Coal measures, 131 fossils of the, 44 Coal plants, tropical character of, 88 Coal and iron associated, 43 Clouded marble, 33 Columnar structure, 18, 99 Compact limestone, 19 Concretionary formations, 99 Conglomerate, 19 of old red sandstone, 38 Connecticut valley-- one of denudation, 87 trap of, 30 Continents-- mean elevation of, 144 total elevation of, 144 elevated gradually, 144 why depressed, 145 Contorted strata, 72 Coral formation, 81, 102 extent of, 102 Coral reefs-- fringing, 81 barrier, 81 Coral rag, 49 Corals in silurian rocks, 35 Copper mines of Lake Superior, 47 Creation, a progressive work, 62 Cretaceous formation, 52 Cretaceous formation, fossils of, 52 geographical range of, 53 Crinoidea in Silurian rocks, 36 Crust of the earth, 16 expansion and contraction of, 143 D. Delta deposits, 114 Denudation of igneous rocks, 85 Denudation of sedimentary rocks, 85 Denudation produced by earthquake waves, 136 Deposition of sediment, 113 Diluvium, 20 Dike, 69, 133 Divisional planes, 68, 98 Dolomite, 13, 19 Drift, 20 extent of, 53 connected with striated surface of the rocks, 54 connected with subsidence, 54, 126 E.