north wall of the ḥaram at an angle of 78°, and by reason of its oblique disposition it cuts off the north-west corner of the ṣaḥn, which is 6·24 metres shorter on the north side than it is on the south side. The east arcade of the ṣaḥn (dated A.D. 1163-1179) lies almost at right angles to the north wall of the ḥaram. Whether the orientation of the west arcade was dictated by a pre-Mohammadan building or, as Dr. Herzfeld has acutely suggested, by the plan of a mosque which stood upon this site before the year A.D. 1091,[427] cannot be determined with certainty. In its present form it is the work of Mohammadan builders of the twelfth century, though it is partly composed of pre-Mohammadan materials. Whence these materials were derived has not been ascertained. There is, however, a further proof that a building older than the existing mosque, oriented in the manner corresponding with that of the west arcade, existed on this site. On the north side of the ṣaḥn, between the two northern madrasahs, there is a lane or passage which communicates with the street beyond the precincts of the mosque. On the east side of the passage there is a fragment of wall, built of large dressed stones, entirely dissimilar from the masonry in any part of the existing mosque, and this fragment lies at the same angle as the west arcade of the ṣaḥn (Plate 93, Fig. 1). Not far from Diyârbekr there is another building which shows in its plan and decorations the influence of the Ulu Djâmi’ in that city. The so-called mosque of Ṣalâḥ al-Dîn at Mayâfârqîn ranks, even in ruin, among the finest of Mohammadan monuments (Plate 92). The wide central aisle has been converted into a chamber almost square (it is not quite rectangular and averages 13·60 x 13·32 metres), which was covered by a dome set on elaborately decorated squinch arches (Plate 93, Fig. 2). Under the dome runs an inscription assigning the building of the mosque to the Ortokid Alpi (A.D. 1152-1176). The square chamber is surrounded on three sides by a corridor consisting of eleven bays, some of which were probably domed, while the others were vaulted. The columns placed against the piers of the dome were taken from a neighbouring early Christian basilica. The wings to east and west are divided by three arcades into four transepts averaging alternately 5 metres and 2·60 metres in width, a narrow transept lying next to the qiblah wall. The eastern miḥrâb in the south wall of the east wing is dated by an inscription of the Ayyûbid Ghâzi in the year A.H. 624 = A.D. 1227. The west wing contains no date, but the very shallow miḥrâb in the south wall is proved by its decoration to belong to a period not earlier than the sixteenth century, and as the whole wing as it stands at present seems to have been rebuilt, it may well be that it all belongs to a late reconstruction or reparation. Still further west are some ruined edifices which formed part of the precincts of the mosque, and here a