Eels, why are their eyes covered with a transparent horny coat, 1130 Falling, what is the cause of bodies, 774 Fanning the face, why does it make us feel cooler, 172 Fata morgana, what is the cause of, 527 Fatigue, why do we feel, 1017 Feather, why does it fall to the earth more gradually than a shilling, 791 Features, why do we preserve the same through life, 903 Feel, why do we, 1004 Feeling, why is it impaired when the hands are cold, 1006 Feeling, why do the fingers prick and sting when they again become warm, 1007 LESSON XXVIII. Feeling, why do persons whose legs or arms have been amputated, for some time continue to feel the part that has been removed, 1008 Fibrin, what is it, 899 Fingers, why can we raise them, 943 Fingers, why can we draw them back after they have been raised, 944 Fire, why does it burn more brightly when blown by a bellows, 27 Fire, what is it, 82 Fire, what are its properties, 83 Fire, what elements take part in its maintenance, 84 Fire, how does its combustion begin, 85 Fire-screens, how do they contribute to keep rooms cool, 217 Fire, why is it sometimes put out by blowing it when it is low, 262 Fire, why does poking it cause it to burn more brightly, 287 Fires, why do "blowers" improve the draft of air, 288 Fire, why does it sometimes appear red, and without flame, 283 Fire, what effect has it upon air, 284 Fires, why do charcoal and coke burn without flame, 292 Fires, why are charcoal and coke difficult to light, 293 Fires, a new plan of kindling, 293 LESSON XXIX. Fires, why in lighting them do we first lay in paper, wood, and coal, 298 Fire, why does a poker laid across the top revive it when dull, 302 Fire-places, why should they be near the ground, 303 Fire, why does the blacksmith sprinkle water upon the coals of his forge, 308 Fires, what is the best method of conveying air to, 684 Fish, why does putrifying look luminous, 95 Fishes, why have they fins, 1053 Fishes, why are their fins proportionately so much smaller than the wings of birds, 1054 Fishes, why have they scales, 1055 Fishes, why do they float in streams, with their heads towards the current, 1056 Fishes, why have they air-bladders, 1057 Fishes, why do not their eyes contract, 1129 Fishes, why have they no eyelids, 1132 Fishes, why have they the power of giving their eye-balls a sudden motion, 1133 Fishes, why are their tails so much larger than their fins, 1137 Flame, what is it, 96 LESSON XXX. Flame, what temperature is required to produce it, 101 Flame of a candle, why does the lower part of the flame appear blue, 246 Flame of a candle, why does the middle of the flame look dark, 217 Flame of a candle, why does the upper part produce a bright yellow light, 248 Flame of a candle, why is there a fringe of pale light around the flame, 249