Among these should certainly be placed a phenomenon of which we often read in the chronicles--the heavens appeared to be on fire. The blaze of it is occasionally so high as to mount to the very stars; occasionally it is so low as to present the appearance of a distant fire. In the reign of Tiberius Caesar the fire brigade hurried off 6 to the relief of the colony at Ostia, supposing it to be in flames; during the greater part of the night there had been a dull glow in the sky, which appeared to proceed from a thick smoky fire. No one has any doubt that these burnings in the heavens contain flame as really as they display it: they have a certain substance in them. As to those formerly discussed, I mean rainbows and halos, it is a 7 question whether they deceive the sight and consist of an illusion; or really contain what appears in them. I and those who think with me cannot convince ourselves that the rainbow and halo have a basis of any definite material in them. For we judge that in a mirror there is nothing but a deception: the mirror only pretends to show a foreign body. What is revealed does not exist _in_ the mirror. Otherwise 8 it would not come out of it, nor would it be forthwith obscured by another image: nor would innumerable forms now fade from it, now be received by it. What follows, then? That these are mere phantoms and the insubstantial imitation of real bodies. Indeed, in certain instances, people have so arranged mirrors that the objects have been distorted and degraded in the reflection. For, as I have already said, there are some mirrors that twist the faces of those who look into them, some that enormously increase them until they exceed all size and proportions of these bodies of ours. XVI