Nine Books on the Nature of Things

It is also most necessary in this book to know the degrees of fire. Fire can be graduated and intensified in many ways; every degree has its particular operation and produces a different effect, as any skilled alchemist knows through daily experience and practice. One kind is living, flaming fire, which reverberates and calcines all bodies. Another is the steady fire of a candle or lamp, which fixes all volatile bodies. Another is charcoal fire, which cements and colours metals, purifies them from slag, raises Gold and Silver to a higher degree, whitens Copper and, in short, renews all metals. Another is the fire of a glowing iron plate, on which metallic tinctures are tested and which has other uses. Iron filings heat in one way, sand another, ashes another, the sea bath another, in which many distillations, sublimations and coagulations occur. The dew bath operates differently, producing many solutions of corporeal things; the horse’s belly differently again, chiefly producing putrefactions and digestions. Invisible fire also operates differently: by this we mean the sun’s rays, manifested through a steel mirror or crystal, which show their operation and effect. The ancients wrote nothing whatever about this fire. Through it the three principles can be separated from any corporeal thing upon a table. Such is its marvellous virtue that metals and all fatty and fusible things melt upon the table without fire, and all readily combustible things are reduced to coals and ashes.