text: Agricola addresses the book to prominent German aristocrats, the most important of whom were Maurice, Elector of Saxony and his brother Augustus, who were his main patrons. He then describes the works of ancient and contemporary writers on mining and metallurgy, the chief ancient source being Pliny the Elder. Agricola describes several books contemporary to him, the chief being a booklet by Calbus of Freiberg in German. The works of alchemists are then described. Agricola does not reject the idea of alchemy, but notes that alchemical writings are obscure and that we do not read of any of the masters who became rich. He then describes fraudulent alchemists, who deserve the death penalty. Agricola completes his introduction by explaining that, since no other author has described the art of metals completely, he has written this work, setting forth his scheme for twelve books. Finally, he again directly addresses his audience of German princes, explaining the wealth that can be gained from this art.