 and air under the earth, which, as Agricola reasoned, is responsible for earthquakes and volcanoes.The ten books of "De veteribus et novis metallis", more commonly known as "De Natura Fossilium" are published in 1546 as a comprehensive textbook and account of the discovery and occurrence of minerals, ores, metals, gemstones, earths and igneous rocks, followed by "De animantibus subterraneis" in 1548 and a number of smaller works on the metals during the following two years.Agricola served as Burgomaster (lord mayor) of Chemnitz in 1546, 1547, 1551 and 1553.