al of the state of the natural sciences in his day. Levi ben
Gerson's chief work became famous not among Jews alone. It was referred
to in words of praise by Pico della Mirandola, Reuchlin, Kepler, and
other Christian thinkers. He was the inventor of an astronomical
instrument, a description of which was translated into Latin at the
express command of Pope Clement VI., and carefully studied by Kepler.
Besides, Levi ben Gerson was the author of an arithmetical work. In
those days, in fact up to the seventeenth century, there was but a faint
dividing line between astronomy and mathematics, as between medicine and
natural history. John of Seville was a notable mathematician, the
compiler of a practical arithmetic, the first to make mention of decimal
fractions, which possibly may have been his invention, and in the Zohar,
the text-book of mediaeval Jewish mysticism, which appeared centuries
before Copernicus's time, the cause of the succession of day and night
is stated to be the earth's revolution on its axis.

In this great translation period scarcely a single branch of human
science escaped the mental avidity of Jews. They found worthy of
translation such essays as "Rules for the Shoeing and Care of Horses in
Royal Stables" and "The Art of Carving and Serving at Princely Boards."
Translations of works on scholasticism now took rank beside those from
Greek and Arabic philosophers, and to translations from the Arabic into
Hebrew were added translations from and into Latin, or even into the
vernacular idiom wherever literary forms had developed. The bold
assertion can be made good that not a single prominent work of ancient
science was left untranslated. On the other hand it is hard to speculate
what would have been the fate of these treasures of antiquity without
Jewish intermediation. Doubtless an important factor in the work was the
encouragement given Jewish scholars by enlightened rulers, such as
Emperor Frederick II., Charles and Robert of Anjou, Jayme I. of Aragon,
and Alfonso X. of Castile, and by popes, and private patrons of
learning. Mention has been made of Jewish contributions to the work of
the medical schools of Montpellier and Salerno. Under Jayme I. Christian
and Jewish savants of Barcelona worked together harmoniously to promote
the cause of civilization and culture in their native land. The first to
use the Catalan dialect for literary purposes was the Jew Yehuda ben
Astruc, and under Alfonso (X.) the Wis