Mercerized cotton, 218.

    Mercury, barometer, 84.
      thermometer, 14-17.

    Metals, electroplating, 317.
      preservation by paint, 253-254.
      veins deposited by precipitation, 72, 73.
      welding, 315.

    Meter, gas, 93, 94.

    Microoerganisms, 132, 133.

    Microscope, 115.

    Milk, boiling point, 32. 
      Pasteurized, 250.

    Minerals, in foods, 62, 63.
      in water, 70, 71.

    Mirrors, 108-112.
      distance of image behind mirror, 111.
      distance of object in front of mirror, 111.
      image a duplicate of object. 111.

    Molding of glass, 40.

    Molecule, 100-103.

    Mordants, 247, 248, 249.

    Morphine, 257.

    Morse, telegraphic code, 324.

    Motion, in sound, 266, 278, 280.
      in work, 156.

    Motor, electric, 336.
      principle of, 333.
      street car, 337.

    Mouth breathing, 50.
      cause of, 51.

    Movable pulley, 167, 168.

    Music, 278.

    Musical instruments, percussion, 299.
      stringed, 284-295.
      wind, 295, 299.

    Musical scale, 282.

    Naphtha in gas engines, 185.

    Naphthalene, 152.

    Narcotics, 255.

    Natural gas, 152.

    Needle, magnetic, 328.

    Negative, electrode, 308.
      photographic, 130.

    Neutral substance, 222.
      and litmus, 222.

    Neutralization, 222.

    Niagara Falls, 176.

    Nitrogen, 66.
      and bacteria, 263.
      and plant life, 261.
      in atmosphere, 261.
      in fertilizer, 262-265.
      in food, 66.
      preparation of, 261.
      properties of, 261.

    Noise in music, 280.

    Non-conductors, of electricity, 321-322.
      of heat, 25.

    Nutcracker, as a lever, 162.

    Oboe, 297.

    Octave, 284.

    Odors, 101.

    Ohm, unit of resistance, 345.

    Oil, gasoline, 149, 150.
      kerosene, 149, 150.
      lubricating, 174.
      olive, 16.

    Orchestra grouping, 299.

    Ore, 72.

    Organ pipes, 297.

    Overtones, 290-293.

    Oxalic acid, 247, 248.

    Oxidation, 45-59.
      and decay, 49.
      heat the result of, 49-52.
      in human body, 49, 53.
      of iron, 48.

    Oxygen, 66.
      and bleaching, 239.
      and combustion, 45.
      and food, 66.
      and plants, 55.
      and the human body, 50.
      and water, 79, 80.
      in the atmosphere, 45.
      preparation of, 46.

    Paint, as wood and metal preservatives, 253, 254.
      removal of stains, 243.