The Jewish community in Babylonia (Persia), which had the appearance of a state, had a peculiar constitution. The Exilarch and the Gaon were of equal rank. The Exilarch's office was political. He represented Babylonian-Persian Judaism under the Caliphs. He collected the taxes from the various communities, and paid them into the treasury. The Exilarchs, both in bearing and mode of life, were princes. They drove about in a state carriage; they had outriders and a kind of body-guard, and received princely homage. The religious unity of Judaism, on the other hand, was embodied in the Gaonate of Sora and Pumbeditha. The Geonim expounded the Talmud, with a view to a practical application of its provisions; they made new laws and regulations; administered them, and meted out punishment to those that transgressed them. The Exilarch shared the judicial power with the Gaon of Sora and the head of the college of Pumbeditha. The Exilarch had the right of nomination to offices, though not without the acquiescence of the college. The head of the college of Sora, however, was alone privileged to be styled "Gaon"; the head of the college of Pumbeditha did not bear the title officially. The Gaon of Sora together with his college, as a rule, was paid greater deference than his colleague of Pumbeditha, partly out of respect to the memory of its great founders, Rab and Ashi, partly on account of its proximity to Kufa, the capital of Irak and of the kingdom of Islam in the East. On festive occasions, the head of the college of Sora sat at the right side of the Exilarch. He obtained two-thirds of certain revenues for his school, and performed the duties of the Exilarch when the office was vacant. For a long time, too, only a member of the school of Sora was elected president of the school of Pumbeditha, this school not being permitted to elect one from its own ranks. Now that the Exilarch everywhere met with the respect due a prince, he was installed with a degree of ceremony and pomp. Although the office was hereditary in the house of Bostanaï, the acquiescence of both colleges was required for the nomination of a new Exilarch, and thus there came to be a fixed installation service. The officials of both the colleges, together with their fellow-collegians, and the most respected men in the land, betook themselves to the residence of the designated Exilarch. In a large open place, which was lavishly adorned, seats were erected for him and the presidents of the two schools. The Gaon of Sora delivered an address to the future Exilarch, in which he was reminded of the duties of his high office, and was warned against haughty conduct toward his brethren. The installation always took place in the synagogue, and on a Thursday. Both officials put their hands upon the head of the nominee, and declared amidst the clang of trumpets, "Long live our lord, the Prince of the Exile."