It must be admitted that, until quite recently, this view furnished a very plausible explanation of the various points of resemblance noted between the civilizations of the two countries. Moreover, the evidence obtained by excavation on early sites certainly appeared to show a distinct break between the predynastic and early dynastic cultures of Egypt. To account for what seemed so sudden a change in the character of Egyptian civilization, the theory of a foreign invasion seemed almost inevitable. But the publication of the results of Dr. Reisner's excavations at Naga-ed-Dêr and other early cemeteries in Upper Egypt,[5] has rendered it necessary to revise the theory; while the still more recent diggings of M. Naville at Abydos prove that the changes, in certain districts, were even more gradual than had been supposed. Put briefly, Dr. Reisner's conclusion is that there was no sudden break of continuity between the Neolithic and early dynastic cultures of Egypt. His extensive and laborious comparison of the predynastic burials with those of the First and Second Dynasties, has shown that no essential change took place in the Egyptian conception of the life after death, or in the rites and practices which accompanied the interment of the body. In early dynastic as in Neolithic times the body of the dead man was placed in a contracted position on its left side and with the head to the south, and the grave was still furnished with food, arms, tools, and ornaments. Moreover, the changes observable in the construction of the grave itself, and in the character of the objects within it, were not due to the sudden influence of any alien race, but may well have been the result of a gradual process of improvement in the technical skill of the Egyptians themselves. The three most striking points of difference beween the products of the predynastic and dynastic periods centre round the character of the pottery and vessels for household use, the material employed for tools and weapons, and the invention of writing. It would now appear that the various changes were all gradually introduced, and one period fades into another without any strongly marked line of division between them. A knowledge of copper has always been credited to the later predynastic Egyptians, and it is now possible to trace the gradual steps by which the invention of a practical method of working it was attained. Copper ornaments and objects found in graves earlier than the middle predynastic period are small and of little practical utility, as compared with the beautifully flaked flint knives, daggers, and lances, which still retained the importance they enjoyed in purely Neolithic times. At a rather later stage in the predynastic period copper dagger-blades and adzes were produced in imitation of flint and stone forms, and these mark the transition to the heavy weapons and tools of copper, which in the early dynastic period largely ousted flint and stone implements for practical use.