In the 1790s, the british naturalist william smith hypothesized that if two layers of rock at widely differing locations contained similar fossils, then it was very plausible that the layers were the same age.
Cishe ngonyaka we-1790, isazi semvelo saseBrithani uWilliam Smith wakucabanga ukuthi uma izingqimba ezimbili zamatshe ezindaweni ezahlukahlukene ziqukethe izinsalela ezifanayo, kungenzeka kakhulu ukuthi zombili izingqimba zavela ngasikhathi sinye.