Coal oil, 149, 150.

    Coal tar dyes, 152, 218, 245.

    Cogwheels, 170.

    Coil, current-bearing, 320.
      magnetic field about, 331-333.

    Coke, 152.

    Cold storage, 97.

    Color, 134-141.
      and heat, 142, 143.
      influenced by light, 137.
      of opaque bodies, 136, 137.
      of transparent bodies, 135, 136.

    Color blindness, 140, 141.
      designs in cloth, 248, 249.

    Colors, compound, 138, 139.
      essential, 139-140.
      primary, 135.
      simple, 138.
      spectrum, 134-135.
      variety in dyeing, 247, 248.

    Combustion, heat of, 45.
      spontaneous, 52.

    Commutator, 335.

    Compass, 328.

    Compound colors, 138, 139.

    Compound machine, 171.

    Compound substances, 103.

    Compression of air, 91, 92.
      cause of heat, 96.

    Compression pumps, 201, 205.

    Concave lens, 118.

    Condensation, 33.
      heat set free, 40.

    Conduction of heat, 25.

    Conductivity metals, 321.

    Conductors, electric, 321, 322.

    Conservation, of energy, 58, 59.
      of matter, 58, 59.

    Convection, 24, 25.

    Convex lens, 118.

    Cooling, by evaporation, 35-36.
      by expansion, 97.

    Copper, in electric cell, 307.

    Core, iron, 319.

    Corn, bleached with sulphurous acid, 242.

    Cotton, mercerized, 218.
      bleaching, 241.
      dyeing, 245-247.

    Cough sirup, 258.

    Crane, compound machine, 172.

    Cream of tartar, 229.

    Creosote oil, 254.

    Crude petroleum, 149, 150.

    Current, electric, 306, 312.
      alternating, 349.
      induced, 346-347.
      measurement of, 340.
      resistance, 312, 343, 345.
      strength, 339, 340, 344.

    Dams, 214-216.

    Decay, 49.

    Decomposition of soil by water, 70-74.

    Degrees Fahrenheit and Centigrade, 15.

    Density, 11.

    Designs in cloth, printed, 248, 249.
      woven, 249.

    Developer in photography, 128.

    Dew, 36, 37.

    Dew point, 38.

    Diarrhea, 251.

    Diet, 62, 66.
      economy on table, 66-69.

    Discord, reason for, 271.

    Disease, and surface water, 76.
      relation of light to, 131-132.

    Disease disinfectants, 250, 251, 252.

    Distillation, 34-35.
      in commerce, 35.
      of petroleum, 149-150.
      of soft coal, 150.
      of water, 34, 35, 77.

    Diving suits, 204.