Japanese Artillery Simplex Slide Rule

This ten-inch, one-sided Japanese brass linear slide rule has a (broken) glass indicator in a brass frame. On the top and bottom of the base and the top edge of one side of the slide are logarithmic scales that are identically marked and run from 10 to 10,000. These are labeled with a Japanese character that signifies kyori (distance). The lowest scale on this side of the slide is also logarithmic, but has 1/10 the values of the other 3 scales (except at the end, where it reads 800 instead of 1,000). This scale is for reading maps drawn to 1/6,400 scale.

In the center of this side of the slide is a scale that runs from .01 to 45. It is labeled on the left with 1/16, for map reading conversions, and is labeled on the right with the character for seisetsu (tangent). The reverse side of the slide has two logarithmically divided scales, divided in the same way. One runs from 1 up to 1,600. The other runs from 3,199 down to 1,600. Both of these scales are labeled with the Japanese character for seigen (sine). The upper edge of the instrument is beveled and has a scale of 28 centimeters, divided to millimeters. The flat front of the instrument is also divided in a scale of equal parts. This scale runs from 1 to 138.

The rule fits in a sturdy brown leather case with a buckle clasp. For a similar object, see "Japanese Gun Laying Slide Rule, 1920–1929" in the Powerhouse Museum, http://www.powerhousemuseum.com/collection/database/?irn=384855. According to the donor, Robert L. Klinger, this instrument was recovered from an artillery dump at Asahigawa in Hokkaido, Japan in October of 1945. Klinger went on to work for the Smithsonian Institution.

Currently not on view