Stringed instruments, 284-295.

    Strings, vibrating, 286-290.

    Sugar, 16, 65.
      fermented by yeast, 234.

    Sulphur, 66.
      as disinfectant, 251.
      in making sulphurous acid, 242.

    Sulphuric acid, in bleaching, 240,241.
      in fire extinguisher, 55.
      in making of hydrogen, 80.
      in voltaic cell, 307.

    Sulphurous acid, in bleaching, 242.
      preparation, 242.

    Sun, energy derived from, 143-144.
      source of heat, 29-30.

    Sunlight, 135.
      and bacteria, 133.
      and chemical action, 126-127.

    Sympathetic vibrations, 274-277.

    Tallow, 105, 148.

    Tartar, cream of, 229.

    Telegraph, 322.
      long distance, 327.
      relay, 325.
      sounder, 324.

    Telephone, 350-351.

    Temperature, 13-14.
      as measurement of heat present, 27.
      in detecting adulterants, 17.
      in forging steel, 16.
      in making sirups, 16.
      measurement of, 14-15.

    Thermometer, 14-17. 
      Centigrade, 15. 
      Fahrenheit, 15.

    Tinder box, 47.

    Transmission, of light, 145-147.
      of sound, 267-271.

    Tuning fork, 266, 273, 278, 290.

    Turbine, steam, 183.
      water, 178.

    Turpentine, and grease, 226.
      by distillation, 35.

    Unleavened bread, 233.

    Vacuum, sound in, 268.

    Vapor, in atmosphere, 36-38.

    Vaporization, heat of, 32.

    Varnish, on candies, 253.

    Vegetable matter, and coal, 30.
      and gas, 30.
      and oil, 30.

    Veins, formation in rock, 72-73.

    Velocity, of sound, 271-272.

    Ventilation, 21-24, 54.
      need of, 38.

    Vibration, of strings, 286-290.
      sympathetic, 274-277.

    Viola, 295.

    Violin, 295.

    Violoncello, 295.

    Vocal cords, 300.

    Voice, 300.

    Volt, 344.

    Voltage, 345.

    Voltaic cell, 306-308, 310.

    Voltmeter, 344.

    Volume, of a stream, 179-180.
      relation of pressure of a gas, 95-96.

    Washing powders, 224-226.
      soda, 229.

    Water, action in nature, 70-74.
      amount used daily per person, 181.
      and hydrogen, 79.
      and oxygen, 79, 80.
      as solvent, 70-71.
      boiling, 77.
      boiling point, 15.
      composition, 79-80.
      condensation, 33.
      dams and reservoirs, 214-216.
      density, 11.
      distilled, 34, 77.
      drinking, 75-77, 195-201.
      electrolysis, 79-80.
      evaporation, 33-34.