Atomic Weights, viii, 92, 383; chemical calculations by, 96; classification of elements by, viii, 177-83, 189, xvi, 163; determination of, viii, 306-7; hydrogen basis, 33; introduction, xvi, 134; physical state and, viii, 297-8; properties dependent on, xvi, 134; radioactivity and, viii, 184, 185-6, 188; regular increase in similar elements, 132, 176, 179; specific gravity and, 313; specific heat and, 308-9; table, vii, 384, viii, 383 Atomists, school of, xvi, 84-6 Atoms, viii, 25-7; asymmetric, 309-10; chromophor groups, 258; defined, iv, 21, vi, 110-11, viii, 374; vii, 362, disintegration, 185-7, 188; dissociated, in ball lightning, vii, 214-15; electrification, vi, 122-3; energy of (see Atomic Energy); Greek theory, xvi, 118; laws involving, viii, 110; Leibnitz on, xvi, 118; magnetic fields of, vi, 117; motion within, viii, 309-10; of body, Epicurean theory, x, 26; size, vi, 112-13, 115; stability, vii, 215; structure of, iv, 23, 55, vi, 113-15, 120-1, viii, 187-9, 307; unchangeableness, 175-6 Attention, xi, 228-36; habit and, 253-5; methods of arousing, in advertising, 344-8; ordinary meaning, 40 Attraction, scientific meaning, vii, 362, iv, 96 Audibility, distances and variations, i, 187-92; vibration limits of, iv, 204, ix, 99 Audion, iv, 315-16, vi, 339 (fig.), vii, 279, xvi, 191-2 (see also Vacuum Tube) Auditoriums, acoustic qualities, iv, 239; cooling system, 188; echoes in, 238 Auditory Nerve, ix, 101 (fig.), 142, xi, 30, 102; internal and external stimulations, iv, 203 Auenbrugger, Leopold, x, 98-9, 110 Augite, iii, 336 Augustinus, Aurelius, xvi, 99-100 Auks, xii, 264-5 Aurelians, xii, 116 Aureoles, i, 184, 370 Aurignac Cave, iii, 305 Aurignacian Implements, xv, 100, 105, 108-9 Aurochs, xii, 331 Aurora, i, 158-62, 367; altitude, 17; magnetic disturbances with, vi, 40; ozone from discharges, i, 16; sun-spots and, ii, 176, 186 Ausable Chasm, iii, 44, 243, xiv, 128, 131 Auscultation, x, 108-10, 371