Liquids, velocity of sound in, 69 —— transmission of musical sounds through, 113 —— constitution of liquid veins, 291 —— action of sound on liquid veins, 294, 303-304 —— Plateau’s theory of the resolution of a liquid vein into drops, 295 —— delicacy of liquid veins, 300 Lissajous, M., his method of giving optical expression to the vibrations of a tuning-fork, 93 —— illustration of beats of two tuning-forks, 390 M Mayer, his formula of the equivalent of heat, 66 Melde, M., his experiments with vibrating strings, 141, 427 —— and with sonorous ripples, 194 Metals, velocity of sound transmitted through, 72 —— determination of velocity in, 73 Molecular structure, influence of, on the velocity of sound, 73, 212 Monochord or sonometer, the, 121 Motion, conveyed to the brain by the nerves, 31 —— sonorous motion. See SOUND. Mouth, resonance of the, 241-242 Music, physical difference between noise and, 82, 117 —— a musical tone produced by periodic, noise by unperiodic, impulses, 83, 117 —— production of musical sounds by taps, 84, 117 —— —— by puffs of air, 89, 117 —— pitch and intensity of musical sounds, 90, 92, 117 —— description of the siren, 97 —— definition of an octave, 105 —— description of the double siren, 110 —— transmission of musical sounds through liquids and solids, 113 —— musical chords, 432-433 —— the diatonic scale, 432-433 —— See also HARMONY. Musical-box, formation of the, 169, 197 N Nerves of the human body, motion conveyed by the, to the brain, 31 —— rapidity of impressions conveyed by, 31 _note_ Newton, Sir Isaac, his calculation of the velocity of sound, 58 Nodes, 131-132 —— the nodes not points of absolute rest, 135 —— nodes of a tuning-fork, 175, 177 —— rendered visible, 177, 180 —— a node the origin of vibration, 251 Noise, physical difference between music and, 82, 117 O Octave, definition of an, 105 Organ-pipes, 219, 256 Organ-pipes, vibrations of stopped pipes, 221, 256 —— —— Pandean pipes, 224 —— —— open pipes, 224, 256, 260 —— state of the air in sounding-pipes, 227, 257 —— reeds and reed-pipes, 234 Otolites of the ear, 425 Overtones, definition of, 153 —— relation of the point plucked to the, 155 —— corresponding to the vibrations of a rod fixed at both ends, 165 —— of a tuning-fork, 177 —— rendered visible, 177, 179 —— of rods vibrating longitudinally, 207 —— of the siren, 415 —— influence of overtones on harmony, 429 P Pandean pipes, the, 224 Piano-wires, clang of, 158 —— curves described by vibrating, 160 Pipes. See ORGAN-PIPES Pitch of musical sounds, 90 —— illustration of the dependence of pitch on rapidity of vibration, 100 —— relation of velocity to pitch, 211-212 —— velocity deduced from pitch, 233 Plateau, his theory of the resolution of a liquid vein into drops, 295