(1) Electrification and Electrical Charges 243 (2) Electric Fields and Electrostatic Induction 247 (3) Electric Theories, Distribution and Electric Charges 252 (4) Potential, Capacity, and the Electric Condenser 257 (5) Electrostatic Generators 262 CHAPTER XI. ELECTRIC CURRENTS PRODUCED BY VOLTAIC CELLS. (1) Electrical Currents and Circuits 267 (2) The Simple Voltaic Cell and its Action 270 (3) Practical Voltaic Cells 274 CHAPTER XII. MAGNETIC EFFECTS OF ELECTRIC CURRENTS, AND ELECTRICAL MEASUREMENTS. (1) The Magnetic Effect of Electric Currents 279 (2) Electrical Measurements 289 (3) Ohm's Law and Electrical Circuits 298 (4) Grouping of Cells and Measuring Resistance 302 CHAPTER XIII. CHEMICAL AND HEAT EFFECTS OF ELECTRIC CURRENTS. (1) The Chemical Effect of Electric Currents 307 (2) The Storage Battery and Electric Power 312 (3) The Heat Effect of Electric Currents 318 CHAPTER XIV. INDUCED CURRENTS. (1) Electromagnetic Induction 326 (2) The Dynamo and the Motor 335 (3) The Induction Coil and the Transformer 343 (4) The Telephone 349 CHAPTER XV. SOUND. (1) Sound, Source, Speed, Media 354 (2) Waves and Wave Motion 357 (3) Intensity and Pitch of Sound 363 (4) Musical Scales and Resonance 368 (5) Interference, Beats, Vibration of Strings 374 (6) Tone Quality, Vibrating Plates and Air Columns 384 CHAPTER XVI. LIGHT. (1) Rectilinear Propagation of Light 388 (2) Photometry and Law of Reflection 393 (3) Mirrors and Formation of Images 400 (4) Refraction of Light 410 (5) The Formation of Images by Lenses 416 (6) Optical Instruments 423 (7) Color and Spectra 430 (8) Nature of Light 442 CHAPTER XVII. INVISIBLE RADIATIONS. (1) Electric waves and Radioactivity 448 CHAPTER XVIII. WIRELESS TELEPHONY AND ALTERNATING CURRENTS.