of a key to the Jewish calendar. He found that the order of the years and festivals repeat themselves after a cycle of two hundred and forty-seven years, and that the forms of the years can be arranged in fourteen tables. This key bears his name; it is known as the cycle of Rabbi Nachshon. The third author of this time was Rabbi Simon of Cairo, or Misr, in Egypt, who, although not an official of the Babylonian school, was in a position to compose a code embracing all religious and ceremonial laws (about 900). This work, directed against the Karaites, bears the title "The Great Halachas" (Halachoth gedoloth), and forms a supplement to Jehudaï's work of a similar nature. The history of the post-exilic period till the destruction of the Temple was also written at this time; its author is unknown. It is written in Arabic, and is based partly upon Josephus, partly upon the Apocrypha, and partly upon tradition. It is called "The History of the Maccabees" or "Joseph ben Gorion." In later times an Italian translated it into Hebrew, and in its expanded form it bears the title Josippon (Pseudo-Josephus), and this work served to awaken in the Jews, who were ignorant of the original sources of Jewish history, interest in their glorious past. The literary activity of the official heads of Judaism in the two schools confined itself to Talmudical subjects. They had no idea of scientific research, would have condemned it, in fact, as a leaning to Karaite doctrine. Outside of the Gaonate, in Egypt and Kairuan, there was a scientific movement among the Rabbanites, weak at first, but increasing in strength every year. The Rabbanite thinkers must have felt that so long as Talmudic Judaism maintained a hostile position towards science, it could not hold its own against the Karaites. Biblical exegesis and Hebrew philology formed the special studies of the Karaites, and in connection with these was developed a kind of philosophy, though only as an auxiliary science. It was in this branch that, towards the end of the ninth century, several Rabbanites emulated them. Famous amongst these was Isaac ben Suleiman Israeli (845-940). He was a physician, philosopher, and Hebrew philologist. He was an Egyptian, and was called to Kairuan about the year 904 as physician to the last Aghlabite prince, Ziadeth-Allah. When the founder of the Fatimide dynasty, Ubaid-Allah, the Messianic Imam (Al-Mahdi, who is said to have been the son of a Jewess), conquered the Aghlabite prince, and founded a great kingdom in Africa (909-933), Isaac Israeli entered his service, and enjoyed his full favor. Israeli had a great reputation as a physician, and had many pupils. At the request of the Caliph Ubaid-Allah, he wrote eight medical works, the best of which is said to be that on fever. His medical writings were translated into Hebrew, Latin, and part of them into Spanish, and were zealously studied by physicians. A Christian physician, the founder of the Salerno school