The survival rate of ancient literature

[Dan Diffendale]

It seems to me that the ashes ought to be found in a stratum that would make it fairly easy to determine at least the century, but I'm not a historian or an archeologist.

Unfortunately, there are no known remains of the library in Alexandria in situ. There's a hollowed out block that may have been used for holding scrolls, but even that's debatable. The sad fact is that very little of ancient Alexandria remains. The visible remains have been plundered for centuries upon centuries, and urban development over the past 100 years has obliterated much more.