Xuē Fèngzuò 薛鳳祚
Style name Yífǔ 儀甫. Native of Yìdū 益都 (a shǔyì — subordinate county — of Qīngzhōu prefecture, Shāndōng); often referred to in late-imperial sources as “[Xuē] of Qīngzhōu” by reference to the prefectural seat. Born Chóngzhēn 1 (1628); died Kāngxī 19 (1680). Almost exactly the contemporary of 王錫闡 Wáng Xīchǎn (1628–1682), with whom he was conventionally paired as the leading independent astronomical-mathematical scholar of the early Qīng — though always with Wáng Xīchǎn ranked above by Méi Wéndǐng’s celebrated judgment.
Xuē Fèngzuò’s intellectual trajectory had two distinct phases. Pre-1652 (the “old method” phase): he studied under Wèi Wénkuí 魏文魁 (the late-Míng-style traditionalist astronomer who had opposed Xú Guāngqǐ’s Chóngzhēn lìshū reform in the 1630s), absorbing the conservative Chinese-traditional astronomical methodology that combined elements of the Yuán Shòushí lì with the elaborated late-Míng conservative critique. Post-1652 (the “new method” phase): encountering the Polish Jesuit Jan Mikołaj Smogulecki (穆尼閣) at Nánjīng around 1652–1655, Xuē Fèngzuò underwent a methodological conversion. He completely abandoned the Wèi Wénkuí tradition and devoted himself to absorbing the European mathematical-astronomical material Smogulecki was teaching — including, crucially, the European invention of logarithms (duìshù 對數).
Xuē’s principal works thereafter:
(1) The Tiānbù zhēnyuán 天步真原 (KR3f0024): a 1-juan exposition of the Smogulecki-transmitted European astronomy, particularly eclipse-prediction methodology. The work is presented as Xuē’s translation of Smogulecki’s oral exposition and survives in the Sìkù.
(2) The Tiānxué huìtōng 天學會通 (KR3f0025): Xuē’s own synthesis of Smogulecki’s material with Chinese-traditional astronomy, in 1 juàn, completed Kāngxī 3 (1664). This work introduces logarithm tables into Chinese practice and demonstrates their use in astronomical computation.
(3) The Lǜlǚ zhèng 律呂正 and other works on music and arithmetic.
(4) The LiǎngHé qīnghuì 兩河清彙 (mentioned in the Sìkù 提要 as a separately-catalogued work) — a compilation on the geography and water-management of the Yellow-and-Yangzi river systems.
Méi Wéndǐng’s celebrated judgment placing Wáng Xīchǎn above Xuē Fèngzuò (“近代厯學以吴江為最，識解在青州之上” — “Of recent calendrical learning, Wújiāng [Wáng Xīchǎn] is the best; his discernment exceeds [Xuē Fèngzuò] of Qīngzhōu”) established the conventional ranking of the two early-Qīng independent astronomers. Méi’s specific reservations about Xuē’s work centered on the differences between Xuē’s Smogulecki-transmitted material and the Schall-Rho-transmitted material in the Xīnfǎ suànshū — Xuē had absorbed an alternative European source-tradition whose details did not always match the Xīnfǎ suànshū synthesis. Méi viewed this as a weakness; modern scholarship would view it as documentation of the diversity of mid-17th-century European astronomical sources reaching China.
Xuē Fèngzuò’s transmission of logarithms — through the Tiānxué huìtōng of 1664 — is one of the foundational moments of Chinese mathematical history. The Kāngxī-period imperial mathematical academy at the Méngyǎng zhāi would absorb and develop the logarithm method, integrating it into the Shùlǐ jīngyùn (1720s) and through it into the standard Chinese mathematical curriculum.