Although no direct contact between Babylonia and Egypt has been proved during the earlier historical periods, the opinion has been very generally held that the Egyptian civilization was largely influenced in its first stages by that of Babylonia. The use of the stone cylinder-seal by the Egyptians certainly furnished a very cogent argument in favour of the view that some early cultural connection must have taken place; and, as the cylinder-seal was peculiarly characteristic of Babylonia during all periods, whereas its use was gradually discontinued in Egypt, the inference seemed obvious that it was an original product of Babylonia, whence it had reached Egypt in late predynastic or early dynastic times. This view appeared to find support in other points of resemblance which were noted between the early art and culture of the two countries. Mace-heads of bulbous or "egg-shaped" form were employed by the early inhabitants of both lands. The Egyptian slate carvings of the First Dynasty were compared with the early bas-reliefs and engraved seals of the Sumerians, and resemblances were pointed out both in subject-matter and in the symmetrical arrangement of the designs. The employment of brick, in place of stone, as a building material, was regarded as due to Babylonian influence; and the crenelated walls of Early Egyptian buildings, the existence of which was proved not only by pictured representations on the slate carvings, but also by the remains of actual buildings such as the mastaba-tomb of King Aha at Nakâda, and the ancient fortress of Abydos, known as the Shunet ez-Zebîb, were treated as borrowed from Sumerian originals. That irrigation was practised on the banks of the Nile as well as in the Euphrates valley, and that wheat was grown in both countries, were cited as additional proofs that Babylonia must have exercised a marked influence on Egyptian culture during the early stages of its development.