Silver assay. Historical engraving of an assayer and his assistant determining if a sample of silver contains gold. The assayer is standing in front of an assay oven (1), while his assistant is washing the metal. Taken from The Laws of Art and Nature, in Knowing, Judging, Assaying, Fining, Refining and Inlarging the Bodies of Confin'd Metals (1863), John Pettus, a translation of the work of Lazarus Erckern.