Babylonia was a land of bricks. Stone was not found nearer than the mountains of Elam on the one side or the desert plains of Northern Arabia on the other. Clay, on the contrary, was plentiful, and the art of making bricks and building a house by means of them must have been invented by the first settlers in the country. The bricks were dried in the sun, the heat of which was sufficient to harden them. The clay was further bound together by being mixed with chopped reeds, though the use of the latter was not universal, at all events in the earlier times. In the later days of Babylonian history, however, they were generally employed, and we learn from the contracts that a bed of reeds grown for the sake of the brick-makers’ trade was by no means an unprofitable investment. Either clay or bitumen took the place of mortar; the bitumen was procured from Hit or from the Kurdish hills, where there are still springs of naphtha; after the conquest of Canaan it may have been brought from the neighborhood of the Dead Sea. Some scholars have thought that this is referred to by Gudea, the priest-king of Lagas (2700 B.C.). The employment of brick had a very direct effect upon the character of Babylonian architecture. Thick walls, supported by buttresses and devoid of sculpture, were necessitated by it. The buildings of Babylonia were externally plain and flat; masses of brick were piled up in the form of towers or else built into long lines of wall of unbroken monotony. The roofs were made of the stems of palm-trees, which rested on the stems of other palm-trees, where the space between one brick wall and another was too great to be safely spanned. The upright stems became columns, which were imitated first in brick and then in stone. Babylonia was thus the birthplace of columnar architecture, and in the course of centuries columns of almost every conceivable shape and kind came to be invented. Sometimes they were made to stand on the backs of animals, sometimes the animal formed the capital. The column which rested against the wall passed into a brick pilaster, and this again assumed various forms.