The present generation has not as yet quite got over the bad habit of making fun of these medieval thinkers for having accepted the idea of the transmutation of metals and searched so assiduously for the philosopher's stone. This supposed absurdity has for most scientific minds during the nineteenth century been quite enough of itself, without more ado, to stamp the generations of the Middle Ages who accepted it, as utterly lacking, if not in common sense, at least in serious reasoning power. At the present moment, however, we are in the full tide of a set of opinions that tend to make us believe not {309} only in the possibility, but in the actual occurrence of the transmutation of metals. Observations made with regard to radium have revolutionized all the scientific thinking in this matter. Radium has apparently been demonstrated changing into helium, and so there is a transmutation of metals. On the strength of this and certain other recently investigated physical phenomena, there is a definite tendency in the minds of many serious students of physics and chemistry to consider that other metals possibly change into one another, and that all that is needed is careful observation to discover it, for this change is supposed to be going on around us all the time. Not very long since, a professor of physical science at an important American university suggested that it would be extremely interesting to take a large specimen of lead ore, say several tons, and having removed from it carefully all traces of silver that might be contained in it, put it away for twenty years, and then see whether any further traces of silver could be found. The idea that possibly lead occasionally changes into silver by some slow chemical process is evidently deep-seated in his mind. It would remind one of Newton's expression some two centuries ago, that he had seen copper and gold ores occurring together in specimens, and that he looked upon this as evidence that copper in the course of time changes into gold. Certain it is that lead ores constantly occur in connection with silver, or at least that silver is found wherever lead is; that a corresponding relationship between gold and copper has also been noted; and that Newton's idea was not near so absurd, in the light of what we now know, or still more, what we surmise on good scientific grounds, as the nineteenth century scientists would have had us believe. {310}