CHAP. XVIII.
Of sight.
AFter that the Gods had placed the eyes (conduits of light) in the face, they included in them a fiery light, which being smooth and in some manner thick, they conceived of kin to diur∣nall light. This breaketh forth every where at the Eyes, but chief∣ly through the Eye-balls, as being there most pure and clear. This agreeing with the externall light, as like with like affordeth the sense of sight, whence in the night, when the light vanisheth and is obscured, this ray of ours no longer mingleth with the im∣mediate air; but, on the contrary, withdrawing it self inwards, smooths and diffuses the motions that are in us, and so bringeth on sleep, whereby the eyelids are shut. If it bring much rest, the sleep is little disturb'd with dreams, but if there remain any moti∣ons behind, we are troubled with many illusions. In this manner phantasies, whether true or false, arise. Of the same Nature are images, which we see in glasses, or other smooth pellucid bodies, which exist only by reflection. For, as the glasse is concave or convex, or oblong, the object is differently represented to the be∣holder. The light being reflected to other parts, those which are dispersed in convex meet in the concave, for in some, the right and left sides seem quite inverted, in others alike; in others, those which are upwards seem downwards, and on the contrary, those which are downwards, upwards.