It is probable that Abraham did not enter Egypt until after the Hyksos conquest. But before the rise of the eighteenth dynasty Egyptian chronology is uncertain. We have to reckon it by dynasties rather than by years. According to Manetho, the Old Empire lasted 1478 years, and a considerable interval must be allowed for the troublous times which intervened between its fall and the beginning of the Middle Empire. We learn from the Turin papyrus—a list of the Egyptian kings and dynasties compiled in the time of Ramses II., but now, alas! in tattered fragments—that the tenth dynasty lasted 355 years and 10 days, the eleventh dynasty 243 years. The duration of the twelfth dynasty is known from the monuments (165 years 2 months), that of the thirteenth, with its more than one hundred and fifty kings, cannot have been short. How long the Hyksos rule endured it is difficult to say. Africanus, quoting from Manetho, as Professor Erman has shown, makes it 953 years, with which the fragment quoted by Josephus from the Egyptian historian also agrees. In this case the Hyksos conquest of Egypt would have taken place about 2550 B.C. Unfortunately the original work of Manetho is lost, and we are dependent for our knowledge of it on later writers, most of whom sought to harmonise its chronology with that of the Septuagint. When we further remember the corruptions undergone by numerical figures in passing through the hands of the copyists, it is clear that we cannot place implicit confidence in the Manethonian numbers as they have come down to us. Indeed, the writers who have recorded them do not always agree together, and we find the names of kings arbitrarily omitted or the length of their reigns shortened in order to force the chronology into agreement with that of the author. The twelfth dynasty reigned 134 years according to Eusebius, 160 years according to Africanus; its real duration was 165 years, 2 months, and 12 days. With the help of certain astronomical data furnished by the monuments, Dr. Mahler, the Viennese astronomer, has succeeded in determining the exact date of the reigns of the two most famous monarchs of the eighteenth and nineteenth dynasties, Thothmes III. and Ramses II. Thothmes III. reigned from the 20th of March B.C. 1503 to the 14th of February B.C. 1449, while the reign of Ramses II. lasted from B.C. 1348 to B.C. 1281. The date of Thothmes III. enables us to fix the beginning of the eighteenth dynasty about B.C. 1570.