GEOLOGY troversy, of which there are two opposing views. Some geologists, following the brilliant researches of Ramsay, 1 claim a glacial origin for this heterogeneous collection of rock fragments. Others 2 maintain them to be scree material swept down by sub-aerial torrents from a pre-Triassic hilly region situated in the south. TRIASSIC SYSTEM To whatever origin the ' Permian ' breccias of Clent and Enville be attributed, the next group the unconformable Triassic rocks affords a typical example of deposits laid down under continental conditions, as was long ago pointed out by Ramsay and Godwin-Austen. The change from the river-borne muds and silts of the Carboniferous period is not only vividly contrasted in the loosely compacted red sandstones and conglomerates of the Trias, but the vast interval of time intervening between the close of the one set of events and the opening of another is forcibly demonstrated by the newer formation reposing horizontally or at gentle angles on the denuded and intensely plicated carboniferous strata. This is recognized by geologists ending the Palaeozoic era with the Carboniferous or Permian systems, and starting an altogether fresh time epoch (Mesozoic) with the red rocks of the Trias. At its commencement in the Bunter period the Triassic continent an elevated Carboniferous sea floor presented a very irregular rocky surface fashioned out of a plane of marine denudation during upheavals succeeding the Carboniferous period, and carved out by long subsequent denudation. This rugged surface of pre-Triassic hill and dale and possibly mountainous country became gradually levelled by dry weather- ing, torrential rains and wind, while the material derived from these sources was swept into and slowly accumulated in the hollows. In the succeeding Keuper stage the broader depressions were further rilled with sediments deposited in a great lake subjected to such intense evaporation as to result in the deposition of thick beds of rock-salt and gypsum. Finally, at the close of the Keuper period the area became depressed, by gentle sinking movements, beneath the waters of the Rhaetic and Jurassic seas. The Triassic system is built up of sandstones and marls of an almost universal red colour due to a thin film of oxide of iron coating each particle. Traced across the district from west to east the individual members show a rapid decrease in thickness : collectively, on the west side of the South Staffordshire Coalfield the thickness amounts to 3,500 feet, which has dwindled to about 1,200 feet on the east side of this coalfield, but there is reason to believe that in the centre of the basin to the north of Stafford the westerly amount is reached or even exceeded. Owing to the general slight inclination of the strata the outcrops are especially broad ; they are narrowest round the Carboniferous tracts in the north 1 'On the Occurrence of Angular, Subangular, Polished and Striated Fragments and Boulders in the Permian Breccia of Shropshire, Worcestershire, etc.,' <$uart. Journ. Geol. Soc. xi. 185 (1855). 3 ' On the Permian Conglomerates of the Lower Severn Basin,' by W. Wickham King, Quart. Joum. Geol. Soc. Iv. 97-128 (1899). 19
