one side of every brick, baked or unbaked, the name and official titles of the reigning prince were stamped by means of a matrix or a die used as a seal; thus, at Tello most of the bricks were marked with the name of Gudea, and at Babylon bricks of Nebuchadnezzar are found by hundreds of thousands. [Illustration: Fig. 1.--Brick from Tello (Louvre).] While describing the construction of the fortifications at Babylon, Herodotus shows the process followed by the Chaldæans in building a wall: “As they dug the moat, they made bricks of the earth taken out of the trench, and when they had made a certain number of bricks they baked them in kilns. Then, using boiling bitumen as mortar, and inserting mats of woven reeds at every thirtieth course of bricks, they built first the borders of the moat, and next the wall itself in the same way.”[4] Mesopotamia possesses abundant wells of bitumen, notably at Hit and at Kalah Shergat; as for the tall reeds which still grow in abundance in the marshes of Lower Chaldæa, their employment in building had the effect of giving more solidity and cohesion to the courses of bricks. For walls less carefully constructed, or for partition-walls in the interior of the houses, a simple mortar of clay was used instead of bitumen. In great structures, such as Birs Nimroud at Babylon, the bricks are bound together by mortar made of lime, solid enough to stand all tests. The ruins of Mugheir have revealed the use of a mixture of ashes and lime, which is still employed by the natives, and called by them _sharûr_. The necessarily limited size of bricks baked in kilns or dried in the sun must have helped to bring about a speedier disintegration of the structures, and have been a serious obstacle to the erection of walls of a height to be compared, for instance, with that of the Egyptian temples. At certain seasons of the year in Mesopotamia the rain falls in torrents, and, filtering through walls in bad repair, would soon open cracks and bring about the ruin of the structure. In these lowlands furrowed with watercourses, the crude brick of the foundations often on this account ran the risk of returning to its condition of clayey mud without consistency. Greek tradition relates that the Medes and Chaldæans saw a part of the walls of Nineveh fall of themselves, when they prolonged a blockade which forced the besieged to admit the waters of the Tigris during many weeks into the moats beneath the ramparts. The cuneiform inscriptions themselves, while the empire founded by Nebuchadnezzar was flourishing, often point out temples and palaces falling to ruin, which the kings strive without ceasing to repair or rebuild.