sources.[324] To the multiplication of horizontal decorations earlier Nabataean tombs had shown a strong inclination. The double band of crenellations in the pylon tombs of Madâin Ṣâliḥ and of Petra, the double attic of the so-called Ḥedjr tombs in both places, point the way to such compositions as the Storied tomb. Everywhere a strong centralization rules the scheme of the façade. It is rare to find more than one door; where doors are placed in the flanking intercolumniations they are insignificant in size, as in the Corinthian tomb. In the Dair (Plate 82, Fig. 2), mock windows occupy the outer intercolumniations. In the Storied tomb, where there are four doors, the two central entrances are higher than the others, and, in the upper story, the central intercolumniation is wider than those on either side. But the long unbroken lines of the horizontal mouldings give an exceptional monotony to this façade. Usually a gable or archivolt, breaking into the attic, emphasizes the centre of the façade and is re-echoed in the pediment, with its central acroterion which crowns the whole, while in the tholos tombs the centralization is even more strongly underlined. The angles are commonly in antis, with a quarter-column set against the corner pier. The archivolt is conspicuous by its absence. It is never used except in exchange for the pediment over aediculae, and, exceptionally, over mock windows, as for example in the lower zone of the Dair. [Illustration: FIG. 30. Petra, the Storied tomb. (From _Provincia Arabia_, by kind permission of Professor Brünnow.)]