Waves and ripples in water, air, and æther

A visit to the seaside—What is a wave?—Wave-motion on water—Definition of a wave—Sea waves—Various forms of wave-motion—Wave length, velocity, and frequency—Atlantic waves—Rules for speed of sea waves—Illustrations of wave-motion—A stone falling on water—Production of a wave-train—Wave-energy—Conditions for the production of wave-motion—Distinction between wave-velocity and wave-train velocity—Why a wave breaks—Waves in canals—Rule for speed of a canal wave—Falling bodies—A “bore”—Tidal waves—Ripples—Distinction between waves and ripples—Surface tension on liquids—A needle floating on water—Experimental production of ripples—Reflection and refraction of ripples and waves—Interference of waves and ripples—Photography of waves and ripples

Ship-waves—The viscosity of liquids—How it is demonstrated—Rotational and irrotational motion in fluids—Eddies and whirls—Smoke rings—Vortex motion—Professor Hele-Shaw’s experiments—Irrotational or stream-line motion in water—The motion of water round a ship—The motion of water along a pipe—Flow in uniform pipes and non-uniform pipes—Relation between fluid velocity and pressure—Skin resistance and wave-making resistance—The movement of a fish—Motion through a perfect fluid—The waves made by moving objects—Waves made by ducks and swans—Echelon waves—Ship bow waves—The form of ship-waves—Mr. Froude’s experiments—Ship-models and experimental tanks—How a ship is designed—Froude’s laws—Testing ship-models—The design of a racing-yacht—Comparison of British and American yachts—The Cup race—Scott Russell’s experiments on canal-boats

Air necessary for the production of sound—A sounding body is in vibration—Harmonic motion—The difference between noise and music—The nature of an air wave—The physical qualities of air—Longitudinal or compressional waves—Wave-models to illustrate the nature of sound waves—Quality of a sound—Velocity of an air wave—An illustration on a gigantic scale—The voice of a volcano heard round the world—The effect of temperature on air-wave velocity—Comparison of theory and experiment—Circumstances affecting distance at which sounds can be heard—Funeral guns—Fog-signals and sirens—Effect of wind and density—Sensitive flames as sound-detectors—Inaudible sounds—The reflection and refraction of sound waves—A sound-lens and sound-prism—The interference of sounds—Two sounds producing silence—The phonograph—A soap-bubble film set in vibration by air waves

The difference between sounds and musical tones—The natural period of vibration of an elastic body—The effect of accumulated impulses—Free and forced vibrations—Breaking down a bridge with a pea-shooter—The vibration of a stretched string—Stationary waves—A string vibrating in segments—Acoustic resonance—Nodes and anti-nodes—The musical scale or gamut—Musical intervals—The natural gamuts and the scale of equal temperament—Concords and discords—Musical beats—Helmholtz’s theory of discords—Musical instruments—Pipes—Strings and plates—A pan-pipe—An organ-pipe—Open and closed organ-pipes—The distribution of air pressure and velocity in a sounding organ-pipe—Singing flames—Stringed instruments—The violin—The Stroh violin—The structure of the ear—The ear a wonderful air-wave detector and analyzer

The conception of an æther—The phenomena of light require the assumption of an æther—The velocity of light—Interference of light—Two rays of light can produce darkness—An electric current—The phenomena of electricity require the assumption of an electro-magnetic medium—Properties and powers of an electric current—Alternating and continuous electric currents—Electromotive force and electric strain—A Leyden jar—The oscillatory discharge of a condenser—Oscillatory sparks—Transformation of electric oscillations—Hertz oscillator—Production of a wave of electric displacement—Detection of electric waves—Metallic filings detectors—The coherer—Inductance and capacity of circuits—Electro-static and electro-magnetic energy—An induction coil—Electric oscillations give rise to electric waves—The electron theory of electricity

The experiments of Heinrich Hertz—Electric radiation—Lecture apparatus for producing and detecting electric radiation—Electric transparency and opacity—Why this difference—The reflection of electric radiation—The refraction of electric rays—An electric prism and an electric lens—The electric refractive index—Interference of electric rays—The velocity of electric radiations identical with that of light—Dark heat rays—Actinic or photographic rays—The cause of colour—The frequency of light waves—The classification of electric or æther waves—The gamut of æther waves—The eye an æther-wave detector of limited power—The electro-magnetic theory of light—Artificial production of light—Use of Hertz waves in wireless telegraphy—Marconi’s methods—Marconi’s aerial and wave-detector—The Morse alphabet—How a wireless message is sent—The tuning of wireless stations—Communication between ships and shore—The velocity of wireless waves—Conclusion

Appendix

Index