cautioning the audience that natural and man-made objects are often easily confused, he asserts that the specific "figures" or "formes that can be distinguished (formes qui les font distingues)" of the stones were man-made, not natural: It was Man's hand that made them serve as instruments (C'est la main des hommes qui les leur a données pour servir d'instrumens...) Their cause, he asserts, is "the industry of our forefathers (l'industrie de nos premiers pères)." He adds later that bronze and iron implements imitate the uses of the stone ones, suggesting a replacement of stone with metals. Mahudel is careful not to take credit for the idea of a succession of usages in time but states: "it is Michel Mercatus, physician of Clement VIII who first had this idea". He does not coin a term for ages, but speaks only of the times of usages. His use of l'industrie foreshadows the 20th century "industries", but where the moderns mean specific tool traditions, Mahudel meant only the art of working stone and metal in general. The three-age system of C. J. Thomsen An important step in the development of the Three-age System came in the period 1816–1825 when the Danish antiquarian Christian Jürgensen Thomsen was able to use the Danish national collection of antiquities and the records of their finds as well as reports from contemporaneous excavations to provide a solid empirical basis for the system. He showed that artefacts could be classified into types and that these types varied over time in ways that correlated with the predominance of stone, bronze or iron implements and weapons. In this way he turned the Three-age System from being an evolutionary scheme based on intuition and general knowledge into a system of relative chronology supported by archaeological evidence. Initially, the three-age system as it was developed by Thomsen and his contemporaries in Scandinavia, such as Sven Nilsson and J.J.A. Worsaae, was grafted onto the traditional biblical chronology. But, during the 1830s they achieved independence from textual chronologies and relied mainly on typology and stratigraphy. In 1816 Thomsen at age 27 was appointed to succeed the retiring Rasmus Nyerup as Secretary of the Kongelige Commission for Oldsagers Opbevaring ("Royal Commission for the Preservation of Antiquities"), which had been founded in 1807. The post was unsalaried; Thomsen had independent means. At his appointment Bishop Münter said that he was an "amateur with a great range of