It is not quite clear to what stage in the national history Berossus intended his sixth dynasty to extend;[67] and in any case, the fact that the figure is wanting for the length of his third dynasty, renders their total duration a matter of uncertainty. But, in spite of these drawbacks, a general agreement has been reached as to a date for the beginning of his historical period, based on considerations independent of the figures in detail. A. von Gutschmid's suggestion that the kings after the Deluge were grouped by Berossus in a cycle of ten _sars, i.e._ 36,000 years,[68] furnished the key that has been used for solving the problem. For, if the first dynasty be subtracted from this total, the remaining number of years would give the total length of the historical dynasties. Thus, if we take the length of the first dynasty as 34,090 years, the duration of the historical dynasties is seen to have been 1910 years. Now the statement attributed to Abydenus by Eusebius, to the effect that the Chaldeans reckoned their kings from Alorus to Alexander,[69] has led to the suggestion that the period of 1910 years was intended to include the reign of Alexander the Great (331-323 B.C.). If therefore we add 1910 years to 322 B.C., we obtain 2232 B.C. as the beginning of the historical period with which the second dynasty of Berossus opened. It may be added that the same result has been arrived at by taking 34,080 years as the length of his first dynasty,[70] and by extending the historical period of 1920 years down to 312 B.C., the beginning of the Seleucid Era.