Relay, telegraph, 325.

    Reservoir, 214.
      artificial, 211.
      construction of, 214-216.
      natural, 211.

    Resistance, electrical, 312.
      internal, of cell, 343.
      unit of, 345.

    Resonance, 276.

    River, volume and value of, 180.

    Roads, application of inclined plane to, 165-166.

    Rochelle salt, 227, 231.

    Rocks, effect of freezing water on, 42-43.
      water as a solvent, 71.

    Rosin, obtained by distillation, 35.

    Safety matches, 47-48.

    Salicylic acid, 253.

    Salt, 227-228.

    Salts, 227.
      general properties, 227.
      in ocean, 227.
      smelling, 222.

    Saturation of air, 37.

    Scale, musical, 282.

    Screw, and inclined plane, 166.

    Seaweed, 265.

    Seidlitz powder, 231.

    Self-raising flour, 231.

    Sewage, disposition of, 198-199.
      of camps, 196.
      source of revenue, 201.

    Sewer gas, 57.

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

    Silver chloride, 127-131.

    Simple colors, 138.

    Simple substances, 103.

    Siren, 280.

    Smelling salts, 222.

    Snow, 36-37.

    Soap, 222-224.
      and hard water, 225.
      liquid, 223-224.
      preparation, 223.

    Soda, baking, 227, 228-229.
      benzoate, 253.
      caustic, 218, 222, 223, 227.
      washing, 225, 226, 229.

    Soda mints, 231.

    Sodium, bicarbonate, 56, 227, 228, 230-231.
      carbonate, 228.
      chloride, 228.

    Soil, deposited by streams, 73.

    Solenoid, 318.

    Solution, 70.

    Soothing sirup, 258.

    Sound, and motion, 266, 278.
      musical, 278.
      nature of, 266.
      reflection, 277.
      speed of, 271-272.
      transmission of, 267-271.
      velocity of, 271-272.
      waves, 272-274.

    Sounder, telegraph, 324.

    Sounding board, 277.

    Sour milk in cooking, 230.

    Specific heat, 28-29.

    Spectrum, 134-135.

    Speed, of sound, 271, 272.

    Spontaneous combustion, 52.

    Stains, removal of, 226, 243.

    Standpipes, 212.

    Starch, 65.

    Steam, and work, 183-184.
      engine, 183-185.
      heat of vaporization, 32.
      heating by, 33.
      turbine, 183-184.

    Steel, forging and annealing, 16.

    Stoves, 18-19.

    Streams, carriers of mud, 73.
      volume of, 179-180.

    Street cars, electric, 337.