CONSTRUCTION. 167 entrances to the town of Khorsabad were passages roofed with barrel vaults ; secondly, the presence amid the debris of the frag- mentary arches above described ; thirdly, the depth of the mass of broken earth within the walls of each chamber ; finally, the singular thickness of the walls, which is only to be satisfactorily explained by the supposition that the architect had to provide solid abutments for arches that had no little weight to carry. It is difficult to say how the Assyrians set about building these arches of crude brick, but long practice enabled their architects to use that unsatisfactory material with a skill of which we had no suspicion before the exhumation of Nineveh. Thanks to its natural qualities and to the experienced knowledge with which it was prepared, their clay was tough and plastic to a degree that astonished the modern explorers on more than one occasion. The arched galleries cut during the excavations sometimes segmental, sometimes pointed, and often of a considerable height and width- could never have stood in any other kind of earth without strong and numerous supports. And yet M. Place tells us that these very galleries, exactly in the condition in which the mattock left them, " provided lodging for the labourers engaged and their families, and ever since they have served as a refuge for the in- habitants of the neighbouring villages. Workmen and peasants have taken shelter under vaults similar to those of the ancient Assyrians. Sometimes we cut through the accidental accumula- tions of centuries, where the clay, far from having been carefully put in place, had rather lost many of its original qualities. Even there, however, the roof of our galleries remained suspended without any signs of instability, as if to bear witness that the Assyrian architect knew what he was about when he trusted so much to the virtues of a fictile material." l We may refer those who are specially interested in constructive methods to M. Place's account of the curious fashion in which the workmen of Mossoul will build a pointed vault without the help of any of those wooden centerings in use in Europe. In our day, certainly, the masons of Mossoul use stone and mortar, but their example none the less proves that similar results may once have been obtained in different materials. 2 A vault 1 PLACE, Ninive, vol. i. p. 264. 2 Ibid. p. 265. RICH made similar observations at Bagdad. He noticed that the masons could mount on the vault a few minutes after each course was 'completed (Narrative of a Journey to the Site of Babylon),
