Erosion, iii, 28-9, 378; agents and processes, xiv, 39-79 (see also Glaciers, Ocean Waves, Streams, Wind); bad lands and canyons due to, iii, 139-40; base level, 30, 377 (see Base Level); by ground water, xiv, 141, xvi, 173; cycles (see Cycles of Erosion); earth movements and, xiv, 39, 40; final effect of, 80; illustration of recent, iii, 64 (Pl. 3); in deserts, 72; in Ice Age, 242; of faulted areas, xiv, 127; of folded areas, 94-6; of mountains, iii, 135, 139, 140-1, 188, 190-1, xiv, 233-4; present relief due to, iii, 32; rate of, xiv, 41; unequal operation of, 35 Erosion Surface (see Unconformity) Errors, fatigue and, xi, 274; of memory, 215-17; in space perceptions, 183-90 (see also Mistakes) Erysipelas, germ of, x, 195; immunity to, 207; puerperal fever and, 114 Eskers, iii, 70, 352 (Plate 20), xiv, 59-60 Eskimos, conditions of life, xv, 123-4; customs concerning dead, 338; ideas of future life, xv, 333, 335; kayaks of, 264 (fig.); language lacking in abstract words, 144; leadership among, 363; meat eating by, ix, 284, 309; polar bear catching by, xv, 224-5; reindeer uses, xii, 320; weapons of, xv, 209 (fig.), 210-12 Esophagus, functions and connections, ix, 230, 231; heartburn in, 232; operations of, xi, 37-9 Esparto Grass, v, 292 Espy, James P., i, 215, 345 Essential Oils, viii, 251-2, 336, 349 Esters, viii, 221, 245, 248, 376 Estuaries, formation of, iii, 37, xiv, 255, 256 Eta Argus, ii, 324 Eternity, real meaning, xi, 196 Ethane, derivatives, viii, 210 Ether, composition and properties, viii, 216-18, 376; density of, iv, 113; explosibility, viii, 62; refrigeration by, iv, 174; use as anesthetic, discovery of, x, 123-5, xvi, 185 Ether of Space (see Æther) Ether Structure, viii, 217, 224 Ethyl, defined, viii, 376; derivatives, 210 Ethyl Acetate, viii, 221 Etna, Mount, xiv, 100, 225, 316-17; flashing arcs, i, 194; water from eruption, iii, 107 Etruscans, vase decorations of, xv, 251 Eucalyptus Tree, xiii, 358; fertilization of, xii, 266-7; used in draining swamps, xiv, 379 Euclid, ii, 29, xvi, 81, 89, 95 Eudoxus, ii, 31, 300 Eugenics, x, 235-6, xvi, 157, 158 Euler, scientific work of, ii, 15, xvi, 125 Euphrates River, union with Tigris, xiv, 185