In the summer of 1677, the wealthy London scientist and "father of modern chemistry" Robert Boyle was approached by a mysterious foreigner who claimed to be the agent of the "Patriarch of Antioch", the supreme head of a society of alchemical masters. It would not be long, the visitor told Boyle, before God granted him the privilege of joining this secret confraternity, so that Boyle himself could become "Master of the Philosopher's Stone". Boyle, usually cautious, responded with enthusiasm. For almost a year, he showered this "ambassador" with lavish gifts for the "Patriarch": a large telescope, assay balances, a globe, copies of the New Testament in Turkish and a case of 100 glass vials for his alchemical laboratory. At the Patriarch's request, he sent gifts for the Turkish court where the mysterious Grand Master was supposed to reside: fine fabric "for the sultana queen mother, eight rods of flesh-coloured moire, eight of gold-coloured moire, and eight of flame-coloured moire", and a chiming clock "more than three feet high".
The whole affair turned out to be an elaborate hoax - large sums in money were extracted from the gullible Boyle, until eventually his credulity was exhausted and the Patriarch's emissary vanished.
One of the remarkable things about alchemy is how readily sensible men have been duped by charlatans promising them access to its powerful secrets - how to transmute base metals into gold, and how to find the elixir that will make men live for ever. Boyle was promised access to the secret of making "red mercury", the vital ingredient for producing unlimited quantities of gold.
He recorded (in code) the many stages in the various methods that he had tried and retried in his laboratory. Among those with whom he corresponded who were equally intent on mastering the process for chemically manufacturing this secret ingredient were such respectable figures as the physician and philosopher John Locke and the president of the Royal Society, Sir Isaac Newton.
In The Philosopher's Stone, Peter Marshall describes how, while in Cairo, he, too, came to be offered access to red mercury, in a similarly clandestine fashion and at a price suitably inflated for the beginning of the 21st century: "When I mentioned that I had come to Egypt in search of the Philosopher's Stone, she lowered her voice and said she might be able to get me a special substance known as Red Mercury . . . 'Many people know about it but it's a secret! You have to be very discreet. There's a shadow about it. With a fraction of a gram you can become very rich.'
" 'How much does Red Mercury cost?'
" 'A million dollars . . .' "
Marshall, alas, has neither the funds nor access to the required Nigerian magician in order to pursue "red mercury" any further. Go to one of the many alchemy-related internet sites, however, and you will find the substance on offer, now with links (set up by dabblers in the occult) to the secrets of weapons of mass destruction.
Marshall is, by his own admission, one of those convinced that "the secrets of alchemy offer profound insights into the nature of science, the character of the human psyche and the structure of the universe". He finds enlightenment in alchemy's arcana, just as he is a devotee of vegetarianism and spiritual meditation. His book panders unashamedly to other such enthusiasts, uncritically amassing data worldwide on occult topics ranging from the mystic resonances of the Great Pyramid in Egypt to how to have inspirational sex without ejaculating.
Marshall's enthusiasm for his subject closes out any contrary, disbelieving voices. The bewildering eclecticism of the huge amounts of material he bundles together under the general rubric "alchemy" makes the book almost useless for anyone trying to decide whether the claims made by its practitioners - from many centuries before the Christian era in China to the modern eastern bloc - have any truth to them, or indeed any interest to the modern reader.
However, one aspect of The Philosopher's Stone is of real interest to the modern historian. Marshall shows that, from pre-antiquity to the end of the Middle Ages, practitioners of the occult sciences in China, India and Egypt have shared a common vocabulary and terminology. They have observed the same chemical reactions between substances, administered the same combinations and distillations of herbs and minerals as medicinal remedies. The fourth-century Chinese alchemist Ko Hung recommends cinnabar and "potable gold" for the prolongation of life; so does Sir Francis Bacon at the beginning of the 17th century in England, although he never refers directly to Chinese sources. To anyone who reaches the end of this book, it will be clear that, throughout history, ideas have been continuously exchanged and cross-fertilised between east and west, in spite of enmity and political isolation, and across boundaries of language and creed.
Apparently, the many manuscript sources now so meticulously made available on the website www.levity.com/alchemy have always enjoyed underground circulation to eager fans of "alternative" science and medicine, beyond the prying eyes of "proper" science. No doubt they have exerted important influence over the development of mainstream practices in the same fields.
It would be fascinating to pursue this idea in the company of a reliable, suitably disinterested guide. Marshall's study, unfortunately, is not the book to help such an enterprise. His own answer to the major questions - Has ancient alchemy brought him untold wealth? Has it prolonged his life or enabled him to decipher the riddle of the universe? - is characteristically infuriating: "Yes and no."
Lisa Jardine's Ingenious Pursuits is available in paperback (Abacus, £15)