Note 750 — Chapter VII · THE ATMOSPHERE

William of Conches follows Theodoric in this explanation of snow and hail (De phil. mundi, III, 4, 8, 9). In the epic poem, Philippis (IX, 672–682), of William the Breton there is a remarkable description of a nocturnal fog lying over the humid and fertile ground near Lille, so thick that a rider could scarcely discern the ears of his horse in front of him. William attributed the fog to damp vapors rising from beneath the muddy surface of the plain rather than to a more probable cause: the cooling and condensation of water vapor in the lower strata of the atmosphere as a result of active radiation from the earth’s surface.