with the result that the circle is not pierced through to the interior, but remains a saucer-shaped motive sunk within the square. I hazard the conjecture that the origin of this ornament is to be sought upon the walls of Assyrian fortifications, and that it represents the row of shields set within rectangular frames which are to be seen on innumerable Assyrian reliefs (Fig. 34). In the great mosque at Sâmarrâ the wooden roof was borne directly (without the interposition of arches) by composite piers having bases 2·07 metres square.[424] These piers were composed of an octagonal core of brick with four slender marble columns placed one at each corner. The columns were sometimes round, sometimes octagonal, and averaged ·30 metre in diameter. Dr. Herzfeld calculates that each column consisted of three sections, placed one on top of the other and bound together with lead and with metal rings. They rested upon bell-shaped bases and carried bell-shaped capitals. Dr. Herzfeld points out that the teak columns of Manṣûr’s mosque at Baghdad were similarly composed of sections joined together in the same manner. The ḥaram and the north riwâq at Sâmarrâ were given a wide central aisle. [Illustration: FIG. 34. Assyrian fortress. From _L’Acropole de Suse_, by kind permission of M. Dieulafoy.] The two small mosques of which Dr. Herzfeld has uncovered the foundations in the palace of Balkuwârâ present further variations. The larger was an oblong chamber of brick, 35 × 15 metres, the roof supported by two rows of eight columns which were probably either of wood or of marble. In the wall opposite the qiblah there were three doors. The smaller mosque was a chamber 10·35 × 7·76 metres, built of sun-dried brick, without columns. The miḥrâb was a deep rounded niche surmounted by a cyma moulding and flanked by engaged columns, and in the opposite wall were three doors. The miḥrâb of the larger mosque, which is totally destroyed, is probably to be reconstructed in the same style. Neither of these mosques has a ṣaḥn, the great palace enclosure in which they stand serving them as court.[425]