Over the 19th and much of the 20th centuries the slide rule was the primary instrument for calculation used by many people engaged in the trades and in engineering. Although originally invented in the 17th century, and widely used for gauging (or estimating the quantities of certain products such as alcoholic spirits) it took until around 1850 for the slide rule to become generally popular with those for whom mathematics was a daily task. This was largely brought about through the increase in accuracy made possible by the development of the dividing engine and Amédée Mannheim's 1850 standardisation of the arrangement of scales utilised. His scales were the "C" and "D" scales, ranging from 1 (the index) to 10 and used for multiplication and division, and the "A" and "B" scales, ranging from 1 (the index) to 100 and used for squares and square roots.

New arrangements of scales appeared in the 20th century with the Rietz arrangement in 1902 and the Darmstadt arrangement in 1934. The Rietz scales added a log "L" scale, a "CI" or C inverted scale which was useful for calculations involving the reciprocal of a number, and the trigonometric scales: sine "S", tangent "T" and "ST" for the small angles were the sine and tangent are the same, to the front face of the stock. The Darmstadt arrangement added a series of Log-Log scales.

The Hemmi Company was considered one of the best slide rules manufacturers in the world and they exported millions of versions of their many types of slide rules to numerous countries (especially the US) between about 1920 and 1976. This object is an early example of the type of slide rule produced by the J. Hemmi company, probably between 1917 and 1929. It uses the basic Mannheim arrangement of scales and was manufactured under Japanese patent no. 22129, which was granted to Hemmi Co in 1912 for the use of bamboo with celluloid facings. It also uses a new type of cursor patented by Hemmi (patent no. 58115) which can be set to indicate the number of decimal places shifted to the right or the left during the calculation. The "Sun" logo was adopted in 1917. [see History tab].

Made by the Hemmi Bamboo Slide Rule Manufacturing Co Ltd, Japan, 1917-1929

Japan began to open up to the US [1] and Europe prior to and during the Meiji restoration of the late 19th century. [2] The new imperial administration sent out many diplomats and bureaucrats to investigate the technologies of the United States and Europe for application to the industrialisation of Japan. According to William Lise [3], an example of a Mannheim slide rule was brought back to Japan after Dr. Ritaro Hirota and Toragoro Kondo, who was the Head of the Construction Section of the Internal Affairs Ministry, visited Europe. This example appears to have been provided to the company Nakamura Surveying Instruments where Jiro Hemmi worked in dividing scales for use on surveying and other instruments. He began researching the manufacture of slide rules for Nakamura in 1895 and sometime between 1896 and 1899, established his own company, Hemmi Jirou & Co., to manufacture them. [4]

He also began researching the use of materials indigenous to Asia for making slide rules settling on bamboo, and in 1912 Hemmi received a Japanese patent for a slide rule with a stock made from bamboo with scale faces of celluloid laminated to the bamboo stock. The patent was reinforced by a British patent of 1917 and an American patent in 1920. The type of bamboo [phyllostachys pubescens] comes from Japan's southernmost island Kyushu and has a large diameter making it more suitable for the flat body of the slide rule. It has a light yellow colour and is easy to mill into strips with the tongue and groove arrangement that allows the slider to slip smoothly in the channel provided by the stocks. [5]

In 1917, the company adopted the "Sun" trademark as a reflection of Japan's rising sun symbol which "was thought to bode well for the future of the firm's business" [6]. The Hemmi Co continued to improve their slide rules, developing in 1923 a new machine for dividing the scales. This brought greater accuracy to the mass production of their slide rules and they began exporting to the US [Post], Canada [Hughes-Owens] and Europe. They also developed new scales, patenting the Pythagorean scales (P and Q) for ?(a2 + b2) in 1925. In 1928 the company became Hemmi Seisakusho & Co and their rules are now marked "SUN Hemmi". By the mid-1930s the company was producing 40,000 slide rules per year. [7]

Sales to the US dropped off with WWII and slide rules were no longer marked "Made in Japan". After the war, the company was renamed Hemmi Keisanjaku [Hemmi Slide Rule Company] and between 1945 and 1951, their export slide rules were marked "Made in Occupied Japan". In the mid 1950s representatives from various companies selling Hemmi slide rules visited the Hemmi company in Japan to develop further export arrangements. These visitors included a Mr. A Richardson from E. Esdaile and Sons P/L of Sydney in 19565 and Mrs E.A. Esdaile in 1958. [8]

Jirou Hemmi died in 1953 having retired from the company in 1941. In the 1950's Hemmi Keisanjaku began manufacturing slide rules out of plastic. It is estimated that before the stopped producing in 1976 they manufactured 15 million slide rules. [9]

Refs:
[1] With the arrival of Commodore Perry's ships in Japan, c 1853
[2] When imperial rule was restored in Japan after the defeat of the Tokugawa Shogunate, c.1867-1869
[3] William Lise, "History of Hemmi Slide Rule and Misc Japanese Slide Rule dates." [http://www.sliderulemuseum.com/SR_Dates.htm] and apparently drawn from a large general catalogue published by Hemmi Slide Rule in 1960.
[4] http://www.sliderulemuseum.com/SR_Terms.htm#H
[5] http://www.sliderulemuseum.com/SR_Terms.htm#B
[6] William Lise, op cit [3]
[7] Peter Hopp, Slide Rules, their History, Models and Makers, Mendham, New Jersey: Astragal Press, 1999.
[8] William Lise, op cit [3]
[9] http://www.sliderulemuseum.com/SR_Terms.htm#H

Slide rule, closed frame, celluloid facings nailed to bamboo, double-sided slide, reverse-C-shaped metal edged glass cursor with digit counter pointer, 10inch ruler on upper bevelled edge and 27cm ruler on lower squared edge of stock, extended ruler (in cms) in slide channel. Tables of useful constants on reverse.

In black cloth covered card case with flap having a press button closure engraved Hemmi Slide Rule. Flap is also gold stamped Patent Hemmi's Slide Rule.

Scales: Mannheim
Stock, upper: A
Slide: B, C
Slide reverse: S, L, T
Stock, lower: D

10inch

Made: 1917 - 1929

Manufacturer and modle number on cursor, embossed in, on top 'J. Hemmi SUN ', on bottom ' No. 58115 '. Patent numbers on slide rule stock, on bottom, printed in black ' J. Hemmi Sun Patent No. 22129. British Patent 107562, Brevette S.G.D.C. Made in Japan '. White paper label on reverse, handwriten in black pen ' Bromely 1985-6 '.

Model name on face of flap, in top center, printed in gold ' Patent / HEMMI'S / Slide Rule ', on press botton, engraved in ' Hemmi / Slide / Rule '. White paper label on top, handwriten in black ' Bromely 1985-6 '.

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1917 - 1929