Marbles, why do they rebound when dropped upon the pavement, 820 Marbles, why do they roll furthest upon smooth surfaces, 821 Marbles, how many forces contribute to stop their rolling, 882 Marbles, why do the stripes upon them disappear when they are spinning rapidly, 823 Marbles, why are the rings upon them most perceptible at the "poles," while they are spinning, 824 LESSON XLIX. Matches, do they ignite spontaneously, 313 Meat, why is it sooner cooked when a tin screen is placed before the fire, 213 Metal, why does it run like a fluid when melted, 333 Mirrors, why do we see our features therein, 209 Mirrors, why do we see our faces in them, 512 Mirrors, what has the glass of to do with the reflection, 514 Mirrors, why do compound mirrors reflect many images of one object, 515 Mirrors, why do reflections appear as far behind a mirror as the object reflected stands before it, 518 Mirage, what is the cause of the, 527 Mists, what are they, 368 Mists and fogs, what is the difference between them, 369 Mists end fogs, why do they disappear at sunrise, 370 Mistletoe, why have its berries a thick viscid juice, 1177 Mistletoe, how are its seeds conveyed to the bark of trees, 1178 Moles, why have they hard flat feet, 1074 Mole's fur, why is it glossy and smooth, 1075 LESSON L. Moles, why are they permanent, 904 Moles, why may rain be expected when they throw up their hills, 1117 Monsoons, what are they, 672 Monsoons, what is the cause of, 673 Mornings, why are they usually clear when frosty, 410 Mother-of-pearl, what causes the rich tints displayed by, 500 Moths, why do they fly by night, 1297 Moths, why are their bodies generally covered with thick down, 1228 Moths, why do they fly against the candle-flame, 1299 Muscles, how many are there in the human body, 941 Muscle, what is the constitution of a, 942 Muscles, what degree of strength do they possess, 945 Muscles, what is the stimulus which sets them in action, 946 Mussels, why have they tendinous cords proceeding from their shells, 1086 Natural phenomena, a world of miniature, 690 Nails, why have we got them at the fingers' ends, 908 Nails, why is there a circular line of whitish colour at the root of the, 909 LESSON LI. Nails, why do white spots occur upon the, 916 Needle, why will it float if laid carefully upon water, 795 Nerves, what are they, 951 Nervous system, of what does it consist, 955 Nerve, what is the constitution of a, 956 Nervous fluid, what is the, 957 Nerves, how many kinds are there, 958 Nerves of motion, what are they, 959 Nerves of sensation, what are they, 960 Nerves of special sense, what are, 961 Nerves of sympathy, what are the, 962 Nights, why are they usually cold when clear, 411 Nitrogen, what is it, 33 Nitrogen, where is it found, 34 Nitrogen, could animals live in it, 37