Light and its Sources—What is Light?—Velocity of Light—Reflection and Refraction—Relative Value of Lights 93 CHAPTER X.—LIGHT (_Continued_). Vision and Optical Illusions—The Eye Described—Accommodation of the Eye—Chromatic Aberration—Spinning Tops 102 CHAPTER XI.—OPTICS. Optical Illusions—Zollner’s Designs—The Thaumatrope—Phenokistoscope—The Zootrope—The Praxinoscope—The Dazzling Top 116 CHAPTER XII.—OPTICS (_Continued_). Optical Illusions Continued—Experiments—The Talking Head—Ghost Illusions 129 CHAPTER XIII.—OPTICS (_Continued_). Vision—The Eye—The Stereoscope—Spectrum Analysis—The Spectroscope—The Telescope and Microscope—Photography—Dissolving Views—Luminous Paint 140 CHAPTER XIV.—SPECTRAL ILLUSIONS. A Spectre Visible—Curious Illusions—Ghosts 161 CHAPTER XV.—ACOUSTICS. The Ear and Hearing—Physiology of Hearing and Sound—Sound as Compared with Light—What is Sound?—Velocity of Sound—Conductibility—The Harmonograph 166 CHAPTER XVI.—ACOUSTICS (_Continued_). The Topophone—The Megaphone—The Autophone—The Audiphone—The Telephone—The Phonograph—The Microphone 180 CHAPTER XVII.—ACOUSTICS (_Continued_). The Tuning-Fork—The Syren—Sound Figures—Singing Flames 193 CHAPTER XVIII.—ELECTRICITY. Derivation of Electricity—Sealing Wax Experiment—The Electrophorus—Leyden Jar—Positive and Negative—The Electroscope—Electric Machines 197 CHAPTER XIX. Velocity of Electricity—Experiments—The Electric Egg—Force of the Electric Spark 212 CHAPTER XX.—GALVANISM. Galvani’s Discovery—The Frogs Electrified—Experiments—Volta’s Pile—The Test—Its Usefulness—Faraday’s “Researches.” 217 CHAPTER XXI.—MAGNETISM. The Loadstone—Magnetic Curves—The Magnetic Needle—The Mariner’s Compass—Magneto-Electricity 254 CHAPTER XXII.—APPLIED ELECTRICITY. Sundry Electrical Appliances—Mr. Edison’s Inventions—The Electric Light—The Gyroscope—A New Electrophorus—Electric Toys 262 CHAPTER XXIII.—AERONAUTICS. Pressure of Air in Bodies—Early Attempts to fly in the Air—Discovery of Hydrogen—The Montgolfier Balloons—First Experiments in Paris—Noted Ascents 293 CHAPTER XXIV.—CHEMISTRY. What Chemistry is—The Elements—Metallic and Non-Metallic—Atomic Weight—Acids—Alkalis—Bases—Salts—Chemical Combination and Study 307 CHAPTER XXV.—CHEMISTRY (_Continued_). Chemistry without a Laboratory 313 CHAPTER XXVI.—CHEMISTRY (_Continued_). Chemistry and Alchemy—Chemical Combinations—The Atmospheric Air 336 CHAPTER XXVII.—THE ELEMENTS. Non-Metallic Elements 348 CHAPTER XXVIII.—NON-METALLIC ELEMENTS (_Continued_). Chlorine—Bromine—Iodine—Fluorine—Carbon—Sulphur—Phosphorus—Silicon— Boron—Tellurium—Arsenic 366 CHAPTER XXIX.—THE METALS.