CHAP. 18. (20.)—WHY THUNDER IS ASCRIBED TO JUPITER.

It is not generally known, what has been discovered by men who are the most eminent for their learning, in consequence of their assiduous observations of the heavens, that the fires which fall upon the earth, and receive the name of thunder-bolts, proceed from the three superior stars[1], but principally from the one which is situated in the middle. It may perhaps depend on the superabundance of moisture from the superior orbit communicating with the heat from the inferior, which are expelled in this manner[2]; and hence it is commonly said, the thunder-bolts are darted by Jupiter. And as, in burning wood, the burnt part is cast off with a crackling noise, so does the star throw off this celestial fire, bearing the omens of future events, even the part which is thrown off not losing its divine operation. And this takes place more particularly when the air is in an unsettled state, either because the moisture which is then collected excites the greatest quantity of fire, or because the air is disturbed, as if by the parturition of the pregnant star.

1. "siderum."

2. The hypothesis of the author is, that the excess of moisture in the orbit of Saturn, and the excess of heat in that of Mars, unite in the orbit of Jupiter and are discharged in the form of thunder.