After five centuries of foreign domination, the Shepherds in their turn were driven out, and the new kingdom founded. This, after witnessing the glories of the 18th and 19th dynasties, declined during the next seven dynasties till they were struck down by the Persian Cambyses. A third period of architectural magnificence arose with the Ptolemys, and was continued by the Cæsars on nearly the same scale of magnificence as the second kingdom; but wanting its exuberant nationality, and far below the quiet grandeur of the earlier epoch. In counting backwards the dates of these dynasties, the first authentic synchronism we meet with is that of Shishak, the first king of the 22nd dynasty, contemporary with Rehoboam, about 970 B.C. The next is the Exode of the Jews, which took place 1312 B.C., under the reign of Meneptah II., the fourth king of the 19th dynasty of Manetho. Many would place it earlier, but none probably would bring that event down to a more modern date. From this date Josephus tells us that Manetho counted 518 years to the expulsion of the Shepherds, and 511 for the duration of their sojourn in Egypt,[25] we thus get back to 2340 for the first year of Salatis. There then remain only fifteen centuries and a half, in which we have to arrange the two great Theban dynasties (the 11th and 12th), which reigned for more than two centuries over the whole of Egypt; while the 12th seems to have extended some distance into the period occupied by the Shepherds. We are thus left with little more than 1300 years over which to spread the ten first dynasties, notwithstanding that some 60 or 70 of their royal sepulchral pyramids still adorn the banks of the Nile; and we have many names to which no tombs can be attached, and many pyramids may have perished during the 5000 years which have elapsed since the greater number of them were erected. Long as these periods may to some appear, they are certainly the shortest that any one familiar with the recent progress of Egyptian research would be willing to assign to them. But in whatever light they may be viewed, they sink into utter insignificance when compared with the periods that must have elapsed before Egypt could have reached that stage of civilisation in which we find her when her existence first dawns upon us. If one point in Egyptian history is proved with more certainty than another, it is that the great Pyramids of Gizeh were erected by the kings of the 4th dynasty: and it seems impossible to find room for the now ascertained facts of Egyptian chronology, unless we place their erection between 3000 and 3500 years before the Christian era.