The roofs of Assyrian buildings must have required the same kind of treatment, and we know that in the present day it is actually practised. M. Place mentions rollers of limestone, weighing from two to three hundredweight, pierced at each end with a square hole into which wooden spindles were inserted to facilitate their management.[196] A certain number of these rollers were found within the chambers, into which they must have fallen with the roofs. As soon as the terraces ceased to receive the care necessary for keeping down the weeds and shrubs and keeping out the water, the process of disintegration must have been rapid. The rains would soon convert cracks into gaping breaches, and at the end of a few years, every storm would bring down a part of the roof. A century would be enough to destroy the vaults, and with them the upper parts of the walls to which they were closely allied by the skill of the constructor. The disappearance of the archivolts and the great heaps of _debris_ are thus accounted for. The roof materials were too soft, however, to damage in their fall the figures in high relief or in the round that decorated the chambers beneath, or the carved slabs with which their walls were lined. In spreading itself about these sculptures and burying them out of sight and memory, the soft clay served posterity more efficiently than the most careful of packers. Among the first observers to suspect the truth as to the use of the vault in Mesopotamia, were Eugene Flandin, who helped Botta to excavate the palace of Sargon,[197] and Felix Thomas,[198] the colleague of M. Place. The reasons by which M. Thomas was led to the conclusion that the rooms in the Ninevite palaces were vaulted, are thus given by M. Place, who may be considered his mouthpiece.[199] He does not deny that some of the Khorsabad reliefs bear the marks of fire, but he affirms, and that after the experience of four digging campaigns, that the conflagration was much less general than might be supposed from the statements of some travellers. He failed to discover the slightest trace of fire in the hundred and eighty-four rooms and twenty-eight courts that he excavated. The marvellous preservation of the reliefs in many of the halls is inconsistent, in his opinion, with the supposition that the palace was destroyed by fire; and if we renounce that supposition the mere action of time is insufficient to account for the disappearance of such an extent of timber roofing, for here and there, especially near the doorways, pieces of broken beams and door panels have been found. "The wood is not all in such condition as the incorruptible cedar of the gilded palm-trees, but wherever it certainly existed, traces of it may be pointed out. In advanced decomposition it is no more consistent than powder, it may be picked up and thrown aside, leaving a faithful cast of the beam or post to which it belonged in the more tenacious clay."