SIMPLE AND HORSESHOE MAGNETS -- INDUCTION-COILS -- AN ELECTRIC BUZZER -- ELECTRIC BELLS -- A LARGE INDUCTION-COIL -- CIRCUIT-INTERRUPTERS CHAPTER V.--ANNUNCIATORS AND BELLS 78 A DRUM-SOUNDER -- A SIMPLE ANNUNCIATOR -- A DOUBLE ELECTRIC BELL -- AN ELECTRIC HORN -- HOW TO MAKE A BURGLAR-ALARM -- ELECTRIC CALL-SIGNALS -- CLOCK-ALARMS -- A DINING-TABLE CALL CHAPTER VI.--CURRENT-DETECTORS AND GALVANOMETERS 102 HOW TO MAKE DETECTORS -- AN ASTATIC CURRENT-DETECTOR -- AN ASTATIC GALVANOMETER -- A TANGENT GALVANOMETER Part II CHAPTER VII.--ELECTRICAL RESISTANCE 125 GOVERNING THE ELECTRIC CURRENT -- OHM’S LAW -- RESISTANCE-COILS AND RHEOSTATS -- HOW TO MAKE SIMPLE APPARATUS -- LIQUID RESISTANCE -- IMPORTANCE OF SWITCHES -- USES OF A HOUSE-CURRENT -- RUNNING A SEWING-MACHINE, FAN, OR TOYS -- AN EASY METHOD FOR A BOY’S USE CHAPTER VIII.--THE TELEPHONE 156 VIBRATORY WAVES -- A BLADDER TELEPHONE -- A SINGLE (RECEIVER) LINE -- PLAN OF INSTALLATION -- A DOUBLE-POLE RECEIVER -- THE TRANSMITTER -- ANOTHER FORM OF TRANSMITTER -- THE WIRING SYSTEM -- A TELEPHONE INDUCTION-COIL -- AN INSTALLATION PLAN -- A PORTABLE APPARATUS CHAPTER IX.--LINE AND WIRELESS TELEGRAPHS 190 A GROUND TELEGRAPH -- HOW TO TALK FROM HOUSE TO HOUSE -- THE MORSE TELEGRAPH CODE -- A STORY OF EDISON -- HOW DETECTIVES USED THE CODE -- WIRELESS TELEGRAPHY -- ITS TRUE CHARACTER -- HOW A BOY CAN MAKE A PRACTICAL APPARATUS -- RECEIVING AND SENDING POLES -- INDUCTION-COILS, BATTERIES, COHERERS AND DE-COHERERS, ETC. -- WORKING PLANS IN DETAIL -- AËROGRAMS ACROSS THE ATLANTIC AND, PERHAPS, AROUND THE WORLD CHAPTER X.--DYNAMOS AND MOTORS 229 DEPENDENCE OF MODERN ELECTRICITY UPON THE DYNAMO -- A FIELD OF FORCE CUTTING ANOTHER FIELD OF FORCE -- VARIETIES OF DYNAMOS -- SIMPLER FORMS OF GENERATORS AND MOTORS -- HOW TO MAKE A UNI-DIRECTION CURRENT MACHINE -- PERMANENT MAGNET, ARMATURE, SHAFTS, WHEELS, ETC. -- A SMALL DYNAMO -- MACHINES TO LIGHT LAMPS, RUN MOTORS, ETC. -- A SPLIT-RING DYNAMO -- A SMALL MOTOR -- THE FLAT-BED MOTOR -- MOTORS OF OTHER TYPES CHAPTER XI.--GALVANISM AND ELECTRO-PLATING 266 A FASCINATING USE OF ELECTRICITY -- A SIMPLE ELECTRO-PLATING OUTFIT -- THE SULPHATE OF COPPER BATH -- HOW TO MAKE THE TANK AND OTHER APPARATUS -- A VARIETY OF BEAUTIFUL AND USEFUL RESULTS -- EXPLANATIONS OF VARIOUS BATTERIES -- THE CLEANSING PROCESS -- THE PLATING-BATH -- SILVER-PLATING -- GOLD-PLATING -- NICKEL-PLATING -- FINISHING -- ELECTROTYPING -- PRACTICAL DETAILS OF INTERESTING WORK CHAPTER XII.--MISCELLANEOUS APPARATUS 294