It would serve no good purpose to attempt to describe the recipes given by various alchemists to prepare this precious substance. With an affectation at times of precision, they were purposely obscure, and always enigmatical. As Boyle said of them, they could scarcely keep themselves from being confuted except by keeping themselves from being clearly understood. One example of their recipes must suffice: “To fix quicksilver.—Of several things take 2, 3 and 3, 1; 1 to 3 is 4; 3, 2 and 1. Between 4 and 3 there is 1; 3 from 4 is 1; then 1 and 1, 3 and 4; 1 from 3 is 2. Between 2 and 3 there is 1, between 3 and 2 there is 1. 1, 1, 1, and 1, 2, 2 and 1, 1 and 1 to 2. Then 1 is 1. I have told you all.” No wonder, after an equally luminous explication, a pupil of Arnaud de Villeneuve should have exclaimed: “But, master, I do not understand.” Upon which the master rejoined that he would be clearer another time. Nor is it necessary to dilate upon the other virtues which were ascribed at various times to the philosophical powder, as, for example, its power of making pearls and precious stones, or of its use in preparing the _alkahest_, or universal solvent, invented by Paracelsus. In their attempts to fathom the depths of human credulity the alchemists at length over-reached themselves. The idea of a universal solvent carried with it, as Kunkel pointed out, its own refutation: if it dissolved everything, no vessel could contain it. And yet, says Boerhaave, a whole library could be filled with writings by the school of Paracelsus on the alkahest. From the latter end of the sixteenth century repeated attempts were made to expose the pretensions and demonstrate the absurdities of alchemy. Among its adversaries may be cited Thomas Erastius, Hermann Conringius, and the Jesuit Kircher. Many of their dupes, potentates and princes who were powerful enough to exercise it, occasionally visited with their vengeance those who, unmindful of the injunctions of Albert the Great, had traded too long upon their credulity. The Emperor Rudolph II., who earned the title of “The Hermes of Germany,” was a zealous cultivator of alchemy, and had a well-equipped laboratory in his palace at Prague, to which every adept was welcome. Ferdinand III. and Leopold I. were also patrons of the hermetic art, as were Frederick I. and his successor, Frederick II., Kings of Prussia. Indeed, at one period nearly every Court in Europe had its alchemist, with the privileges of the Court fool or the poet laureate. The fraud and imposture to which the practice gave rise led occasionally to the promulgation of stringent laws against it, and at times the pursuit of operative chemistry became well-nigh impossible in some countries. In the fifth year of the reign of Henry IV. (1404) it was enacted that “None from henceforth shall use to multiply gold or silver, or use the craft of multiplication; and if the same do he shall incur the pain of felony.” According to Watson, the true reason