Immanuel Bonfils

Immanuel ben Jacob Bonfils (c. 1300 – 1377) was a French-Jewish mathematician and astronomer in medieval times who flourished from 1340 to 1377, a rabbi who was a pioneer of exponential calculus and is credited with inventing the system of decimal fractions.[1] He taught astronomy and mathematics in Orange and later lived in Tarascon, both towns in the Holy Roman Empire that are now part of modern-day France .[2] Bonfils studied the works of Gersonides (Levi ben Gershom), the father of modern trigonometry[citation needed], and Al-Battani and even taught at the academy founded by Gersonides in Orange.[3][4] Bonfils preceded any attempt at a European decimal system by 150 years,[5] publishing the treatise Method of Division by Rabbi Immanuel and Other Topics (Hebrew: דרך חילוק) on the general theory of decimal fractions around 1350. This was a forerunner to Simon Stevin, the first to widely distribute publications on this topic, and employed decimal notation for integers, fractions, and both positive and negative exponents.[2][6][7]

While living in Tarascon in 1365, Bonfils published the work for which he would become best known, Sepher Shesh Kenaphayim (Book of Six Wings) (Hebrew: שש כנפים), a manuscript on eclipses that featured astronomical tables predicting future solar and lunar positions (divided into six parts).[1][8] The book included data for every important date on the Jewish calendar and even correction factors necessary for those who lived as far away as Constantinople.[6] Breaking the tables into six parts was an allusion to the six wings of the seraphim as mentioned in the Bible in Isaiah 6:2, earning Bonfils the nickname master of the wings.[1]

For 300 years, Bonfils' calculations which were extensively used by sailors and explorers well into the 17th century.[5] The book was translated from Hebrew into Latin in 1406 by Johannes Lucae e Camerino and into Greek in 1435 by Michael Chrysokokkes. The book inspired Chemist George Sarton to publish his own version of Six Wings nearly 600 years later.[1] Bonfils translated a number of books from Latin to Hebrew. He also wrote a treatise on the relationship between the diameter and circumference of a circle and methods of calculating square roots.[2]

## Works

* Bonfils, Immanuel (1365), The Wings of Eagles, Hebrew: שש כנפים, in six books. Other name: Book of Six Wings, Hebrew: שש כנפים. The main astronomical work of Bonfils.
* Bonfils, Immanuel (c. 1350), The Invention of the Decimal Fractions and the Application of the Exponential Calculus by Immanuel Bonfils of Tarascon[9]
* Bonfils, Immanuel (c. 1350), Method of Division by Rabbi Immanuel and Other Topics, Hebrew: דרך חילוק, a course of decimal arithmetics, including decimal fractions.

## References

1. ↑ 1.0 1.1 1.2 1.3 Vucinich, Alexander (1963). Science in Russian Culture, A History to 1860. Stanford, CA: Stanford University Press
2. ↑ 2.0 2.1 2.2 "Bonfils, Emmanuel Ben Jacob". JewishEncyclopedia.com. http://www.jewishencyclopedia.com/articles/3530-bonfils-immanuel-ben-jacob. Retrieved 2015-02-20.
3. ↑ Dimont, Max I. (2004). Jews, God, and History. Signet Classics
4. ↑ Shatzmiller, Joseph (2013). Cultural Exchange; Jews, Christians, and Art in the Medieval Marketplace. Princeton, NJ: Princeton University Press
5. ↑ 5.0 5.1 Blech, Benjamin (2004). The Complete Idiot's Guide to Jewish History and Culture. Indianapolis, IN: Alpha Books
6. ↑ 6.0 6.1 Suzuki, Jeff (2009). Mathematics in Historical Context. Washington, DC: The Mathematical Association of America
7. ↑ Ben-Menahem, Ari (2009). Historical Encyclopedia of Natural and Mathematical Sciences. Springer Verlag
8. ↑ Solon, Peter (1971). "The Six Wings of Immanuel Bonfils and Michael Chrysokokkes". Centaurus 15: 1–20. doi:10.1111/j.1600-0498.1971.tb00147.x. Bibcode: 1971Cent...15....1S.
9. ↑ Ragep, F. Jamil and Sally P. Ragep (1996). Tradition, Transmission, Transformation. Netherlands: Brill Academic Pub

* Gandz, S.: "The invention of the decimal fractions and the application of the exponential calculus by Immanuel Bonfils of Tarascon (c. 1350)", Isis 25 (1936), 16–45.
* P. Solon: The Six Wings of J. Bonfils and Michael Chrysokokkes, in: Centaurus, 15 (1970) 1–20

## External links

* BONFILS, IMMANUEL BEN JACOB in Jewish Encyclopedia.
* Six Wings.

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