The Scottish geologist James Hutton (1726–1797), in his Theory of the Earth (1785), had studied the stratification of rocks (their arrangement in superimposed layers or strata), establishing principles which were to be the basis of archaeological excavation, as foreshadowed by Jefferson. Hutton showed that the strati-fication of rocks was due to processes still ongoing in seas, rivers, and lakes. This was the principle of “uniformitarian-ism.”