Although alchemy, at least in its decadent days, lived for the most part by its appeal to some of the lowest instincts of mankind, and is only worth notice as a transient phase in the history of science, a few details concerning the tenets and practices of its professors may be of interest to the curious reader. And first as regards the nature of the philosopher’s stone—the grand magistery, the quintessence. Many alchemists professed to have seen and handled it. It is usually described as a red powder. Lully mentions it under the name of _Carbunculus_. Paracelsus says that it was like a ruby, transparent and brittle as glass; Berigard de Pisa that it was of the colour of a wild poppy, with the smell of heated sea salt; Van Helmont that it was like saffron, with the lustre of glass. Helvetius describes it as of the colour of sulphur. Lastly, an unknown writer, under the pseudonym of “Kalid,” says that it may be of any colour—white, red, yellow, sky-blue, or green. As the substance was wholly mythical, a certain latitude of description may reasonably be expected. Some of the alchemists were of opinion that the magistery was of two kinds—the first, the _grand_ magistery, needed for the production of gold; the second, the _small_ magistery, only capable of ennobling a metal as far as the stage of silver. Then, as to the amounts required to effect a transmutation, accounts are equally discrepant. Arnaud de Villeneuve and Rupescissa assert that one part of the grand magistery will convert a hundred parts of a base metal into gold; Roger Bacon, a hundred thousand parts; Isaac of Holland, a million. Raymond Lully states that philosopher’s stone is of such power that even the gold produced by means of it will ennoble an infinitely large amount of a base metal.