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About Slide Rules
Slide Rule History
Slide Rule History
Slide rules have a long history that began in the 15th century. At that time, navigators were studying a way to calculate the position of stars but were struggling with various heavy mathematical operations. It is during that time of study and research that mathematicians and astronomers developed the logarithmic rule. John Napier, a Scottish aristocrat, is considered to be the first in 1614 to theorize and publish this rule. The logarithmic rule laid down the foundation of the slide rule history.
Edmund Gunter, an English astronomer, developed the Gunter's line, a logarithmic linear measurement scale. By adding a pair of compasses, it was used has the Gunter's scale to perform various navigation calculations.
The English mathematician William Oughtred improved the Gunter's scale by combining two scales that could be used by sliding them and without a pair of compasses.
Seth Partridge introduced a improved model of this rule, which soon won a great popularity.
(The Partridge's rule was made of three rules with one sliding in the middle. This was the first model of actual double side sliding rules.)
Coggeshall designed a slide rule based on his "Treatise of Measuring by a Two-foot Rule" and improved his model in 1682.
In late 17th century in England, even if the structure and configuration of slide rules, as well as the idea of inverted and sliding rules, were not thoroughly developed, Coggeshall refined the basic design of slide rules and continued to make improvement to set fundamental standards. He is considered as the spiritual father of the cursor system and it is said that his work even helped Newton to resolve cubic equations.
The Londoner John Warner improved the Coggeshall's rule by adding scale on both sides, which enabled multiplication, division and square calculations. It was late called the "English rule".
The physician Peter Mark Roget invented the log log rule, which was maybe the most significant advancement in slide rule design.
(Rules from England introduced to France were well regarded and their study and sale quickly spread throughout the country.)
Slide rules developed spectacularly in England until the beginning of the 19th century when they declined after the drastic changes made in the metrological system in 1824.
Birth in France of Amédée Mannheim, known as the father of modern slide rules.
During his assignment in Metz as an artillery lieutenant, Mannheim introduced a new slide rule design with an innovative scale configuration. Slide rules using this design were after know as Mannheim slide rules.
Kondo Toragoro from the Civil Engineering Department of Ministry of Home Affairs and Hirota Ritaro, a mechanical engineer, bought a Mannheim slide rule in France when returning back from a series of visits in America and Europe, and introduced this tool for the first time in Japan.
Jiro Hemmi, known as the best Japanese maker of precision tool at the time, started to study slide rule fabrication.
Slide rules dimensions tend to change and scales to lose their accuracy due to the great variations in meteorological conditions between seasons in Japan, particularly to high temperature and humidity in summer. To deal with these problems, Jiro Hemmi made a great number of prototypes with different woods, such as cherry, boxwood, quince and mahogany.
After many tries, Jiro Hemmi made his first slide rule using moso bamboo plywood, a species of bamboo found mainly in Japan.
Moso bamboo cultivated in Miyazaki or Kagoshima in Kyushu is 15 to 20 meter tall, has a circumference of 45 cm at people height, and a pulp of 1 cm thickness. In principle, only the outer hard bark is used to make thin square timber, but as the bark tends to bend to the inside, it is used as plywood by sticking to pieces together.
A patent was obtained for the method to make slide rule with no defect using treated moso bamboo.
A patent was obtained in England and France.
A patent was obtained in China, the United States and Canada.
Demand for slide rules increased sharply inside and outside Japan after the German slide rule production, the world standard, stopped as a result of the First World War. Large scale production was applied to Japanese bamboo slide rules using an original mechanical cut out method and they soon won a large renown.
Hisashi Okura was traveling around the world when he found a Japanese Hemmi's slide rule in a shop in London. He was proud as a Japanese and cherished the dream to further development this business.
A fire badly damaged the wooden house used by Jiro Hemmi as a shop and workshop in Sarugaku district in Tokyo.
Hisashi Okura visited Jiro Hemmi, who was in a difficult situation because of the fire, and offered to participate in the business management.
Using his ability to deal with foreign demand, he launched the "Taisho 15th year slide rule" under the Sun brand.
(This slide rule was made from a Mannheim rule to which a third rule with inverted CI scale and three unit logarithmic K scale was added. The products from the American company K&E were taken as model as they were being sold successfully worldwide at that time.)
Hemmi Workshop founded as a partnership company.
To get free from the influence of American slide rules, the innovative "square scale PQ" rule (Miyazaki Jisuke patented) was developed with a Japanese original design and the "double side slide rule (universal slide rule)" was sold under the Sun brand.
Hemmi Workshop became a limited company.
During the Second World War, Hemmi made slide rules used for battleship artillery calculations or to design the battleship Yamato.
The executive director Ono Tatsusaburo went to the United States and Canada to work with distributors in order to expand the business in these two countries which had the best demand at the time.
Slide rules became a compulsory tool from the second year in Japanese junior high schools.
Jiro Hemmi passed away.
The Japan Chamber of Commerce and Industry established the system of proficiency tests. Examinations were held twice a year and grades were classified from 6th to 1st.
The All Nippon Slide Rule Games were organized. Competitors were selected in each chamber of commerce and industry and competed in Tokyo for the title of "Best slide rule in Japan".
Hisashi Okura passed away.
At that time, 1 million slide rules were shipped annually.
The price of some of the Hemmi slide rules, the best quality on the market, amounted sometimes to one's wages. Also as they were precious articles, they were exported not by boat but by plane.
The English company Sumlock Comptometer developed the world's first electronic calculator ANITA.
Sony developed the desktop calculator MD-5.
Hemmi Slide Rule had 98% of the slide rule market share in Japan and 80% worldwide.
All Nippon Junior High School Slide Rule Games and Kanto Industrial High School Tournament were organized.
Scientific calculators popularized in Japan.
Ordinary slide rules production discontinued as the scientific calculators developed.
Hemmi Slide Rule sold well regarded products for more than 80 years and was successful in that market inside Japan and globally.
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