Rose Line is a fictional name given to the Paris Meridian and to the sunlight line defining the exact time of Easter on the Gnomon of Saint-Sulpice, marked by a brass strip on the floor of the church in the Priory of Sion mythology, where the two are conflated. The fictional name Rose Line was also popularized by Dan Brown in his 2003 novel, The Da Vinci Code.
Chapter XIII of Circuit is devoted to the Zero Meridian, with de Chérisey claiming it was established by Till Eulenspiegel (before Jean Picard), listing key sites that it passes through (in a fictional work attributed to Abbé François-Pierre Cauneille). In this chapter Roseline is called 'Fisher Woman', preferring herself to be known as "Di O Nysos, DON" ("dondon" is French slang for "fat woman"), an otherworldly being who organises funerals for the dead who are still living in her new Citroen 2CV (the make of car she was killed in).
Dan Brown's The Da Vinci Code
The term Rose Line has been popularized by Dan Brown in his novel The Da Vinci Code as an alternate name for "the world's first prime meridian", identified as the Paris Meridian. Brown's novel also conflates this meridian with a gnomon in the Parisian church of Saint-Sulpice marked in the floor with a brass line, as did the 1967 Priory Document Le Serpent Rouge - Notes sur Saint-Germain-des-Près et Saint-Sulpice de Paris. The Paris Meridian actually passes about 100 metres east of the gnomon, which according to author Sharan Newman and a sign in the church was "never called a Rose-Line". A St Sulpice booklet dating from 2000, in the page about the history of the gnomon describes the brass line as "a meridian", it does not use the term Roseline or Rose Line. Author Paul Murdin describes such sun lines as a "Meridian", or meridiana.
"Rosslyn Chapel's entrance was more modest than Langdon expected. The small wooden door had two iron hinges and a simple oak sign, Roslin. This ancient spelling, Langdon explained to Sophie, derived from the Rose Line meridian on which the chapel sat; or, as Grail academics preferred to believe, from the 'Line of the Rose' — the ancestral lineage of Mary Magdalene..."
Quoting Mark Oxbrow and Ian Robertson from their book Rosslyn and the Grail:
"Dan Brown simply invented the 'Rose Line' linking Rosslyn and Glastonbury. The name 'Roslin' definitely does not derive from any 'hallowed Rose Line'. It has nothing to do with a 'Rose Bloodline' or a 'Rose Line meridian'. There are many medieval spellings of 'Rosslyn'. 'Roslin' is certainly not the 'original spelling': it is now the most common spelling for the village."
At the climax of the novel, the protagonist follows the line of Arago medallions to the Louvre museum, where (according to the book) the Paris Meridian passes beneath the so-called Inverted Pyramid in an underground mall in front of the museum. Following the tradition of esoteric interpretations of this meridian, the novel hints that this is the final resting place of the Holy Grail. The fact that the meridian passes near the Inverted Pyramid is also noted in the book Le guide du Paris maçonnique by Raphäel Aurillac, who likewise ascribes some deeper, esoteric significance to this.
In the Louvre area, the meridian line marked by the Arago medallions actually runs through the museum and the great courtyard at a spot considerably to the east of the Inverted Pyramid. The medallions in the museum are behind ticketed access points, while the Inverted Pyramid is located in a public mall next to the museum.
Other landmarks said to lie on the line are Arques and Conques, the Lady of the Roses cathedral in Rodez, St. Vincent's in Carcassonne, and the Church of St. Stephen's in Bourges, and Rennes-les-Bains.
While Dan Brown presents the Rose Line as "the world's first prime meridian", the idea of establishing a Prime Meridian dates back to antiquity, with suggested meridians running through Rhodes or the Canary Islands. When Greenwich was adopted as the universal zero longitude in 1884 (not 1888 as the novel says), it had at least nine rivals besides Paris (Berlin, Cadiz, Copenhagen, Lisbon, Rio, Rome, Saint Petersburg, Stockholm, and Tokyo).
- Dan Brown, 'The Da Vinci Code, p. 106
- Philip Coppens, The Stone Puzzle of Rosslyn Chapel, Adventures Unlimited Press, 2004, p. 11. ISBN 1-931882-08-8
- Richard Benishai, Saint Sulpice and the "Rose-Line".
- Tim O'Neill, History versus The Da Vinci Code.
- Sharan Newman, The Real History Behind The Da Vinci Code, Berkley Publishing Group, 2005, p. 268.
- Paul Roumanet, Saint-Sulpice, Paroisse Saint-Sulpice, 2000 (English translation by Laurence Terrien), p. 23-26.
- Paul Murdin, Full Meridian of Glory: Perilous Adventures In The Competition To Measure The Earth. pages 77-85 (Copernicus Books, 2009). ISBN 978-0-387-75533-5
- Dan Brown, The Da Vinci Code, p. 567.
- Mark Oxbrow, Ian Robertson, Rosslyn and the Grail, Mainstream Publishing Company, Edinburgh, 2005, p. 182.
- Alan James, The Enduring Enigma of Rennes-le-Chateau.
- Ptolemy's Almagest use the meridian through Alexandria as prime. Maimonides, Hilchot Kiddush Hachodesh 11:17, calls this point אמצע היישוב, "the middle of the habitation", i.e. the habitable hemisphere. Evidently this was a convention accepted by Arab geographers of his day.
- Bill Putnam, John Edwin Wood, The Treasure of Rennes-le-Château, A Mystery Solved, p. 146 (Sutton Publishing, 2005; revised paperback edition, ISBN 0-7509-4216-9.