For Hebrew chronology, therefore, we must look outside the Bible itself. At certain points Hebrew history comes into touch with the monumental records of Egypt, Babylonia, and Assyria; and if we are to date the events it records, it must be by their aid. Egypt can assist us only after the rise of the eighteenth dynasty; before that period it is as much without a chronology as the Israelites themselves. But the case is different as regards Babylonia and Assyria. In Babylonia time was dated by the reigns of the kings and the events of the several years of each reign. The extensive commercial relations of the country, and the contracts that were constantly being drawn up, made accurate dating a matter of necessity. The Assyrians were even more exact than the Babylonians; they were distinguished among Oriental nations by their strong historical sense, and at an early epoch had devised an accurate system of chronology. The years were reckoned by a succession of officers called _limmi_, each of whom held office for a year and gave his name to it, the king himself, during the earlier period of Assyrian history, taking the office in the first year of his reign. Lists of the _limmi_ were kept, and a reference to them would show at once the exact age of a document dated by the name of a particular _limmu_. None of the lists hitherto discovered are, unfortunately, older than the tenth century B.C.; but, thanks to those that have been found, from B.C. 909 to 666 we have a continuous and accurate register of time. Abraham was the contemporary of Chedor-laomer and Amraphel, and the position of Amraphel among the Babylonian kings has been given us by the native annalists. He was the sixth king of the first dynasty of Babylon, and reigned fifty-five years. Unfortunately, the only copy we possess at present of the native Babylonian list of dynasties is broken, and owing to the fracture of the tablet, a doubt hangs over his precise date. The most probable restoration of the text would make it about B.C. 2300.[146] Between this and the Exodus there would be an interval of more than a thousand years. Dr. Mahler has attempted to fix astronomically the dates of the two leading Pharaohs of the eighteenth and nineteenth dynasties, Thothmes III. and Ramses II., and his dates have been accepted by Brugsch and other Egyptologists. If his calculations are correct, Thothmes III. will have reigned from the 20th of March B.C. 1503 to the 14th of February B.C. 1449;[147] and Ramses II., the Pharaoh of the oppression, from B.C. 1348 to 1281. The eighteenth dynasty, accordingly, would have commenced about B.C. 1600, and the Exodus would have taken place subsequently to B.C. 1280.