Ryoichi Yazu

In his short life, the Japanese inventor Ryoichi Yazu (1878-1908) was mainly interested in the mechanics of flight and at the end of the 1890s designed one of the first airplanes in the world, but remained best known for his invention of Japan’s first mechanical calculator (in fact, there is another Japanese inventor, who patented a mechanical calculator several years before Yazu—Shohé Tanaka, but his device remained only on paper).

Yazu left his home village at the age of 16 and went to Osaka to pursue his interest in flight, studying mathematics and engineering at a private school. At the age of 22, he returned home and began work on a thesis on the mechanics of flight. It is believed, that at the same time he got the idea for the calculating machine while helping with his father’s clerical work, and conducted research on calculating machines. Two years later he brought the thesis Principles of Flight and a model of his biquinary mechanical calculator on a visit to the novelist and army physician Mori Ogai (1862-1922) in Kokura, Kyushu. Interestingly, Mori Ogai studied together with Shohé Tanaka in the late 1880s in Germany (in 1908 Tanaka married a relative of Ogai), so we may suppose that Ogai was informed about Tanaka’s works in the area of adding machines and shared his knowledge with Yazu. Anyway, Ogai was very impressed by Yazu and wrote recommendations that led to a special research position at the Tokyo Imperial College of Engineering, where Yazu worked on the design of a propeller-driven airplane.

In March 1902, Yazu applied for a patent on his Jido Soroban (automatic abacus) and completed a prototype, made entirely of metal. The patent (see the nearby patent drawing) was granted in January 1903 (pat. No. 6010), and in March a shop was established in Tokyo, where the first calculator in Japan (known as Patent Yazu Arithmometer) was manufactured. In 1910 Yazu (posthumously) got another patent (pat. No. 18119) for an improved version of his calculator. The latter mechanism could shift numbers automatically during multiplication and division and to stop calculations automatically when finished. Interestingly, in 1912 the same device was patented in the USA by one Doichi Yadu (an accidental resemblance of names, or misspelled name of the inventor?!) of Sudamura, Fukuoka, Japan (see US patent 1029655).

The Yazu Arithmometer was a manual desktop gear type calculator with pin-wheel mechanism, which performed decimal arithmetical operations (it may be used to add, subtract, multiply and divide), using a single cylinder and 22 gears with biquinary number setting (a mixed base-2 and base-5 number system, familiar to the users of Japanese abacus soroban). It was capable of arithmetic calculations up to 16 digits, as the carry and end of the calculation were determined automatically. A revolution counter is also available.

The price of Patent Yazu Arithmometer was rather high (¥250) for the time (more than ten times the monthly salary of a lower-level government official), but nevertheless, more than machines 200 were sold, mainly to government agencies, including the Ministry of War, the Home Ministry, the Statistics Bureau, and agricultural experimental stations, but also to big companies such as Nippon Railway. The profits from the sales Yazu invested into his airplane research.

In the introductory pamphlet Yazu stated:
Today, calculators are everywhere in the cities of Europe and America… However, these calculators were invented by foreigners with no knowledge of our abacus, and although they are superior to the abacus in many ways, there are more than a few points where they are still inconvenient. This new automatic abacus can meet the needs of those who wish to combine the abacus and the calculator to realize a fast calculation machine, and is being purchased by many customers who previously used foreign-made calculators…

Biography of Ryoichi Yazu

Ryoichi Yazu was born on 30 June 1878, in the village of Iwaya, located some 10 km SW of Buzen, a town located in Fukuoka Prefecture, Japan, in the family of a village mayor.

As a boy, Ryoichi attended primary and middle school in his home village and the city of Buzen. At the age of 16, he left middle school and moved to Osaka to pursue his interest in flight, studying mathematics and engineering at a private school. There he learned the basic subjects and did research on flight and desktop calculators. With a model of his mechanical calculating machine (automatic abacus), which took three years of hard work to complete, and a paper on “Principles of Flight”, which summarized the results of his years of research, he met a man named Takahashi (probably Takahashi Shigeru, who studied medicine in Europe in the 1880s and was a friend of Mori Ogai), who was the editor in chief of the Fukuoka Nichinichi Shimbun newspaper. Takahashi was greatly impressed by Yazu’s abilities and wrote a letter of introduction to his friend Mori Rintaro (Mori Ogai), who was a medical officer in the Ogura 12th Medical Corps. Ogai described his meeting with Yazu in the entry for 22 February 1901 in his Kokura Nikki (Kokura Diary), and he also was deeply impressed by Yazu’s character and research, and worked as a go-between with the professors of Tokyo Imperial University, recommending Yazu to get a special research position at the Tokyo Imperial College of Engineering.

In his short life, Yazu proved himself as a very clever inventor in many fields ranging from the dictionary to airplanes and mechanical calculating machines.

Ryoichi Yazu died from pleurisy only 30 years old, on 16 October 1908, in Tokyo. The Japanese proverb Pegasus flies in the sky is what Mori Ogai wrote in his diary concerning Yazu’s premature death.

Later his father tried to improve the machine and resume the business but had no success. Nobody remembered his calculating machine, but after that several companies have begun to sell similar calculating machines. One machine of Yazu was found in 1977 by Uchiyama (IBM) in the house of his sister’s descendants.