of medicine, made use of his researches, and even republished some of his works without giving credit to Israeli for them. He was thus an important contributor to the development of medical science, but as a philosopher he did not do much. His work on "Definitions and Descriptions" shows scarcely the rudiments of philosophical knowledge. His lectures must have made a greater impression than his writings. He instructed two disciples, a Mahometan, Abu-Jafar Ibn-Aljezzar, who is recognized as an authority in medicine; and a Jew, Dunash ben Tamim, who continued the work of his master. Isaac Israeli lived to be more than one hundred years old, and survived his patron the Caliph Ubaid-Allah, whose death was hastened by his disregard of the advice of his Jewish physician. When Isaac Israeli died, about 940, his example had made a place in the Rabbanite studies for the scientific method that shaped the activity of succeeding generations. Whilst the Rabbanites were making the first attempt to follow a scientific method, the Karaites were disporting on the broad beaten path of Mutazilist philosophy. Although young in years, Karaism showed signs of advanced old age. All its strength was given to Biblical exposition, combined with philology, but even here it made no progress. In the central community of the Karaites, in Jerusalem, it assumed an ascetic character. Sixty Karaites agreed to leave their homes, their property and their families, live together, abstain from wine and meat, go poorly clad, and spend their time in fasting and prayer. They adopted this mode of living, as they said, with the object of promoting Israel's redemption. They called themselves the mourners of Zion and Jerusalem (Abele Zion), and every one of them added to his signature the term "The Mourner." It was through them that the religious life of the Karaites took on an ascetic tinge. They not only observed the Levitical laws of purity in the strictest manner, but they shunned intercourse with non-Jews. They would not buy bread from them, nor eat anything they had touched. The more rigorous the Karaites became, the more they looked upon the Rabbanites as reprobates and sinners, whose houses it was a sin to visit. The Karaites gradually spread from Babylonia and Judæa to Egypt on the one side and to Syria on the other, and northwards as far as the Crimea. There were large Karaite communities in Alexandria and Cairo, and also in the Crimea, on the Bosporus (Kertch), Sulchat and Kaffa (Theodosia). The zeal of individuals contributed much to spread Karaism. By means of disputations, sermons, and letters, they endeavored to secure followers amongst the Rabbanites. Like every other essentially weak sect the Karaites relied upon propaganda, as though numbers could atone for lack of real strength. There was amongst them a certain proselytizer, a cunning man, Eldad by name, who related wonderful adventures, and made a great stir in his day. Eldad's romantic travels throw a lurid