The First Commercial Installation of an Electric Light 25 Further Dynamo Developments 27 Russian Incandescent Lamp Inventors 30 The Jablochkoff “Candle” 31 Commercial Introduction of the Differentially Controlled Arc Lamp 33 Arc Lighting in the United States 33 Other American Arc Light Systems 40 “Sub-Dividing the Electric Light” 42 Edison’s Invention of a Practical Incandescent Lamp 43 Edison’s Three-Wire System 53 Development of the Alternating Current Constant Potential System 54 Incandescent Lamp Developments, 1884–1894 56 The Edison “Municipal” Street Lighting System 62 The Shunt Box System for Series Incandescent Lamps 64 The Enclosed Arc Lamp 65 The Flame Arc Lamp 67 The Constant Current Transformer for Series Circuits 69 Enclosed Series Alternating Current Arc Lamps 69 Series Incandescent Lamps on Constant Current Transformers 70 The Nernst Lamp 71 The Cooper-Hewitt Lamp 72 The Luminous or Magnetite Arc Lamp 74 Mercury Arc Rectifier for Magnetite Arc Lamps 77 Incandescent Lamp Developments, 1894–1904 78 The Moore Tube Light 79 The Osmium Lamp 82 The Gem Lamp 82 The Tantalum Lamp 84 Invention of the Tungsten Lamp 85 Drawn Tungsten Wire 87 The Quartz Mercury Vapor Arc Lamp 88 The Gas-Filled Tungsten Lamp 89 Types and Sizes of Tungsten Lamps Now Made 91 Standard Voltages 93 Cost of Incandescent Electric Light 93 Statistics Regarding the Present Demand for Lamps 94 Selected Bibliography 95 LIST OF ILLUSTRATIONS PAGE Portion of the Electrical Exhibit in the United States National Museum viii