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THE REASON WHY:
THE REASON WHY:
A CAREFUL COLLECTION OF MANY HUNDREDS OF REASONS FOR THINGS WHICH, THOUGH GENERALLY BELIEVED, ARE IMPERFECTLY UNDERSTOOD. A BOOK OF CONDENSED SCIENTIFIC KNOWLEDGE FOR THE MILLION. By THE AUTHOR OF "INQUIRE WITHIN." This collection of useful information on "Common Things" is put in the interesting form of "Why and Because," and comprehends a familiar explanation of many subjects which occupy a large space in the philosophy of Nature, relating to air, animals, atmosphere, caloric, chemistry, venti
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PREFACE.
PREFACE.
We are all children of one Father, whose Works it should be our delight to study. As the intelligent child, standing by his parent's knee, asks explanations alike of the most simple phenomena, and of the most profound problems; so should man, turning to his Creator, continually ask for knowledge. Not because the profession of letters has, in these days, become a fashion, and that the man of general proficiency can best work out his success in worldly pursuits; but because knowledge is a treasure
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CHAPTER I.
CHAPTER I.
1. Why should we seek knowledge? Because it assists us to comprehend the goodness and power of God . And it gives us power over the circumstances and associations by which we are surrounded: the proper exercise of this power will greatly promote our happiness. 2. Why does the possession of knowledge enable us to exercise power over surrounding circumstances? Knowledge enables us to understand that, in order to live healthily, we require to breathe fresh and pure air. It also tells us that animal
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CHAPTER II.
CHAPTER II.
4. Why do we breathe air? Because the air contains oxygen , which is necessary to life. 5. Why is oxygen necessary to life? Because it combines with the carbon of the blood, and forms carbonic acid gas . "Be not as the horse, or as the mule, which have no understanding: whose mouth must be held with the bit and bridle."— Psalm xxxii. 6. Why is this combination necessary? Because we are so created that the substances of our bodies are constantly undergoing change, and this resolving of solid matt
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CHAPTER III.
CHAPTER III.
25. What is oxygen? Oxygen is one of the most widely diffused of the elementary substances. It is a gaseous body. "Stand in awe and sin not: commune with your own heart upon your bed and be still"— Psalm iv. 26. Why do persons who are walking, or riding upon horseback feel warmer than when they are sitting still? Because as they breathe more rapidly, the combustion of the carbon in the blood is increased by the oxygen inhaled, and greater heat is developed. 27. Why does the fire burn more bright
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CHAPTER IV.
CHAPTER IV.
49. What is hydrogen? Hydrogen is an elementary gas, and is the lightest of all known bodies. 50. Will hydrogen support animal life? It will not. It proves speedily fatal to animals. 51. Will hydrogen support combustion? Although it will burn, yielding a feeble bluish light, it will, if pure, extinguish a flame that may be immersed in it. Hydrogen will therefore burn , but will not support combustion . 52. Why will hydrogen explode, if it will not support combustion? When hydrogen explodes it is
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CHAPTER V.
CHAPTER V.
71. What is heat? Heat is a principle in nature which, like light and electricity, is best understood by its effects . We popularly call that heat, which raises the temperature of bodies submitted to its influence. 72. What is caloric? Caloric is another term for heat. It is advisable, however, to use the term caloric when speaking of the cause of heat, and of heat as the effect of the presence of caloric . "While the earth remaineth, seed-time and harvest, and cold and heat, and summer and wint
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CHAPTER VI.
CHAPTER VI.
93. How many kinds of combustion are there? There are three , viz., slow oxydation, when little or no light is evolved ; a more rapid combination, when the heat is so great as to become luminous ; and a still more energetic action, when it bursts into flame . 94. Why does phosphorous look luminous? Because it is undergoing slow combustion . 95. Why do decayed wood, and putrifying fish, look luminous? Because they are undergoing slow combustion . In these cases the heat and light evolved are at n
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CHAPTER VII.
CHAPTER VII.
118. Why does not a piece of wood which is turning at one end, feel hot at the other end? Because wood is a bad conductor of heat . 119. Why is wood a bad conductor of heat? Because the arrangement of the particles of which it is composed does not favour the transmission of caloric . 120. Why do some articles of clothing feel cold, and others warm? Because some are bad conductors of heat, and do not draw off much of the warmth of our bodies ; while others are better conductors , and take up a la
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CHAPTER VIII.
CHAPTER VIII.
146. Which are the better conductors of heat, fluids or solids? Generally speaking, solids , especially those of them that are dense in their substance. 147. Why are dense substances the best conductors of heat? Because the heat more readily travels from particle to particle until it pervades the mass. 148. Why are fluids bad conductors of heat? Because of the want of density in their bodies; and because a portion of the imbibed heat always passes off from fluids by evaporation . "He casteth for
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CHAPTER IX.
CHAPTER IX.
181. What is Radiation? The radiation of heat is a motion of the particles , in a series of rays, diverging in every direction from a heated body. 182. What is this phenomena of Radiation understood to arise from? From a strongly repulsive power, possessed by particles of heat, by which they are excited to recede from each other with great velocity. 183. What is the greatest source of Radiation? The sun, which sends forth rays of both light and heat in all directions. 184. When does a body radia
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CHAPTER X.
CHAPTER X.
196. But if (as stated in the Lessons upon Conduction) metal is a better conductor of heat than stone or earthenware, why does not the metal jug conduct away the heat of the water sooner than the earthenware jug? It would do so, if it were in contact with another conductor ; but, being surrounded by air, which is a bad conductor , the heat must pass off by radiation , and as bright metal surfaces are bad radiators, the metal jug would retain the heat of the water longer than the earthenware one
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CHAPTER XI.
CHAPTER XI.
208. Why, if you hold a piece of looking-glass at an angle towards the sum, will light fall upon an object opposite to the looking-glass? Because the rays of the sun are reflected by the looking-glass. 209. Why, when we stand before a mirror, do we see our features therein? Because the rays of light that fall upon us are reflected upon the bright surface of the mirror. 210. Why, if a plate of bright metal were held sideways before a fire, would heat fall upon an object opposite to the plate? Bec
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CHAPTER XII.
CHAPTER XII.
226. How do we know that plants operate upon the solar and atmospheric heat? A delicate thermometer, placed among the leaves and petals of flowers, will at once establish the fact, not only that flowers and plants have a temperature differing from that of the external air, but that the temperature varies in different plants according to the hypothetical, or supposed requirements, of their existences and conditions. 227. What is the chief cause of variation in the temperature of flowers? It is ge
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CHAPTER XIII.
CHAPTER XIII.
"Neither do men light a candle, and put it under a bushel, but on a candlestick; and it giveth light unto all that are in the house."— Matt. v. 244. Why will a piece of paper, held three or four inches over the flame of a candle, become scorched? Because the hot air and gas produced by the burning of the candle ascends rapidly. 245. Why will a piece of paper held about an inch below the flame of a candle scarcely become warmed? Because the heat ascends ; and only a little of it falls upon the pa
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CHAPTER XIV.
CHAPTER XIV.
271. What is coal? Coal is a " vegetable fossil ." 272. What is meant by a vegetable fossil? It is a substance originally vegetable , which, by pressure and other agencies within the earth, has been brought to a condition approaching that of mineral or earthy matter. 273. Why do we know that coal is of vegetable origin? By the chemical components of its substance; and also by the vegetable forms that are found abundantly in coal beds. Professor Buckland, in his Bridgewater Treatise , speaking of
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CHAPTER XV.
CHAPTER XV.
294. Why does paper ignite more readily than wood? Because its texture is less dense than that of wood; its particles are therefore more readily heated and decomposed. 295. But if articles of loose texture are bad conductors of heat, why do they so easily ignite? The fact that they are bad conductors assists their ignition. The heat which would pass from particle to particle of the dense substance of iron, and be conducted away , accumulates in the interspaces of paper, and ignites it. 296. Why
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CHAPTER XVI.
CHAPTER XVI.
321. Why does friction produce heat? Because all bodies contain latent heat , that is, heat that lies hid in their substance, and the rubbings of two bodies against each other draws the latent heat to the excited surfaces . 322. Why does the rubbing of two surfaces together attract latent heat to those surfaces? Because it is a law of nature that heat shall always attend motion ; and it is generally found that the intensity of heat bears a specific relation to the velocity of motion . 323. What
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CHAPTER XVII.
CHAPTER XVII.
341. Since all bodies expand by heat and contract by cold, why does water, when it reaches the freezing point, expand? Because, in freezing, water undergoes crystallization, in which its particles assume a new arrangement occupying greater space . 342. Why does water never freeze to a great depth? Because the covering of ice which is formed upon the surface of the water prevents the cold air from continuing to draw off the caloric of the water. "For he saith to the snow, Be thou on the earth; li
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CHAPTER XVIII.
CHAPTER XVIII.
373. What are clouds? Clouds are volumes of vapour , usually elevated to a considerable height. 374. Whence do clouds arise? From the evaporation of water at the earth's surface. 375. Why do we not see them ascend? We do, sometimes, in the form of what we call mists , but generally the vapours that rise and contribute to the formation of clouds are so thin that they are invisible . "With clouds he covereth the light, and commandeth it not to shine by the cloud that cometh betwixt."— Job xxxvi. 3
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CHAPTER XIX.
CHAPTER XIX.
396. Why are cloudy days colder than sunny days? Because the clouds intercept the solar rays in their course towards the earth. 397. Why are cloudy nights warmer than cloudless nights? Because the clouds radiate back to the earth the heat which the earth evolves? Because, also, the clouds radiate to the earth the heat they have derived from the solar rays during a cloudy day. 398. Why is the earth warmer than the air during sunshine? Because the earth freely absorbs the heat of the solar rays ;
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CHAPTER XX.
CHAPTER XX.
416. What is rain? Rain is the vapour of the clouds which, being condensed by a fall of temperature, forms drops of water that descend to the earth. It is the return to the earth in the form of water , of the moisture absorbed by the air in the form of vapour . 417. Does rain ever occur without clouds? It sometimes, but rarely happens, that a sudden transition from warmth to cold will precipitate the moisture of the air , without the formation of visible clouds . "Canst thou lift up thy voice to
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CHAPTER XXI.
CHAPTER XXI.
440. What is snow? Snow is congealed vapour , which would have formed rain ; but, through the coldness of the air, has been frozen in its descent into crystalline forms . ( Fig. 1 .) 441. Why is snow white? Because it reflects all the component rays of light . 442. Why is snow said to be warm, while white garments are worn for coolness? Snow is warm by virtue of its light and woolly texture. But it is also warm on account of its whiteness ; for, had it been black , it would have absorbed the hea
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CHAPTER XXII.
CHAPTER XXII.
451. What is light? Light, according to Newton, is the effect of luminous particles which dart from the surfaces of bodies in all directions. According to this theory, the solar light which we receive would depart from the sun and travel to the earth . According to Huyghens, light is caused by an infinitely elastic ether, diffused through all space . This ether, existing everywhere, is excited into waves, or vibrations, by the luminous body . The theory of light is so undetermined that neither t
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CHAPTER XXIII.
CHAPTER XXIII.
472. What is the refraction of light? When rays of light fall obliquely upon the surface of any transparent medium , they are slightly diverted from their course. This alteration of the course of the rays is called refraction , and the degree of refraction is influenced by the difference between the densities of the mediums through which light is transmitted . "Let your light so shine before men, that they may see your good works, and glorify your father which is in heaven."— Matt. v. 473. If a
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CHAPTER XXIV.
CHAPTER XXIV.
502. What is the difference between the refraction and the reflection of light? Refraction is the deviation of rays of light from their course through the interference of a different medium; reflection is the return of rays of light which, having fallen upon a surface, are repelled by it. 503. What is the radiation of light? The radiation of light is its emission in rays from the surface of a luminous body . 504. Do all bodies radiate light? All bodies radiate light; but those that are not in th
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CHAPTER XXV.
CHAPTER XXV.
518. Why, when we move before a mirror, does the image draw near to the reflecting surface as we draw near to it, and retire when we retire? Because the lines and angles of reflection are always equal to the lines and angles of incidence . 519. What is the line of incidence? If a person stands in a direct line before a mirror, the line through which the light travels from him to the mirror is the line of incidence . Incidence —falling on. "Blessed be the Lord, who daily loadeth us with benefits,
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CHAPTER XXVI.
CHAPTER XXVI.
540. What is the difference between light and heat? The most obvious distinction is, that light acts upon vision , and heat upon sensation , or feeling. Another distinction is, that heat expands all bodies , and alters their atomic condition; while light , though usually attended by heat, does not display the same expansive force, but produces various effects which are peculiar to itself . "Ye are the light of the world. A city that is set on a hill cannot be hid."— Matthew v. 541. Are light and
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CHAPTER XXVII.
CHAPTER XXVII.
561. What is electricity? Electricity is a property of force which resides in all matter, and which constantly seeks to establish an equilibrium . 562. Why is it called electricity? Because it first revealed itself to human observation through a substance called, in the Greek language, electrum . This substance is known to us as amber . 563. In what way did electrum induce attention to this property of force in matter? Thales, a Greek philosopher, observed that, by briskly rubbing electrum , it
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CHAPTER XXVIII.
CHAPTER XXVIII.
586. Why does lightning sometimes travel through a "zigzag" course? Because the electricity, being resisted in its progress by the air, flies from side to side , to find the readiest passage. 587. Why does lightning sometimes appear forked? Because, being resisted in its progress by the air, the electricity divides into two or more points, and seeks a passage in different directions . 588. Why is lightning sometimes like a lurid sheet? Because the flash is distant, and therefore we see only the
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CHAPTER XXIX.
CHAPTER XXIX.
614. What is thunder? Thunder is the noise which succeeds the rush of the electrical fluid through the air. 615. Why does noise follow the commotion caused by electricity? Because, by the violence of the electric force, vast fields of air are divided ; great volumes of air are rarefied ; and vapours are condensed , and thrown down as rain . Thunder is therefore caused by the vibrations of the air , as it collapses, and seeks to restore its own equilibrium . 616. Why is the thunder-peal sometimes
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CHAPTER XXX.
CHAPTER XXX.
638. What is the atmosphere? The atmosphere is the transparent and elastic body of mixed gases and vapours which envelopes our globe, and which derives its name from Greek words, signifying sphere of vapour . 639. To what height does the atmosphere extend? It is estimated to extend to from forty to fifty miles above the surface of the earth. 640. Why is it supposed that the atmosphere does not extend beyond that height? Because it is found, by experiment and observation, that the air becomes les
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CHAPTER XXXI.
CHAPTER XXXI.
666. What is wind? Wind is air in motion . ( See 234 .) 667. What are the velocities of winds? A breeze travels ten feet in a second; a light gale , sixteen feet in a second; a stiff gale , twenty-four feet in a second; a violent squall , thirty-five feet in a second; storm wind , from forty-three to fifty-four in a second; hurricane of the temperate zone, sixty feet in a second; hurricane of the torrid zone, one hundred and twenty to three hundred feet in a second. When wind flies at one mile a
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CHAPTER XXXII.
CHAPTER XXXII.
691. What is a barometer? A barometer is an instrument which indicates the pressure of the atmosphere , and which takes its name from two Greek words signifying measurer of weight . 692. Why does a barometer indicate the pressure of the atmosphere? Because it consists of a tube containing quicksilver , closed at one end and open at the other, so that the pressure of the air upon the open end balances the weight of the column of mercury (quicksilver), and when the pressure of the air upon the ope
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CHAPTER XXXIII.
CHAPTER XXXIII.
709. What is the thermometer? The thermometer is an instrument in which mercury is employed to indicate degrees of heat . Its name is derived from two Greek words, meaning heat measurer . 710. Why does mercury indicate degrees of heat? Because it expands readily with heat , and contracts with cold ; and as it passes freely through small tubes, it is the most convenient medium for indicating changes of temperature . "When ye see a cloud rise out of the west straightway ye say, There cometh a show
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CHAPTER XXXIV.
CHAPTER XXXIV.
716. What is sound? Sound is an impression produced upon the ear by vibrations of the air . 717. What causes the air to vibrate and produce sounds? The atoms of elastic bodies being caused to vibrate by the application of some kind of force, the vibrations of those atoms are imparted to the air , and sound is produced. 718. How do we know that sounds are produced by the vibrations of the air, induced by the vibrations of the atoms of bodies? If we take a tuning fork, and hold it to the ear, we h
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CHAPTER XXXV.
CHAPTER XXXV.
748. What is water? Water is a fluid composed of two volumes of hydrogen to one of oxygen , or eight parts by weight of oxygen to one of hydrogen . It is nearly colourless and transparent. 749. Why, if a saucer of water be exposed to the air, will it gradually disappear? Because water is highly expansive, and rises in thin vapour , when in contact with warm and dry air. "Behold there ariseth a little cloud from the sea, of the bigness of a man's hand. And it came to pass in the meantime, that th
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CHAPTER XXXVI.
CHAPTER XXXVI.
772. What is attraction? Attraction is the tendency of bodies to draw near to each other . It is called attraction , from two Latin words signifying drawing towards . 773. How many kinds of attraction are there? There are five principal kinds of attraction :— 1. The attraction of gravitation . 2. The attraction of cohesion . 3. The attraction of chemical affinity . 4. The attraction of electricity . 5. And capillary attraction . "Behold, the nations are as a drop of a bucket, and are counted as
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CHAPTER XXXVII.
CHAPTER XXXVII.
"Where wast thou when I laid the foundations of the earth? declare, if thou hast understanding." 792. What is repulsion? Repulsion is that property in matter by which it repels or recedes from , those bodies for which it has no attraction or affinity . 793. Why does dew form into round drops upon the leaves of plants? Because it repels the air , and the substances of the leaves upon which it rests. Because, also, its own particles cohere . 794. Why do drops of water roll over dusty surfaces? Bec
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CHAPTER XXXVIII.
CHAPTER XXXVIII.
810. Why does a humming-top make a humming noise? Because the hollow wood of the top vibrates, and the edges of the hole in its sides strike against the air as it spins ; the air is thereby set in vibration. 811. Why does a peg-top hum less than a humming-top? Because, being a solid body of wood , and having no hole in its sides , its particles are not so easily thrown into vibration ; consequently it does not so readily impart vibrations to the air. 812. Why does a peg-top sometimes hum, and at
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CHAPTER XXXIX.
CHAPTER XXXIX.
825. Why are soap-bubbles round? Because they are equally pressed upon all parts of their surface by the atmosphere. 826. Why are bubbles elongated when being blown? Because the unequal pressure of the current of breath by which they are being filled, alters the relative pressure upon the outer surfaces. 827. Why does the bubble close, and become a perfect sphere, when shaken from the pipe? Because the attraction of cohesion draws the particles of soap together, directly the bubble is set free f
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LESSON XL.
LESSON XL.
846. Why does a mouse, painted upon one side of a card, and a trap upon the other, represent to the eye a mouse in a trap when the card is rapidly twirled upon a string? Because the image of the mouse is brought to the retina of the eye before the image of the trap has passed away. The two impressions, therefore, unite upon the retina , and produce the image of a mouse in a trap. "Honour thy father and thy mother * * That it may be well with thee, and thou mayest be long on the earth."— Ephesian
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CHAPTER XLI.
CHAPTER XLI.
869. Why do we eat food? Because the atoms of which our bodies are composed are continually changing . Those atoms that have fulfilled the purposes of nature are removed from the system, and, therefore, new matter must be introduced to supply their place. 870. Why do we eat animal and vegetable food? Because their substances are composed of oxygen , hydrogen , carbon , and nitrogen —the four chemical elements of which the human system is formed. They are, therefore, capable of nourishing the bod
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CHAPTER XLII.
CHAPTER XLII.
883. Why does some portion of the food we eat nourish the system, while other portions are useless? Because most food contains some particles that are indigestible, or that, if digested, are innutritious, and not necessary for the system. The liver is the organ by whose secretion the useful is separated from the useless ; for when the bile enters through the duct ( Fig. 49 ) and mixes with the grey cream coming from the stomach, it remains no longer a grey cream, but turns into a mass coloured b
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CHAPTER XLIII.
CHAPTER XLIII.
892. Why do we know that the blood has become endowed with vital powers? Because, in the course of its formation, it has not only undergone change of condition and colour; but, if examined now by the microscope, it will be found to consist of millions of minute cells, or discs, which float in a watery fluid. The paste produced by mastication consisted of a crude admixture of the atoms of food; the cream ( chyme ) formed from this in the stomach, presents to the microscope a heterogeneous mass of
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CHAPTER XLIV.
CHAPTER XLIV.
902. Why when we cut our flesh does it heal? Because the blood coagulates over the cut, and throws out a kind of lymph , which forms an incipient flesh, and excludes the air while the blood-vessels are engaged in repairing the part . "And God said, Let us make man in our own image, after our likeness; and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing."— Gen. i. 903. Why, since all the subs
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CHAPTER XLV.
CHAPTER XLV.
923. How many bones are there in the human body? There are two hundred and forty-six , and they are apportioned to the various parts of the body in the following numbers:— "Our bones are scattered at the grave's mouth, as when one cutteth and cleaveth wood upon the earth."— Psalm cxli. 924. Of what substances are the bones composed? One hundred parts of bone consist of 925. What are the uses of the bones? They protect soft and delicate organs; they form a framework to which the organs are attach
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CHAPTER XLVI.
CHAPTER XLVI.
937. What are ligaments? Ligaments consist of bands and cords of a tough , fibrous , and smooth substance , by which the bones are bound together and held in their places, allowing them freedom to move, and supplying smooth surfaces over which they glide. 938. Why are the joints bound with ligaments? Because the bones would otherwise be constantly liable to slip from their places . "That which is born of the flesh is flesh; and that which is born of the Spirit is spirit."— John iii. 939. What ar
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CHAPTER XLVII.
CHAPTER XLVII.
951. What are nerves? The nerves are branches of the brain and the spinal cord ; they are distributed in great numbers to all the active and sensitive parts of the body. 952. What is the spinal cord? The spinal cord is a long and large cord of nervous matter, which extends from the brain through a continuous tube formed by corresponding hollows in the bones of the back. It serves as a nervous trunk for the distribution of nerves , just as the aorta distributes branches of blood-vessels. 953. Why
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CHAPTER XLVIII.
CHAPTER XLVIII.
963. Why do we see objects? Because the light which is reflected from them enters our eyes and produces images of their forms upon a membrane of nerves called the retina , just as images are produced upon a mirror. 964. Why does this enable us to see? Because the membrane which receives the images of objects is connected with the optic nerve which transmits to the brain impressions made by the reflections of light, just as other nerves convey the effects of feeling, hearing, tasting, &c.
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CHAPTER XLIX.
CHAPTER XLIX.
983. Why do we hear? Because the tympanum of the ear receives impressions from sounds , and transmits those impressions to the brain in a similar manner to that in which the retina of the eye transmits the impressions made upon it by light. 984. Why is one part of the ear spread out externally? The external ear is a natural ear-trumpet , and serves to collect the vibrations of sound, and to conduct them towards the internal ear. 985. Why is the ear allowed to project, whilst the eye is carefully
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CHAPTER L.
CHAPTER L.
996. Why do we taste? Because the tongue is endowed with gustatory nerves, having the function of taste as their special sense , just as the optic , the auditory , and the olfactory nerves, have their special duties in the eyes, ears, and nose. 997. Why do some substances taste sweet, others sour, others salt, &c.? It is believed that the impressions of taste arise from the various forms of the atoms of matter presented to the nerves of the tongue. 998. Why do we taste substances most sa
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CHAPTER LI.
CHAPTER LI.
1009. Why do we perspire? Because the skin is filled with very minute pores , which act as outlets for a portion of the water of the blood, that serves to moisten and cool the surface of the body, and to carry away some of the matter no longer needed in the system . 1010. How is the perspiration formed? By very small glands , which lie embedded in the skin. It is estimated that there are about 2,700,000 perspiratory glands distributed over the surface of the body, and that these glands find outl
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CHAPTER LII.
CHAPTER LII.
1029. Why are there so many bodily forms in the animal creation? Because the various creatures which God has created have different modes of life, and the forms of their bodies will be found to present a perfect adaptation to the lives allotted to them . Because, also, the beauty of creation depends upon the variety of objects of which it consists . And the greatness of the Creator's power is shown by the diversity of ends accomplished by different means . 1030. Why are birds covered with feathe
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CHAPTER LIII.
CHAPTER LIII.
1052. Why have birds with long legs short tails? Because the tails of birds are used to guide them through the air, by a kind of steerage . When birds with long legs take to flight, they throw their legs behind, and they then serve the same purpose as a tail . 1053. Why have fishes fins? The fins of fishes are to them, what wings and tails are to birds , enabling them to rise in the fluid in which they live by the reaction of the motions of the fins upon its substance . "Speak to the earth, and
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CHAPTER LIV.
CHAPTER LIV.
1074. Why has the mole hard and flat feet, armed with sharp nails? Because the animal is thereby enabled to burrow in the earth , in search for worms. Its feet are so many shovels . 1075. Why is the mole's fur exceedingly glossy and smooth? Because its smoothness enables it to work under ground without the soil sticking to its coat , by which its progress would be impeded. From soils of all kinds, the little worker emerges shining and clean. "I know all the fowls of the mountains, and the wild b
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CHAPTER LV.
CHAPTER LV.
1091. Why do quadrupeds that are vegetable eaters feed so continually? Because their food contains but a small proportion of nutrition , so that it is necessary to digest a large quantity to obtain sufficient nourishment. 1092. Why do flesh eating animals satisfy themselves with a rapid meal? Because the food which they eat is rich in nutritious matter , and more readily digestible than vegetable food; it does not therefore, require the same amount of grinding with the teeth . 1093. Why has the
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CHAPTER LVI.
CHAPTER LVI.
1103. Why when the perfume of flowers is unusually perceptible may wet weather be anticipated? Because when the air is damp it conveys the odours of flowers more effectively than it does when dry. 1104. Why when swallows fly low may wet weather be expected? Because the insects which the swallows pursue in their flight are flying low, to escape the moisture of the upper regions of the atmosphere . 1105. Why do ducks and geese go to the water, and dash it over their backs on the approach of rain?
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CHAPTER LVII.
CHAPTER LVII.
1125. Why can gossamer spiders float through the air? Because, having no wings, and being deficient in the active muscular powers of other spiders, they have been endowed with the power of spinning a web which is so light that it floats in the air, and bears the body of the gossamer spider from place to place. Each web acts as a balloon, and the spider attached thereto is a little aeronaut . 1126. Why do crickets make a peculiar chirping sound? Because they have hard wing cases, by the friction
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CHAPTER LVIII.
CHAPTER LVIII.
1140. What is the difference between an animal, a plant, and a mineral? The great naturalist, Linnæus, used to say that animals grow , live , and feel ; plants grow and live ; and minerals grow . Animals are here defined to enjoy three conditions of existence; plants two conditions; and minerals one condition. This definition has, in latter days, been held to be unsatisfactory, since there are a few plants that are supposed to feel , and a few animals that are supposed to have even less feeling
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CHAPTER LIX.
CHAPTER LIX.
1155. Why, if we break the stem of a hyacinth, do we see a glutinous fluid exude? Because, by breaking the stem, we rupture the vessels of the plant, and cause the nutritive fluid to escape. The sap of the plant is analogous to the blood of man , and the vessels, to the arteries and veins of the animal body. 1156. Why, if we split the petal of a tulip, do we see cells containing matter of various colours? Because, by splitting the petal of the flower, we disclose the anatomy of its structure, an
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CHAPTER LX.
CHAPTER LX.
1167. Why do some plants droop, and turn to the earth after sunset? Because, when the warmth of the son's rays is withdrawn, they turn downwards, and receive the warmth of the earth by radiation . 1167. Why does the young ear of corn first appear enfolded in two green leaves? Because the light and air would act too powerfully for the young ear ; two leaves therefore join, and embrace the ear, and protect it until it has acquired strength, when they divide, and leave the ear to swell and ripen. 1
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CHAPTER LXI.
CHAPTER LXI.
1189. Why are vegetable productions so widely diffused? Because they everywhere form the food of the animal creation . Without them, neither man nor beast could exist. Even the flesh-eating animals are sustained by them, since they live by preying upon the bodies of vegetable-eaters. They also enrich and beautify the earth. They present the most charming diversities of proportions and features. From the cowslip, the primrose, and the blue-bell of our childish days, to the broad oak under which w
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CHAPTER LXII.
CHAPTER LXII.
1204. What are vegetable oils and fats? Vegetable oils and fats constitute, next to starch and sugar, the most important secretion of the vegetable creation. There are very few plants from which some amount of oil cannot be obtained; and those which are famed for yielding it owe their celebrity rather to the abundance that they yield, and the peculiar qualities of their oil, than to the secretion of oil being rare—for probably there is no plant without it. Oil is most commonly found in seeds, as
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CHAPTER LXIII.
CHAPTER LXIII.
1254. What are vegetable gums? Vegetable gums are secretions of plants which are generally soluble in water , and which subserve various useful purposes. Gum Arabic is one of the most important of this class of vegetable productions. Gutta-percha is an invaluable substance lately added to the list of known vegetable productions. It is obtained by cutting the bark of trees of the class called Sapotacea . Its proper name is gutta Pulo Percha, gutta meaning gum, and Pulo Percha is the island whence
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CHAPTER LXIV.
CHAPTER LXIV.
1273. Why are there curious markings in walnut, mahogany, rose-wood, satin-wood, &c.? Because those markings are produced by the various structure of the vessels by which the wood is formed; and by successive zones of wood, which indicate the periods of growth. The inclosure of zone within zone is owing to the mode in which the wood is produced, and the position in which it is deposited. Wood is formed by the leaves during the growing season, and passes down towards the root between the
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CHAPTER LXV.
CHAPTER LXV.
1286. Why are the seeds of plants indigestible? Because they are encased in a hard covering upon which the gastric juice of animals takes no effect. This provision has been made by the Creator, for the preservation of seeds , the productions of which are so essential to animal life. The gastric juice can dissolve any other part of the plant, even the woody fibre, and yet upon the seed it takes no effect. When, however, the seed is crushed , and, thereby, the vital principle destroyed, so that no
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CHAPTER LXVI.
CHAPTER LXVI.
1292. Why does the caterpillar become torpid when passing into the state of the chrysalis? Because in all probability, where the difference between the first and the ultimate form is considerable, the organs of the insect having to undergo great changes, it would suffer considerable pain. Torpor comes upon the insect, it is thrown into a state similar to that of a person who has inhaled chloroform; and after what has, in all probability, proved a pleasant dream, the insect awakes to find itself
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