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 largest and most significant libraries of the ancient world, but details about it are a mixture of history and legend. The earliest known surviving source of information on the founding of the Library of Alexandria is the pseudepigraphic "Letter of Aristeas", which was composed between 180 and 145 BC. The "Letter of Aristeas" claims that the Library was founded during the reign of Ptolemy I Soter ( 323– 283 BC) and that it was initially organized by Demetrius of Phalerum, a student of Aristotle who had been exiled from Athens and taken refuge in Alexandria within the Ptolemaic court. Nonetheless,