Plants, progressive discovery of new species, 1211 Plants, what are the three great classes of, 1212 LESSON LVIII. Plants, what are the characteristics of exogenous, 1213 Plants, what are the characteristics of cryptogamus, 1216 Plants, what are the effects of diverse climates upon, 1242 Plants, what are the effects of altitude upon mountains, 1243 Plants, what agencies influence their geographical distribution, 1250 Plants, what are the chief facts connected with the distribution of by man, 1251 Plants, why are herbaceous less solid than woody, 1265 Plants, why are the stalks of herbaceous generally cylindrical, 1266 Plants, what are the stomata of, 1267 Plants, why are their stomata generally on the underside of their leaves, 1268 Plants, why have they pith in their centres, 1269 Porter, why does bottled produce large volumes of froth, 801 Pulse, why do we feel it beat, 900 Quadrupeds, geographical distribution of, 1331 Quicksilver, why does it reflect light from mirrors, 513 LESSON LIX. Radiation, why does scratching a bright metal surface increase its powers of, 199 Radiation of heat, what benefits arise from it, 415 Radiation of light, what is it, 503 Radiation, do all bodies radiate light, 504 Rain, what is it, 416 Rain, does it ever occur without clouds, 417 Rain-drops, why are they sometimes large, and at other times small, 418 Rains, at what seasons are they most prevalent, 419 Rainy days, in what months of the year are they most frequent, 420 Rainy days, why are there more from September to March, 421 Rain, in what part of the world does the greatest quantity fall, 422 Rain, in what part of the world do the heaviest rains fall, 423 Rain, in what part of the world does the least rain fall, 424 Rainy days, how many are there in a year, 425 Rain, in what part of England does the greatest quantity fall, 426 Rains, why do the heaviest occur in hot countries, 427 LESSON LX. Rain, why does the greatest quantity fall at the equator, 428 Rain, why are some parts of the earth without it, 429 Rain, why does it purify the air, 433 Rainy localities, why are mountainous countries more rainy than flat ones, 434 Rain, why does more fall by night than by day, 435 Rain, why do bunches of dried sea-weed indicate its coming, 436 Rain, why do weather-toys foretell its coming, 437 Rain, the Capuchin toy; mysterious walk of a wooden horse, 438 Rain, why does ladies' hair drop out of curl as rain approaches, 438 Rain, why is it said to be coming, when the mountains are "putting on their night-caps", 439 Rainbow, what causes a, 486 Rainbow, why does it exhibit colours, 487 Rainbows, why are there sometimes two, 488 Rainbows, why are the columns of the secondary bow, arranged in the reverse order of those of the primary, 489 LESSON LXI.