Crystallization and the fairy land of change, 93; how the pebble caught cold and what came of it, 94; crystals in sugar and granite, 94; the great melting pot and the remaking of the rocks, 96; how old rocks hatch new ones by sitting on one another, 96; how mountain making helps, 97; how Mother Nature uses salt and soda in cooking rocks over and how she keeps these materials handy, 99; an illustration of how men of science study things out for the fun of it, 104; the crystal fairies and their curious ways, 106; how crystals help tell about dikes, 243 Dead Sea, its deadness and how it died, 207; and the story of Sodom and Gomorrah, 209; what "Lot's Wife" looks like to-day, 210; ancient history on the Dead Sea's walls, 249 Deltas, why delta river mouths always multiply by two, 167 Descent of Man, how man has risen as he descended, 269 Desert, origin of Lybian (myth), 2; enigmas of, 161; the desert and the Sphinx, 162; physiography and coloring, 163; "Baths of the Damned," 165; river "skeletons," 166; indications of former heavier rainfall, 166; Roman aqueducts, 166; "sand roses," 168; how the desert makes its sands, 168; its trade-mark on its sand grains, 172; why deserts are so cold at night, 170; how a simoom looks from the outside, 173; how it begins business, 184; the plant people of the desert, 174-175; how the Rose of Jericho goes to sea, 176; the cactus wren and how she bars her front door against her bad neighbors, 177; the "wind witches" of the steppes, 178; animal life in the desert, 178; the coyote as a ventriloquist, his night song, 179; bird life, 180; why the desert humming-birds have rusty coats, 180; how the trap-door spider slams the door in the centipede's face, 182; a beetle that uses poison gas, 182; wonderful flight of the vulture, 183; a day with the Arabs in the Sahara desert, 183; the cat, the dog, the Arab, and the struggle for life, 187, 188 Diamonds, form of their crystals, 107 Dikes, what one in New York City tells about marble making, 97; the iron walls near Spanish Peak, 235, 241; dikes in the rocks at Marblehead, 242; how dikes get their driving power, 244 Dinosaurs, their dreadfulness, their habits and their family name, 23 Diplodocus, his name, his gentle nature, his defensive tail and how it helped him at his meals, 24 Domes (Mt.), 123 Drift theory, 120 Drowned valleys, 212 Drumlin, why an Irish boy would know what "drumlin" means, 122 Dunes, 163