The Da Vinci Code: Chapter 22

Summary: At the Chapel of Saint-Sulpice, Silas observes the strip of brass that runs diagonally across the church building: the Rose Line, a north-south axis, “a vestige of the pagan temple that had once stood on this very spot” and which predated the official establishment of “zero longitude” through Greenwich in 1888. Silas’ Teacher had told him, “The Priory keystone has been said to lie ‘beneath the Sign of the Rose,’” and Silas presumes the Rose Line explains that report. Believing he is alone and unobserved, Silas follows the Rose Line to the obelisk at its north end. At the same moment, Bishop Aringarosa arrives in Rome, confident that, when Silas finishes his task, the bishop will soon possess “something that would make him the most powerful man in Christendom.”
Analysis: Part of The Da Vinci Code’s popularity derives from the way in which Brown explains how arcane and esoteric symbols still resonate in readers’ everyday lives. The Rose Line, introduced in this chapter, is a good example of Brown’s technique. In addition to providing a brief history lesson on the establishment of zero longitude, “the line from which all other longitudes on earth would be measured” (p. 114), Brown explains why “the fundamental navigational tool [is] still known as a Compass Rose, its northernmost direction still marked by an arrowhead… or, more commonly, the symbol of the fleur-de-lis” (p. 114). The brass line Brown describes does indeed run through the chapel at Saint-Sulpice, and can be seen online at such sites as The line, or gnomon, is not, in fact, the remnant of an ancient temple, but an astronomical tool, useful to the church for calculating the date of Easter. Furthermore, a note at Sant-Sulpice displayed to tourists in recent years reads, “Contrary to fanciful allegations in a recent best-selling novel… [the gnomon] was never called a Rose-Line. It does not coincide with the meridian traced through the middle of the Paris Observatory which serves as a reference for maps where longitudes are measured in degrees East or West of Paris. Please also note that the letters P and S in the small round windows at both ends of the transept refer to Peter and Sulpice, the patron saints of the church, and not an imaginary Priory of Sion.”