THE SIBYLLINE ORACLES
There is a figure about the duration of the Deluge that is ignored by all the commentators on Genesis that I have consulted. The Sibylline Oracles state that the Deluge lasted 200 days. The only way I can make sense of this information is that the Sibylline Oracles in their cryptic form mean that the water rose for 200 days and ebbed for 200 days. Genesis preserves a version according to which the Deluge ended on the first day of the second year. Therefore it is possible to assume a version according to which it began on the first day of the first year. If, having begun on this date, it ended on the 17th day of the second month of the second year, the duration by a lunar calendar would be 354 + 30 + 16 = 400 days.
The calculation of the Sibylline Oracles may be presumed to be based on the assumption that the water rose 100 trimmed natural barley cubits a day, reaching a height of 20,000 cubits = 9998.128 meters. Since the Hebrews reckoned the radius of the Earth by the round figure of 14,400,000 Roman cubits, the same value expressed in trimmed barley cubits is 12,800,000 cubits, a figure which may be broken down as 2 x 40 x 400 x 400 cubits. This reckoning combines the basic figure of a Deluge lasting 40 + 40 days with the duration of 400 implied by the Sibylline Oracles.
The Hebrews reckoned the circumference of the Earth as 90,000,000 Roman cubits. The same value expressed in trimmed barley cubits is 80,000,000 cubits. Given this value, it is understandable that the Sibylline Oracles considered a duration of 400 days for the Deluge, a figure most apt to express the numerical structure of the cosmic order implied in the story of the Deluge.
According to my interpretation, the Sibylline Oracles proceeded to a most simple adaptation of the first version of the duration of the Deluge, which assumed a duration of 80 days (40 days of rising water and 40 days of ebbing water).
Since the duration of 80 days fits best of all a calculation by trimmed barley cubits, which was a lineal standard used in Mesopotamia, it can be presumed that the writers of Genesis tookthe figure of 40 + 40 days from a Mesopotamian source. We know that there was a version of the Epic of Gilgamesh according to which the Deluge lasted 8 days. Since in Mesopotamian mathematical texts the decimal points are not listed and left to be filled in by the reader, it may be presumed that the figure of 8 days was at some point understood as 80 days (40 + 40). The Sibylline Oracles worked over the same figures, arriving at a duration of 400 days.
The Sibylline Oracles may have reckoned that the water rose 160 (= 4 x 40) Greek feet a day for 200 days, reaching a level of 32,000 Greek feet.