PREFACE.
THE TELEPHONE.
ELECTRICITY.
MAGNETS.
THE GALVANIC BATTERY.
OTHER MEANS FOR GENERATING ELECTRICITY.
THERMO-ELECTRICITY.
MAGNETO-ELECTRICITY.
MAGNETIC INDUCTION.
MAGNETO-ELECTRIC MACHINES.
SECONDARY CURRENTS.
WHAT IS ELECTRICITY?
THEORIES.
VELOCITY.
SOUND.
CONSTITUTION OF A SINGLE SOUND-WAVE.
PITCH.
LIMITS OF AUDIBILITY.
EFFECTS OF SOUND UPON OTHER BODIES.
SYMPATHETIC VIBRATIONS.
RESONANCE.
TONE COMPOSITION.
FORM OF A COMPOUND SOUND-WAVE IN AIR.
CORRELATION.
HELMHOLTZ' ELECTRIC INTERRUPTOR.
REISS' TELEPHONE.
GRAY'S TELEPHONES.
BELL'S TELEPHONE.
FIRST FORM OF SPEAKING-TELEPHONE.
THE AUTHOR'S TELEPHONE.
