We must also point out that the state in which the interiors of rooms are found by explorers, is more consistent with the hypothesis of a domed roof than with any other. They are covered to a depth of from fifteen to twenty feet with heaps of _debris_, reaching up to the top of the walls, so far as the latter remain standing.[195] This rubbish consists of brick-earth mixed with broken bricks, and pieces of stucco. Granting wooden roofs, how is such an accumulation to be accounted for? Roofs supported by beams laid across from one wall to the other, could never have safely upheld any great weight. They must have been thin and comparatively useless as a defence against the sun of Mesopotamia. On the other hand if we assume that vaults of pise were the chosen coverings, all the rest follows easily. They could support the flat roof with ease, and the whole upper structure could be made of sufficient thickness to exclude both the heat and the rain, while the present appearance of the ruins is naturally accounted for. Those who have lived in the East, those, even, who have extended a visit to Athens as far as Eleusis or Megara, must have stretched themselves, more than once, under the stars, and, on the flat roofs of their temporary resting-places, sought that rest that was not to be found in the hot and narrow chambers within. They must then have noticed, as I have more than once, a large stone cylinder in one corner. In Greece and Asia Minor, it will be in most cases a "drum" from some antique column, or a funerary _cippus_, abstracted by the peasantry from some neighbouring ruin. This morsel of Paros or Pentelic has to perform the office of a roller. When some heavy fall of rain by wetting and softening the upper surface of the terrace, gives an opportunity for repairing the ravages of a long drought, the stone is taken backwards and forwards over the yielding pise. It closes the cracks, kills the weeds that if left to themselves would soon transform the roof into a field, and makes the surface as firm as a threshing-floor.