Book II — [The Nature of Air. Thunder and Lightning]
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Every inquiry into the nature and constitution of the universe falls into three divisions—astronomy, meteorology, and geography. The first investigates the nature of the heavenly bodies, the size and shape of the fires that ring-in the world. It inquires whether the heavens are solid, composed of strong rigid material, or woven of a fine thin stuff; whether they receive or impart motion; whether the heavenly bodies are beneath them or fixed in their texture; in what manner the sun maintains the succession of the seasons; whether he returns upon his track or not, and all the other questions of a similar character. The second division deals with what lies between heaven and earth, to wit, clouds, rain, snow, and Thunder that frights the heart of man:
in short, all that the atmosphere does or suffers. This subject is called meteorology (sublimia = raised on high), because it deals with phenomena exalted above the low earth. The third part inquires about waters, lands, trees, crops, or to use a legal phrase, everything that is contained in the soil.
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How comes it, you ask me, that you have put the question of earthquakes in the division under which you are going to treat of thunder and lightning? For that is my plan. Well, the earthquake is due to air, and air is the atmosphere in violent motion. Now, though the air may enter the earth in order to produce earthquakes, the treatment of earthquakes does not fall under geography, but more properly belongs to meteorology, which deals with the sphere to which nature has assigned the atmosphere. I can tell you something that will sound stranger still: I must speak of the earth when dealing with the heavenly bodies. Why? you ask. For this reason: we discuss in their own proper place, as part of geography, the properties of the earth, for example, whether it is broad, projecting unequally in a huge bulge to one side, or whether it all assumes the shape of a ball, gathering up its parts into a globe; whether it binds its waters or is itself bound by them; whether it is an animal or a lifeless mass without feeling, full of air no doubt, but not its own breath. These, and all other questions of the kind, as often as they crop up, will be relegated to geography, and be placed in the lowest category. But when the question comes to be the situation of the earth, the part of the universe in which it has settled, its position with respect to the heavens and heavenly bodies, then the inquiry will take its place in the higher category,34 and obtain higher rank so to speak.