Plutarch ( AD 46 â `` 120 ) wrote that during his visit to Alexandria in 48 BC , Julius Caesar might have accidentally burned the library when he set fire to his own ships to frustrate Achillas ' attempt to limit his ability to communicate by sea . Plutarch ( AD 46 â `` 120 ) wrote that during his visit to Alexandria in 48 BC Julius Caesar accidentally burned the library down when he set fire to his own ships to frustrate Achillas ' attempt to limit his ability to communicate by sea .