VI. On the signficance of the sequence of rocks and fossils: theoretical considerations on the upper secondary rocks, as seen in the section at Ely.

Extract

Clays are generally the mud of rivers; sandstones, the detritus of old crystalline rocks; while limestones are organically or chemically formed. If, therefore, there is a great clay, it bespeaks a great river draining lands that were; though small and local clay-bands may be but the ruins of denuded sea-cliffs. The sandstone is the evidence of coast and reef, where and wave disintegrated plutonic rocks, or constructed over again the palæozoic or older sand-rocks. And limestones have been formed either from the denudation of calcareous cliffs in shallow seas.