CONTENTS.
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CHAPTER I. | ||
WATER WAVES AND WATER RIPPLES. | ||
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A visit to the seaside—What is a wave?—Wave-motion on water—Definitionof a wave—Sea waves—Various forms of wave-motion—Wavelength, velocity, and frequency—Atlantic waves—Rulesfor speed of sea waves—Illustrations of wave-motion—Astone falling on water—Production of a wave-train—Wave-energy—Conditionsfor the production of wave-motion—Distinctionbetween wave-velocity and wave-train velocity—Whya wave breaks—Waves in canals—Rule for speed of acanal wave—Falling bodies—A “bore”—Tidal waves—Ripples—Distinctionbetween waves and ripples—Surfacetension on liquids—A needle floating on water—Experimentalproduction of ripples—Reflection and refraction of ripples andwaves—Interference of waves and ripples—Photography ofwaves and ripples |
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CHAPTER II. | ||
WAVES AND RIPPLES MADE BY SHIPS. | ||
Ship-waves—The viscosity of liquids—How it is demonstrated—Rotationaland irrotational motion in fluids—Eddies and whirls—Smokerings—Vortex motion—Professor Hele-Shaw’s experiments—Irrotationalor stream-line motion in water—The motionof water round a ship—The motion of water along a pipe—Flowin uniform pipes and non-uniform pipes—Relation betweenfluid velocity and pressure—Skin resistance and wave-makingresistance—The movement of a fish—Motion through a perfectfluid—The waves made by moving objects—Waves made byducks and swans—Echelon waves—Ship bow waves—The formof ship-waves—Mr. Froude’s experiments—Ship-models andexperimental tanks—How a ship is designed—Froude’s laws—Testingship-models—The design of a racing-yacht—Comparisonof British and American yachts—The Cup race—ScottRussell’s experiments on canal-boats |
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CHAPTER III. | ||
WAVES AND RIPPLES IN THE AIR. | ||
Air necessary for the production of sound—A sounding body is invibration—Harmonic motion—The difference between noise andmusic—The nature of an air wave—The physical qualities ofair—Longitudinal or compressional waves—Wave-models toillustrate the nature of sound waves—Quality of a sound—Velocityof an air wave—An illustration on a gigantic scale—Thevoice of a volcano heard round the world—The effect oftemperature on air-wave velocity—Comparison of theory andexperiment—Circumstances affecting distance at which soundscan be heard—Funeral guns—Fog-signals and sirens—Effectof wind and density—Sensitive flames as sound-detectors—Inaudiblesounds—The reflection and refraction of soundwaves—A sound-lens and sound-prism—The interference ofsounds—Two sounds producing silence—The phonograph—Asoap-bubble film set in vibration by air waves |
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CHAPTER IV. | ||
SOUND AND MUSIC. | ||
The difference between sounds and musical tones—The naturalperiod of vibration of an elastic body—The effect of accumulatedimpulses—Free and forced vibrations—Breaking down a bridgewith a pea-shooter—The vibration of a stretched string—Stationarywaves—A string vibrating in segments—Acousticresonance—Nodes and anti-nodes—The musical scale or gamut—Musicalintervals—The natural gamuts and the scale ofequal temperament—Concords and discords—Musical beats—Helmholtz’stheory of discords—Musical instruments—Pipes—Stringsand plates—A pan-pipe—An organ-pipe—Open andclosed organ-pipes—The distribution of air pressure and velocityin a sounding organ-pipe—Singing flames—Stringed instruments—Theviolin—The Stroh violin—The structure of theear—The ear a wonderful air-wave detector and analyzer |
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CHAPTER V. | ||
ELECTRIC OSCILLATIONS AND ELECTRIC WAVES. | ||
The conception of an æther—The phenomena of light require theassumption of an æther—The velocity of light—Interferenceof light—Two rays of light can produce darkness—An electriccurrent—The phenomena of electricity require the assumptionof an electro-magnetic medium—Properties and powers of anelectric current—Alternating and continuous electric currents—Electromotiveforce and electric strain—A Leyden jar—Theoscillatory discharge of a condenser—Oscillatory sparks—Transformationof electric oscillations—Hertz oscillator—Productionof a wave of electric displacement—Detection ofelectric waves—Metallic filings detectors—The coherer—Inductanceand capacity of circuits—Electro-static and electro-magneticenergy—An induction coil—Electric oscillations giverise to electric waves—The electron theory of electricity |
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CHAPTER VI. | ||
WAVES AND RIPPLES IN THE ÆTHER. | ||
The experiments of Heinrich Hertz—Electric radiation—Lectureapparatus for producing and detecting electric radiation—Electrictransparency and opacity—Why this difference—Thereflection of electric radiation—The refraction of electric rays—Anelectric prism and an electric lens—The electric refractiveindex—Interference of electric rays—The velocity of electricradiations identical with that of light—Dark heat rays—Actinicor photographic rays—The cause of colour—Thefrequency of light waves—The classification of electric oræther waves—The gamut of æther waves—The eye an æther-wavedetector of limited power—The electro-magnetic theoryof light—Artificial production of light—Use of Hertz waves inwireless telegraphy—Marconi’s methods—Marconi’s aerial andwave-detector—The Morse alphabet—How a wireless messageis sent—The tuning of wireless stations—Communicationbetween ships and shore—The velocity of wireless waves—Conclusion |
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Appendix |
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Index |
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