comprised the whole duration of the world in twenty-five Sothis periods, _i.e._ in 36,525 Egyptian years. Regarded in this light, the Sothis periods of the priests of Egypt must lead to a cyclic treatment of their history, to which also the want of any definite era was forcing them, while the antiquity and number of the lists of kings offered abundant material for it. The history of Egypt must comprise a definite number of Sothis periods. It was known that in the fourteenth century B.C. such a period ended, and a new one commenced; the difficulty was to fill up two or three periods anterior to this. Before the Sothis period of the kings, the gods had ruled over Egypt, to whom, therefore, a number of Sothis cycles, naturally more extensive than those given to the rule of men, was allotted. Thus the priests of Thebes were able to tell Herodotus that, from the time when the Twelve Gods ruled over Egypt, down to the days of King Amosis, 17,000 years had passed; that from Menes, down to Sethos, 341 kings ruled in succession over Egypt, and that in this space of time the sun had four times risen in an unusual way--it had twice risen where it then set, and had twice set where it then rose; and nothing in Egypt had been changed by this, either in the gifts of the earth or the river, in sickness or in mortality.[30] This change of the rising and setting of the sun is nothing more than the symbolical astrology of the priests, who must have expressed the completion of the movable solar year by the opposite quarters of the sky; and it means no more than that two Sothis periods had elapsed between Menes and Sethos; but to Herodotus the statement as given naturally appeared quite incredible.[31] What the priests told Herodotus, Manetho, following far older authorities, had already fixed in a systematic form before Diodorus found that the gods ruled 18,000 years, and the human kings had begun to reign 4,700 years before his arrival in Egypt. To the gods and demigods Manetho allows twelve Sothis periods, _i.e._ 17,520 Julian years. Then follows the history of the men, the beginning of which Manetho places in the commencement of that period of the Dog-star which begins with the year 5702 B.C. From this point the series of kings runs through three complete Sothis periods down to Menephta; in the fourth period Manetho closed the lists of his thirty dynasties with the last native ruler in 340 B.C., the 984th year of the fourth Sothis period of the human kings. Thus it would be possible to make the scheme clear on which the priests of Egypt dealt with the history of their land, and the lists of Manetho would then lay claim to complete historical credibility for the ancient periods in isolated items, though certainly not in their combination as a whole.