Carpenters constructing a stamping mill for breaking up ores and extraction of metals. Men on the left are measuring up a baulk of timber, K, to form a cam-shaft. A completed cam-shaft at H fitted with cams I. B is the stem of a single stamp, A. All the pieces of the mechanism are made of wood. From "De re metallica", by Agricola, pseudonym of Georg Bauer (Basle, 1556). Woodcut. Mining.