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 The Great Days of the Arabs 245 Photo : Lehjie: VIEWJ.OF CAIRO MOSQUES the two Semitic races worked together through the medium of Arabic. Long after the poHtical break up and enfeeblement of the Arabs, this iatellectual community of the Arab-speaking world endured. It was still producing very considerable results in the thirteenth century. So it was that the systematic accumulation and criticism of facts which was first begun by the Greeks, was resumed in this astonish- ing renascence of the Semitic world. The seed of Aristotle and the museum of Alexandria that had lain so long inactive and neglected, now germinated and began to grow towards fruition. Very great advances were made in mathematical, medical and physical science. The clumsy Roman numerals were ousted by the Arabic figures we use to this day and the zero sign was first employed. The very name algebra is Arabic. So is the word chemistry. The names of such stars as Algol, Aldebaran and Bootes preserve the traces of Arab conquests in the sky. Their philosophy was destined to reanimate