321-322.
cost of, energy, 352.
current, 306, 312.
flatiron, 313.
heating pad, 314.
lights, 314.
street cars, 337.

Electricity, heat, 312-315, 339.
as a magnet, 319, 331-333.
practical uses of, 312-317.

Electrodes, of cell, 308.

Electrolytic metals, 317.

Electromagnets, 319.

Electromotive force, 308.
unit of, 344.

Electroplating, 315.

Electrotyping, 317.

Elements, 102-103.

Emulsion, 224.

Energy, conservation of, 58, 59.
transformations of, 58, 59.

Engine, steam, 183-185.
gas, 185-186.
horse power, 173.

Erosion, 73-74.

Essential colors, 139-140.

Evaporation, 35-39.
cooling effect, 35-36.
effect of temperature on, 35, 36.
effect of air on, 38.
freezing by, 98.
heat absorbed, 36.
of perspiration, 38.

Expansion, of air, 10, 11.
cooling effect of, 97.
disadvantage and advantage of, 11-13.
of liquids, 9-11.
of solids, 10, 11.
of water, 9, 10, 11, 12.
Eye, 122-125.
headache, 124, 125.
how focused, 122, 123.
nearsighted and farsighted, 123.
strain, 125.

Fahrenheit thermometer, 15.

Fats, 65.
in soap making, 223.

Fermentation, 232-236.
by yeast, 234-236.

Ferric compounds, 248.

Fertilizers, 262-265.
nitrogen, 262.
phosphorus, 263, 264.
potash, 263-265.

Field magnet, 336.

Filings, iron, 329.

Film, photographic, 129.

Filter, charcoal, 57.

Filtering water, 77.

Fire, 9.
and oxygen, 45, 47.
and tinder box, 47.
making of, 51.
primitive production of, 47.
produced by friction, 47.
spontaneous combustion, 52.
sores and burns, 52-53.
extinguisher, 55, 56.

Fireless cooker, 25, 26.

Fireplaces, 17, 18.

Fixing, in photography, 128.

Flame, hydrogen, 80.

Flood, Johnstown, 214, 215.
relation to forests, 217.

Flour, self-raising, 231.

Flume, 177.

Flute, 297.

Focal length, 118.

Focus, of lens, 118.

Fog, 37.

Food, 60-69.
carbohydrates, 64, 65.
economy in buying, 66-69.
fats, 65.
fuel value of, 60-62.
need of, 63, 64.
preservatives, 252.
proteids, 66.
value, 67.
waste, 60.