The way in which these slabs were fixed is hardly worthy of such clever builders, and, in fact, the Assyrians seem to have never succeeded in mastering the difficulties inherent in the association of two heterogeneous materials. The slabs were of gypsum or limestone, the wall of pise, materials which are not to be easily combined. The Assyrians contented themselves with simply placing the one against the other. No trace of any tie is to be found. A "tooth" has been given to the inner faces of the slabs by seaming them in every direction with the chisel, and, perhaps, some plastic substance may at the last moment have been introduced between them and the soft clay, but no trace of any other contrivance for keeping the two materials together has been found. After the general mass of the building--its clay walls and vaults--were complete, a different class of workmen was brought in to line its chambers and complete their decoration. The crude brick would by that time have become dry, and no longer in a condition to adapt itself to the roughnesses of the alabaster slabs. The liquid clay, like that of an earthenware "body," wets and softens the surface of the brick while it enters into every hollow of the stone and so allies the one with the other. We recommend this conjecture to those who may undertake any future excavation in Assyria. It lies with them to confirm or refute it. However this may have been, the constructor made use of more than one method of giving greater solidity to his walls as a whole. His slabs were not only let into each other at the angles, in some chambers there were squared angle pieces of a diameter great enough to allow them to sink more deeply into the crude brick behind, and thus to offer steady points of support in each corner. Finally the separate slabs were held together at the top by leaden dovetails like the metal clamps used to attach coping stones to each other. Such precautions were rendered comparatively useless by the fact that the whole work was faulty at the base. Halls and chambers had no solid foundation or pavement, so that the heavy slabs of their decoration rested upon a shifting soil, quite incapable of carrying them without flinching. In many places they sank some inches into the ground, the soft earth behind pushing them forward, and in their fall the row to which they belonged was inevitably involved. The excavators have again and again found whole lines of bas-reliefs that appeared to have fallen together. Such an accident is a thing for posterity to rejoice over. Prone upon a soft and yielding soil the works of the sculptor are better protected than when standing erect, their upper parts clear, perhaps, of the ruin that covers their feet, and exposed to the weather at least, and, too often, to the brutality of an ignorant population.