748 Ulisse Aldrovandi

cause other than vapor and a cloud, in which the brightness of the star is refracted—a refraction that meteorologists call a "halo." For when the rays of the stars cannot be carried beyond our sight, they are refracted uniformly within the cloud itself. If they encounter a uniform cloud, a perfect circle will appear; however, if they meet an uneven cloud, then only a semicircle, rather than a full circle, will be seen.

Furthermore, halos appear less frequently around the Sun and more often around the Moon. This is because the Sun’s heat, being much greater than the Moon’s, more easily dissipates approaching clouds. The Moon, having a weaker heat, permits these clouds to persist more easily and thus experiences halos more frequently.

As for parhelia, they can be produced neither right next to the Sun nor at a great distance from it. The Sun’s proximity would dissolve the cloud before it could serve as a mirror, while a great distance so diminishes the refraction of sight that a cloud far from the Sun cannot take on the form of even a tiny mirror. Consequently, it is rendered unable to reflect the whiteness and the colors that the appearance of a parhelion requires.

For this reason, images of this kind cannot form above the Sun, nor too close to it, nor too far away. It is necessary that they be produced only at the Sun’s sides, and at a moderate distance, so that the Sun’s proximity does not hinder their generation by dissolving the cloud, nor does a great distance strip away the cloud's power to act as a mirror. These are the conclusions we can offer regarding the physical causes of the aforementioned effects. However, when celestial wonders of this sort proceed directly from the hand of the Divine Craftsman, the sharpness of human intellect can neither penetrate nor explain their causes.

The End of the History of Monsters.

Praise be to God and the Ever-Virgin Mother of God.