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
The Crown of Ptolemy The Crown of Ptolemy The Crown of Ptolemy is the third and last book in the "Percy Jackson and the Olympians" and "The Kane Chronicles" crossover series. It was released in the back of the paperback version of "The House of Hades" on March 31, 2015, and later as an ebook and audiobook. The ebook edition was released May 12, 2015. On January 15, 2015, Rick Riordan announced a third crossover story titled "The Crown of Ptolemy" on his Twitter account. His announcement included the fact that the short story would be first published in the paperback version of "The