Rainbow colours, why do glass lustres and chandeliers exhibit them, 498 Rainbows, why are the colours of the secondary bow fainter than those of the primary, 491 Rainbow, what is a lunar, 492 Rainbow, why is a lunar bow fainter than the solar, 493 Rainbow, why is one in the morning the shepherd's warning, 538 Rainbow, why is one at night the shepherd's delight, 539 Refraction of light, what is it, 472 Refraction and reflection of light, what is the difference, 502 Reflections, why are they reversed, 490 Reflection, why do black bodies reflect any light, 505 Reflection, why does a window-pane appear to reflect better by night than by day, 516 Reflection, what is the line of, 520 Reflection, what is the angle of, 522 Repulsion, what is it, 792 Respiration, why does the chest expand when we breathe, 889 Respiration, how does blood communicate with the air in the lungs, 890 Rest, why does it invigorate us, 1018 Rice, where is it cultivated, 1219 Rosewood, what is it, 1191 LESSON LXII. Saliva, why does saliva enter the mouth while we are eating, 872 Sea, why is it salt, 764 Sea, what is the estimated amount of salt in the, 765 Sea, what is the depth of the, 766 Sea-gulls, why are they numerous in fine weather, 1119 Sea-gulls, why do they fly over the land on the approach of stormy weather, 1120 Sea-crow, why is its lower bill longer than the upper, 1135 Sealing-wax, why does rubbing it attract to it small particles of matter, 565 See, why do we, 963 Seeds, why are they generally enveloped in hard cases, 1152 Seeds, why do they throw out roots before they form leaves, 1153 Seeds, why does the leaf-germ come up to the light and the root-germ penetrate the earth, 1285 Seeds, why are they indigestible, 1286 See-saw, why may a little boy balance a larger boy, 863 See-saw, why does the little boy sink to the earth, when the larger boy kicks the ground, 861 LESSON LXIII. See-saw, why may the little boy keep the larger one up, when once he is up, 864 Shadows, what is the cause of, 508 Shadows, why is there some light where shadows fall, 510 Shadows, why do they lengthen as the sun goes down, 526 Shuttle-cock, why does it travel slowly through the air, 836 Shuttle-cock, why do we hear a noise when we strike it with the battledore, 837 Sight, why are two persons able to see each other, 551 Sight, why can we see so many upon the small retina, 966 Sight, why are we able to see at long or short distances, 974 Sigh, why do we, 1025 Silica, what is it, 1260 Silk, what is it, 1200 Skin, why does a chill of the produce inflammatory action in the lungs, 1014 Sky, what is it, 530 Sky, why is it red at sunset, 532 Sleet, what is it, 447 Sleep, what is it, 1019 Smell, why do we, 992 Smoke, what is it, 102 Smoke, why is there so little when the fire is red, 105