Early 19th century theories explaining fossils are presented, with primary emphasis upon Parkinson's work. This work indicated a breakthrough in interdisciplinary contributions: chemistry was applied to the science of palaeontology. Pepys conducted an analysis (distillation) of opaline fossil wood. Similarly calcareous woods were also tested with acid, and various coals were examined. The identification and classification of fossil vegetable remains were undertaken. The test of applying dilute muriatic acid to the limestone or marble in which a fossil coral was embedded substantiated the claim that fossilization involved impregnation of materials rather than substitution. -- AATA