Radiation, electric, 238 ——, nature of, 263 —— of energy from the sun, 284 Rayleigh, Lord, an acoustic experiment with an open pipe by, 174 Receiver for wireless telegraphy (Marconi), 275 Reflection of a beam of sound, 132, 133 —— of an electric ray, 241 —— of a wave, 55 —— of ripples, 46, 47 Refraction, explanation of, 53, 54 —— of a beam of sound, 133, 134 —— of an electric ray, 243 —— —— by an ice prism, 242 —— of ripples, 52 Refractive index, 54 Relation of wave-velocity and wave-length, 9 Relay, telegraphic, 236 Resistance curves of ships, 92 —— to a body moving through a fluid, causes of the, 68 Resonance, 148 ——, an experiment on, 158 Ripple and wave, distinction between, 40 —— mark, 30 ——, reflection of a, 45, 46 ——, scientific definition of a, 42 Ripples, 1 ——, apparatus for producing, 43 ——, interference of, 48 ——, intersecting, 49 —— in the air, 103 —— on a lake, photographs of, 19 ——, photography of, 51 ——, by J. H. Vincent, 54 —— produced by stone thrown into water, 19 ——, velocity of, 41, 42, 43 Rotational motion, 59 Russell, Scott, Mr., 81 —— experiments of, on canal-boat waves, 101 S Scale, musical, notes of the, 160 —— of equal temperament, 162 Sea waves, 2 —— ——, motion of, 3 —— ——, relation of velocity and length in case of, 10 Semitone, 161 Sensitive flame, influence of sound upon a, 129 Severn bore, 38 _Shamrock II._, trials of, 97 Ship bow wave, mode of production, 75, 76 —— design, 87, 88 —— ——, the problem of, 73 —— models, the testing of, 85, 86 —— resistance, Froude’s law of, 82, 83 —— waves, 57 —— ——, complete system of, 78 —— ——, various systems of, 73 Short wave, 7 Sine curve, mode of drawing a, 108 Singing flame, 175 Siren, 123 Skin friction, 59, 68 —— —— for various classes of ships, 91 Soap film thrown into vibration by air waves, 145 —— solution for making bubbles, 144 Solitary wave, 26 —— —— and wave-train, difference between, 26 Sound, and music, 147 ——, causes in variation in quality of, 142 —— due to air waves, 103, 104 —— lens, method of making a, 130 —— prism, 136 ——, quality of, 115 —— signals, 123 ——, velocity of, in various cases, 126 Sounding body is in vibration, 104, 105 Speed of a falling body, 35 —— of sound, 115 Stationary waves, 155, 156 Stone falling into water, photographs of a, 17 Stream-lines, 64 —— —— round an ovoid, 71 Stroh violin, 179 Structure of the human ear, 181 Surface tension of liquid, 40 T Temperature, effect of, on sound-velocity, 118 Tesla coil, 205 Tidal wave, 38 —— ——, speed of, 39 Tides, 39 Time of vibration of a stretched string, 154 Tone, 161 Torpedo, motion of, in water, 67 Transference of wave-motion, 27 Transverse ship wave, 79 —— wave, 7 True wave, conditions for producing a, 15 —— ——, definition of a, 12 Tubes of flow, 64 —— —— in a liquid, 71 U