Bonfils, Immanuel ben Jacob

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BONFILS, IMMANUEL BEN JACOB

BONFILS, IMMANUEL BEN JACOB (14th century), of Tarascon (in Provence, France), mathematician and astronomer. He is chiefly known for his astronomical tables called Shesh-Kenafayim ("Six Wings" – cf. Isa. 6:2) which were written in Hebrew about 1365 and which were subsequently translated into both Latin (in 1406) and Byzantine Greek (c. 1435). These tables are preserved in many manuscript copies and the Hebrew version was published (Zhitomir, 1872). The author is often referred to in Hebrew as Ba'al ha-Kenafayim ("Master of Wings"). Each "wing" contains a number of astronomical tables concerning the movements of the sun and the moon for determining the times and magnitudes of solar and lunar eclipses as well as the day of the new moon. The tables themselves are largely based on the tables of the ninth-century Arab astronomer al-Battānī (known in Latin as Albategnius), as the author acknowledges in the preface. But they are presented according to the Jewish calendar and adapted to the longitude and latitude of Tarascon. These tables were consulted by European scholars as late as the seventeenth century. Bonfils is also known to have made astronomical observations, and his discussion of decimal fractions is among the earliest presentations of the subject.

bibliography:

Renan, Ecrivains, 692–99; je, 3 (1902), 306; M. Steinschneider, Mathematik bei den Juden (1964), 155ff.; The Hexapterygon [Six Wings] of Michael Chrysokokhes, ed. and tr. by P.C. Solon (unpublished thesis, Brown University, 1968); Gandz, in: Isis, 25 (1936), 16–45; Saidan, ibid., 57 (1966), 475–89; Petri Gassendi Opera Omnia, 5 (1964), 313.

[Bernard R. Goldstein]

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