Richard Heath writes in http://www.amazon.com/Sacred-Number-Origins-Civilization-Unfolding/dp/1594771316 that Jesus here is Lord of the World in this Vesica Piscis. He reconciles opposites and creates sacred space–in this cathedral, for example–via the square root of three. He rules the Age of Pisces. The four apocalyptic beasts represent the two equinoxes and two solstices.
The vesica for this blogger is an excellent symbol of the equinoxes. In both hemispheres, the opposites of the cold of winter and the heat of summer meet now and the result is reconciliation. Neither hot, nor cold (in temperate zones). Day and night are equal worldwide. The Sun and Moon naturally marry at this point and the result is Jesus. The essence of Christianity is contained in this symbolism.
The equinoxes are portals, canals into other realms, another shore. Here in Japan, during the equinoxes people traditionally visit family graves and pay respect to the departed. The custom is called “Higan” http://en.wikipedia.org/wiki/Higan. Three days before and three days after the equinox. Seven days; more evidence of the universality of Number.
Kenneth Clark visits Chartres Cathedral (1969) here
Fast forward to 34:48 and stay tuned to the end of the show.