Aristotle's Theory of the Formation of Metals and Minerals

Abstract

The Twofold Exhalation. Aristotle explains in Book I of the Meteorologica (341b6 ff.) that the heat of the sun causes the earth to give off an exhalation (ναθνμασις), which is of two kinds. One kind, derived from the moisture within the earth and on its surface, is a moist vapour (cf. De Sensu 443a26–7), ‘potentially like water’ (340b28–9); the other, which comes from the earth itself, is hot, dry, and smoky, highly combustible ‘like a fuel’ (οἷον ὑπκκανμα 341b18–19), ‘the most inflammable of substances’ (341b16–17), ‘potentially like fire’ (340b29), and compounded of Air and Earth (De Sensu 443a21–2, 27–8).