Grape juice, fermented with millet, 233.
Gravity cell, 309, 310.
Grease, and lye, 221.
and soap making,
223.
Gulf Stream, 24.
Hard water, and soap, 225.
Harp, 295.
Headache, 124, 125.
powders, 259.
Health, effect of diet, 62, 64.
Heat, 9.
absorbed in boiling,
31-32.
and disease germs,
250.
and food, 252.
and friction,
47.
and light, 142,
147.
and oxidation,
45, 48, 49.
and wave motion,
145-147.
conduction, 25.
convection, 24,
25.
from burning hydrogen,
80.
from electricity,
312-315, 339.
needed to melt
substances, 39.
of fusion, 40.
of vaporization,
32.
produced by compression,
96.
relation of water
to weather, 29, 40.
set free by freezing
water, 40.
sources of, 29-30.
specific, 28-29.
temperature, 27.
unit of, 27, 28.
Heating effect of electric current, 312-315.
Heating of buildings:
central heating plant, 19.
fireplaces, 17-18.
Heating, furnaces, 19.
hot water, 19-22.
Helix, 318.
Horse power, 173, 351.
Hot water heating, 19-22.
Hues, primary, 135.
Humidity, 38.
proper percentage
for health and comfort, 38, 39.
Humus, 216, 217.
Hydrocarbons, 149.
Hydrochloric acid, composition,
227.
in bleaching,
241.
to make a salt,
227.
to make carbon
dioxide, 55.
to make chlorine,
238.
to make hydrogen,
80.
Hydrogen, 65, 66.
and chlorine,
239.
and water, 79.
chemical conduct,
126-127.
flame, 80.
in voltaic cell,
307.
peroxide, 53,
252.
preparation, 80.
to liquefy, 97.
Ice, lighter than water, 42.
manufacture of,
98, 99.
Ice cream freezers, 44.
Illuminating gas, manufacture
of, 150, 151.
measurement of
quantity consumed, 93, 94.
test of pressure,
92, 93.
Illumination, intensity of, 105, 106.
Image, in mirror, 108, 111.
Incandescent lighting, 107, 314.
Incidence, angle of, 110.
Inclined plane, 162-166.
screw, 166.
wedge, 166.
Indigo, 218.
Induced current, 346-347.
Ink spots, removal of, 243.
Insoluble substances, 71.
Insulators, electric, 324.
Intensity, of light, 105-107.
of sound, 270-271.
Interval, in musical scale, 283.
Iron, forging, 41.
filings, 329.
galvanizing, 49.
oxidation of,
48.