XI
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Such being the divisions of the atmosphere, I may observe that in its lowest layer it is most variable, unstable, and changeful. It is near the earth that the air is, so to speak, most enterprising and most long-suffering, as it tosses or is tossed. But withal, it is not all affected in the same way, but at different times at different points its different parts are in unrest and turmoil. The reasons of the changefulness and inconstancy are in part derived from the earth: her position turning hither and thither is a potent factor in determining the quality of the atmosphere. Other reasons are due to the heavenly bodies, chiefly the sun, whose course directs the year, whose solstices determine winter and summer. Next in importance is the moon’s influence. But even the other stars produce an effect alike on the earth and on the air that rests upon the face of the earth. Their rising or their corresponding setting and their disturbances cause now cold, now rain, now other damage such as earth is subject to.
It was necessary for me to make these preliminary remarks before going on to speak of thunder and thunderbolts and lightnings. For as these phenomena occur in the atmosphere, I had to explain the nature of the latter, that it might more readily appear what active or passive capacities it possessed.