Momokawa Jibei - Momokawa Jibei

Japanese: 百川治兵衛 - ももかわ・じべえ

Year of death: Kan'ei 15? (1638)
Year of birth: Tensho 8? (1580)
A Japanese mathematician of the early Edo period. He moved from Etchu Province (Toyama Prefecture) to Sado Shibamachi around 1630 (Kan'ei 7), and stayed at the home of Izumiya Tabei, where he taught Japanese mathematician. He had many students, and established the Hyakukawa school. He was imprisoned on suspicion of being a Christian, but was pardoned after his student testified. In Tahara Yoshiaki's Shinkan Sanpo Ki (1652), he is listed alongside Yoshida Mitsuyoshi as a teacher of contemporary mathematics. Only the second volume of his book Shokanbunmono (1622) remains. There are other manuscripts whose dates and titles are unknown. His mathematics was for practical purposes, and the level was not high, but he used a different calculation method from other Japanese mathematicians, such as not using the eight-fold calculation method for division, and this calculation method, called Kamei-san, continued until the Meiji period.

(Kenichi Sato)

Source: Asahi Japanese Historical Biography: Asahi Shimbun Publications Inc. About Asahi Japanese Historical Biography

Japanese:

没年：寛永15?(1638)
生年：天正8?(1580)
江戸前期の和算家。越中国(富山県)から寛永7(1630)年ごろ佐渡柴町に渡り,泉屋多兵衛の家に寄宿して和算を教授する。弟子が多く,百川流を成した。キリシタンの類族の疑いで入牢したが,弟子が証人となり許された。田原嘉明の『新刊算法起』(1652)には,当代算法の師として吉田光由と並び記されている。著書『諸勘分物』(1622)は第2巻のみ現存。他に成立年・稿名不明の稿本が存在する。その数学は実用を目的とするもので,レベルは高くはないが,割り算の計算に八算を使わないなど他の和算家たちとは違う計算法を使っており,亀井算と呼ばれるこの計算法は明治時代まで存続した。

(佐藤健一)

出典　朝日日本歴史人物事典：（株）朝日新聞出版朝日日本歴史人物事典について　情報

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