Pineal gland, 424 Pipes broken by frost, 351 Piston, 102 PLANTS collect dew, 208 deleterious in bedrooms, 405 grow out of walls, 316 Plaster of Paris, 426 of stoves falls away, 124 Plasterers cannot work in frost, 359 Platinum, 261 its use, 261 never tarnishes, 261 Plate warmer, 188, 193 Ploughing, promotes warmth, 161 Plumbago, 258 prevents rust, 258 Poison for flies, 422 Poker draws up fire, 52 cold, 172, 238 how to carry it when hot, 237, 238 rusts, 258 prevented, 258 Polar current, 298 Poor averse to cleanliness, 93 ventilation, 94 lazy, 89 Pores of wood, 106 Porter, froth of, 109 set before a fire, 109 stale, 275 Positive electricity, 16 Potatoes, green, 405 yellow, 404 Potassium, 262 burns in water, 262 Primrose, 402 Prisms divide light, 393 Pump handle cold, 168 water hard, 363 Purple steel rusts, 259 its rust prevented, 259 PUTREFACTION, 277, 278 Putrefying bodies smell, 284, 285 Quadrupeds swim, 362 RADIATION, 195 cools iron, 247 Radiators are absorbers, 197 Rags catch fire spontaneously, 58 Railway steamers, 218 RAIN, 331, 336 affected by wind, 337 after lightning, 11 arrests sound, 413 cause of, 326, 336 cools air, 159 differs from dew, 226 falls in drops, 336 fertilizing, 307, 337 from passing clouds, 336 heaviest in summer, 341 least at the poles, 342 melts salt, 346 sugar, 345 most in mountainous places, 338 most in winter, 341 near the equator, 341 not salt, 347 on dust, 223 prognostics of, 137 purifies air, 338 sudden change, 326 RAINBOW, 394, 397 colours reversed, 396 morning, 141 night, 141 two, 395 Rain drops, 336 vary in size, 337 Rain-water smells offensively, 345 soft, 344 stagnant, 347 Rainy months, 308 parts of England, 340 Rattling of kettle-lid, 116 Ray of light divided, 393, 400 Reading aloud produces hunger, 88 RED colour, 401 rose, 401 sky, 132, 399 sun-rise, 139 sun-set, 139 Reflected light, 364 REFLECTION of HEAT, 192, 370 REFLECTORS, 192 help the roast, 194 keep kitchen cool, 194 not absorbers, 192 should be clean and bright, 189, 192 should not be painted, 189 REFRACTION, 386, 394 Refrangible, 132 Retina, 388 Reverberation, 417 Rice for food, 93 RIVERS flow slowest at sides, 348 freeze unequally, 354 never frozen at bottom, 352 not wholly frozen, 353 shallow freeze fastest, 354 seem shallower than they are, 387 warm when frozen, 354 Roast apples, 105 soft, 106 chestnuts, 104