In 1815 he published the first geological map of Britain. Conventional symbols were used to mark canals, tunnels, tramways and roads, collieries, lead, copper and tin mines, together with salt and alum works. The various geological types were indicated by different colours; the maps were hand coloured. The map is remarkably similar to modern geological maps of England. He also published his "Delineation of the strata of England" in the same year. In another of his books "Strata identified by organized fossils" (London 1816–1819) he recognised that strata contained distinct fossils. These fossil assemblages could be used to match rocks between regions. This marks Smith as an important figure in the history of stratigraphy.