Luminous or Magnetite Arc Lamp, 1902 75 Diagram of Series Magnetite Arc Lamp 76 Mercury Arc Rectifier Tube for Series Magnetite Arc Circuits, 1902 77 Early Mercury Arc Rectifier Installation 78 The Moore Tube Light, 1904 79 Diagram of Feeder Valve of Moore Tube 80 Osmium Lamp, 1905 82 Gem Lamp, 1905 83 Tantalum Lamp, 1906 84 Tungsten Lamp, 1907 86 Drawn Tungsten Wire Lamp, 1911 87 Quartz Mercury Vapor Lamp, 1912 88 Gas Filled Tungsten Lamp, 1913 89 Gas Filled Tungsten Lamp, 1923 90 Standard Tungsten Lamps, 1923 92 [Illustration: PORTION OF THE ELECTRICAL EXHIBIT IN THE UNITED STATES NATIONAL MUSEUM. Section devoted to the historical development of the electric light and dynamo.] FOREWORD In the year 1884 a Section of Transportation was organized in the United States National Museum for the purpose of preparing and assembling educational exhibits of a few objects of railroad machinery which had been obtained both from the Centennial Exhibition held in Philadelphia in 1876 and still earlier as incidentals to ethnological collections, and to secure other collections relating to the railway industry. From this beginning the section was expanded to include the whole field of engineering and is designated at present as the Divisions of Mineral and Mechanical Technology. The growth and enlargement of the collections has been particularly marked in the fields of mining and mineral industries; mechanical engineering, especially pertaining to the steam engine, internal combustion engine and locomotive; naval architecture, and electrical engineering, particularly the development of the telegraph, telephone and the electric light.