In like manner at Nippur, the finger-marked bricks of which the city-gate was constructed were laid in bitumen, though the bricks composing the early arch found on this site were set in mud, probably an indication that at the time when the arch was built bitumen was not used; around the base of Ur-Engur’s ziggurat on the other hand there was a coating of bitumen, while the crude brick altar found by Haynes in the lowest stratum at Nippur had a rim of bitumen; but in later times it was supplemented by the more tenacious lime-mortar, though only partially was this the case, for even as late as Nebuchadnezzar’s time (604-561 B.C.) its practical utility as a preventive against the destructive forces of rain were still recognized, the burnt brick retaining walls of his palace at Babylon being actually laid in bitumen. In like manner the bricks composing the old fortification wall, are rendered adhesive by means of a lavish prodigality of asphalt, so adhesive in fact, that it is often very difficult to separate them. Fortunately the side bearing the stamped inscription has its face downwards and therefore is not in immediate contact with the asphalt from which it is separated by the layer of reeds and clay already alluded to. In the later buildings at Babylon, however, lime-mortar is also used, the transition period being marked by the employment of both in one and the same building, and in point of fact Koldewey found that in the case of one of the walls of a building of Nebuchadnezzar, one half of the wall was cemented together by means of asphalt, while in the other half lime-mortar alone was used. But in the new castle which Nebuchadnezzar built for himself on the Kasr, the very finest materials were employed, the bricks being of a pale yellow colour and extremely hard, contrasting with the bricks used in his earlier buildings, which are of a reddish-brown colour and less durable, while in this new structure, pure white lime-mortar alone is used. Lime-mortar, as well as mud-cement and bitumen, was employed at Nippur, as also at Birs-Nimrûd (Borsippa), and the mortar used has such adhesive properties that the bricks can only be separated by breaking them, while at Muḳeyyer (Ur) a mortar composed of a mixture of lime and ashes was employed.