Answer:
Geologic timescale
Step-by-step explanation:
William Smith, Benjamin Richardson, and Joseph Townsend, were all friends that had common interest is fossils and rock layers. They managed to gather lot of fossils and examine lot of layers of rocks, which gradually was improving their knowledge of the past of the Earth. Their main focus though was on the fossils, thus on the animals that lived in the past, so they were responsible for the creation of the Faunal Succession theory. The Faunal Succession theory was based upon the fossils that were found in a particular layers of rock strata. Even though it was not their purpose, these three men actually managed to set the basis for the geological timescale that we now and use nowadays.