Whatever difficulty modern criticism may find in regard to the event called “The Return of the Herakleids,” no doubt is expressed about it even by the best historians of antiquity. Thucydidês accepts it as a single and literal event, having its assignable date, and carrying at one blow the acquisition of Peloponnêsus. The date of it he fixes as eighty years after the capture of Troy. Whether he was the original determiner of this epoch, or copied it from some previous author, we do not know. It must have been fixed according to some computation of generations, for there were no other means accessible,—probably by means of the lineage of the Herakleids, which, as belonging to the kings of Sparta, constituted the most public and conspicuous thread of connection between the Grecian real and mythical world, and measured the interval between the Siege of Troy itself and the first recorded Olympiad. Hêraklês himself represents the generation before the siege, and his son Tlepolemus fights in the besieging army. If we suppose the first generation after Hêraklês to commence with the beginning of the siege, the fourth generation after him will coincide with the ninetieth year after the same epoch; and therefore, deducting ten years for the duration of the struggle, it will coincide with the eightieth year after the capture of the city;[25] thirty years being reckoned for a generation. The date assigned by Thucydidês will thus agree with the distance in which Têmenus, Kresphontês, and Aristodêmus, stand removed from Hêraklês. The interval of eighty years, between the capture of Troy and the Return of the Herakleids, appears to have been admitted by Apollodôrus and Eratosthenês, and some other professed chronologists of antiquity: but there were different reckonings which also found more or less of support. [25] The date of Thucydidês is calculated, μετὰ Ἰλίου ἅλωσιν (i. 13). SECTION II.—MIGRATION OF THESSALIANS AND BŒOTIANS. In the same passage in which Thucydidês speaks of the Return of the Herakleids, he also marks out the date of another event a little antecedent, which is alleged to have powerfully affected the condition of Northern Greece. “Sixty years after the capture of Troy (he tells us) the Bœotians were driven by the Thessalians from Arnê, and migrated into the land then called Kadmêïs, but now Bœotia, wherein there had previously dwelt a section of their race, who had contributed the contingent to the Trojan war.”