746 Ulisse Aldrovandi

...tend to do. However, that superior nature is eternal and moves through infinite time; therefore, it possesses both the beginning and the end of its own motion, whereas other bodies are finite and have finite motions, and are consequently subject to all manner of corruption.

From this, we must conclude that this supreme nature is the cause of all other effects—not to mention meteorological ones—and these effects are subsequently received into elemental matter. We believe no further explanation is needed, as there are no other bodies besides the elements capable of receiving these described impressions. Indeed, in meteorological matters, the elements act more as the subject than the matter, since they are truly what undergo these meteorological impressions and receive celestial actions. This is unless we wish to call these actions "divine power," which is undoubtedly found in every single thing, or the force of the sun, which also deserves the title of "celestial virtue" due to its excellence, as it seems to govern the light and motion of all other stars. All other specific causes of such effects depend on these universal causes.

Furthermore, the general causes of the aforementioned impressions generated in the upper region of the air can be reduced to two. One is called *hypocauma* (as explained earlier), which acts as the material cause; the other is circular motion, which is said to perform the function of the efficient cause. For when that drier spirit, raised from the earth, ascends to that height, it must grow hot in the same way that any object draws heat from rapid motion—a heating that proceeds until it catches fire.

If we turn our attention to the causes of impressions that occur without actual ignition, they do not differ much from the previous ones. Openings, chasms, or "celestial abysses" occur (as we previously explained) when a more turbulent exhalation takes on a certain blackness, which is the typical color of thick and dark images. However, on the outside, due to the proximity of light, it becomes thinner and brighter. Because of this contrast, the part that is deeper inside presents the appearance of a certain depth, which observers then mistake for a literal gap or chasm.

It then happens that white strikes our vision more forcefully and thus appears closer to the eyes; black, for the opposite reason, seems to be at a greater distance and is believed to gape open in a way. Consequently, ordinary people seeing this think there are chasms or openings in the heavens and marvel at them as if they were monsters.

The causes that produce blood-red colors in the sky and around the stars are not much different. When a similarly turbulent exhalation and a lack of celestial light meet, they can produce no other color than a purple close to that of blood, provided a certain proportion and equality is maintained between the two.

Otherwise, if the exhalation is so turbulent that it far exceeds the brilliance of the light, the color will appear more black than red or any other hue, because the light cannot spread through it. Conversely, when that same light is abundant and overcomes the thickness of the exhalation, it produces a white color. Thus, if neither overcomes the other, neither of those colors emerges, but rather another that participates in the nature of both—which must be called blood-red or purple.

This also explains why such colors are seen more often at night than during the day: the cause of this effect is a lack of light. Since daylight is always more abundant than night light, everything appears whiter during the day. However, if such blood-red colors are by chance seen during the day—which certainly cannot be denied, as we have shown with the examples mentioned earlier—then we must assert that this occurs mostly in the summer. At that time, due to the abundance of heat and the "smoke" of turbulent exhalations, the *hypocauma* is more active. As a result, the clarity of the primary light is removed, or at least weakened, and so the stars and luminaries are seen not as bright white, but as if stained with a blood-red color.

As for the causes of the circles that are sometimes seen surrounding the Sun, the Moon, or any star, it should be noted that there is no other cause for these circles or halos...