The layers and courses of clay bricks of which the buildings in Mesopotamia were for the most part composed, were cemented together by mud in the earliest times; this clay-mud is generally distinguishable from the bricks which it unites by the difference of its colour. Mud-mortar has been found on some of the earliest sites and in some of the most ancient buildings, while in Assyria it appears to have been the regular form of cement used at all times. In the city of Babylon, strange to say, clay mortar appears to have been used instead of lime or asphalt in the late buildings of Sassanidian times. This mud-mortar consisted of clay mixed with water and perhaps a little straw, as was the case in the cone-wall at Warka,[51] while sometimes reeds embedded in clay were laid between the bricks, as was the case at both Warka and Hammam, but at an extremely remote period the Babylonian architect began to avail himself of the rich supply of bitumen gratuitously yielded by the soil of his native land, for the purpose in question. The most famous bituminous springs in Mesopotamia were those at Ḥit on the Euphrates. Their fame had reached Egypt as early as the time of the eighteenth dynasty, for Thothmes III brought bitumen thence to Egypt. Herodotus a millennium later—about 450 B.C.—alludes to Ḥit as famous for her bitumen, and subsequent writers make similar mention of the springs there. A good example of the early use of bitumen in Babylonia was found at Abû Shahrein, the site of ancient Eridu, where a very early building was excavated by Taylor, the antiquity of which was proved by the pre-Sargonic plano-convex bricks used in its construction, and these bricks were all laid in bitumen; the same was found to be the case in a building composed of finger-marked bricks at Ur (Muḳeyyer), all of which were embedded in bitumen. The platform upon which Ur-Ninâ’s storehouse at Tellô was erected consisted of three layers of plano-convex and finger-marked bricks, all set in bitumen, while in the building underneath that of Ur-Ninâ, bitumen was also freely used.[52]