Irrigation, 193-194.

    Isobaric lines, 88, 91.

    Isothermal lines, 89, 91.

    Johnstown flood, 214, 215.

    Kerosene, 149, 150.

    Kilowatt, 351.

    Lactic acid, 230.

    Leaves, 132, 262.

    Lens, 117-121.
      concave, 118.
      converging, 118.
      crystalline, of eye, 122.
      focal length, 118.
      material, 119.
      refractive power, 119.

    Lever, 158-162.
      examples, 160-162.
      fulcrum, 159, 160.

    Life, and carbon dioxide, 54.
      and nitrogen, 261.
      and oxygen, 49, 54.

    Lifting pumps, 189-192.

    Light, absorption, 135-138.
      and heat, 142-147.
      a wave motion, 145-147.
      bent rays, 113, 114.
      chemical action, 126-127.
      disease, 131-132.
      essential to life, 131, 132.
      fading illumination, 105, 106.
      influence on color, 134.
      reflection of, 109-112.
      refraction of, 113-125.
      travels in a straight line, 108.
      white, composed of colors, 134.

    Lighting, artificial, 148-153.

    Lime, chloride of, 240, 251.

    Limewater, 220.
      and carbon dioxide, 228.

    Linen, bleaching, 241.
      dyeing, 245-247.

    Lines, of force, 329-331, 334.
      isobaric, 88, 91.
      isothermal, 89, 91.

    Liquefaction of gases, 97, 98.

    Liquid air, 98.

    Liquid soap, 223, 224.

    Litmus, action of acids, 220.
      action of bases, 221, 222.
      action of neutral substance, 222.

    Logwood dyes, 245, 247, 248.

    Los Angeles aqueduct, 211.

    Lye, 221, 222.

    Machines, compound, 171.
      inclined plane, 162-166.
      lever, 158-162.
      pulley, 166-169.
      wheel and axle, 169-171.

    Madder, for dyes, 245.

    Magnet, 328.
      electro-, 319.
      field of, 329-331.
      lines of force about, 329-331.
      poles of, 330-332.
      properties of electricity, 318.

    Magnetic, needle, 328.
      poles, 329-331.

    Magnifying power, of a lens, 115.
      of a microscope, 115.
      of a telescope, 115.

    Mammoth Cave of Kentucky, 71.

    Manganese dioxide, 46.
      chlorine made from, 238.
      oxygen made from, 46.

    Marble, for carbon dioxide, 55.

    Matches, 47.
      safety, 47-48.

    Matching colors, 137.

    Matter, conservation of, 58, 59.

    Meat, 66.
      preservation of, 253.

    Mechanical devices, 154, 155.

    Melting, 39, 40.

    Melting point, 40.

    Melting substances without a definite melting point, 40.