We learnt from Diodorus that the great pyramids were erected 1,000, or, according to some, 3,400 years before his time. According to the list of Manetho, Cheops, Chephren, and Mycerinus belonged to the fourth dynasty. If we accept the incredible reigns of sixty-three, sixty-six, and again, sixty-three years, which Manetho allows to those three kings, they reigned over Egypt, according to Lepsius' dates, from the year 3095 B.C., to 2903 B.C. At a period subsequent to these kings the list of Manetho speaks in the sixth dynasty of a king Phiops, who came to the throne as a child in his sixth year, and lived to be 100 years old. The list of Erastosthenes mentions a king Apappus, who reigned for 100 years. The monuments show us a king Pepi, in whom we recognise Phiops and Apappus, and in consequence a reign of ninety-five years is assigned to him (2654-2559 B.C.). Yet hitherto the sixteenth year is the highest found on the monuments for the reign of Pepi; and in the inscription on a tomb at Abydus, now in the museum at Cairo, a man of the name of Una declares that he had filled the highest offices in the kingdom under Teta, the predecessor of Pepi, under Pepi, and again under his successor, Merenra. If one person could be the minister of three successive rulers, it is clear that the second of these reigns could not have lasted 95 or 100 years. Under the reign of Pepi, as well as his immediate predecessors and successors, _i.e._, in the sixth dynasty of Manetho, the development of Egypt must have undergone a certain change. The kings, previous to this family, are represented on the monuments with a cap falling to one side, or with a tall head-dress; Pepi is represented on one relief with this head-dress, but on another with one of a lower shape. The tall white cap is the crown of Upper Egypt, the lower red one is the crown of Lower Egypt. It is no longer on the plateau of Memphis, and among the tombs there, but in Middle Egypt, near El Kab, and in the valley of Hamamat, which leads from Coptus to the Red Sea, that we find the monuments of Pepi and his race, and the tombs of their priests and magistrates are at Abydus. Under this dynasty, therefore, the central point of the kingdom appears to have been moved from Memphis in the direction of Middle Egypt. On the west coast of the peninsula of Sinai, in the Wadi Maghara, Pepi is seen striking down an enemy; and from the inscription on the tomb of Una, it is clear that Pepi's kingdom extended up the Nile as far as the negroes, that his successor caused dockyards to be built in Nubia, and that Una had to procure blocks of fine stone for the sarcophagus of Pepi and his successor, and also for the pyramid of the latter.[153]