- LESSON I.
- Acids, vegetable, whence are they obtained, [1256]
- Actinism, what is it, [552]
- Actinism, what effect has it upon vegetation, [559]
- Actinism, at what season of the year is it most abundant, [560]
- ærial spectra, what is the cause of, [527]
- Affinity, what is the attraction of, [777]
- Air, why do we breathe it, [4]
- Air, what is the composition of it, [12]
- Air, what is its state after it has been breathed, [13]
- Air, is that sent from the lungs light or heavy, [14]
- Air, is it a good or bad conductor of heat, [150]
- Air, why is a still summer said to be sultry, [171]
- Air, why does it feel cooler when in motion, than when still, [175]
- LESSON II.
- Air, when is it hot enough to destroy life, [179]
- Air, why is it often excessively hot in chalk districts, [219]
- Air, is it heated directly by the sun's rays, [221]
- Air, why does it ascend the chimney, [240]
- Air, why does it fly through the doors and windows towards the fire-place, [241]
- Air, what does the motion of it in our rooms illustrate, [242]
- Air, why does it become charged with watery vapour, [346]
- Air, when is it said to be saturated with vapour, [430]
- Air, what proportion of water is air capable of holding in the form of vapour, [431]
- Air, what is its weight relative to that of water, [647]
- LESSON III.
- Air, which is heavier, dry or vaporised, [697]
- Air-pistol (or pop-gun), why does pressure applied to the handle propel the cork, [854]
- Air-pistol, why must the handle be drawn out before the cork is placed in, [855]
- Air, why does fresh impart a healthy appearance, [915]
- Albumen, what is it, [899]
- Alkalies, what are they, [36]
- Amber, or electrum, what is it, [564]
- Animals, how is their greater warmth in winter provided for, [168]
- Animal forms, why are there so many, [1029]
- Animal furs, why do they become thicker in the winter, [1035]
- Animals, why have carnivorous, long pointed teeth, [1038]
- LESSON IV.
- Animals with long necks, why have they large throats, [1049]
- Animals, why cannot flesh-eaters live upon vegetables, [1071]
- Animals, why can ruminating recover the food from their paunches, [1089]
- Animals, why can ruminating keep the chewed from the unchewed food in their stomachs, [1090]
- Animals, why do the smaller animals breed more abundantly than the larger ones, [1094]
- Animals, domestic, why may change of weather be expected when they are restless, [1107]
- Animals, plants, and minerals, what are the differences between them, [1140]
- Animals that graze, why do they crop the tender blades, but leave the tall grass, [1287]
- LESSON V.
- Animals, distribution of, [1326]
- Arms and hands, why do we see blue marks upon them, [896]
- Arms and legs, why does it require the influence of the will to set them in motion, [917]
- Arms and legs, why are they made subject to the will, [919]
- Ascending, what is the cause of bodies, [775]
- Atmosphere, how is it heated, [232]
- Atmospheric humidity, why does it sometimes form clouds, at others form dews, fogs, mists, &c., [409]
- Atmospheric pressure, how high will it raise water, [652]
- Atmosphere, what is the, [639]
- Atmosphere, to what height does it extend, [639]
- Atmosphere, what is the amount of its pressure, [641]
- Atmosphere, what is the proportion of watery vapour in the, [642]
- Atmosphere, why are its upper regions intensely cold, [444]
- Atmosphere, what is the greatest height ever reached in the, [648]
- LESSON VI.
- Atmospheric pressure, what is the total amount on the earth's surface, [644]
- Atmosphere, what is the amount of its pressure upon the human body, [645]
- Atmosphere, why do we not feel its pressure, [646]
- Atmosphere, to what extent may its pressure vary, [702]
- Attractive agent, what is an, [76]
- Attraction, what is it, [772]
- Attraction, how many kinds are there, [773]
- Aurora Borealis, what is the cause of, [590]
- Bananas or plantains, where are they cultivated, [1220]
- Bark Peruvian, where is it produced, [1228]
- Barometer, what is a, [691]
- Barometer, why does it indicate the pressure of the atmosphere, [692]
- Barometer, why is it also called a "weather-glass", [693]
- Barometers, why are they constructed with circular dials, [694]
- Barometer, why does the hand change its position when the mercury rises or falls, [695]
- Barometer, why does tapping its face cause the hand to move, [696]
- Barometer, why does its fall denote the approach of rain, [699]
- LESSON VII.
- Barometer, why does its rise denote the approach of fine weather, [700]
- Barometer, how does it enable us to calculate the height of the mountains, [701]
- Barometer, when does it stand highest, [704]
- Barometer, when does it stand lowest, [705]
- Barometer, what effect has heat upon the, [707]
- Barometer, what effect has cold upon the, [708]
- Balloons, why do they ascend in air, [830]
- Balloons, why do air balloons become inflated, [831]
- Balloons, why do they sometimes burst when they reach a high altitude, [832]
- Bat and ball, what principles of natural philosophy are illustrated in the play, [867]
- Bats, why have they hooked claws in their wings, [1079]
- Bats, why do they fly by night, [1080]
- LESSON VIII.
- Bats, why do they sleep during winter, [1081]
- Beds, why should they be raised two feet from the ground, [15]
- Bed-room windows, why are they sometimes covered with ice crystals, [344]
- Beer, why will it not run out of a cask until a hole is made at the top, [660]
- Beer, why does it get flat, [805]
- Bees, why have they stings, [1101]
- Bees, why may we expect fine weather when bees wander far from their hives, [1114]
- Beetles, why are they called "coleoptera", [1319]
- Beetles, why have they hard horny wing-cases, [1320]
- Beetles, why have many of them hard horns, [1321]
- Bile, why does it separate nutritious from innutritious matter, [884]
- Birds, why have water-fowls feathers of a close and smooth texture, [1033]
- Birds, why are they covered with feathers, [1030]
- Birds, why does black down grow under their feathers on the approach of winter, [1036]
- Birds, why have they hard beaks, [1040]
- Birds, why are their beaks generally long and sharp, [1041]
- Birds, why are their bones hollow, [1050]
- Birds, why do they lay eggs, [1051]
- LESSON IX.
- Birds, why have those with long legs short tails, [1052]
- Birds, why have aquatic web-feet, [1059]
- Birds, why have those that swim and dive short legs, [1060]
- Birds, why have some deep rough notches on the under surfaces of their feet, [1061]
- Birds, why have they gizzards, [1072]
- Birds of prey, why have they no gizzards, [1084]
- Birds, why may wet and thunder be expected when they cease to sing, [1121]
- Birds of passage, why, if they arrive early, may severe weather be expected, [1121]
- Birds, geological distribution of, [1326]
- Birds, tameness of in unfrequented countries, [1327]
- Birds, why are birds of song not also remarkable as birds of plumage, [1328]
- Birds, what are the velocities of their flights, [1329]
- Birds, what is the cause of their migrations, [1330]
- Black, why should parts of kettles and saucepans be allowed to remain, [204]
- Blood, in what proportions are the gases found in it, [39]
- LESSON X.
- Blood, what is venous, [41]
- Blood, what is arterial, [42]
- Blood, what is the constitution of the, [899]
- Blood, what quantity does the human body contain, [920]
- Blood, how frequently does the whole quantity pass through the system, [922]
- Blowing upon tea, why does it cool it, [174]
- Bow, why does it propel the arrow, [847]
- Bow and arrow, what line does the arrow describe, [848]
- Bow and arrow, what forces tend to arrest the arrow, [849]
- Bow and arrow, why are there feathers at the ends of arrows, [850]
- Bones, how many are there in the human body, [923]
- Bones, of what substances are they composed, [924]
- Bones, what are the uses of the, [925]
- Bones, why are those of the back hollowed out, [927]
- Bones, why are those of the skull arched, [930]
- Bones, why are those of the skull divided by small sutures, [931]
- Bones, why are they hollow, [934]
- LESSON XII.
- Bones, why are those of the arms and legs formed into long shafts, [935]
- Bones, why are those of the feet and hands numerous and small, [936]
- Botanical geography, [1208]
- Brain, why is it placed within the skull, [926]
- Bread-fruit trees, where are they natives of, [1223]
- Breathing, is it a kind of combustion, [17]
- Breaths, have people ever been poisoned by their own, [24]
- Breezes, why are summer said to be cool, [170]
- Breezes, what is the cause of sea and land, [235]
- Bubbles, why do they ascend in the air, [236]
- Bubbles, why do they fall, after having ascended, [237]
- Bubbles, why do they display rainbow colours, [499]
- Bubbles, why are they round, [825]
- Bubbles, why are they elongated when being blown, [826]
- Bubbles, why do they close, and become perfect spheres when shaken from the pipe, [827]
- Bubbles, why do they change their colours in the sunshine, [828]
- Bubbles, why do they burst, [829]
- LESSON XI.
- Burning or supporting combustion, what is the difference, [45]
- Burning-glasses, why do they appear to set fire to substances, [80]
- Butterflies, why do they lay their eggs upon cabbage-leaves, [1099]
- Butterflies' eggs, why do they lie dormant in the winter, [1288]
- Butterflies, why do they fly by day, [1296]
- Calms, why do they prevail at the equator, [671]
- Caloric, what is it, [72]
- Caloric, what is the source of it, [73]
- Caloric, what are the effects of it, [74]
- Caloric, why is it called a repulsive agent, [75]
- Caloric, how may it be excited to develope heat, [79]
- Caloric, is there any in ice, snow, water, marble, &c., [89]
- Caloric, how do we measure the quantity of in any substance, [329]
- Caloric, how does it travel, [332]
- Caloric, how do we know that it is caloric which fuses metals, [334]
- Calves and lambs, why have they no horns, [1069]
- Camel, why has its stomach a number of distinct bags, [1065]
- Candles, why do tallow require snuffing, [264]
- LESSON XIII.
- Candles, why do composite and wax not require snuffing, [265]
- Candle, what becomes of it after it is burnt, [269]
- Capillary blood-vessels, why are they found in every part of the system, [919]
- Capillary attraction, what is it, [780]
- Carbonic acid gas, how is it formed, [9]
- Carbonic acid gas, what becomes of it, [10]
- Carbonic acid gas, is it heavier or lighter than air, [11]
- Carbonic acid gas, what are the chief sources of, [16]
- Carbonic acid gas, what is its effect upon the human system, [21]
- Carbonic acid gas, what becomes of that formed by combustion, [59]
- Carbonic acid gas, what proportion is dangerous to life, [60]
- Carbonic acid, what is it, [798]
- Carbonic acid, where does it chiefly exist, [799]
- Carbonic acid, what are its pure states, [800]
- Carbon, what is it, [18]
- Carbon, will it produce flame when burnt in oxygen, [106]
- Carbon and hydrogen, what differences characterise the combustion of, [268]
- LESSON XIV.
- Carbon, what is the purest form of it, [277]
- Card, why do the images on each side blend while a card is revolving, [846]
- Caterpillars, why do they appear in the spring, [1289]
- Caterpillars, why do they eat voraciously, [1290]
- Caterpillars, why do they pass into the state of the chrysalis, [1291]
- Caterpillars, why do they become torpid in the chrysalis, [1292]
- Caterpillars, why do they attach themselves to the leaves of plants when in the chrysalis, [1294]
- Cats, &c., why do they see in the dark, [981]
- Cats' eyes, why are the pupils of nearly closed by day, [982]
- Cats, &c., why have they whiskers, [1096]
- Cattle, why if they run round in meadows may thunder be expected, [1122]
- Ceiling, how did Mr. Sands walk on the, [664]
- Champagne, why does it effervesce, [806]
- Champagne, why do bubbles rise from it in two or three columns, [807]
- Charcoal, why is it dangerous to burn it in rooms, [20]
- LESSON XV.
- Charcoal fires, why do they not give flames, [107]
- Charcoal, what is it, [275]
- Charcoal, why does it act as a disinfectant, [809]
- Chicory, what is it, [1196]
- Chimney, why does it cease smoking after the fire has been lighted a little while, [680]
- Chimney, why does a long one create a better draught than a short one, [681]
- Chimneys, why do some smoke when windows and doors are closed, [683]
- Chimneys that stand under elevated objects, why do they smoke, [685]
- Chimneys, why do sooty smoke, [687]
- Chimneys, why do they smoke in damp and gusty weather, [688]
- Chimney, why does it smoke when first lighted, [679]
- Chocolate, what is it, [1194]
- Circulation, why are the venous blood and chyle sent to the lungs, [887]
- Circulation, what is the course of the arterial blood, [888]
- Circulation, why does the blood impart vitality, [891]
- LESSON XVI.
- Circulation, how do we know the blood is alive, [892]
- Circulation, why does the blood circulate, [893]
- Circulation, how is the body renewed by the blood, [894]
- Circulation, how does the blood return to the lungs after it has reached the extremities, [895]
- Circulation, why are the veins more perceptible than the arteries, [897]
- Circulation, why when we prick the flesh does it bleed, [893]
- Circulation, what occurs during the, [899]
- Circulation, what becomes of the matter collected by the blood, [901]
- Circulation, how is the blood propelled through the arteries, [916]
- Circulation, why are the capillary vessels capable of receiving the quantity of blood sent through larger vessels, [917]
- Cinnamon, where is it produced, [1239]
- Cleanliness, why does it promote health, [1015]
- Clothes on fire, why should persons throw themselves down, [252]
- Clothing, why do some articles feel cold, and others warm, [120]
- LESSON XVII.
- Clothing, are conductors or non-conductors the warmer, [121]
- Clothing, why are white and light-coloured articles cool, [218]
- Clothing, why are dark-coloured dresses worn in winter, and light in summer, [230]
- Clouds, what are they, [373]
- Clouds, why do we not see them ascend, [375]
- Clouds, why are they invisible when they rise, but become visible when they have ascended, [376]
- Clouds, why do they not descend to the earth, [377]
- Clouds, at what altitudes do they fly, [378]
- Clouds, how many descriptions are there, [379]
- Clouds, what produces their various shapes, [380]
- Clouds, what are their dimensions, [381]
- Clouds, how are they affected by winds, [382]
- Clouds, what do Cirrus foretell, [389]
- Clouds, what do Cumulus foretell, [390]
- Clouds, what do Stratus foretell, [391]
- Clouds, what do Nimbus foretell, [392]
- Clouds, what do Cirro-cumulus foretell, [393]
- Clouds, what do Cirro-stratus foretell, [394]
- Clouds, what do Cumulo-stratus foretell, [395]
- LESSON XVIII.
- Clouds, why are cloudy days colder than sunny days, [396]
- Clouds, why are cloudy nights warmer than clear nights, [397]
- Cloudy days and nights, why are they not always wet, [432]
- Clouds, why are they white, [531]
- Clouds, why are they sometimes yellow, [533]
- Clouds, what develops the electricity in the, [581]
- Clouds, why do they sometimes move towards each other from opposite directions, [778]
- Clouds, why do they gather around mountain tops, [781]
- Cloves, where are they produced, [1231]
- Coal, what is it, [271]
- Coal, why do we know that it is of vegetable origin, [273]
- Coal, what are the chemical components of, [274]
- Coals, why do they produce yellow flame, [279]
- Cockles, why have they stiff muscular tongues, [1087]
- Cocoa, what is it, [1195]
- Cocoa, what tree produces it, [1221]
- Coffee-pot, why has it a wooden handle, [125]
- LESSON XIX.
- Coffee, what is it, [1193]
- Coffee, where is it cultivated, [1224]
- Cohesion, what is the attraction of, [776]
- Coke-fires, why do they not give flames, [107]
- Coke, what is it, [278]
- Cold, when is a body said to be, [78]
- Cold, what is the cause of the sensation, [133]
- Cold, does it radiate, [207]
- Colour, why is a substance white, [466]
- Colour, why is a substance black, [467]
- Colour, why is a rose red, [468]
- Colour, why is a lily white, [469]
- Colour, why is a primrose yellow, [470]
- Colour, why are there so many varieties of colour and tint in nature, [471]
- Colours, remarks upon, [501]
- Combustion, what takes place during, [48]
- Combustion, how many kinds are there, [93]
- Conductors of heat, what substances are good, [110]
- Conductors of heat, why do bad conductors readily ignite, [295]
- Combustion, what is spontaneous, [311]
- Combustibles used for lighting, which vitiates the air most, [62]
- Conduction of heat, what is the, [113]
- Convection, what is the chief effect of the law of, [243]
- LESSON XX.
- Cork, what is it, [1271]
- Cork-tree, why does it shed its own bark, [1272]
- Corns, why when they ache may rain be expected, [1115]
- Corn, why does the young ear come up enfolded in two leaves, [1167]
- Cotton, what is it, [1199]
- Cough, why do we, [1023]
- Crickets, why do they make a chirping noise, [1123]
- Cross-bills, why do their mandibles overlap each other, [1136]
- Cup in a pie, why does it become filled with juice, [631]
- Cup in a pie, does it prevent the juice from boiling over, [662]
- Dates, what are they produced by, [1221]
- Death-watch, why does it make a ticking noise, [1301]
- Dew, what is it, [345]
- Dew, what causes the decline of temperature which produces it, [347]
- Dew, why is there little or none, when the nights are cloudy, [348]
- Dew, why does it form most abundantly on cloudless nights, [349]
- Dew, why is there little under the branches of thick foliage, [351]
- LESSON XXI.
- Dew, why is there none formed on windy nights, [352]
- Dew, why are valleys and low places chiefly subject to it, [353]
- Dew, what bodies receive little of it, [355]
- Dew, what bodies receive most of it, [354]
- Dew, at what period of the night is it chiefly formed, [356]
- Dew, why is it chiefly formed at that period, [357]
- Dew, in what parts of the world is the greatest quantity formed, [358]
- Dew, in what parts of the world is the least quantity formed, [359]
- Dew, why is it seldom formed at sea, [360]
- Dew, why is it, when heavy, regarded as a precursor of rain, [361]
- Dew, what is honey-dew, [364]
- Dew, why does it lie on the exposed sides of screens of plants, [401]
- Dew, why does it rest upon the upper surfaces of leaves, [402]
- Dews, why are cultivated lands more subject to them than those that are uncultivated, [403]
- LESSON XXII.
- Dew, why does the gravel-walk receive less dew than the grass, [404]
- Dew, why does little of it form at the base of hedges, walls, and trees, [406]
- Dews, why do morning dews and mists usually come together, [407]
- Dew, what effect have winds upon its formation, [408]
- Dew, why does it form in round drops upon leaves, [794]
- Diamond, what causes the brilliant colours of the, [501]
- Digestion, why does food flow more freely to the stomach during, [879]
- Digestion, why does excess in eating impair, [880]
- Digestion, what changes occur to food in the stomach, [881]
- Digestion, what causes bilious attacks, [882]
- Digestion, how is the nutritious matter taken from that which is innutritious, [885]
- Digestion, what becomes of the nutrition when it enters into the circulation, [886]
- Dish-covers, why should they be plain in form, and have bright surfaces, [203]
- Dogs, geographical distribution of, [1333]
- Dream, why do we, [1020]
- Drowsiness, why is it felt in crowded rooms, [22]
- LESSON XXIII.
- Ducks and geese, why do they dash water over their backs on the approach of rain, [1105]
- Ducks and geese, why have they square-pointed bills, [1044]
- Dyes, vegetable, what are they, [1259]
- Ear, why is it spread out externally, [984]
- Ears, why do hairs grow across them, [986]
- Ear-wig, why is it so called, [986]
- Ears, why is wax secreted in the, [987]
- Ears, why do singing noises occur in the, [988]
- Ears, why do people become deaf, [989]
- Ears, why do people accustomed to loud noises feel no inconvenience from them, [990]
- Ears of animals of prey, why do they bend forward, [1063]
- Ears of animals of flight, why do they bend backward, [1064]
- Earth, why is it warmer than air during sunshine, [398]
- Earth, why is it colder than air after sunset, [399]
- LESSON XXIV.
- Earth, how can man weigh the, [784]
- Earth, what is the weight of the, [788]
- Earth-worms, why have they no feet, [1085]
- Echoes, why do some occur immediately after the sounds, [742]
- Echoes, why do some occur at a considerable interval after the sound, [743]
- Echoes, why do some change the tone and quantity of sounds, [744]
- Echoes, why are there sometimes several to one sound, [745]
- Echoes, are they caused only by distant objects, [746]
- Echoes, what are they, [741]
- Electricity, what is it, [561]
- Electricity, why is it so called, [562]
- Electric fluid, why is it so called, [566]
- Electrics, what substances are, [567]
- Electricity, what is positive, [568]
- Electricity, what is negative, [569]
- Electricity, what is vitreous, [570]
- Electricity, what is resinous, [570]
- Electrical phenomena, what produces them, [571]
- Electricity, how does its equilibrium become disturbed, [572]
- Electricity, how does it seek to regain its equilibrium, [573]
- Electricity, what substances are conductors, [574]
- Electricity, what substances are non-conductors, [575]
- Electricity, what substances are insulators, [576]
- LESSON XXV.
- Electricity, what is the effect when a current of electricity meets with an insulator, [577]
- Electric sparks, what is the cause of, [578]
- Electricity, why does lightning attend it, [584]
- Electricity, why does it affect the shape of clouds, [613]
- Electric storms, why are they more frequent in hot than in cold weather, [624]
- Electric storms, why do they frequently occur after dry weather, [625]
- Electric storms, why do they purify the air, [629]
- Electricity, what is Voltaic, [636]
- Electrical attraction, what is it, [778]
- Elementary body, what is meant by, [19]
- Element, what is the most abundant in nature, [756]
- Elephant, why has it a short unbending neck, [1076]
- Elephant, why has it a trunk, [1077]
- Elephants' hind legs, why do they bend forward, [1078]
- Etna, what are the botanical regions of Mount, [1240]
- Endogenous stems, what are they, [1280]
- LESSON XXVI.
- Endogenous stems, why do they abound in tropical climates, [1281]
- Endogenous stems, why have they no bark, [1282]
- Endogenous stems, why do they grow to a great height, [1283]
- Exogenous stems, what are they, [1279]
- Exercise, why does it promote health, [1016]
- Exercise, why does it make us feel warm, [839]
- Explosions of gas, what is the best method of preventing, [65]
- Eye-balls, why are they white, [911]
- Eye-balls, why do they sometimes become blood-shot, [912]
- Eyes, why are they placed in the sockets of the skull, [929]
- Eyes, why are we able to move them, [965]
- Eye, why does the pupil look black, [968]
- Eye, why is the pupil larger sometimes than at others, [969]
- Eyes, why have we two, [970]
- Eyes, why having two, do we see singly, [971]
- Eyes, why are they provided with eyelids, [972]
- Eyelids, why are they fringed with eyelashes, [973]
- Eyes, whence are their humours derived, [976]
- LESSON XXVII.
- Eyes, why do we feel inconvenienced by sudden light, [978]
- Eyes, why if we look upon a bright object and turn away, are we unable to see, [979]
- Eyes, why are we able to see better after a little while, [980]
- Eyes, why do cats, bats, owls, &c., see in the dark, [981]
- 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]
- Flame of a candle, why does it terminate in a point, [250]
- Flame of a candle, why does it lengthen when anything is held over it, [251]
- Flame or spark, why does pressing it put it out, [253]
- Flame of a candle, why does holding a candle upside down put it out, [257]
- Flame of a candle, why is it more difficult to blow out the flame of a candle with a cotton wick than one with a rush wick, [258]
- Flame of a candle, why does blowing sharply on it put it out, [259]
- Flame of a candle, why will a gentle puff of air sometimes relight it, [260]
- LESSON XXXI.
- Flame of a candle, why will not a similar puff rekindle a rushlight, [261]
- Flame of a candle, why will a piece of paper twisted to form an extinguisher put it out, [263]
- Flame of a candle, why does it become dim when the wick is loaded with carbon, [267]
- Flames of a fire, why do some appear much whiter than others, [280]
- Flames of a fire, why do some of them appear blue, [282]
- Flesh, why does it heal when we cut it, [902]
- Flesh-eaters, why do they satisfy themselves with a rapid meal, [1092]
- Flesh, why do the marks of deep cuts remain, [905]
- Flesh, why does that under the nails look red, [907]
- Flies, how can they walk on the ceiling, [663]
- Flies, why have they fine hairs growing on the extremities of their legs, [1102]
- Flowers, what is the chief cause of the differences of their temperatures, [227]
- Flowers, why may wet weather be expected when their perfume is strong, [1103]
- LESSON XXXII.
- Flowers, why, if certain close, may rain be expected, [1116]
- Flying-top, why does it rise on the air, [843]
- Flying-top, why does it return to the earth, when its rotations are expended, [844]
- Focus, what is a, [81]
- Fogs, what are they, [365]
- Fogs, why are certain coasts very liable to them, [366]
- Fogs, what are dry, [367]
- Fogs, why do they frequently rise in the morning and fall in the evening, [371]
- Fogs, why do they sometimes rest upon a locality for days together, and then disappear, [372]
- Food, why do we eat it, [869]
- Food, why do we eat animal and vegetable, [172]
- Food, why do we masticate it, [871]
- Food, how does it descend into the stomach, [875]
- Food, why do we not feel it being transmitted through the throat, [876]
- Food, why do we feel uneasy after eating to excess, [877]
- Food, why do we feel drowsy after eating heartily, [878]
- Food, why do some portions nourish us, while other portions are useless, [883]
- LESSON XXXIII.
- Fossil, vegetable, what is it, [272]
- Friction, why does it produce heat, [321]
- Friction, why does rubbing two surfaces together attract latent heat, [322]
- Frost, why is the air warmer during, [163]
- Frost, what is white, [412]
- Frost, what is black, [413]
- Frost, why are black frosts said to last, [414]
- Fruit, why do gooseberries, plums, &c., taste acid, [1184]
- Fruit, why do ripe taste sweet, and unripe sour, [1185]
- Fruits, why are succulent most abundant in tropical climates, [1207]
- Fruits and vegetables, why do they ripen in succession, [1284]
- Furs, why are they worn in winter, [166]
- Galvanism, what is it, [635]
- Gas, what kind lights our streets, [56]
- Gas, why does it expand in thin air, [833]
- Geology, what has been its influence upon botanical geography, [1249]
- Giraffes, why have they small heads, [1322]
- Giraffes, why have they long necks, [1323]
- Giraffes, why have they long and flexible tongues, [1324]
- LESSON XXXIV.
- Giraffes, why are their nostrils narrow and small, and studded with hairs, [1325]
- Glass upon a lamp, why does it increase the brilliancy of the light, [266]
- Glass, why is it transparent, [506]
- Glass, does transparent reflect any light, [507]
- Glow-worms, why have they brushes attached to their tails, [1127]
- Glow-worms, why do they emit light, [1128]
- Gnats, why are their larvæ and pupæ found in water, [1314]
- Gnats, why may fine weather be expected if they fly in large numbers, [1110]
- Grasses, why are they so widely diffused throughout nature, [1166]
- Grasshoppers, why are they comparatively active in their pupa stages, [1293]
- Gravitation, what is the attraction of, [774]
- Guano, why is it a good manure, [1262]
- Gum resins, what are they, [1255]
- Gums, vegetable, what are they, [1254]
- Gunpowder, why does it explode, [808]
- Gutta-percha, whence is it obtained, [1254]
- LESSON XXXV.
- Hail, what is it, [448]
- Hail, why is it supposed that the electrical state of the clouds affects the formation of hail, [449]
- Hail-storms, why do they usually occur by day, [450]
- Hairs, why do they grow across the passages of the nostrils, [993]
- Halo, what is a, [494]
- Halo, what is the cause of a, [495]
- Haloes, why are they sometimes large, and at other times small, [496]
- Haloes, why do they foretell wet weather, [497]
- Hands, why when we hold them against the candle do we perceive a crimson colour, [906]
- Hay-stacks, why do they sometimes take fire spontaneously, [316]
- Head, why is it set upon the neck, [928]
- Hearing, why do people engaged in battle frequently lose their, [991]
- Hearing, death of a dog through noise, [991]
- Heart, why does it beat without any effort of the will, [948]
- Heart, why is it placed in the chest of the body, [932]
- Heart and lungs, why are they enclosed by ribs, [933]
- Heart, why are its motions made independent of the will, [950]
- LESSON XXXVI.
- Heat, what is it, [71]
- Heat, what are the properties of, [86]
- Heat, what is animal, [87]
- Heat, what is latent, [88]
- Heat, what is a conductor of, [108]
- Heat, what is a non-conductor of, [109]
- Heat, how is it transmitted from one body to another, [119]
- Heat, what is the radiation of, [114]
- Heat, what is the reflection of, [115]
- Heat, what is the absorption of,[116]
- Heat, what is the convection of, [117]
- Heat, what is the cause of the sensation, [134]
- Heat, what becomes of that which the hearth-stone receives, [136]
- Heat, how long does a substance feel hot or cold to the touch, [139]
- Hearth-rug, and hearth-stone, their relative states of heat, [142]
- Heat, which are the better conductors, fluids or solids, [146]
- Heat, why are dense substances the best conductors, [147]
- Heat, why are fluids bad conductors, [148]
- Heat, why are woollen fabrics bad conductors, [149]
- Heat, is air a good or bad conductor, [150]
- LESSON XXXVII.
- Heat, is water a good or a bad conductor, [151]
- Heat, how do we know that air is not a good conductor, [155]
- Heat, how do we know that water is not a good conductor, [156]
- Heat, why are bottles of hot water wrapped in flannel, [158]
- Heat, why are hot rolls wrapped in flannel, [159]
- Heat, what is the highest degree that man can bear, [176]
- Heat, why may man endure a high degree without injury, [178]
- Heat, why may we believe that the internal heat of the earth does not arise from terrestrious combustion, [224]
- Heat, what is the radiation of, [181]
- Heat, what becomes of that which is radiated, [186]
- Heat, when does a body radiate it, [184]
- Heat, does the movement of the air affect the radiation of, [188]
- Heat, why will not the motion of air disturb the rays of, [190]
- Heat, what bodies are good radiators of, [192]
- Heat, what bodies are bad radiators of, [193]
- Heat, why does water keep hot longer in a bright metal jug, [195]
- LESSON XXXVIII.
- Heat, may it be reflected, [210]
- Heat, are light or dark-coloured bodies the best reflectors, [211]
- Heat what bodies are the best reflectors of, [212]
- Heat, why is that which is reflected less intense than the primary, [214]
- Heat, can it be reflected in any great intensity, [215]
- Heat, are good reflectors also good absorbers, [216]
- Heat of the sun's rays, how is it diffused, [219]
- Heat, how do we know that it is absorbed by the earth, [222]
- Heat, do plants absorb it, [225]
- Heat, how is it diffused through the atmosphere, [232]
- Heat, how is it diffused through the ocean, [233]
- Heat, why is it developed during chemical changes, [312]
- Heat, what are the sources of, [323]
- Heat, what is the accepted theory of, [328]
- Heat, what is the point at which it becomes luminous, [545]
- Heat, what is the relative intensity of primary and reflected, [548]
- Heat to cold, why does a sudden change bring on illness, [1013]
- LESSON XXXIX.
- Heat of the earth, Humboldt's opinion upon the internal, [1335]
- Heat of the earth, Hunt's opinion upon the internal, [1336]
- Hear, why do we, [983]
- Hiccough, why do we, [1027]
- Hoar-frost, what is it, [362]
- Hoar-frost, why does it foretell rain, [363]
- Hoar-frosts, why are they so frequent, and black-frost so unfrequent, [412]
- Hogs, why have Indian large tusks turning back towards their eyes, [1068]
- Hog, why is the under-jaw of the, shorter than the upper-jaw, [1039]
- Hoop, why does it roll without falling to the ground, [861]
- Hoop, why does it when falling make several side revolutions, [862]
- Horses, why have they smaller stomachs proportionately than other animals, [1097]
- Horse, why has it no gall-bladder, [1098]
- Horses, why is the secretion of their eyes thick and glutinous, [1134]
- Horses and cattle, why do they stretch out their necks, and snuff the air on the approach of rain, [1106]
- Horse-chestnut, why is it unfit for food, [1203]
- Hot, when is a body said to be, [77]
- LESSON XL.
- Hot water, why does it feel hotter in a metal jug than in an earthenware one, [126]
- Hot metal, why does it feel hotter than hot wool, [130]
- Hot metal and hot wool, which would become cold first, [131]
- Hot and cold bodies, why, when placed near each other, do their temperatures approximate, [331]
- Humming-tops, why do we see the figures painted on them before they spin, but not while they are spinning, [813]
- Humming-top, why does it make a noise, [810]
- Hydrogen, what is it, [49]
- Hydrogen, will it support animal life, [50]
- Hydrogen, will it support combustion, [51]
- Hydrogen, why will it explode, [52]
- Hydrogen, where does it chiefly exist, [54]
- Hydrogen, how is it obtained from coal, [57]
- Hydrogen-gas, is an escape of it dangerous to life, [63]
- Hydrogen-gas, what proportion mixed with air will explode, [64]
- Hydrogen-gas, does it rise or fall, [66]
- LESSON XLI.
- Hydrogen-gas, what proportion is dangerous if inhaled, [67]
- Hydrogen-gas, what proportion may be recognised by its smell, [68]
- Hydrogen-gas, may the use of it be considered dangerous, [70]
- Hydrogen-gas, what sources of it are there in our dwellings, [69]
- Hydrogen, why will it burst into flame when coals become heated, [100]
- Hydrogen, why does hi-carburetted burn with a whiter flame than common coal-gas, [281]
- Ice, why are blocks of it wrapped in flannel in summer time, [154]
- Ice, why does it melt, [325]
- Ice, why does it occupy more space than water, [752]
- Ignis fatuus, what is it, [318]
- Incidence, what is the line of, [519]
- Incidence, what is the angle of, [521]
- India-rubber, where is it obtained, [1254]
- Infants, why have they no teeth, [1070]
- Insects, why have they a large number of eyes, [1083]
- Insects, why have they long projections from their heads, [1100]
- Insects, why do they attach their eggs to leaves, [1295]
- Insects, why do they multiply so numerously, [1300]
- LESSON XLII.
- Insects, what is a larva, [1302]
- Insects, what is a pupa, [1303]
- Insects, what is a chrysalis, [1304]
- Insects, what is a nymph, [1305]
- Insects, why do they abound in decaying substances and in putrid waters, [1313]
- Insects, why do we see them in tanks of rain-water, [1314]
- Iron articles, why are they intensely cold in winter, [132]
- Iron articles, why do they usually feel cool, even when near a fire, [132]
- Ironing-box, why does the iron sometimes become too large for the box to receive it, [335]
- Ironing-box, why does the iron enter it, when partially cooled, [336]
- Iron, why does it rust when wetted, [768]
- Jew's-harps, why do they give musical sounds, [851]
- Jew's-harps, why will they not produce loud sounds unless they are applied to the mouth, [852]
- Jew's-harps, why does the alteration of the form of the mouth alter the sounds, [853]
- Kangaroos and opossums, why have they pouches in which they carry their young, [1139]
- LESSON XLIII.
- Kettle-holders, of what use are they, [128]
- Kettles and saucepans, why should the lids and fronts of be kept bright, [206]
- Kettles, why do they become encrusted with stony deposits, [762]
- Kite, why does it rise in the air, [840]
- Kite-string, why does it feel hot when running through the hand, [841]
- Kite, why does running with it cause it to ascend, [812]
- Knowledge, why should we seek it, [1]
- Knowledge, why does the possession of it give us power, [2]
- Knowledge, what are the benefits of, [3]
- Latent heat, will the abstraction of it reduce the bulk of bodies, [337]
- Latent heat, how do we know that it exists in air, [339]
- Laugh, why do we, [1026]
- Ligaments, what are they, [937]
- Ligaments, why are they wrapped around the joints, [938]
- Light, what is it, [451]
- Leaves, why are they green, [1181]
- Leaves, why do some turn yellow, [1186]
- Leaves, why do they fall off in the autumn, [1187]
- Leaves, how to make skeleton, [1159]
- LESSON XLIV.
- Leaves, why do they turn brown in autumn, [1183]
- Legs crossed, why do we see the elevated leg move at regular intervals, [918]
- Light, at what velocity does it travel, [453]
- Light, how long does it take to travel from the sun to the earth, [454]
- Light what are the minor sources of, [457]
- Light, what is a ray of, [458]
- Light, what is a medium of, [459]
- Light, what is a beam of, [460]
- Light, what is a pencil of, [461]
- Light, what is the radiant point, [462]
- Light, what is the focus of, [463]
- Light, what is the constitution of a ray of, [464]
- Light, why are its rays white, [465]
- Light, what are the estimated vibrations of, [465]
- Light, what is the refraction of, [472]
- Light, is it refracted when it falls upon a surface in a straight line, [473]
- Light, is the direction in which its rays are best dependent on the densities of the media, [474]
- Light, why does a spoon look bent when placed in a basin of water, [477]
- Light, why do we see the rays of the sun burst through the clouds in different directions, [478]
- LESSON XLV.
- Light, why is the apparent depth of water always deceptive, [479]
- Light, why are some substances opaque to it, [511]
- Light, how do we know that bodies reflect it in every direction, [517]
- Light, meditation on, [517]
- Light and heat, what are the differences between, [540]
- Light and heat, are they combined in the sun's rays, [541]
- Light and heat, how do we know that they are separate elements, [542]
- Light and heat, in what respects are they similar, [543]
- Light and heat, in what respects are they dissimilar, [544]
- Light, what is polarized, [549]
- Light, what is the velocity of artificial, [546]
- Light, at what rate does the light of the stars travel, [547]
- Light, why does it tarnish silver, [553]
- Light, why does it affect colours, [554]
- Light, why can pictures be taken by the sun's rays, [555]
- Light, when does it scorch plants, [558]
- Lightning, what is the cause of, [580]
- Lightning, why does it sometimes become zigzag, [586]
- Lightning, why is it sometimes forked, [587]
- LESSON XLVI.
- Lightning, why is it sometimes like a lurid sheet, [588]
- Lightning, when is the flash straight, [587]
- Lightning, when does the flash appear blue, [591]
- Lightning, why is it sometimes red, at others blue, yellow, or white, [592]
- Lightning, does it ever pass from the earth to the clouds, [593]
- Lightning, does it pass from the clouds to the earth, [594]
- Lightning, what is the force of, [595]
- Lightning, why is it dangerous to stand near a tree during a storm, [596]
- Lightning, why is it dangerous to sit near a fire during a storm, [598]
- Lightning, why is it dangerous to be near water during a storm, [599]
- Lightning, are iron houses dangerous, [600]
- Lightning, why does it seize upon bell wires, &c., [601]
- Lightning, are umbrellas with steel frames dangerous, [603]
- Lightning, are iron bedsteads dangerous, [604]
- Lightning, what is the safest situation during a storm, [606]
- Lightning-conductors, do they attract electricity, [608]
- LESSON XLVII.
- Lightning-conductors, which is the best metal for, [610]
- Lightning-conductors, why have they sometimes been found ineffective, [609]
- Lightning-conductors, why should large buildings have several, [611]
- Lightning-conductors, why should they have several branches penetrating the earth, [612]
- Lightning, through what distance will its light penetrate, [622]
- Lightning, how may we calculate the distance of a storm, [623]
- Lightning, why is the flash generally succeeded by heavy rain, [626]
- Lightning, why is a flash generally followed by a gust of wind, [627]
- Lime-kilns, why do persons viewed through the hot air of, appear distorted and tremulous, [483]
- Limpets, why is it difficult to strike them from rocks, [665]
- Lips, why are they red, [913]
- Liver, what effect has it upon the circulation, [901]
- Looking-glass, why, if you hold one at an angle towards the sun, will light be thrown in an opposite direction, [208]
- Loss, is there any such thing in the operations of nature, [270]
- LESSON XLVIII.
- Lungs, why are they placed in the chest of the body, [932]
- Magnetism, what is it, [633]
- Magnetic bodies, what are they, [634]
- Magpie, why is a single one said to foretell bad weather, [1118]
- Mahogany, what is it, [1190]
- Mahogany and other woods, why are there curious markings in, [1273]
- Man, why is he born without a covering, [1034]
- Man, why has he no external appendage to his mouth, [1037]
- Marbles, why do they revolve when propelled along the ground, [818]
- Marbles, why do striped appear to have more stripes when they are rolling than when at rest, [819]
- 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]
- Nitrogen, is it taken into the blood from the air, [40]
- Nitrogen, will it burn, [44]
- Nitrogen, what becomes of that which is inhaled, [46]
- Nitrogen, where does it find a fresh supply of oxygen, [47]
- Nitrous oxide, why does it excite the system, [38]
- Non-conductors of heat, what substances are, [111]
- Nostrils, why are they directed downwards, [994]
- LESSON LII.
- Nose, why is it placed over the mouth, [995]
- Nutmegs, where are they produced, [1232]
- Ocean, how is it heated, [233]
- Oils and fats, what are vegetable, [1204]
- Oils and fats, animal, why are they found most abundantly in cold climates, [1205]
- Oils and fats, vegetable, why are they found most abundantly in hot countries, [1206]
- Opium, what is it, [1258]
- Ostriches, why have they small wings, [1031]
- Ostriches, why are their feathers soft and downy, [1032]
- Otters, seals, &c., why have they web-feet, [1062]
- Owls, why does their screeching denote change of weather, [1111]
- Owls, why does their moping foretell death, [1112]
- Oxen, sheep, deer, &c., why do they ruminate, [1088]
- Oxen, and other quadrupeds, why have they a tough elastic ligament in their necks, [1138]
- Oxygen, why is it necessary to life, [5]
- Oxygen, what is its union with carbon called, [7]
- LESSON LIII.
- Oxygen, what is it, [25]
- Oxygen of the air, why does it not take fire, [28]
- Oxygen, why do we know that it will not burn of itself, [29]
- Oxygen, why do we know that it is necessary to our existence, [30]
- Oxygen, where is it found, [31]
- Oxygen, why is it mixed with nitrogen in the air, [32]
- Oxygen of water, why does it not support fire, [307]
- Oxygen, in what way does man use it, [757]
- Ozone, what is it, [630]
- Ozone, why do we know that electricity produces it, [631]
- Ozone, what are the properties of, [632]
- Paleness, what is the cause of, [914]
- Palms, what are their characteristics, [1221]
- Paper held over a candle-flame, why does it become scorched, [244]
- Paper held below a candle-flame, why does it scarcely become warm, [245]
- Paper, why does it more readily ignite than wood, [294]
- Paper, why, if it is laid flat upon the fire, will it "char" before it ignites, [304]
- LESSON LIV.
- Paper on a fire, why will it ignite when you send a puff of air to it, [305]
- Parachutes, why do they fall gradually to the ground, [834]
- Parrots, &c., why have they crooked bills, [1047]
- Parrots, why can they move their upper as well as their lower beak, [1048]
- Particles of matter, why do they draw near each other, [776]
- Particles of matter, why will they attach themselves to sealing-wax excited by friction, [779]
- Pea and pin, why do they rotate upon a jet of air blown through a tobacco-pipe, [845]
- Peg-top, why does it make less noise than a humming-top, [811]
- Peg-top, why does it sometimes hum, and at other times not, [812]
- Pelican, why has it a large pouch under its bill, [1093]
- Pepper, where is it produced, [1229]
- Perspiration, why does it cool the body, [173]
- Perspire, why do we, [1009]
- Perspiration, how is it formed, [1010]
- Perspiration, what is insensible, [1011]
- Perspiration, what is sensible, [1012]
- LESSON LV.
- Phosphorous, why does it look luminous, [94]
- Phosphorous, does it ignite spontaneously when placed upon a hot surface, [314]
- Phosphorous, why does it ignite when sprinkled with powdered charcoal, [315]
- Photographic pictures, how does light produce them, [556]
- Photographic rooms, why are they glazed with blue glass, [557]
- Pith-tumblers, why do they always pitch on one end, [868]
- Planets, how can man weigh them, [785]
- Planets, how can man measure their distances, [786]
- Plants, do they absorb heat, [225]
- Plants, how do we know that they absorb heat, [226]
- Plants, why do screens prevent frost from killing them, [400]
- Plants, why, if we cut across their stems, do we see tubes arranged in parallel lines, [1159]
- Plants, why do some droop and turn to the earth after sunset, [1167]
- Plants, why are the seeds of many enclosed in rich juice or pulp, [1172]
- Plants, why have some tough curly tendrils, [1173]
- LESSON LVI.
- Plants, why have peas tendrils, and beans none, [1174]
- Plants, why have grasses, &c., joints or knots in their stalks, [1176]
- Plants, what is the circulation of sap in, [1179]
- Plants, why does their sap ascend and descend, [1180]
- Plants, why do they suffer from the smoke of cities, [1188]
- Plants, why is it understood that some of them feel, [1141]
- Plants, why is it understood that some of them move, [1142]
- Plants, of what elementary substances are they composed, [1143]
- Plants, whence do they derive their elementary substances, [1144]
- Plants, how do they obtain carbon, [1145]
- Plants, how do they obtain oxygen, [1146]
- Plants, their decomposition of gases by day and by night, [1147]
- Plants, how do they obtain hydrogen, [1147]
- Plants, how do they obtain nitrogen, [1148]
- Plants, how do they apply their elements to the formation of their structures, [1149]
- Plants, how is their nutritive sap applied to their growth and nourishment, [1150]
- LESSON LVII.
- Plants, why do they grow, [1154]
- Plants, why if we break the stem of a hyacinth do we see a glutinous fluid exude, [1155]
- Plants, why if we split the petal of a tulip do we see cells containing different colouring matters, [1156]
- Plants, why if we break a pea-shell across do we find a transparent membrane, [1157]
- Plants, why if we cut through a cabbage-stump do we find a tough coating enveloping a cellular substance, [1158]
- Plants, why are their seeds formed within the corollas of flowers, [1168]
- Plants, why does the flower of the poppy turn down during the early formation of seed, [1169]
- Plants, why have those of the pea-tribe a folding blossom, [1170]
- Plants, why are leaf-buds enclosed in scales which fall off as the leaves open, [1171]
- Plants, what is meant by "species" of, [1209]
- Plants, what is meant by "genus" of, [1210]
- 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.
- 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]
- Smoke, what is it, [289]
- LESSON LXIV.
- Smoke, why do fresh coals increase the quantity of, [291]
- Smoke, why does it issue in folds and curls, [632]
- Smoke, why does it ascend in mild and fine weather, [689]
- Snails, why can they move in an inverted position, [666]
- Snails, where do they obtain their shells, [1306]
- Snails, why do their shells grow, [1307]
- Snails, why are their shells spiral, [1308]
- Snails, why have they four tentacula attached to their heads, [1309]
- Snails, why are they able to move without feet, [1310]
- Snails, why do we see none in the winter time, [1311]
- Snails, why can they live in sealed shells, [1312]
- Sneeze, why do we, [1024]
- Snipes and woodcocks, why have they long, tapering bills, [1042]
- Snore, why do we, [1028]
- Snow, why does it keep the earth warm, [160]
- Snow, why is it a good non-conductor of heat, [162]
- Snow, what is it, [440]
- Snow, why is it white, [441]
- LESSON LXV.
- Snow, why is it warm, though white garments are cool, [442]
- Snow, why is it always on the tops of high mountains, [443]
- Snow-line, what is meant by the, [445]
- Snow, what is red, [446]
- Soda-water, why does it effervesce, [802]
- Soils, why are clayey unfavourable to vegetation, [1160]
- Soils, why are sandy unfavourable to vegetation, [1162]
- Soils, why are chalk unfavourable to vegetation, [1162]
- Soils, why are mixed favourable to vegetation, [1163]
- Soils, why do farmers manure their land, [1165]
- Soot, why should it be prevented from accumulating at the bottom and sides of saucepans, [205]
- Soot, what is it, [290]
- Sound, what is it, [716]
- Sounds, what causes the air to produce, [717]
- Sounds, how do we know that they are produced by vibrations, [718]
- Sounds, how do we know that without air there would be none, [719]
- Sounds, how are the vibrations of sonorous bodies imparted to the air, [720]
- LESSON LXVI.
- Sounds, how rapidly do the vibrations of travel, [721]
- Sounds, do all sounds travel at the same rate, [722]
- Sounds, why are bells and glasses stopped from ringing by touching them with the finger, [723]
- Sounds, why does a cracked bell give discordant, [724]
- Sounds, why do we see the flash of a gun before we hear the report, [725]
- Sound, why does the marching of long ranks of soldiers appear to be irregular, [726]
- Sounds, what are the numbers of vibrations that produce various, [727]
- Sounds, why does the length of a wire or string influence the sounds it produces, [728]
- Sound, why does the tension of a wire or string affect its vibrations, [729]
- Sound, why are some notes low and solemn, and others high and quick, [730]
- Sound, why can our voices be heard at a greater distance when we speak through tubes, [731]
- Sound, is air a good conductor, [732]
- Sounds, why can we hear them at a greater distance on water than on land, [733]
- LESSON LXVII.
- Sound, why do sea-shells give a murmuring noise when held to the ear, [734]
- Sound, why can people in the arctic regions converse when more than a mile apart, [735]
- Sounds, why do savages lay their heads upon the earth to catch sounds, [736]
- Sounds, why can church clocks be heard striking more plainly at some times than at others, [737]
- Sound, why may the scratching of a pin at one end of a long pole be heard at the opposite extremity, [738]
- Sound, why is the hearing of deaf persons assisted by ear-trumpets, [739]
- Sounding-boards, why are they used to improve the hearing of congregations, [740]
- Sounds, why, when we are walking under arches or tunnels, do our voices appear louder, [747]
- Spark, what causes it when a horse's shoe strikes against a stone, [340]
- Specific gravity, what is it, [789]
- Spiders, why have they the power of spinning webs, [1082]
- Spiders, why may fine weather be expected when they build their webs, [1108]
- LESSON LXVIII.
- Spiders, why may wet weather be expected when they hide, [1109]
- Spiders, why may wet weather be expected when they break off their webs and remove them, [1113]
- Spider, why, if the webs of the gossamer fly about in autumn, may east winds be expected, [1124]
- Spiders, gossamer, why can they float through the air, [1125]
- Spinal cord, what is the, [952]
- Spinal cord, why is it placed in the back-bone, [953]
- Spinal-cord, how do the branches pass out from it, [954]
- Spontaneous combustion, what substances are liable to it, [317]
- Spontaneous combustion, has it ever occurred in living bodies, [319]
- Spontaneous combustion, why does it occur in the case of the drunkard, [320]
- Spoon-bill, why has it a long expanded bill, lined with sharp, muscular points, [1045]
- Spoon-bill, why has it long legs, [1046]
- Squint, why do some people, [967]
- Starch, what is it, [1202]
- Star-lit nights, why are they usually colder than cloudy nights, [350]
- Stars, why do they twinkle, [484]
- LESSON LXIX.
- Stars, why does their twinkling foretell bad weather, [485]
- Steam, why does it issue from the spout of a kettle, [750]
- Storms, what is the cause of, [676]
- Storms, why do the most violent occur in and near the tropics, [677]
- Straw, why is it frequently used for manure, [1264]
- "Sucker," why does it raise a stone, [860]
- Sugar, what is it, [1197]
- Sugar-cane, where is it cultivated, [1226]
- Sun, what is its distance from the earth, [452]
- Sun, what is the, [455]
- Sun, from what does its luminosity arise, [456]
- Sun and moon, why do they appear smaller when near the meridian, than when near the horizon, [525]
- Sun, why do we see it before sunrise, and after sunset, [482]
- Sun, what is the magnitude of the, [787]
- Suppers, why do they cause dreams, [1021]
- Swallows, why may wet weather be expected when they fly low, [1104]
- Syringe, why does pressing in the handle force out a jet of water, [856]
- Syringe, why will not the water run out, unless the handle is pressed in, [857]
- LESSON LXX.
- Syringe, why will the water leak out, but not run, [858]
- Syringe, why cannot the handle be pressed in, if a finger is kept on the orifice, [859]
- Tannin, what is it, [1257]
- Taste, why do we, [996]
- Taste, why are some substances sweet, others sour, &c., [997]
- Taste, why is it most powerful after substances have been a little while in the mouth, [998]
- Taste, why if we put out the tongue and touch it with a nub of sugar, shall we perceive no taste, [999]
- Taste, why when we draw in the tongue do we then perceive the taste of the sugar, [1000]
- Taste, through what nerves are we made sensible of the contact of sugar with the tip of the tongue, [1001]
- Taste, why do connoisseurs of wines hold wine in their mouths a few seconds when judging of it, [1002]
- Taste, why do they also pass the fumes of the wine through their nostrils, [1003]
- Tea-pot, why does a bright metal one produce better tea than a black earthenware, [200]
- LESSON LXXI.
- Tea-pot, if the earthenware one were set by the fire, why would it then make the best tea, [201]
- Tea, what is it, [1192]
- Tea, where is it cultivated, [1225]
- Tears, what is the cause of, [977]
- Temperature, why do some articles feel colder than others, [138]
- Temperature, why does it feel warmer after a frost has set in, [163]
- Tendons, what are they, [939]
- Tendons, why are they used to attach the muscles to the bones, [940]
- Teneriffe, what are the botanical regions of the Peak of, [1241]
- Thaumatrope, why do the figures on appear to dance, [869]
- Thaw, why is it colder when a thaw takes place, [164]
- Thermometer, what is the, [709]
- Thermometer, why does it indicate degrees of heat, [710]
- Thermometer, why are there Reaumur's and Fahrenheit's, [711]
- Thermometer and barometer, what is the difference, [712]
- Thermometer, in what season of the year does it vary most, [715]
- Thunder, what is it, [614]
- Thunder-peal, why is it sometimes loud and continuous, [616]
- LESSON LXXII.
- Thunder-peal, why is it sometimes broken and unequal, [617]
- Thunder-peal, why is it sometimes a low, grumbling noise, [618]
- Thunder-peal, why does it sometimes follow immediately after the flash of lightning, [620]
- Thunder, through what distance will the sound travel, [621]
- Thunderbolt, what is a, [628]
- Tinder-box, the history of a, [340]
- Toasting-fork, why has it a wooden handle, [124]
- Tops, why do they stand erect while they spin, but fall when they stop, [814]
- Tops, why do they "sleep", [816]
- Tops, why do they cease to spin, [817]
- Touch, in what part of the body is the sense of most perfect, [1005]
- Toxicologists, what are they, [61]
- Trap and ball, why is the ball propelled upward, when the trigger is struck, [866]
- Trees, what are the estimated ages of, [1214]
- Trees, what are the northern limits of, [1237]
- Trees, why are they covered with bark, [1270]
- LESSON LXXIII.
- Trees, why have those with large trunks a great number of leafy branches, [1274]
- Trees, why have poplars comparatively few leaves, [1275]
- Trees, why had the mammoth comparatively few leaves, [1276]
- Trees, why have oaks an abundance of leaves, [1277]
- Trees, why are their trunks generally round, [1278]
- Twilight, what is the cause of, [482]
- Vacuum, what is a, [649]
- Vacuum, is it possible to obtain a perfect, [650]
- Vegetables, have they any heat, [90]
- Vegetable structures, of what do they consist, [1151]
- Vegetables, why do farmers sow different crops in rotation, [1164]
- Vegetables, why are the hearts of cabbages, &c., pale yellow, [1182]
- Vegetable productions, why are they so widely diffused, [1189]
- Vegetable eaters, why do they feed so continually, [1091]
- Vegetation, geographical distribution of, [1208]
- Vegetation, what are the characteristics of tropical, [1218]
- Vegetation, what are the changes in on quitting the tropics, [1232]
- LESSON LXXIV.
- Vegetation, what are the characteristics of, upon approaching the polar zones, [1234]
- Vegetation, what are the characteristics of mountain, [1238]
- Vines, where are their favourable climates, [1233]
- Walking, why does it make us warmer, [26]
- Water, what becomes of that formed by combustion, [58]
- Water, is it a good or bad conductor of heat, [151]
- Water, why does it extinguish fire, [306]
- Water, why, when a blacksmith thrusts a hot iron into a tank, do we perceive a peculiar smell, [309]
- Water, why does it freeze, [324]
- Water, why does it become steam, [326]
- Water, how many degrees of latent heat are hidden in its several states, [327]
- Water, why does it expand when freezing, while bodies generally contract with cold and expand with heat, [341]
- Water, why does it never freeze to a great depth, [342]
- Water, how much deeper is it than it appears to be, [480]
- LESSON LXXV.
- Water, why has the exceptional law, by which it expands when freezing, been ordained, [343]
- Water, why can we seldom succeed in the first attempt to touch anything lying at the bottom of, [481]
- Water, what causes it to flow from a pump, [651]
- Water, why does it run through a syphon, [655]
- Water, what is it, [748]
- Water, why does it become solid when it freezes, [751]
- Water, why does it boil, [753]
- Water, what proportion of the earth's surface is covered by it, [554]
- Water, why does it dissolve substances, [758]
- Water, why does hot dissolve more readily than cold, [759]
- Water, why is it sometimes hard, [760]
- Water, why is rain-water soft, [761]
- Water, why is it difficult to wash in hard, [763]
- Waters, why are some impregnated with mineral matters, [767]
- Water, why does stagnant become putrid, [769]
- Water, is there danger attending drinking it on account of animalculæ, [770]
- Water, what are the means by which it may be purified, [771]
- LESSON LXXVI.
- Water, what is the pressure of, [775]
- Water, why will a drop upon the blade of a knife leave a dark spot, [777]
- Water, why does it roll in agitated globules when dropped upon hot iron, [796]
- Water, why does oil float upon it, [797]
- Water, why is spring fresh and invigorating, [803]
- Water, why is boiled flat and insipid, [804]
- Weather, why does a yellow sunset foretell wet, [534]
- Weather, why does a red sunset foretell fine, [535]
- Weather, why does a red sunrise foretell wet, [536]
- Weather, why does a grey sunrise foretell dry, [537]
- Weather, barometrical indications of, [708]
- Whales, why have they a large development of oily matter about their heads, [1068]
- Whale, why has it feathery bones extending from its jaws, [1095]
- Whales, why are, their eyes provided with very thick coats, [1131]
- Wheat, why do the ears stand up by day and turn down by night, [1175]
- Wheat, what is it, [1199]
- LESSON LXXVII.
- Wheat, what is the northern limit of, [1235]
- Wheat, why is silica diffused over its stem, [1261]
- Wheat-crops, why do they greatly exhaust the soil, [1263]
- Whirlwinds, what are they, [678]
- Why do we see, [963]
- Why do we wink, [975]
- Why do we weep, [977]
- Why do we hear, [983]
- Why do we taste, [986]
- Why do we smell, [992]
- Why do we feel, [1004]
- Why do we sleep, [1019]
- Why do we dream, [1020]
- Why do suppers produce dreaming, [1021]
- Why do we yawn, [1022]
- Why do we cough, [1023]
- Why do we sneeze, [1024]
- Why do we sigh, [1025]
- Why do we laugh, [1026]
- Why do we hiccough, [1027]
- Why do we snore, [1028]
- Why do we feel hungry, [1337]
- Why do we feel thirsty, [1338]
- Wick of a candle, why does it turn black as it burns, [225]
- Wick of a candle, why is there a spark generally at the end of it, [256]
- Will-o'-the-wisp, what is it, [318]
- Winds, what is the cause of, [234]
- Winds, why are east usually dry, [384]
- Winds, why are west usually wet, [385]
- Winds, why are north usually cold and dry, [386]
- LESSON LXXVIII.
- Winds, why are south warm and rainy, [387]
- Wind, what is it, [666]
- Winds, what are the velocities of, [667]
- Winds, what are trade, [668]
- Winds, what is the cause of trade, [669]
- Winds, why do trade winds blow from east to west, [670]
- Winds, what determines the character of, [674]
- Wind-mills, why do their wings turn round, [690]
- Windows, why do they reflect the sun's rays in the evening, [523]
- Windows, why do they not reflect the sun's rays at noon, [524]
- Wood, why does decayed look luminous, [95]
- Wood, burning at one end, why does it not feel hot at the other, [118]
- Wood, why is it a bad conductor of heat, [119]
- Wood that is green, why does it hiss and steam when burning, [285]
- Wood, why does it ignite less readily than paper, [297]
- Woodcocks and snipes, why have they nerves running down to the tip of their bills, [1043]
- Woodpeckers, why do they "tap" at old trees, [1066]
- Woollens, why are they worn in winter, [166]
- Wool, what is it, [1201]
- Yawn, why do we, [1026]
- Zoological geography, [1326]
"God looked down from heaven upon the children of men, to see if there were any that did understand that did see God."—Psalm liii.