William Smith (1769-1839), British geologist. The son of a blacksmith, Smith became a canal surveyor, which allowed him to study geology. He discovered that geological strata could be reliably identified at different places on the basis of the fossils they contained. He also proposed the principle of superposition, that if a strata overlays another then it was laid down at a later time. In 1815 he published the first geological map of England and Wales. He is considered the father of English geology. This 1837 portrait, by the French artist Hugues Fourau (1803-1873), is from the Geological Society collection and shows Smith aged 69.