The heavy rains of the winter season coursing down these declivities for so many centuries, have in places worn deep ravines in the mounds, through which the torrents have carried the crumbling debris far out upon the plain. In this way many valuable relics have come to light; bits of pottery, inscribed bricks, seals and cylinders, the form and style of the inscriptions upon some of these indicating great antiquity. These indications of greater antiquity include inscriptions on bricks for building purposes as well as those used for record and literature. They include also the form and character of the inscriptions, whether archaic or later cuneiform, and again the use of bitumen or cement in masonry. In primitive times the first bricks which succeeded the mud wall were sun-dried and were laid up with reeds and plastered with soft mud or bitumen. This bitumen was applied hot and adhered so firmly to the bricks that it is almost impossible to break them apart to obtain the cement and is one cause why the masonry consisting of sun-dried bricks has in many cases withstood the ages. Later the sun-dried bricks came to be used only for interior walls, while for the outer walls bricks were made from selected clay and were carefully prepared and burned, forming bricks of superior quality and strength. So well have these withstood the ravages of time that some of the mounds, notably those of the later Babylonian period, are veritable quarries of building brick. It is stated that the bricks of which the temples and palaces of Babylon were built, have for the past two thousand years supplied cities of the surrounding region with the material used in the construction of public and private edifices, and that certain families of the Babili tribe, who claim to be direct descendants of the Babylonians, are exclusively employed in quarrying them. As has been stated, bitumen was used for laying the masonry in the remoter times long before Babylon was built. Of this substance an abundant supply was to be obtained at various places in southern Mesopotamia, near the Arabian desert, notably in the neighborhood of Ur, now Mugheir, “the bitumened,” so called from the bitumenous springs of the vicinity. In time, the use of this for masonry gave place to a fine white mortar made from a peculiar calcareous clay, found near the Arabian frontier to the west of the Euphrates in southern Mesopotamia, which for lightness and strength has never been surpassed. These evidences, including also the inscriptions originally stamped upon the bricks, with the name of the king or ruler under whose orders they had been prepared, furnish indications of their time and place in history. It thus came about that explorers following the work of Botta, Layard, George Smith and others, found their way to sites more ancient by many centuries than the beginnings of Nineveh or Babylon, and have obtained from these records of great historical importance.