Fig. 9. Parthian palace at Niffer. (By kind permission of Messrs. Holman.)
which indicates the road that led from the Hellenistic façade in two orders[90] to the stucco façades of Ctesiphon and Ukhaiḍir.[91] At Hatra a building which looks like the Parthian conception of a temple in antis stands in the court of a monumental lîwân palace,[92] but so far as can be judged without excavation the Hellenistic house is conspicuous by its absence. Not only the royal palace ([Fig. 10]) but also such of the smaller palaces as are known to us through the admirable publication of the Deutsche Orient-Gesellschaft, show a strongly characterized lîwân plan. To the Parthian interpretation of the venerable khilâni scheme the Moslem East has remained unswervingly true. The lîwân, as it is to be seen at Hatra, dominated the fancy of the Sasanian and of the early Mohammadan architects, and it continues to be an indispensable part of the modern house of Damascus or Baghdâd—except indeed the post-modern, which are wretched imitations of the worst European styles, but these are found more often in ultra-civilized Syria than in Mesopotamia. The huge Parthian lîwân was possibly a result of the introduction of the vault. The great hall, in which, no matter what its size, the interior space was unbroken by pier or column, was a setting for princely state which could not be enhanced by any
Fig. 10. Hatra palace. (From Hatra, by kind permission of the D. Orient-Gesellschaft.)
architectural device. Portico and audience chamber were blended together, and the columns of the one served to enrich the walls which flanked the monumental archway of the other.
The vault itself was not a new feature. It was well known to Babylonian and to Assyrian builders, by whom it was used to cover spaces of narrow span.[93] Vaulted drains and tombs are of frequent occurrence, and Place found a barrel vault with a span of 4 metres in the gateways of Sargon’s palace at Khorsâbâd.[94] But though the principles of vault construction were familiar, the vault does not seem to have been developed to any notable extent before the second Babylonian empire at the earliest. Félix Thomas claims to have found the remains of monumental vaults in Sargon’s palace, but the proofs which he adduces are not convincing. There is no direct evidence for the domes which Place reconstructs over the rectangular chambers adjoining the temples, the area of the palace which was known in his days as the Harâm.[95] Layard found no trace of monumental vaults in his excavations of Assyrian palaces,[96] nor have any been discovered by the German excavators at Assur. Professor Koldewey is of opinion that the great hall at Babylon was vaulted, since, in the absence of all trace of columns, no other way of covering it is conceivable; and though direct evidence is not forthcoming, there is a strong likelihood that the proportions of the vault may have been greatly increased, and its structural value much more fully realized towards the end of the seventh or the beginning of the sixth century before Christ.[97] There are no data for its employment in Mesopotamia during the Hellenistic period, but it may safely be assumed that the absence of vaulted buildings in the eastern parts of the Seleucid kingdom is fortuitous. From the fourth century B.C. onwards western Asia shows a continuous series of cut stone vaults of small span,[98] many of which exhibit traits which point to their derivation from the sun-dried brick vaults of Assyria or from the cut stone vaults of the Saitic period in Egypt, themselves a derivation from sun-dried brick construction. In the second half of the third century, vaults with similar characteristics appear under Hellenistic influence in central Italy, where, after the middle of the second century, they underwent a development to which the Hellenistic East can offer no parallel.[99] At the end of the second century, while Latin builders threw their stone vaults securely over a span of 14·50 metres, as in the Ponte di Cecco in the Via Salaria, and even of 18·50 metres, as in the Pons Mulvius,[100] the Greeks of Asia Minor did not venture upon a span wider than 7·10 metres,[101] and confined themselves as a rule to vaults under 4 metres in span. It was now the part of the East to learn from Imperial Rome. Western Asia took back its own creation from the hands of Roman builders in the vast proportions which the proficiency of the latter had given to it, and over the whole of the Roman Empire the monumental vault sprang into being. The earliest extant examples on Mesopotamian soil are the great vaults of the palace at Hatra.[102] Throughout the city, so far as our knowledge goes, the vault is systematically used, and for the first time it is constructed of dressed stone, not of brick. For it must be borne in mind that the expansion in Asia of the Roman Imperial stone and mortar vaulted architecture encountered a similar expansion of brick vaulted architecture in which both material and structure point to an ancient oriental tradition and an independent Asiatic origin.[103] If Hatra is the oldest example of the systematic use of the vault in a monumental building, the very presence there of a method so fully developed postulates a long evolution. That this evolution was oriental is suggested by the fact that the forms which the vault assumes at Hatra can be traced back, almost without exception, to Asiatic brickwork, while the systematic employment of the vault is foreshadowed in hollow substructures which date from the Hellenistic era, and even from earlier times.[104] In Babylon such substructures, several stories high, roofed with stone slabs, would seem to have been devised before Alexander’s conquest, while Strabo’s description, which probably applies to a Hellenistic reconstruction, mentions terraces in which the vaults rested on cube-shaped piers, vaults and piers being built of burnt brick with a mortar of asphalt. Moreover, Strabo notes that in Seleucia, the capital of the Hellenistic kingdom on the Tigris, all the houses were vaulted on account of the want of timber.[105] That these vaults were of brick goes without saying; stone was even more difficult to obtain at Seleucia than wood. In this connexion the possibility that Nebuchadnezzar’s great hall at Babylon may have been covered with a vault should not be overlooked.
The vaults of Hatra fall into five groups.