To really understand what Newton was seeing in his laboratory, Newman realized in 2002, he needed to repeat some of the old alchemical experiments himself. (See the slideshow of Newman's recreated alchemy lab.) He started by building replicas of alchemical furnaces and glassware, including distilling apparatus, with the help of Indiana University’s chemistry department. One key alchemical experiment was called the Tree of Diana, a magical-looking demonstration that metals could grow like vegetation. Newman learned that the Tree of Diana really works. “If you immerse a solid amalgam of silver and mercury in nitric acid with dissolved silver and mercury, you produce tiny, twiglike branches of solid silver,” he says. Today this process is regarded as a simple matter of chemistry. But to Newton, the Tree of Diana was evidence that metals could be made to grow and, therefore, “possessed a sort of life.”
The image of the growing metallic tree can be found in another type of experiment, one that Starkey, Boyle, and very likely Newton all conducted: the attempt to synthesize the Philosophers’ Stone. Principe, who had studied the alchemical work of all three men, came to the same conclusion as Newman and decided that he, too, had to replicate the long-abandoned alchemical experiments firsthand. He culled recipes from alchemists like Starkey and, after “a lengthy process involving various materials and numerous distillations,” obtained Philosophical Mercury, just as Boyle had 350 years earlier. Principe mixed the Philosophical Mercury with gold, sealed it in a glass egg, and watched. Just as Starkey and other alchemists reported, strange things started to happen inside the egg. The mixture began to bubble, rising “like leavened dough,” Principe says. Then it turned pasty and liquid and, after several days of heating, transformed into what he likens to a “dendritic fractal”: another metallic tree, like the trees the miners saw underground, only this one was made of gold and mercury.
Principe’s tree, like all the trees any alchemist managed to create, did not actually grow any gold, of course; the gold that came out was no greater than the amount that he put in. But the experiments proved something that Principe had long suspected. Alchemists were not just tinkering blindly. In fact, they produced what he calls “a solid body of repeated and repeatable observations of laboratory results.” In their tightly controlled experiments they made metals bubble, change colors, and grow sparkling filaments, and they did it over and over again, establishing, in a crude way, the foundations of scientific experimentation. In the process they were learning fundamental principles of chemistry: breaking down ores, dissolving metals with acids, and precipitating metals out of solution.
Ever since he found that singular Newton manuscript, Principe has wondered what was going on in the mind of one of history’s most brilliant scientists. How close did Newton and Boyle think they had come to making gold? Did they believe that with just a few more tweaks, their experiments would eventually work? Principe says yes, they probably did. Why, otherwise, would the highly apolitical Boyle have lobbied the Houses of Parliament to overturn a law forbidding gold making? “He was a very scrupulous man, and before he went about doing transmutation, he wanted to make sure it wasn’t against the law,” Principe says.
Further evidence of their seriousness emerged after Boyle’s death in 1691. In life, Boyle had guarded his recipe for red earth as if it were the most precious thing in the world. But upon his death, his executor, the philosopher John Locke, also an alchemist, was more generous, sending Newton the recipe along with a sample that Boyle had made before his death.
No one knows what Newton did with the red earth. Principe notes that Newton suffered a mental breakdown a year after Boyle’s death and wonders if that episode might have been brought on by mercury poisoning. After all, the first steps in making red earth require repeatedly heating and cooling mercury. “Shortly after he would have gotten copies of this recipe, he was distilling mercury,” Principe says. But Newman thinks that Newton’s breakdown is just as likely to be related to Locke’s trying to set him up with a well-to-do widow. “Newton had a sort of pathological fear of females, and around that time Locke was pressuring him to date. That may be what pushed him over the edge,” he notes. (Newton is believed to have died a virgin, according to historian Gale Christianson.)
No matter how skillfully the two giants of 17th-century science manipulated the red earth and set their sights on the Philosophers’ Stone, they would have failed to make gold. We know now that such a transformation requires not a chemical reaction but a nuclear one, far beyond the reach of the technology of the time. By the early 18th century, alchemists had given up on their quest for gold. “They’d figured out that in a practical way their attempts to make the Philosophers’ Stone never worked,” Newman says. That does not mean that their other work was abandoned, however. As Newman says, “The goals of 18th-century chemistry—namely, to understand the material composition of things through analysis and synthesis and to make useful products such as pharmaceuticals, pigments, porcelain, and various refined chemicals—were largely inherited from the 16th- and 17th-century alchemists.”
Without the pioneering alchemists, none of that would have been possible. “They were the masters of premodern chemical technology,” Newman says. As the true power and limitations of chemistry came into focus, interest in the Philosophers’ Stone simply faded away, much as the belief in the classical Four Elements had faded away centuries before. Almost overnight, the perception of alchemy became conflated with an unforgiving view of the protoscientific world as one populated by mystics and superstitious fools.
As for Isaac Newton’s prized sample of red earth from John Locke, it was very likely thrown out after Newton died in 1727. Unless someone kept it. Imagine a little packet of Philosophers’ Stone stuck between the pages of a book from Newton’s library. If it is out there, for the sake of alchemy and science, let’s hope Newman and Principe are the ones who find it.