Like the other antiquarians Thomsen undoubtedly knew of the three-age model of prehistory through the works of Lucretius, the Dane Vedel Simonsen, Montfaucon and Mahudel. Sorting the material in the collection chronologically he mapped out which kinds of artefacts co-occurred in deposits and which did not, as this arrangement would allow him to discern any trends that were exclusive to certain periods. In this way he discovered that stone tools did not co-occur with bronze or iron in the earliest deposits while subsequently bronze did not co-occur with iron – so that three periods could be defined by their available materials, stone, bronze and iron.