double line of fortification following the contours of the slopes. The lower ring is provided with towers at the angles of the wall, and with round bastions of very slight projection. Within the inner enclosure stands the citadel, now completely ruined and bearing evidences of frequent reconstruction. The oldest parts are unmistakably of Byzantine masonry, and contain a chapel of which the apse is well preserved (Fig. 193). The castle must have been rebuilt during the Mohammadan period, and then again rebuilt, for in one of the walls of the citadel there is a fragment of an Arabic inscription, which is not in its original position, neither is the inscription complete.[192] The Yezîdîs declare that the castle was one of their strongholds until it passed into the hands of the Ṭâi, and this might account for a reconstruction of the citadel at a late period. The only other inscription which I could find is also Arabic. It is apparently a name, with no date or further qualification, cut upon the main gate of the outer wall.[193] In the space between the two walls there are a number of small rock-hewn cisterns, some of which were probably intended to hold corn and other provisions. The main water supply was drawn from a large cistern in the citadel. So far as I could judge, the ruins, therefore, exhibit Yezîdî or Arab work (or both) upon Byzantine foundations, and I think it exceedingly likely that the castle of Ḥâtim Ṭâi is that Rhabdium which, according to Procopius, was fortified by Justinian. It lay, says he, on a steep rock upon the frontiers of the Roman and the Persian empires, two days from Dara. Below it was the Ager Romanorum, which has been identified with the plain between Môṣul and the Ṭûr ’Abdîn. Since there was no water near it (there is none, as I have said, in the Ṭûr ’Abdîn), Justinian was obliged to cut a number of cisterns.[194] The whole of this description exactly fits the castle of Ḥâtim Ṭâi, and the presence of Byzantine masonry among the ruins is strongly in favour of the identification. The position of the fortress is exceedingly fine. The hills drop down sharply from its very walls into the Mesopotamian plain, where the long line of the Jebel Sinjâr, a mountain occupied almost exclusively by the Yezîdîs, alone breaks the desolate expanse.