This intellectual movement extended over a long period of years and can be split into two periods. The first period extends from about 306 to 30 BC, the time from the foundation of the Ptolemaic dynasty to the conquest by the Romans; the second extends from 30 BC to the destruction of the Alexandria Library sometime before or upon the capture of Alexandria by 'Amr ibn al-'As in 641 AD. The clear differences between these two periods explains the variety and vagueness of meaning attaching to the term "Alexandrian School."[2]