In their work at Babylon the excavators have, of course, employed modern methods, which differ considerably from those of the age when Layard and Botta brought the winged bulls of Assyria to the British Museum and to the Louvre. The extraordinary success which attended those earlier excavators has, indeed, never been surpassed. But it is now realized that only by minuteness of search and by careful classification of strata can the remains of the past be made to reveal in full their secrets. The fine museum specimen retains its importance; but it gains immensely in significance when it ceases to be an isolated product and takes its place in a detailed history of its period. [Illustration: (i) The temple-tower of E-zida at Borsippa. (ii) The Lion of Babylon on the Ḳaṣr Mound] In order to grasp the character of the new evidence, and the methods by which it has been obtained at Babylon, it is advisable to bear in mind some of the general characteristics of Babylonian architecture and the manner in which the art of building was influenced by the natural conditions of the country. One important point to realize is that the builders of all periods were on the defensive, and not solely against human foes, for in that aspect they resembled other builders of antiquity. The foe they most dreaded was Hood. Security against flood conditioned the architect's ideal: he aimed solely at height and mass. When a king built a palace for himself or a temple for his god, he did not consciously aim at making it graceful or beautiful. What he always boasts of having done is that he has made it "like a mountain." He delighted to raise the level of his artificial mound or building-platform, and the modern excavator owes much to this continual filling in of the remains of earlier structures. The material at his disposal was also not without its influence in the production of buildings "like mountains," designed to escape the floods of the plain. The alluvial origin of the Babylonian soil deprived the inhabitants of an important factor in the development of the builder's art: it produced for them no stone. But it supplied a very effective building-material in its place, a strongly adhesive clay. Throughout their whole history the Babylonian architects built in crude and in kiln-burnt brick. In the Neo-Babylonian period we find them making interesting technical experiments in this material, here a first attempt to roof in a wide area with vaulting, elsewhere counteracting the effects of settlement by a sort of expansion-joint. We shall see, too, that it was in this same medium that they attained to real beauty of design.