Copper extraction. Historical engraving of workers extracting copper from copper ore. A number of ovens and hearths used in the process are shown. At centre right is a drying oven (1), at upper centre is a Hungarian oven (2), with its hearth (5) and at centre left is a drying hearth (3). At bottom left a worker is cooling copper cakes (6) in water. Taken from The Laws of Art and Nature, in Knowing, Judging, Assaying, Fining, Refining and Inlarging the Bodies of Confin'd Metals (1683), John Pettus, a translation of the work by Lazarus Erckern.