and their accounts are freely confirmed by classic writers.[149] AGE OF THE ZEND-AVESTA. There is no data by which the age of the Zend-Avesta may be definitely determined. It is certain, however, that as the Zend is later than the Sanskṛit, so also the Avesta is later than the Vedas. It is also certain that this work is not the product of any one generation, as several centuries have intervened between the dates of the earliest and latest portions. The Gāthas which form the earliest portion of the work, are written in the old Āryan metre, but the favorite deities of the Hindūs are absent from the Gāthas, although they reappear in various forms in the later portions of the Avesta. It is evident that the migrating tribes, in consequence of their separation from their brethren in Īrān, soon became estranged from them, and their most favored gods fell slowly into neglect or disfavor. Considerable time must have been required for the accomplishment of so great a change. The oldest portions of the Avesta may therefore fall a few centuries this side of the hymns of the Ṛig-veda, while the oldest portions of the later Avesta may be placed at a period somewhat later than Darius.[150] We have a right to suppose that the hymns and other portions of the Avesta which were then in existence were gathered together and committed to writing about the time of Darius, and according to Dr. Oppert’s rendering of the Behistun inscription, the Persian king says: “By the grace of Ormazd, I have made the writings for others in the Āryan language, which was not done before; and the _text_ of the law and the _collection_.... I made and wrote, and I sent abroad; then the old writings among all countries I restored for _the sake_ of the people.”[151] Thus Darius claims to have restored the writings that had been destroyed or injured by the Magian revolt, but the word Avesta had not yet become a technical term;[152] it was the care of Darius that gave it a fixed and restricted sense. Five centuries afterwards, during the Sassanian period, these books were again gathered, either from scattered manuscripts or from oral traditions, and the later Avesta took a definite form in the hands of Adarbad under King Shapur II,[153] who, like another Diocletian, aimed at the extirpation of the Christian faith. Mazdeism having been shaken by the Manichean heresy, a definite form was thus given to the religious code of Īrān, and it was then promulgated as the sacred law of the nation. We may conclude, therefore, that even the most modern portions of the Avesta cannot belong to a later date than the fourth century of the Christian era.