Heart Muscle, ix, 74-5, 84, x, 333-4; "eight-hour day" of, ix, 210; hypertrophy of, x, 331-2, 335; nervous control of, ix, 207-335; nervous control of, ix, 207-9 Heartwood, xiii, 24, 25, 26, 177 (fig.) Heat, absorbers of, iv, 182; absorption by colors, x, 309; absorption by gases, viii, 309; absorption by mixtures, iv, 175; artificial, man's dependence on, ix, 308; available supply in universe, iv, 193; bacteria destroyed by, viii, 332; "caloric" or "imponderable" theory, iv, 47, xvi, 125; capacity, iv, 154-5; change of state by, 151-3, 192-3; chemical reactions and, viii, 12, 15, 53, 62, 95-6, 100, 308, 360; chemical reactions hurried by, 310; "closeness" due to, ix, 268-9, 270; compression and, i, 26-7, 90, v, 126-8, 161, 351; conduction and conductors of, iv, 138, 176-7, 178-9, x, 307, 308, 309; convection of, iv, 139, 177-8; demagnetization by, 253, vi, 34-5, 38, 117; direction of flow of, iv, 190, v, 351, xvi, 135; effects of, on bodies, iv, 144-59; electrical production of, iv, 310-12, vii, 89, 337-8, 303-5, viii, 283-4; electricity generated by, vi, 340 (see also Thermal Couples); electromagnetic theory, vii, 371; energy form, iv, 138, 140, 189; "engineer" of physics, 50; entropy, iv, 193; expansion by, i, 27, iv, 134-5, 138, 140, 145, 151, viii, 25, 107; forms, ii, 383; from charcoal, viii, 186-7; from foods, 361, 367, x, 269, 271; from infrared waves, iv, 366; from moon, ii, 200; from radium, viii, 186-7; from sun, ii, 169-71, iv, 181-2, 183, 194, ix, 25-6; insulators, iv, 178, 184-5, vii, 307-8; kindling temperature, viii, 53-4; latent (see Latent Heat); measurement for fuels and foods, viii, 360-1; measurements, physico-chemical, 307-8; measurement of quantity of, iv, 154; mechanical equivalent of, (see Mechanical Equivalent); mechanical (dynamical) theory of, iv, 48-9, 140; molecular activity and, iv, 138-9, 140, viii, 25, 37-8; motive power, xvi, 135; of earth's interior, iii, 108, 120-1, 160, 162, v, 178-81, xiv, 11-16, 31-2, 312; of electric arc, iv, 311, vi, 280; of electric lamp, vi, 268; of volcanoes, iii, 106; power from, v, 139-54, 351; pressure of gases increased by, iv, 140; production, electrical, 310-12; production of, by friction, iv, 48-9; production by mixtures, 174-5; production by solidification, 160, 161; radiant energy, vibration rate, ix, 114, 115; radiation of, iv, 180-4; reflectors of, 182-3; resistance of charcoal, vii, 306; rolling friction and, v, 204; scientific meaning of, iv, 139-40; sensation of, ix, 93, xi, 109, 113-14; shrinkage in relation to, ii, 170 (see Lane's Law); solvent action and, viii, 112; specific, iv, 155-6, viii, 308-9; "stuffiness due to", i, 321, x, 237-8; temperature and, iv, 14-45;