Heronis Alexandrini spiritalium liber

higher place, where fire also is; but those which are a little thicker than these, into the air; and those which are still thicker, having been lifted up somewhat together with these, because of continuous motion, descend again into a lower place and are joined to earthy things. Water also, corrupted by fire, is changed into air; for the vapors from burning cauldrons are nothing other than the thinnings of moisture which pass into air. Therefore, it is manifest from the things already said that fire dissolves all things thicker than itself and transmutes them. And from these things which are made from the exhalations of the earth, thicker bodies are transmuted into thinner substances; for dews are not carried upward otherwise than if the water which is in the earth has been thinned by an exhalation. This exhalation itself is made by a certain fiery substance of the sun existing under the earth and heating that place, and mostly one that is either sulfurous or bituminous, which, when heated, generally generates an exhalation. And the hot waters which are found in the earth are made for the same reason. The thinner parts of the dew, however, are transmuted into air, while the thicker ones, having been lifted up somewhat because of the force of the exhalation...