Text-book of Geology

abundant accumulated acid altered Ammonites appear augite bands basalt basin beds brachiopods calcareous calcite carbonate Carboniferous chalk character chemical chiefly clay coal cone conglomerates consist containing corals Cretaceous crust crystalline rocks crystals denudation deposits depth Devonian diabase dolomite dykes earth Eocene Europe evidence fauna feet thick felspar fissures foliated formations forms fossils fragments genera geological geologists glaciers gneiss granite graptolites grey greywacke hornblende igneous iron lakes land lava layers lime limestone lithological Lower Silurian marine marls mass massive metamorphism microscope miles mineral mountain North numerous observed occur Old Red Sandstone organic remains original orthoclase oxide Paleozoic period Permian porphyritic portions present Q. J. Geol quartz region river round sand schists Scotland sediment sedimentary shales sheets shells siliceous Silurian sometimes species stone strata stratified structure surface temperature terrestrial Tertiary traced tuffs unconformably Upper Silurian usually valleys vapours veins volcanic zone