We have seen in a former section that the institutions of Egypt, based on a theocratic monarchy, reach back into a dim and doubtful antiquity. Monuments, extending through thirty-five centuries, attest an age preceding all written history. These monuments, so far as deciphered by modern Egyptologists, have confirmed the accuracy of the lists of kings which have come to us from Manetho. We have no monument anterior to the fourth dynasty, but at that epoch we find the theocracy fully organized.[171] The general accuracy of Manetho's list has been demonstrated by the latest discoveries of M. Mariette, and has rendered doubtful the idea of any of the dynasties being contemporaneous. The main chronological points, however, are by no means as yet fixed. Thus, the beginning of the first dynasty is placed by Böckh at B.C. 5702, by Lepsius B.C. 3892, by Bunsen B.C. 3623, by Brugsch B.C. 4455, by Lauth B.C. 4157, by Duncker 3233.[172] The period of the builders of the great Pyramids is fixed by Bunsen at B.C. 3229, by Lepsius at B.C. 3124, by Brugsch at B.C. 3686, by Lauth at B.C. 3450, and by Böckh at B.C. 4933.[173] The Egyptian priests told Herodotus that there were three hundred and thirty-one kings, from Menes to Moeris, whose names they read out of a book. After him came eleven others, of whom Sethos was the last. From Osiris to Amasis they counted fifteen thousand years, though Herodotus did not believe this statement. If the three hundred and forty-two kings really existed, it would make Menes come B.C. 9150,--at an average of twenty-five years' reign to each king. Diodorus saw in Egypt a list of four hundred and seventy-nine kings. But he says in another place that Menes lived about four thousand seven hundred years before his time. Manetho tells us that from Menes there were thirty dynasties, who reigned five thousand three hundred and sixty-six years. But he gives a list of four hundred and seventy-two kings in these dynasties, to the time of Cambyses. The contradictions are so great, and the modes of reconciling Manetho, Herodotus, Diodorus, Eratosthenes, and the monuments are so inadequate, that we must regard the whole question of the duration of the monarchy as unsettled. But from the time when the calendar must have been fixed, from the skill displayed in the Pyramids, and other reasons independent of any chronology, Duncker considers the reign of Menes as old as B.C. 3500. The history of Egypt is divided into three periods, that of the old, the middle, and the new monarchy. The first extends from the foundation of the united kingdom by Menes to the conquest of the country by the Hyksôs. The second is from this conquest by the Hyksôs till their expulsion. The third, from the re-establishment of the monarchy by Amosis to its final conquest by Persia. The old monarchy contained twelve dynasties; the Hyksôs or middle monarchy, five; the new monarchy, thirteen: in all, thirty.