Digby asserted that the secret of the powder was imparted to him by a Carmelite monk whom he met at Florence. His laboratory assistant, George Hartman, published a “Book of Chymicall Secrets,” in 1682, after Sir Kenelm’s death, and therein explained that the Powder of Sympathy, which was then made by himself (Hartman), and “sold by a bookseller in Cornhill named Brookes” was prepared “by dissolving good English vitriol in as little warm water as will suffice, filter, evaporate, and set aside until fair, large, green crystals are formed. Spread these in the sun until they whiten. Then crush them coarsely and again dry in the sun.” Other recipes say it should be dried in the sun gently (a French formula says “amoureusement”) for 365 days. Sir Kenelm’s scientific explanation of the action of his sympathetic powder is on the same lines as the others I have quoted. Briefly it was that the rays of the sun extracted from the blood and the vitriol associated with it the spirit of each in minute atoms. At the same time the inflamed wound was exhaling hot atoms and making way for a current of air. The air charged with the atoms of blood and vitriol were attracted to it, and acted curatively. In a letter written by Straus to Sir Kenelm, it is related that Lord Gilborne had followed the system, but his method was described as “the dry way.” A carpenter had cut himself severely with an axe. The offending axe still bespattered with blood was smeared with the proper ointment and hung up in a cupboard. The wound was going on well, but one day it suddenly became violently painful again. On investigation it was found that the axe had fallen from the nail on which it was hung.