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 A HISTORY OF DERBYSHIRE and also for ornamental purposes, though the introduction of iron mantel- pieces has greatly reduced the output of encrinital marble previously used. The various grits and sandstones are used for buildings and millstones, the clays for making bricks, and the Bunter sandstone for moulding. The Keuper marl supplies gypsum and alabaster for making plaster of Paris ornaments and rock work, and calcareous tufa is largely quarried for grottoes. The following table gives a list of the strata found in Derbyshire : TABLE OF STRATA Quarternary or Port Tertiary Secondary or Mesozoic Recent Pleistocene Triassic Keuper. Bunter , Alluvium, peat bogs, calcareous tufa, stalactitic formations Cavern deposits, glacial drift, boulders, sands and clays /Red marl, with gypsum Waterstones /Pebble beds or conglomerate Lower mottled sandstone Permian Magnesian Limestone Series Marls and sandstones Lower magnesian limestone Marls and sandstones Coal Measures Millstone Grit Primary or Palseozoic Carboniferous Yoredale Rocks , Mountain Limestone Middle coal measures Lower or Gannister series 1. Rough rock Shales 2. Sandstone and shales Shales 3. Chatsworth grit Shales 4. Kinder Scout grit Shales 5. Shale grit Shales, with thin sandstones Shales, with thin beds and nodules of earthy limestones and con- temporaneous volcanic rocks (Limestone, with chert, thin shales and clay partings and contempo- raneous and intrusive igneous rocks MOUNTAIN LIMESTONE A careful examination of a geological map will show isolated patches of rock. A patch or band of older rock surrounded by newer is called an inlier, and a patch or band of newer rock surrounded by older an outlier. Both of these may be due to denudation of horizontal strata in which case the former are situate in the valleys and the latter 4