lintel, re-used in a doorway of a later period, bears a second inscription of the Ayyûbid Ghâzi and the date A.H. 624 = A.D. 1227. There are no remains of a minaret, and the ṣaḥn is completely ruined and filled with débris, but the north façade, which is almost entirely preserved, is of remarkable interest in the history of Mohammadan decoration. (The photograph of a section of this façade has been given on Plate 84, Fig. 3.) The wings and the north façade show many signs of reparation, and no doubt the mosque shared the fate of all great buildings in these stormy regions, and suffered frequent ruin and subsequent restoration; but it seems probable that the two wings were originally built between A.D. 1226 and 1228, and that they were added to the domed chamber with its corridor which had been erected some fifty years earlier. In the Ayyûbid mosques at Ḥasan Kaif, all of which are dated in the first half of the fifteenth century, no suggestion of an early plan can be traced. At Môṣul, the great mosque as it exists at present dates from the time of Nûr al-Dîn Maḥmûd (A.D. 1146-1173), but the plan shows traces of an earlier riwâq constructed with piers, and lying immediately to the north of the present ḥaram; while fragmentary inscriptions in decorated Kufic must belong, according to M. van Berchem, to the eleventh century A.D.[428] That we have no further information concerning the Mesopotamian mosque shows how insufficient are the data which bear upon its architectural history. From the facts which I have briefly summarized one conclusion may, however, be drawn. The mosque builders were guided by a scheme of extreme simplicity, the details of which were executed according to the nature of the building material which was available. When that material could be taken from older buildings the Mesopotamian artificers were not slow to profit by so fortunate a circumstance; elsewhere they reverted to the system of construction which from time immemorial had prevailed in those regions. They built with sun-dried or with burnt bricks, or where stone could be obtained they built with stone. Sometimes they imported stone from Ahwâz for the columns of their riwâqs, and sometimes wood; sometimes they raised columns of stone masonry, or again they combined brick piers with colonnettes of marble. But since imported wood and stone were expensive, and the Sasanian monuments, which had served as quarries, were speedily exhausted, there was a natural tendency to return to the old local forms, and piers of brick or stone masonry were the obvious solution for the supports of the riwâqs. Ukhaiḍir is the only example which remains to us of a mosque in which the riwâqs were covered with a vault; probably the vault was seldom employed. It is certain that all the mosques of the early Abbâsid period, of which the ruins are preserved, must have been roofed with wood. CHAPTER VII THE DATE OF UKHAIḌIR