Among the minerals and metals known to the Egyptians are also mentioned the emerald, malachite, copper in alloys, iron, lead, tin, and mercury, the mobility of which caused it to be regarded as living; whence the name quicksilver. Their tinctorial art included dyeing in yellow, white, and black; and they could also dye purple by means of alkanet and archil. All these changes brought about in the appearance of bodies seemed to be modifications of their properties, and consequently to legitimize the expectation of effecting transmutation. We should, however, recollect that the idea of the fixedness of the properties of bodies is wholly modern. Even Bacon wrote in the seventeenth century: "Observing all the qualities of gold, we find that it is yellow, very heavy, of a certain specific gravity, malleable, and ductile to a certain degree; and whoever is acquainted with the formulas and processes necessary to produce at will the yellow color, the high specific gravity, the ductility, and knows, also, the means of producing these qualities in different degrees, will perceive the means and be able to take the measures necessary to unite these qualities into a definite body; and from this will result its transmutation into gold." This was, in fact, the dream and the mastering passion of the alchemy of the middle ages and the Renaissance.
These conceptions were very ancient, and must be looked for in their original forms in the Greek philosophy. The germ of the doctrine of transmutation is in the Timæus. It rests on the idea of primitive matter, the indifferent supporter of all the qualities that can be heaped upon it. Plato insists upon the idea, which he regards as fundamental, that "the thing which receives all bodies never comes out from its own substance. It is the common basis of all the different substances, and is deprived of all the forms which it would receive otherwise." The primary matter was supposed to be composed of fire, which made it visible, earth, which made it tangible, air, and water, which assured the union of the earth and the fire—these four elements being formed of minute corpuscles, susceptible of changing into one another; for we see, says Plato, "that water, in condensing, becomes stone and earth, and in melting and dividing itself up, becomes wind and air. Air inflamed becomes fire; fire, condensed and extinguished, resumes the form of air; air, thickening, changes into mist, and then flows as water; and from water are formed earth and stones."
All bodies were believed to be the seat of a transformation of this kind. Under the influence of this thought, Proclus wrote, "Things being never able to preserve a nature of their own, who shall dare affirm that one of them is this rather than the other?" It is, therefore, by virtue of a necessary law of nature that bodies
