APOLOGIA

...[qualities that] are not present in the other metals, and why. Therefore, the fact that silver and gold are not burned or consumed by fire becomes clear because, when melted by fire, they breathe out no sulfurous or flammable vapor.

The cause is that they are devoid of all sulfurous, flammable, and oily substance. For almost every natural body consists of a double moisture original: "duplici humore"; a reference to the Aristotelian theory that matter is composed of various 'fluids' or principles: one is greasy, oily, and flammable—such as sulfur here meaning the "principle of combustibility" rather than just the mineral, oil, or fat; the other is watery, which acts like a "glue" to hold the earthy parts of bodies together, and which is common to all things created from the mixing of the Elements. Therefore, whatever body is subject to burning possesses a moisture similar to oil, and it is by this kind alone that a thing catches fire. Indeed, because this oily moisture arises from the Air, it retains the hot quality of the Air. But the watery moisture, which is the glue of the earthy parts, cannot be conquered by fire. For that moisture is cold and wet, while fire is hot and dry. And since they fight against each other with contrary qualities (as has already been said), neither yields to the other. Therefore, the watery moisture alone protects original: "tuetur"; this is the catchword for the page continuity silver and gold so they are not consumed by fire. For they partake in no oily or sulfurous moisture that might assist the fire in gaining a victory over the watery moisture within them. However, the remaining metals—because they partake in a certain sulfurous moisture that can even be detected by its smell—are burned and contract a blackness from the fire.

Furthermore, the fact that the essential parts of silver and gold—namely, the Moist and the Dry from which they are composed—are not dissolved or separated by fire is proven by their repeated melting [colliquatio] in the fire. For nothing of their weight is lost. Indeed, I remember that in former years I took one ounce of the purest gold enclosed in a small earthenware vessel, and another ounce of pure silver likewise enclosed in a separate vessel. I placed them in that spot where glass is kept perpetually melted in a glassmaker’s furnace. There, both remained fused and liquefied for two continuous months. When those months had passed and I removed them from both the vessels and the furnace, I weighed them on scales. I observed that the gold had not lost even the smallest amount of weight, while the silver had lost only a twelfth part. This is certainly worthy of admiration, yet I have learned through experience itself that it is most true.

The cause of this is the perfect mixing and union of the Dry and the Moist, which are joined in such a tight bond that they are indissoluble even by the most violent fires. For the Moist is tempered by the Dry, and the Dry by the Moist; in both silver and gold, they become one equal substance, homeomerous original: "homeomera"; a philosophical term meaning that every part of the substance is identical in nature to the whole and uniform in its similar parts. Hence, when the fire strives to rarefy and dissolve them, and to carry off the watery Moist into vapor...