Barrell's research determined that the layers of strata had not all been laid down at the same rate, and so current rates of geological change could not be used to provide accurate timelines of the history of Earth.
Barrells forskning viste, at ikke alle stratalag var aflejret med samme hast, hvorfor hastigheden af nutidens geologiske ændringer ikke kunne bruges til at udforme nøjagtige tidslinjer for Jordens historie.