Article: Charles Lyell's dream of a statistical palaeontology [Twentieth Annual Address delivered 16 March 1977]

The terms Eocene, Miocene, and Pliocene were first used in 1833 in Charles Lyell's analysis of Cainozoic earth-history. Their original meaning and intention in Lyell's mind is here reconstructed, against the background of other contemporary research on the Tertiary strata. Lyell's terms were not originally intended to define contiguous periods of geological time: instead they defined relatively short isolated 'moments', randomly preserved from a far longer span of time. The ages of these 'moments' of preserved time were thought to be determinable in quantitative terms (however approximate and uncalibrated), by reference to the percentage of extant molluscan species that each group of strata contained. This palaeontological 'chronometer' depended on a biological theory of the continuous piecemeal formation and extinction of species at a uniform rate. Lyell originally hoped that his 'chronometer' could be extended backwards beyond the Tertiary and into even earlier periods. Although this ambitious project soon failed, it is conceptually important as an early attempt to use palaeontology to make a general quantitative time-scale for geology.