, 40.

Molecule, 100-103.

Mordants, 247, 248, 249.

Morphine, 257.

Morse, telegraphic code, 324.

Motion, in sound, 266, 278, 280.
in work, 156.

Motor, electric, 336.
principle of, 333.
street car, 337.

Mouth breathing, 50.
cause of, 51.

Movable pulley, 167, 168.

Music, 278.

Musical instruments, percussion, 299.
stringed, 284-295.
wind, 295, 299.

Musical scale, 282.

Naphtha in gas engines, 185.

Naphthalene, 152.

Narcotics, 255.

Natural gas, 152.

Needle, magnetic, 328.

Negative, electrode, 308.
photographic, 130.

Neutral substance, 222.
and litmus, 222.

Neutralization, 222.

Niagara Falls, 176.

Nitrogen, 66.
and bacteria, 263.
and plant life, 261.
in atmosphere, 261.
in fertilizer, 262-265.
in food, 66.
preparation of, 261.
properties of, 261.

Noise in music, 280.

Non-conductors, of electricity, 321-322.
of heat, 25.

Nutcracker, as a lever, 162.

Oboe, 297.

Octave, 284.

Odors, 101.

Ohm, unit of resistance, 345.

Oil, gasoline, 149, 150.
kerosene, 149, 150.
lubricating, 174.
olive, 16.

Orchestra grouping, 299.

Ore, 72.

Organ pipes, 297.

Overtones, 290-293.

Oxalic acid, 247, 248.

Oxidation, 45-59.
and decay, 49.
heat the result of, 49-52.
in human body, 49, 53.
of iron, 48.

Oxygen, 66.
and bleaching, 239.
and combustion, 45.
and food, 66.
and plants, 55.
and the human body, 50.
and water, 79, 80.
in the atmosphere, 45.
preparation of, 46.

Paint, as wood and metal preservatives, 253, 254.
removal of stains, 243.

Paper making, 219.

Paraffin, 150, 321.

Pasteurized milk, 250.

Patent medicines, 257-260.

Peas, sources of nitrogen, 263.

Pelton wheel, 177.

Percussion instruments, 299.

Period of a body, 273.

Peroxide of hydrogen, 53, 252

Petrolatum, 150.

Petroleum, 149, 150.

Phonograph, 303-305.

Phosphorus, in fertilizer, 263, 264.
in making nitrogen, 261.
in matches, 47, 48.
poisoning by, 47.

Photography, 127-131.

Photometer, 107.

Pianos, 284-292.

Pin whee