The facts one relies upon to determine whether a rock is young or old are, firstly, the nature of the fossils contained in the particular stratum, that is, the palæontological evidence; and secondly, the mineral constitution of the stratum, that is, the lithological evidence. Werner was the first to recognize that there is a definite order of the superposition of rocks, and he grouped the various sediments into four main divisions: those very much altered, Urgebirge, which we now call Archæan; those in a transition state, Uebergangsgebirge, which we call Palaeozoic; those showing normal stratification, Flötzgebirge, which we call Mesozoic; and those not yet consolidated into definite strata, Aufgeschwemmtes Gebirge, which we call Tertiary and Recent. It was William Smith, however, who first worked out the arrangement of rocks in detail. He was a land surveyor who, in surveying the banks of canals and the cuttings made for roads, noticed that wherever he went certain rocks with characteristic fossils were always underlain and overlain by similar rocks, each with their own characteristic fossils. Smith's Tabular View of the British Strata was published in 1790, and his first geological map of the whole of England was published in 1815. Since then the knowledge of Stratigraphical Geology has increased enormously; geologists have penetrated every corner of the globe, and a geological map of the whole face of the earth is now in course of publication.
In South Africa geological investigation was begun by Dugald Carmichael (1817) and Clarke Abel (1818), who wrote descriptions of Cape Town. Dr. Lawrence Jamieson, who was district surgeon at Grahamstown in 1828, wrote descriptions of the Eastern Province; but the first serious work was done by Andrew Geddes
