047 issued November 14, 1950).