The gradual attainment of skill in the working of copper ore on the part of the early Egyptians had a marked effect on the whole status of their culture. Their improved weapons enabled them by conquest to draw their raw materials from a far more extended area; and the adaptation of copper tools for quarrying blocks of stone undoubtedly led to its increased employment as a stronger and more permanent substitute for clay. The use of the copper chisel also explains the elaborate carvings upon the early dynastic slates, and the invention of the stone borer brought about the gradual displacement of pottery in favour of stone vessels for household purposes. Thus, while metal-casting and stone-working improved, they did so at the expense of the older arts of flint-knapping and the manufacture of pottery by hand, both of which tended to degenerate and die out. Dr. Reisner had already inferred that for ceremonial purposes, as distinct from the needs of everyday life, both flint implements and certain earlier types of pottery continued to be employed. And M. Naville's diggings at Abydos, during the season of 1909-10, seem to prove that the process was even slower and less uniform than had been thought possible. In fact, according to the excavators, it would appear that in certain districts in Egypt a modified form of the predynastic culture, using the characteristic red and black pottery, survived as late as the Sixth Dynasty; while it is known that in Nubia a type of pottery, closely akin to the same prehistoric ware, continued in use as late as the Eighteenth Dynasty.[6] However such survivals are to be explained, the beginning of the dynastic period in Egypt does not appear to present a break in either racial or cultural continuity. Indeed, a precisely parallel development may be traced between the early dynastic period, and that represented by the Third and Fourth Dynasties, when there is no question of any such break. As the stone vessels of the first two dynasties had proved themselves superior to hand-made pottery for practical purposes, so they in turn were displaced by wheel-made pottery.[7] These changes may be traced to gradual improvements in manufacture; arts such as mat-weaving and bead-making, which were unaffected by the new inventions, continued to be practised without change in the early dynastic as in the predynastic periods.