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.

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.

S