Automobiles, American, v, 213-14; benzene fuels, viii, 235-6; carburetors, vii, 124-8; clutches, 143; clutches, magnetic, vi, 104; crank shafts, vii, 130-1; cylinders, 130-1; cylinder test, 128; electric systems, 120-50; engines, v, 156-61; engine operation, vii, 123-33; frost around exhaust, v, 128; freezing of radiators, prevention, viii, 299; future fuels, 209; generator output regulation, vii, 144-50; high and low speed air mixtures, 126-7; history of development, v, 207, 212-13, 377, 383; horns, iv, 240-1; ignition system, vii, 130-41, 243; ignition test, 128; ignorance of drivers, 122-3; lighting systems, 122, 135, 141-2; limitations on use, i, 41-2; lubrication, vii, 300; magnesium parts, viii, 127-49; magnetos, vii, 135, 139-41; motion pictures of, iv, 349; mufflers, v, 165; Owen's magnetic, vi, 104; power source, ix, 15, 74; present attitude toward, vii, 299; racing cars, v, 214; roads and, 214-15; springs air-cushioned, 134; starters, vi, 99, 238-9, vii, 120, 127, 135, 142-3; steel alloys used in, xiv, 238; steering-gear, v, 38; storage battery care, vii, 121, 127, 144; tires, v, 133-4, 204; tires burst by heat, iv, 151; unit systems, vii, 135-6; voltmeters, 163 Autonomic Nervous System, xi, 134-5, 137 Autophytes, xiii, 96-7 Autosuggestion, xi, 305-10; in hypnotism, 311-20; in salesmanship, 336-41; in sleep, 287-8; positive, 278 Autotransformers, vi, 327-8, 337 (fig.); in wireless systems, vii, 266-91 Autumn, frosts, i, 258; leaves in, xiii, 79, 175; rate of advance (U. S.), i, 256 Aviators, altitude effects, i, 303; complete rainbow seen by, 175; fog effects, 300-1; heights attained by, ix, 267-8; sense of balance, v, 343; sixth sense, i, 292; training of, x, 242; visibility obstacles, i, 303; weather service for, 206, 227, 230, 231, 233, 286, 304-5 Avicenna, x, 32-3; arterial bleeding unknown to, 39; books burned by Paracelsus, 47; translation of, 38; views of fossils, iii, 14 Avitaminoses, x, 264 Avocations, importance of, xi, 375-6 Avogadro's Hypothesis, viii, 108-9, xvi, 133 Awe, sentiment of, xi, 147 Axolotl, xii, 173 Axons, of nerves, ix, 123-4, 125, 126, xi, 19 Aye-Ayes, xii, 374 Azaleas, xiii, 202, 203 (fig.), 289 Azores, xiv, 276, 289; ocean depths near, 289; rediscovery of, 309; volcanic activity in, 316 Azores Plateau, xiv, 288 Aztecs, civilization, in temperate climate, xv, 123; kings' oath, 366; picture writing of, 169-78 (fig.); tobacco use among, xiii, 257 Azurite, iii, 323 Baal, Phœnician sun-god, ii, 20 Babakotos, xii, 375 Baboons, xii, 379-81; primates, 373 Babylon, wind-blown sand over, iii, 75; world metropolis, xvi, 61 Babylonian Language, xv, 162