The Pneumatics of Hero of Alexandria

BOOK ON PNEUMATICS.

...are carried to a higher place, where fire also resides; but those which are a little thicker than these move into the air. Those which are even thicker, having been lifted up somewhat along with these due to the continuous motion, fall back down again to a lower place and are joined with earthly things.

Furthermore, water is also changed into air when it is broken down original: "corrupta." In this scientific context, Hero uses the term to mean the breakdown or dissolution of a substance's current state, rather than moral corruption. by fire; for the vapors from boiling cauldrons lebetibus are nothing other than the thinning of moisture, which passes into the air. Thus, it is manifest from what has been said that fire dissolves all things thicker than itself and transforms them.

And from the exhalations exhalationibus Hero uses "exhalatio" to describe the process of evaporation or the rising of gases from the earth. that arise from the earth, thicker bodies are transformed into thinner substances; for dews are not carried upward in any other way unless the water that is on the earth has been thinned by exhalation. This exhalation itself is caused by a certain fiery substance of the sun existing beneath the earth Ancient physics often posited that the sun's heat remained active underground during the night, or that subterranean heat was of a solar nature., which heats that place—especially if it is sulfurous or bituminous—and when heated, it generally produces an exhalation. Warm springs, which are found in the earth, are produced from this same cause. The thinner parts of the dew are transformed into air, while the thicker parts, having been lifted somewhat by the force original: "vim." This is the catchword for the following page. of the exhalation...