Asada Goryu

A mid-Edo period astronomy and calendar scholar. Born as the fourth son of Ayabe Yasumasa (Keisai), a Confucian scholar from Kitsuki, Bungo Province (Oita Prefecture). His given name was Yasuaki and his pen name was Goryu. He called himself Shoan (Shoan). He loved astronomy from an early age and studied it on his own. He also studied medicine on the side, and in 1767 (Meiwa 4) became the court physician of the feudal lord. However, he was unable to devote himself to astronomy and calendar studies, and requested to resign three times, but his request was not granted. In 1772 (An'ei 1), he escaped to Osaka, changed his surname to Asada, and devoted himself to studying calendars while working as a doctor. At the beginning of the Tenmei era (1781-1789), he settled in Osaka Honmachi 4-chome, where he educated his children under the name Senjikan. He invented and improved his own measuring instruments, engaged in observations day and night, and created the family calendar "Jichuho." In 1786 (Tenmei 6), a solar eclipse on the first day of the New Year was more accurately predicted using "Jichuho" than the official calendar, further increasing Goryu's fame. In 1795 (Kansei 7), the shogunate discussed calendar reform and tried to appoint Goryu, but he declined, instead recommending his disciples Takahashi Yoshitoki and Hazama Shigetomi. From around the beginning of 1798, he gradually succumbed to old age, and passed away on May 22, the following year (Kansei 11). He was 66 years old. He was buried at Joshun-ji Temple (Yuhigaoka, Tennoji Ward, Osaka City). Among his disciples were many famous scholars, including Takahashi, Hazama, Nishimura Tachu (1767-1835), and Adachi Shintō. Although no writings by Gōryū himself remain, his achievements can be known from the writings of his students. His most famous works are Jikkenrokusuihoho (Records of Experiments in Tui-Hō-Hō) and Shōchōho (Shochō-Hō), which were the basis for Jichun-Hō. His other works include Koshigenronkai (Explanation of the Arc and String of the Arrows), Gekkei moite nisshoku osuho (The Method of Pushing the Sun in the Moonlight), and Goseikyōchi no kiho (The Strange Method of Distancing the Five Stars). Gōryū had no children, and adopted Naoshi (Ryūtatsu, 1771-1827), the third son of his elder brother Yasutane (1720-1782). Nao had an excellent skill at polishing telescope lenses.

[Toshio Watanabe]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

江戸中期の天文暦学者。豊後(ぶんご)国（大分県）杵築(きつき)の儒者綾部安正(あやべやすまさ)（絅斎(けいさい)）の四男に生まれる。名は妥彰(やすあき)、字(あざな)は剛立。璋庵(しょうあん)（正庵）と号した。幼年より天文を好み、独学でその道に通じ、かたわら医術を修め、1767年（明和4）藩侯(はんこう)の侍医となった。しかし天文暦学に専心できないので、辞職を願うこと三たびに及んだが許されず、1772年（安永1）大坂へ脱藩、姓を麻田と改め、医を生業としながら暦学の研究に没頭した。天明年間（1781～1789）の初め、大坂本町四丁目に居を構え、先事館と称し子弟を教育した。自ら測器をくふう改良、日夜観測に従事し、家暦『時中法』を作製した。1786年（天明6）正月朔(ついたち)の日食が、官暦よりも『時中法』による推算のほうがよく適中し、剛立の名声をますますあげることになった。1795年（寛政7）幕府で改暦の議があり、剛立を起用しようとしたが応ぜず、弟子の高橋至時(たかはしよしとき)、間重富(はざましげとみ)を推挙した。1798年初めごろから老衰がしだいに加わり、翌寛政(かんせい)11年5月22日没した。66歳。浄春寺（大阪市天王寺区夕陽ヶ丘）に葬。門下からは高橋、間をはじめ西村太冲(にしむらたちゅう)（1767―1835）、足立信頭(あだちしんとう)ら著名の士が輩出した。剛立自身の書いたものは残っていないが、弟子たちの遺著によってその業績を知ることができる。『時中法』のもととなった『実験録推歩法(じっけんろくすいほほう)』『消長法』はことに有名で、そのほか『弧矢弦論解(こしげんろんかい)』『以月景推日食法(げっけいをもってにっしょくをおすほう)』『五星距地之奇法(ごせいきょちのきほう)』などがある。剛立には子がなく、長兄妥胤(やすたね)（1720―1782）の第3子直(なおし)（立達(りゅうたつ)。1771―1827）を養嗣子とした。直は望遠鏡の玉磨きで優れた腕をもっていた。

［渡辺敏夫］

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