irregular, how produced, 115 Striated surfaces, 87 Submerged forests, 79 Subsidence of land, 79, 145 Subsidence of land in Greenland, 82 Subsidence and elevation in the Pacific, 80 Sulphate of lime, 15 Sulphur, 12 Sun-cracks, 48 Sunken areas, 142 Syenite, 17 Synclinal axes, 72 T. Taconic system, 32 Talc, 15 Talcose slate, 20, 32 Temperature at great depths, 127 Temple of Jupiter Serapis, 83 Tertiary system, 53 age, how determined, 53 fossils, 54 divisions of, 53 geographical range, 56 Tilestones of the old red sandstone, 38 Trachyte, 18 Tracks in new red sandstone, 49 Transportation of sediment, 111 Trappean rocks, 17 localities of, 29 Tremolite, 15 Trias, 47 Trilobite, 37, 40 V. Valley, 69 of elevation, 71, 75 of subsidence, 72