One of the greatest difficulties that has always faced the students of antiquity was the construction of an accurate and detailed chronology. The early Egyptians paid no attention whatever to chronological sequence, but dated the episodes and events which they recorded by the year of the contemporary monarch. Among the Chaldeans and the Sumerians, however, lists of eponyms were carefully kept. In the Assyrian meaning of this word an eponym was an official whose name was used in a chronological system to designate a certain year of office. From these consecutive records of the eponyms, king-lists of unusual and detailed accuracy were compiled. A great deal of the difficulty in harmonizing the chronological factors in the study of antiquity has recently been solved by a close study of these canons, which studies were first begun by Sir Henry Rawlinson. As an instance, we note that one such consecutive list gives all of the eponyms from B. C. 893 to 666. Another magnificent aid to the Biblical chronologist is found in the astronomical data which were so carefully kept at the same historical period. Through these credible records we have the material to check the accuracy of the king-lists that adds to their tremendous value. For instance, a tablet has come to us stating that in the eponym of one Pur-sagali, there was an eclipse of the sun which took place in the month Sivan. Since Sivan would be composed, according to our calendar, of the last two weeks of May and the first two weeks of June, it is easy to make an astronomical calculation to fix this date. We are delighted to find that there was an eclipse of the sun which would have been visible at Nineveh on June 15, 763 B. C. With this factor fixed, we can now date all of the events of that period of antiquity from these king-lists to the time of the beginning of the reign of Assur-bani-pal. Another such tablet, which came from Babylon, gives us an opportunity to check back the other way. This tablet merely states, “In the seventh year of the reign of Cambyses, between the 16th and 17th of the month Phemenoth, at one hour before midnight, the moon was obscured in the vicinity of Babylon by one-half of her diameter on the north.” We then turn to our modern astronomical sources and learn from them that there _was_ just such an eclipse of the moon which would have been visible in Babylon in the year 522 B. C. Since this was the seventh year of Cambyses, it follows that he must have ascended in the year 529.