Sheikh Adi is a semi-mythical personage who may be described as the Yezidi Prophet. He is sometimes identified with Mar Adai (St. Thaddeus) the Apostle of the Christians; but there seems some historical evidence that he lived in the tenth century, and that he was originally a Magian who had fled from Aleppo when the Magian cult was suppressed. He was probably the author or compiler of the sacred books; and is said to have been the first who taught disciples. According to some traditions he is considered almost divine; and at the Last Day he will carry all the Yezidis to heaven in a tray on his head, and pass them through unquestioned. But according to another legend he was a mere mortal, who had in life bitter experience of the devilment of his peculiar deity. For while he was gone on pilgrimage to Mecca, _Melek Taüs_ personated him among his disciples; dwelling with them, instructing them, and at last ascending visibly to Heaven. Thus when poor Sheikh Adi returned he was promptly slain as an impostor; and then _Melek Taüs_, reappearing, confessed the trick that he had played, and gave orders that the ill-used devotee was henceforth to be honoured as a saint. The Yezidis have a regular hierarchy of seven orders of priesthood. They hold a great annual feast at Sheikh Adi in October; which is continued for eight days, and is attended by all the faithful who can come. Layard was present on two such occasions, and shared in the feasting and merry-making; but no unbeliever has ever been permitted to witness the rites and ceremonies enacted within the temple itself. Pilgrimage to Sheikh Adi is incumbent on every Yezidi; but he is not commanded to pray; and he leaves that duty to his priests. Fasting can also be performed by deputy; and a group of Yezidis will select one of their number to do all their fasting for them, confessing to him the acts which need expiation, and paying him a capitation fee for carrying out the corresponding penances. The Yezidis understand the nature of an oath, but the oath must be properly administered; and, lest any of the sect should appear as witnesses in our own courts of justice, it may be convenient to state exactly how the thing is done. A circle is drawn round the man to whom the oath is propounded, and he is told "All within that circle is the property of _Melek Taüs_. Now answer falsely if you dare!" One would have thought that to the Father of Lies falsehood would be the one thing most pleasing. But apparently when you are put to your purgation it is most emphatically otherwise. So we may conclude that the Prince of Darkness is really a gentleman after all. The distinctive costume of the men consists of white tunic, trousers and jacket, with a scarlet turban and sash. The women wear the same costume, except that the tunic is longer and reaches nearly to the ankle; and they also have an oblong red mantle, draped from the left shoulder under the right arm.