IV. Such, however, was not the case with the Imamee, the most dangerous enemies of the house of Abbas. Agreeing with the Ghoollat in the doctrine of an _invisible_ imam, they maintained that there had been a series of _visible_ imams antecedent to him, who had vanished. One branch of this sect (thence called the Seveners--_Sebiïn_) closed the series with Ismaïl, the grandson of Mohammed Bakir, the _seventh_ imam, reckoning Ali himself the first. These were also called Ismaïlites, from Ismaïl. The other branch, called Imamites, continued the series from Ismaïl, through his brother Moosa Casim, down to Askeree, the twelfth imam. These were hence called the Twelvers (_Esnaashree_). They believed that the imam Askeree had vanished in a cavern at Hilla, on the banks of the Euphrates, where he would remain invisible till the end of the world, when he would again appear under the name of the Guide (_Mehdee_) to lead mankind into the truth. The Imamee, wherever they might stop in the series of the visible imams, saw that, for their political purposes, it was necessary to acknowledge a kind of _locum tenentes_ imams; but, while the Zeidites, who agreed with them in this point, required in these princes the royal virtues of valour, generosity, justice, knowledge, the Imamee declared themselves satisfied if they possessed the saintly ones of the practice of prayer, fasting, and alms-giving. Hence artful and ambitious men could set up any puppet who was said to be descended from the last of the visible imams, and aspire to govern the Mohammedan world in his name. The Twelvers were very near obtaining possession of the khalifat in the time of the first Abbassides; for the celebrated Haroon Er-Rasheed's son, Al-Mamoon, the eighth khalif of that house, moved either by the strength or preponderance which the Sheäh party had arrived at, or, as the eastern historians tell us, yielding to the suggestions of his vizir, who was devoted to that sect, named Ali Riza, the eighth imam, to be his successor on the throne. He even laid aside the black habiliments peculiar to his family, and wore green, the colour of Ali and the Prophet. But the family of Abbas, which now numbered 30,000 persons, refused their assent to this renunciation of the rights of their line. They rose in arms, and proclaimed as khalif Al-Mamoon's uncle Ibrahim. The obnoxious vizir perished, and the opportune death of Ali Riza (by poison, as was said) relieved the son of Haroon Er-Rasheed from embarrassment. Ali Riza was interred at Meshed, in the province of Khorasan; and his tomb is, to the present day, a place of pilgrimage for devout Persians[14]. [Footnote 14: See Frazer's Khorasan.] The Ismaïlites were more successful in their attempts at obtaining temporal power; and, as we shall presently see, a considerable portion of their dominions was wrested from the house of Abbas.