Fig. 89.—Tomb-chamber at Mugheir; from Taylor.
Like all the other forms of Assyrian architecture the arch was invented in Chaldæa. The use of small sized materials must have led to its early discovery in that country. But the only arches now standing occur in the better preserved monuments of Assyria. On the other hand the tombs of Lower Chaldæa furnish more than one example of that false, corbelled or off-set vault, that we have already encountered in Egypt.[280] The chamber figured below is taken from the necropolis of Mugheir, formerly "Ur of the Chaldees." It is built of crude brick bound with mud. The vault is supported by walls sloping upwards and outwards like those of a modern tunnel ([Fig. 89]).[281]
Such a method of construction is only adapted to buildings of small dimensions; it could not be used for chambers with wide roofs, or where any great weight was to be upheld. The arches upon which, according to both Strabo and Diodorus,[282] the hanging gardens of Babylon were supported, must have been real centred arches. As to whether they were of pisé, like those of Khorsabad, the Greek writers tell us nothing. From what we know of the habits of the Chaldæan builder we may conclude that they were true arches with voussoirs either of bricks burnt in the kiln, or so well dried that they were almost as hard and durable as those that had passed through the fire. This conjecture is confirmed by the fact that the structures in question lasted till the Macedonian conquest. Strabo and Diodorus speak of the great temple of Bel as so ruinous that its original height could not be guessed, even approximatively. It was otherwise with the hanging gardens. Of these they give the measurements, on plan, of the platforms and piers, together with their heights, and the heights of the arches. We should find it difficult to explain the preciseness of these measurements and their agreement one with another, unless we supposed that both writers had some exact authority, such as one of the companions or historians of Alexander, to refer to. The kings of Persia lived at Babylon for a part of the year. These princes may well have been indifferent to the preservation of the national fanes, they may even have hastened their destruction, as Xerxes is said to have done, in order to punish and humiliate the rebellious Babylonians. But in their own interest they would see that proper care was taken of those hanging gardens by which their stay in the city would be rendered more pleasant than it would otherwise have been, from whose lofty platforms their watchful eyes could roam over the city and the adjoining plain, and follow the course of the great river until it disappeared on the south amid groves of waving palm. After the rise of Seleucia and Ctesiphon, however, the gardens would rapidly hasten to decay, but they must have been solidly built in the first instance to last as long as they did. The pisé vaults of the Ninevite palaces could never have stood so well. In spite of the layers of lead and bitumen which, as Diodorus tells us, were spread upon their terraces, the summer rains must in time have found their way into their walls and set up a process of disintegration which could have but one end. Real brick with good mortar could alone resist such influences, and those, no doubt, were the materials used in the Babylonian gardens. If their substructures should ever be found and laid open, we have little doubt that arches as carefully built as those of the Assyrian ruins will be brought to light.
The gateways of the town built by Sargon at the foot of his palace mound were roofed with semicircular vaults.[283] In order to study their construction more closely, M. Place demolished one of these arches piece by piece, the one numbered three on his plan.[284] It was already condemned to destruction by the necessity for carrying off its sculptures.
The total height from pavement to keystone, was twenty-four feet six inches, from the centre of the keystone to the springing of the arch itself was eight feet, the total width of the opening, measured at the feet of the caryatides, was fourteen feet four inches.
The bricks had not been burnt in a kiln but they had been subjected to a prolonged desiccation. The system of construction was as simple as possible. The perpendicular side walls passed into the vault without any preparation, and the arch when complete had no inward projection and no structural ornament but the inner faces of the carefully placed voussoirs; as all the bricks were of the same size and shape something more than their slightly trapezoidal form was required to keep them in place, and a softer clay was used to bind them together. With the addition of this rude cement each brick became a long and narrow wedge and determined the curve of the vault in which it was placed. Some idea of the appearance of this triple arch may be formed from the illustration we have compiled from M. Thomas's elevation of an alcove in one of the harem apartments at Khorsabad ([Fig. 90]). This vault is not in existence, but its component parts were found among the ruins of Sargon's palace.[285]
Fig. 90.—Interior of a chamber in the harem of Sargon's palace at Khorsabad; compiled from Place.
There is one detail in the decoration of these doorways that should be carefully noted. Wherever the architect makes use of a round-headed opening he reinforces its outlines with a kind of semicircular frieze, to which brilliant colours or bold reliefs would give no little decorative value. In what M. Place calls portes ornées, this ornamental archivolt is of enamelled bricks, in the subordinate entrances it is distinguished from the rest of the wall merely by its salience. In neither case, however, does it end in any kind of impost, it returns horizontally without the arch and forms an ornament along a line corresponding to the spring of the vault within. We give an example of this peculiarly Assyrian arrangement from one of the gateways at Dour-Saryoukin ([Fig. 91]). Nothing like it is to be found, so far as we know, among the buildings of any other ancient people.