A Gaon of Sora, Natronaï II, son of Hillaï (859-869), kept up a prolific correspondence with foreign communities in the Arabic language. His predecessors had employed a mixture of Hebrew and Chaldee as the medium of their communications. Natronaï II also corresponded with the Jewish-Spanish community at Lucena, whose members doubtless understood Arabic better than Hebrew. He opposed the Karaites as bitterly as the Geonim had done at the time of the rise of this sect, "because they despised the words of the sages of the Talmud, and set up for themselves an arbitrary Talmud of their own." His pupil and successor, Mar-Amram ben Sheshna (869-881), was the compiler of the liturgical order of prayers in use amongst European Jews. At the request of a Spanish community, preferred by their religious leader, Isaac ben Simeon, he collected everything that the Talmud and the custom of the schools had ratified concerning prayer and divine service (Siddur Rab Amram). The form which the prayers had assumed in the course of time was by him declared to have the force of fixed law. Every one that deviated from it was considered a heretic, and excluded from the community of Israel. The poetical compositions for the festivals were not yet in general use at this time, and Mar-Amram left the selection to the taste of the individual. During Mar-Amram's Gaonate, there were two successive heads of the schools in Pumbeditha, Rabba ben Ami (869-872), of whom nothing is known, and Mar-Zemach I. ben Paltoi (872-890), who heads the list of literary Geonim. Hitherto, the leaders of the school had occupied themselves with the exposition of the Talmud, with the regulation of the internal affairs of the communities, and with answering questions which were submitted to them. The one or the other of them, it is true, made a collection of Agadic sayings, but for literary activity, they either had no leisure, or opportunity, or inclination. But when the zeal for the study of the Talmud increased in the different communities in Egypt, Africa, Spain and France, and students of the Talmud spent their time in studying obscure and difficult passages, they often had to appeal to the schools for the solution of their difficulties. Their questions soon concerned only theoretical points, and the Geonim found it necessary to write treatises on certain portions of the Talmud, instead of simple and short answers. These books were used by students as Talmudical handbooks. The Gaon Zemach ben Paltoi, of Pumbeditha, arranged an alphabetical index of difficult words in the Talmud, under the title of "Aruch." In it he shows acquaintance with the Persian language. This dictionary forms the first contribution to the constantly growing department of Talmudical lexicography. The second literary Gaon was Nachshon ben Zadok of Sora (881-889), Zemach's contemporary. He, too, wrote a book giving explanations of difficult words in the Talmud. Nachshon made himself famous through his discovery