Parallel (geometry) as a pair of straight lines in a plane which do not meet appears as Definition 23 in Book I of Euclid's Elements. Alternative definitions were discussed by other Greeks, often as part of an attempt to prove the parallel postulate. Proclus attributes a definition of parallel lines as equidistant lines to Posidonius and quotes Geminus in a similar vein. Simplicius also mentions Posidonius' definition as well as its modification by the philosopher Aganis. At the end of the nineteenth century, in England, Euclid's Elements was still the standard textbook in secondary schools. The traditional treatment of geometry was being
Library of Alexandria scrolls in its collection, so, during the reign of Ptolemy III Euergetes, it opened a satellite collection in the Serapeum of Alexandria, a temple to the Greco-Egyptian god Serapis located near the royal palace. Aristophanes of Byzantium (lived 257– 180 BC) became the fourth head librarian sometime around 200 BC. According to a legend recorded by the Roman writer Vitruvius, Aristophanes was one of seven judges appointed for a poetry competition hosted by Ptolemy III Euergetes. All six of the other judges favored one competitor, but Aristophanes favored the one whom the audience had liked the least. Aristophanes declared that