Fig. 19. Ctesiphon. (From L’Acropole de Suse, by kind permission of M. Dieulafoy.)
Fig. 20. Karkh. (From L’Art antique de la Perse, by kind permission of M. Dieulafoy.)
The second building is at Karkh, the town known in Syriac as Karkhâ de Lâdan. It was founded by Shapûr II (309—379)[181] when he rebuilt Susa, from which it is not far removed. Of this palace we have nothing but a fragment, possibly a monumental entrance ([Fig. 20]). The central chamber is covered by a dome which was set over squinches upon four wide archways.[182] The cutting away of the walls under a dome is thus very highly developed at Karkh. Four transverse arches span each of the wings, and the space between the arches is covered by a vault. In connexion with Ukhaiḍir this scheme of the wings at Karkh is of special interest because it is repeated in room 32, where even the windows under the vaults are reproduced by blind niches. The material used at Karkh is brick, and it may here be noticed that at Susa and in Babylonia, where brick was the only available local material, it is invariably used by Sasanian architects; in Fars and in the Qaṣr-i-Shîrîn district, where stone was more easy to obtain than brick, they constructed in unsquared stones, roughly coursed, using brick only for the larger vaults and domes and for those portions of the walls which were finely finished. The latter system was employed at Ukhaiḍir. Vault construction in stone was facilitated there by the fact that the stone broke naturally into thin slabs and could be made to assume more or less the proportions of brick tiles. For this reason stone vaults could be built without the use of centering. At Qaṣr-i-Shîrîn this was not the case. The stones are smooth rounded blocks like large pebbles; it would have been impossible to use them for vaults unless the cement in which they were laid had been peculiarly strong, and the vaults thus formed are of the rudest kind. Coursed and undressed stone held together by a clay mortar was used for vaulting purposes as early as Lydian times; a vault of that character covers the tomb chamber of the tumulus of Alyattes near Sardis. The same masonry is found in the terrace of the Takht-i-Mâder-i-Suleimân at Pasargadae (fifth century B.C.), and is still in common use in Asia Minor.[183] Masonry of dressed and undressed stones set in a mortar of clay or pitch has been found in Assyrian buildings,[184] but gypsum mortar was not known in Mesopotamia till the seventh century. Its earliest appearance was in the palace of Nebuchadnezzar at Babylon. In Egypt it is of much earlier occurrence, and the use of mortar in the Aegean region during the second millennium B.C. (Mycenae, Argos) was probably due to Egyptian influence.[185] Hatra is the earliest Mesopotamian monumental building in dressed stone and mortar; it was an example which was not followed by Sasanian architects. The method was foreign to local tradition; native workmen returned to their own systems and continued to construct wall, vault, and dome of brick or of undressed stone.
A survey of Sasanian buildings leads to the conclusion that a singular want of technical skill was displayed in their vaulting system. The vault and the dome may have been born in Mesopotamia, but they lingered there in a state of immaturity. The barrel vault, the vault on transverse arches, the dome on Persian squinches, or in smaller dimensions on the horizontal bracket, these were the only forms which were employed. If an inclined plane was to be covered, the barrel vault was split up into sections and raised in steps; if the barrel vaults met at right angles, they were carefully separated from one another. At Ukhaiḍir the groined vault is added to this slender stock of forms, but it is not used in many places where it might be expected to appear, and when it is employed, it is only with the utmost precaution. As far as the invention shown in the Mesopotamian regions is concerned, we might to-day be obliged to content ourselves with the barrel vault and the dome poised carefully upon four walls (or little better); but the Greek builders of the Mediterranean coast-lands stepped into the breach, and it is primarily to them that we owe the development of the elementary principles of oriental vaulting.
I have already alluded to a series of early Mohammadan buildings which are of the utmost importance to the study of Ukhaiḍir, the Umayyad ḥîrahs which stand upon the frontiers of Syria. On the western side of the desert the authority of the khalifs had been preceded by the authority of Imperial Rome. Lands which were occupied by Roman armies were endowed with a solid heritage, more enduring than any political domination has proved to be. To this day the traveller to Petra has the paved Roman road under his feet for many a mile; he can reckon his journey by Roman milestones, and daily he will pass by shattered wall and piles of ruin which mark the site of Roman watch-tower and Roman fortified camp. After the lapse of eighteen hundred years these massive structures still offer a meagre shelter to the Beduin shepherds and their flocks, and in the seventh century, when the Umayyad khalifs fled from their cities to the beautiful solitudes of the Syrian desert, most of the castles of the Roman limes, which had been re-occupied by the Ghassânid allies of Byzantium, were standing in all their towered strength. Here indeed was an inheritance for those who loved the wilderness; where the Roman legionaries had languished in interminable exile, the children of the desert held their court.
The Arabian limes did not differ in its system of military defence from the limites of Europe, but whereas the European camps were originally laid down as stockaded earthworks and were not systematically clothed in stone till the time of Hadrian,[186] on the Syrian frontier the camps and forts were from the first built of solid stone masonry. The comparatively late date of the oriental defences was no doubt partially responsible for this peculiarity, but it must also be borne in mind that fortification by means of earthworks was foreign to the regions through which the Arabian limes ran. As early as the time of Vespasian, the camps of Flavius Silva at Masada, near the Dead Sea, were surrounded by walls of rudely piled stones,[187] while in the Flavian period the European camps were still fortified by earthworks and stockades. The Roman province of Arabia Petraea was created in A.D. 105, and the fortification of the first limes dates therefore from the time of Trajan. On this inner limes one great camp stands in ruins, the camp of Odhruḥ.
Archaeological research on the Roman frontiers in Germany, Austria, and Britain, as well as in North Africa, has made us familiar with the general disposition of the legionary camps; moreover, we have two literary sources of information. Polybius, writing in 150 B.C., has left a description of the camp in his day, and Hyginus, writing not earlier than a period shortly before the time of Hadrian, has given an accurate account of the camp as he knew it.[188] Architecturally there is no fundamental difference between the two. The camp of Hyginus was a rectangular enclosure, with a length one-third greater than its width. It had four gateways, the Porta Praetoria and the Porta Decumana in the centre of each of the short sides, the Porta Principalis Sinistra in one of the long sides, but not in the centre, and the Porta Principalis Dextra opposite to it in the other. Round the interior of the walls lay an open space, the Intervallum. The interior area was divided by thoroughfares placed in a regular order. Between the Porta Principalis Dextra and the Porta Principalis Sinistra ran a cross street, the Via Principalis. At right angles to it, the Via Praetoria ran up to the Porta Praetoria. These two were the most important of the roads; they were wider than the others, and in the later stone-built camps they were sometimes flanked by colonnades, while at their point of junction was set a tetrapylon. The colonnades and the tetrapylon are common in cities which were laid out on the Roman camp plan.[189] Opposite the point of junction of the two streets, the centre of the camp was occupied by official and public buildings. Here lay the Forum and the Praetorium, with the Sacellum wherein the eagles of legion and cohort were deposited. Behind the Praetorium, the Via Quintana crossed the camp from side to side, while numerous small roads at right angles to it gave access to the lodgings of the troops; the Via Sagularis, within and parallel to the Intervallum, was carried round the whole rectangle. To this general scheme the camps which have been excavated conform, with little divergence.[190] I give as an example the fort at Housesteads, on the Roman Wall ([Fig. 21]). The sanctuary, X, which is here rectangular, is not infrequently apsed.[191] As a rule not much remains of the interior buildings except the Praetorium and a few large public edifices, such as granaries and armouries. The Praetorium varies considerably in detail, but in general disposition it resembles the Greek peristyle house. A typical, well-preserved example is to be found at Wiesbaden.[192]