Hemmi 153 Duplex Slide Rule

This bamboo rule is coated on both sides and its long outer edges with white celluloid. The rule is held together with metal posts. The glass indicator has a metal frame with bamboo and celluloid sides. The rule is marked in the lower right corner of the base front: "SUN" (between two drawings of the sun) (/) HEMMI (/) MADE IN JAPAN. The scales are 25 cm (9-7/8") long.

Hemmi designed this model for electrical engineers. The front of the base has L, K, A, D, T, and Gθ scales. The front of the slide has B, CI, and C scales. The back of the base has θ, Rθ, P, LL3, LL2, and LL1 scales, with Q, Q', and C scales on the back of the slide. The P, Q, and θ scales were used for trigonometric relationships in right triangles and for hyperbolic functions. They were developed in 1929 for Hemmi rules and credited to Sadatoshi Betsumiya and Jisuke Miyazaki. These scales were not used in the West, and even Hemmi did not use these scales on all of its models.

The rule is stored in a black rectangular cardboard box which is opened by removing the right end. This end is marked in silver: "SUN" (between two drawings of the sun (/) "HEMMI" BAMBOO (/) SLIDE RULE. There are two stars where the box joins together.

Hemmi, a Japanese firm, manufactured this model of slide rule between 1933 and 1967. From 1942 through 1946, Hemmi exports to the English-speaking world were severely limited. From 1946 to 1950, Hemmi rules were marked, MADE IN OCCUPIED JAPAN. After 1950, Hemmi rules were stamped with codes indicating the year and month of manufacture. Hence, it seems likely that this rule was made between 1933 and 1942.

Dr. Robert P. Multauf, who owned this rule, was an early director of the Museum of History of Science and Technology (later the National Museum of American History). Previously, he served in the U.S. Navy in postwar Japan.

References: Brian Borchers and Noël H. Cotter, "The Sun Hemmi System of Trigonometric and Hyperbolic Scales," Journal of the Oughtred Society 9, no. 2 (2000): 28–31; Hisashi Okura, "Hyperbolic Scale Rule" (U.S. Patent 2,079,464 issued May 4, 1937).

Currently not on view