The immediate object of Boyle’s visit to London was probably to be present at some of the performances of Valentine Greatrakes, the “Stroaker,” who was making a great sensation in London by his semi-miraculous cures. Greatrakes had originally been a lieutenant in Lord Broghill’s regiment in Munster, and had more recently—having felt an “impulse”—practised his cures in county Cork. He had come to England by Lord Broghill’s advice, and had made his _début_ in an attempt to cure Lady Conway’s violent headaches. In this he failed; but he was more successful with other patients, and the King sent for him to Whitehall, and he was patronised by Prince Rupert. Of course, the Faculty was divided, and the Royal Society cautious. Mr. Stubbe, a worthy doctor of Stratford-on-Avon, went so far as to publish in Oxford a tract, “The Miraculous Conformist”, addressed, without permission, to Mr. Boyle—to which, very naturally, Mr. Boyle took exception. It was followed by a London-published tract, “Wonders no Miracles”; and the controversy still waged about the “Stroaker” when Boyle went to London and was present at some of his “stupendous performances.” Mr. Boyle made careful notes, and submitted to Mr. Greatrakes a series of written questions—which do not seem to have been answered. But in the end, Robert Boyle was one of those who, having seen the “Stroaker” at work, gave him a testimonial before he left London. The Greatrakes episode stands on the threshold of a whole realm of medical treatment undreamed of in 1666. Meantime, Boyle’s treatise, _Hydrostatical Paradoxes_, that had been slowly printing for several months, appeared early in that year. This was shortly followed by his _Origin of Forms_; and a good many of his philosophical transactions also belong to this year. Later in the summer, when the London season was over, he was living in his Chelsea lodging; but he had been ill again; and Lady Ranelagh was back in her house in Pall Mall.