Entropy, iv, 193, xvi, 135 Environment, adaptation to (see Adaptation to Environment); change of, to relieve fatigue, x, 247; changes of, new species from, xv, 24-5; defined, x, 228; geographical, influence on civilization, xiv, 30-1, xv, 31, 122-39; habit and, xi, 249; health and disease factor, x, 237-44, 249-55, 303; heredity and, ix, 344, x, 228-30, xvi, 47; instincts as response to, xi, 49-53; man creature of, 57-8; man's conquest of, xv, 25-6; man's regulation to, x, 249-51; man the product and molder, of, xi, 33; mental effects of, x, 354; mind as response to, xi, 12, 24, 58; plant response to, xiii, 355-7; selection of, xi, 257; will and, 265 Envy, sentiment of, xi, 148 Enzymes, viii, 376, ix, 227, xiii, 83; in digestive processes, viii, 103, 226, 228, 357, 358, ix, 227, 228, 229-30, 235, 242; in infants, ix, 346; in tea, xiii, 230; in tobacco curing, 257 Eocene Period, animals of, xii, 306, 366; birds of, xv, 71 Eolithic Period, xv, 103-5 Epic Poetry, development of, xv, 321 Epicurus, atom theory, x, 26 Epicycles, ii, 35-6 Epidemics, Sydenham on, x, 74; tainted water and, xiv, 140 Epigenesis, xvi, 118 Epileptics, multiplication of, x, 235-6; primitive ideas of, xv, 350, 353 Epiphytes, xiii, 185, 362-3, 366; in tropical forests, xiv, 368 Epithelial Cells, x, 201, 202 Epsom Salts, viii, 149 Epyornis, eggs of, xii, 249 Equator, altitude of stratosphere at, i, 20; bulging at, ii, 69, 71; magnetic, xiv, 246; of wind system, xiv, 347; solar eclipses seen at, ii, 215; upper air temperatures, i, 20; weight of bodies at, ii, 69, iv, 75, 101; winds at, i, 127, xiv, 351 Equatorial Belt, winds and weather of, xiv, 348, 349 Equilibrium of Chemical Reactions, viii, 103-5, 190-1 Equilibrium of Forces, v, 183-4; science of, iv, 25 Equilibrium Sense, ix, 89-90, 156, x, 126, xi, 64, 126, 127; in infants, ix, 350 Equinoxes, defined, ii, 70-1; observed in Egypt, 25, 26, xv, 269-70; precession of (see Precession of Equinoxes) Eras, Geological, iii, 19-21, 378 Erasistratus, x, 23-4 Eratosthenes, ii, 10, 30 Erbium, symbol and atomic weight, viii, 383 Erg, energy unit, iv, 80; table of equivalents, vii, 382 Ericsson, air engine, v, 380; Monitor, 380; solar engine, ii, 169; steam fire engine, v, 378 Erie Canal, importance to New York, xiv, 267-8; through Mohawk Valley, 194 Erie, Lake, salt in, viii, 139; water constituents, 40; water supplies from, v, 260-1 Ermines, xii, 349-50 Eros (asteroid), ii, 191; distance, 132, 259