Dr. Willis had a secret preparation of iron of which Dr. Walter Harris, physician in ordinary to Charles II, in “Pharmacologia Anti-Empirica” (1683), writes:--“The best preparation of any that iron can yield us is a secret of Dr. Willis. It has hitherto been a great secret and sold at a great price. It was known as Dr. Willis’s Preparation of Steel.” Dr. Harris thinks it will not be an unacceptable service to the public to communicate this masterpiece of that eminent and ever famous man. “It was no strained stately magistery, no sublimation or salification, no calcined crocus, and no chemical mystery; but an easy and a natural way of opening this hard body that it may open ours.” It was given particularly for the removal of obstructions. The formula was equal parts of iron filings and crude tartar powdered and mixed with water in a damp mass in a glazed earthen vessel. This was to be dried over a slow fire or in the sun; wetted and dried again; and this process repeated four or five times. It might be given in white wine, or made into a syrup, or into pills, electuary, or lozenges. Dr. Willis preferred the crude tartar because the cream of tartar sold by the druggists was generally a cheat, often combined with alum. The crude could be bought at 6d. to 8d. per lb. In the apothecaries’ shops cream of tartar was sold at 3s. to 3s. 6d. per lb. [Illustration: THOMAS WILLIS, M.D. 1621-1675.] Quincy (1724), who frequently offers explanations of the exact way in which medicines exercise their remedial power, thus scientifically describes the action of iron in removing obstructions:--“Mechanics teach nothing more plainly than that the momenta of all percussions are as the rectangles under the gravities and celerities of the moving bodies. By how much more gravity then a metalline particle has more than any other particle in the Blood, if their celerities are equal, by so much the greater will the stroke of the metalline particle be against everything that stands in its way than of any other not so heavy; and therefore will any Obstruction in the Glands and Capillaries be sooner removed by such particles than by those which are lighter. This is a way of reasoning that is plain to the meanest Capacity.”