In Medieval Angelology, There Are Nine Orders of Snow Issue no. 219 Winter 2016 The highest hierarchy of the crystalline sky begins just beyond the orbit of the fifty-second Aristotelian planet. This part of the cosmos already belongs to the INVISIBLE HORIZON. Isidore of Seville, who describes it, never saw snow himself. Nor does he claim to know the creatures of flame, the six-winged, eyeless beings that make up the order of the seraphim.