PLATE FACING PAGE 1 Granite Weathering to Soil Leaving Residual Cores of Joint Blocks (_Upper picture_) 32 Looking-Glass Rock, Utah. Stratified Sandstone Sculptured by Wind Erosion (_Lower picture_) 32 2 Grand Canyon of the Yellowstone River. A Channel Worn by Erosion 33 3 Gorge of the Niagara River Below the Falls. A Sample of Recent Erosion 64 4 Winding Stream in the St. Lawrence Valley with Flood Plain (_Upper picture_) 65 Davidson Glacier, Alaska, Showing Action on the Valley's Walls and Floor (_Lower picture_) 65 5 Swift Current Valley in Glacier National Park, Formed by Stream and Glacier Action 96 6 Yosemite Valley from Western Entrance. The Result of Glacial Action 97 7 An Upbend Fold or Anticline in Maryland 128 8 Ledge of Igneous Rock Showing Joints (_Upper picture_) 129 Fault Fracture in Limestone Formations (_Lower pictures_) 129 9 Molten Lava Flowing Over a Cliff in Hawaii (_Upper picture_) 160 Dikes of Granite Cutting Old Rock (_Lower picture_) 160 10 Lassen Peak, California, in Eruption (_Left picture_) 161 Devil's Tower, Wyoming, Once a Mass of Molten Rock Forced Through Strata (_Right picture_) 161 11 Mammoth Hot Springs Terrace in Yellowstone National Park (_Upper picture_) 224 Crater Lake, Oregon, Formed by the Subsidence of a Volcano (_Lower picture_) 224 12 Archeozoic Rock, Oldest Known Rock Formation on Earth (_Upper picture_) 225 Twisted Mass of Stratified Limestone, Surrounded by Granite (_Lower picture_) 225 13 Paleozoic Rock, Covered with Oldest Known Animal Remains 256 14 "Stone-Lily" Stems in Ordovician Strata (_Upper left picture_) 257 Various Brachiopods in Ordovician Strata (_Upper right picture_) 257 Stratified Limestone of Middle Ordovician Era Containing Fossils (_Lower picture_) 257 15 A Landscape of the Coal Age (_Upper picture_) 288 Fossil Fern on a Piece of Shale (_Lower picture_) 288 16 Restoration of Huge Animals of the Mesozoic Era 289 17 Skeleton of Two-Legged Carnivorous Dinosaur (_Large picture_) 320