,,first ,,lessons ,,in ,natural ,philosophy ,,for ,,beginners4 ,,by ,,joseph ,c4 ,,martindale1 ,m4,d41 ,,late ,,principal ,,of ,,madison ,,grammar ,,school1 ,,philadelphia2 ,,author ,,of ,a ,,history ,,of ,,the ,,united ,,states ,,for ,,schools1 ,,etc4 ,illustration3 ,paddlewheel steamboat4 ,,philadelphia3 ,,eldredge ,,brother1 ,no4 #ag ,north ,seventh ,street4 #ahha4 ,entered1 according to ,act of ,congress1 in the year #ahgb1 by ,,eldredge ,,brother1 in the ,office of the ,librarian of ,congress at ,washington4 ,j4 ,,fagan ,a ,,son1 ,,electrotypers1 ,,philad',a4 ,illustration3 ,,keystone ,,press ,,of ,w,m4 ,j4 ,,dornan ,preface4 ,illustration3 ,decoration ,in preparing this little work1 our desire has been to afford both pleasure and profit to those who may read or study its pages4 ,the most interesting1 as well as the most useful things to us1 are those with which we meet in every-day life2 but we must have some knowledge of these things1 ere we can contemplate them with much pleasure1 or use them to our greatest profit4 ,simple truths in natural science may be learned at an early age2 for it requires no more than the ordinary intelligence possessed by boys and girls to understand them4 ,such facts are not only valuable in themselves1 but they are also useful in disciplining the mind by teaching it to observe the many changes constantly going on around us1 and to reason and reflect in regard to the same4 ,habits of observation and reflection thus formed are likely to go with us through life2 and they may prove a blessing in a thousand ways2 for they will not only add to our comfort and our enjoyment1 but they will also produce many a pleasing thought4 ,we have endeavored to make a book that can be easily understood2 but few scientific terms will be found in it1 for its language is the language in familiar use2 hence1 it may serve to interest the fireside circle1 and it may be referred to by intelligent boys and girls for answers to the many perplexing questions which are so often presented to their inquiring minds4 ,many pupils have not the chance to attend even an ,academy or a ,high ,school4 ,it is to such that this book is especially adapted1 for it is believed to contain as much matter as can be taught with satisfaction and profit in our public or our private schools2 but to other pupils1 it will prove a valuable introduction to larger and more comprehensive works4 ,whenever a drawing would illustrate a fact1 and make its application plainer1 it has been made2 but by far the best illustrations of hundreds of facts1 explained in the text1 will be found in the world around us1 and the attention of both pupil and teacher should always be directed to this reliable and never-ending source4 ,in presenting these ,familiar ,lessons in ,natural ,philosophy to the youth of our country1 it is with the earnest hope that it may make them better acquainted with the natural objects surrounding us2 that it may lead them to observe the order1 the harmony1 and the beauty in nature everywhere2 and that it may help to turn their thoughts more and more to ,him1 who is the ,creator and ,ruler of all things4 ,j4 ,c4 ,m4 ,illustration3 ,decoration ,illustration3 ,,contents ,,page ,,chapter ,i4--,astronomy4 #i ,the ,earth and other ,planets #i ,the ,moon #ad ,eclipses #ah ,,chapter ,,ii4--,light4 #bb ,color #bb ,refraction of ,light #cb ,reflection of ,light #cd ,the ,eye #ch ,,chapter ,,iii4--,heat4 #db ,sources of ,heat #db ,expansion by ,heat #df ,conduction of ,heat #ed ,convection of ,heat #ei ,liquefaction #fa ,latent ,heat #fc ,ebullition #fe ,vaporization #ff ,evaporation #fi ,radiation #ga ,reflection #gc ,absorption #gd ,,chapter ,,iv4--,the ,air4 #gg ,winds #if ,,chapter ,v4--,water4 #ii ,springs and ,streams #ajd ,fogs and ,clouds #ajf ,dew #aji ,frost #aab ,rain1 ,snow1 and ,hail #aac ,ice #aaf ,,chapter ,,vi4--,sound4 #aah ,conduction of ,sound #abb ,trumpets and ,speaking-tubes #abe ,velocity of ,sound #abg ,reflection of ,sound #abh ,,chapter ,,vii4--,matter4 #aca ,,chapter ,,viii4--,attraction4 #acg ,cohesion and ,adhesion #acg ,capillary ,attraction #adj ,gravitation #ada ,centre of ,gravity #ade ,specific ,gravity #aej ,,chapter ,,ix4--,motion4 #aed ,,chapter ,x4--,mechanical ,powers4 #afd ,lever #afd ,wheel and ,axle #agd ,pulley #agf ,inclined ,plane #agg ,wedge #ahj ,screw #aha ,,chapter ,,xi4--,electricity4 #ahc ,magnetism #ahg ,electro-,magnetism #ahi ,,first ,,lessons ,,in ,natural ,philosophy4 ,,chapter ,i4 ,astronomy4 ,the ,earth and ,other ,planets4 ,illustration3 ,fig4 #a4 ,illustration3 ,illustrated ,capital ,w ,what is the shape of the ,earth on which we live8 ,it is round like a ball4 ,what other names are given to the ,earth8 ,it is called the ,world or ,globe4 ,what else is it sometimes called8 ,it is called a ,planet4 ,are there any other planets8 ,yes2 some of the stars are called planets4 ,is our earth or world a star8 ,it is a star4 ,why do the other stars seem to us different from the earth8 ,because they are so far away from us4 ,what gives light to the planets8 ,the ,sun gives light to the planets4 ,of what is the sun the centre8 ,the sun is the centre of the solar system4 ,do the planets remain in one place8 ,the planets do not remain in one place1 but are always moving4 ,how do the planets move8 ,they move around the sun4 ,are some planets nearer the sun than others8 ,yes2 some planets are much nearer the sun than others4 ,which planet is nearest the sun8 ,the planet called ,mercury4 ,which is next to ,mercury8 ,the planet called ,venus4 ,and which is third in distance from the sun8 ,our own planet1 the ,earth4 ,are there any planets still farther from the sun8 ,yes2 ,mars1 ,jupiter1 ,saturn1 ,uranus1 and ,neptune1 and many smaller planets4 ,how does each planet move8 ,it moves in its own track or orbit around the sun1 as is represented in ,fig4 #b4 ,illustration3 ,fig4 #b4 ,does the earth always move in the same orbit around the sun8 ,yes2 the earth moves in the same orbit around the sun1 year after year4 ,how long does it take the earth to move around the sun8 #cfe days1 #e hours and #di minutes1 or one year4 ,what makes a year to us8 ,a year to us is the time required by the earth to move around the sun4 ,if the earth is in a certain place at noon1 on ,new ,year's day1 when will it be in that place again8 #e hours and #di minutes after noon on ,new ,year's day of the next year4 ,what1 then1 does the earth do every year8 ,the earth moves around the sun and comes back to the place whence it started1 once every year4 ,has the earth any other motion than the one around the sun8 ,it has2 it turns over and over4 ,does the earth stay in one place as it turns over and over8 ,it does not2 it moves on in its track around the sun4 ,how many times does it turn over while going around the sun8 ,three hundred and sixty-five times4 ,how many times1 then1 does it turn over in one year8 ,the earth turns over three hundred and sixty-five times in a year4 ,what is the time which it takes to turn over once called8 ,it is called a day4 ,how many days in a year8 ,there are three hundred and sixty-five days in a year4 ,what two motions1 then1 has the earth8 ,it turns over and over1 and at the same time it moves around the sun4 ,what change is produced on the earth by its moving around the sun8 ,the change of ,seasons4 ,will you name the seasons8 ,winter1 ,spring1 ,summer1 and ,autumn4 ,do they follow each other in regular order8 ,they do2 ,spring follows ,winter1 ,summer follows ,spring1 ,autumn follows ,summer1 ,winter follows ,autumn1 and ,spring follows ,winter again4 ,how often have we these seasons8 ,as often as the earth moves around the sun1 which is once a year4 ,what change is produced on the earth by its turning over8 ,the change of day and night4 ,where is it day8 ,it is day on that part of the earth which is turned towards the sun4 ,where is it night8 ,it is night on that part of the earth which is turned away from the sun4 ,how often do we have the change from day to night8 ,as often as the earth turns over1 which is once in twenty-four hours4 ,what is a day8 ,a day is the time from sunrise till sunrise again1 from sunset till sunset again1 from noon till noon again1 or from midnight till midnight again4 ,what does a day include8 ,it includes the night-time as well as the day-time1 of the twenty-four hours4 ,when it is day-time on one part of the earth1 what is it on the opposite part8 ,it is night-time on the opposite part4 ,when it is morning to us1 what is it to people living on the opposite side of the earth8 ,when it is morning to us1 it is evening to them2 when it is day-time to us1 it is night-time to them2 and when it is noon to us1 it is midnight to them4 ,on how much of the earth is it always day8 ,it is day on one-half of the earth1 while on the other half it is night4 ,the sun seems to move around the earth2 does it really do so8 ,no2 it does not move around the earth4 ,does the earth move8 ,yes2 it turns over once every day4 ,why does it not seem to us to be moving8 ,because we move along with it4 ,if we are on a railroad car1 the trees and houses along the road appear to move1 and the car to stand still2 but the car really moves1 while the trees and houses stand still4 ,in what direction does the earth turn on its axis8 ,the earth turns from west to east4 ,where do the sun1 moon1 and stars rise8 ,the sun1 moon1 and stars rise in the east4 ,the teacher may1 by means of a ball or small globe1 readily make these things so plain that they can be understood even by small children4 ,when is it sunrise to us8 ,when the part of the earth on which we are1 first comes into the sun's rays4 ,when is it sunset to us8 ,when the part of the earth on which we are1 moves out of the sun's rays4 ,the ,moon4 ,we have been told that the earth moves around the sun2 does any planet move around the earth8 ,yes2 one planet moves around the earth4 ,what is that planet called8 ,it is called the ,moon4 ,illustration3 ,fig4 #c4 ,how often does the moon move around the earth8 ,once in #bg d4 #g h4 #dc min4 ,how long is the time from new moon to new moon again8 ,it is #bi d4 #ab h4 #dd min4 ,how often do we have new moon8 ,once every #bi d4 #ab h4 #dd min4 ,what is the period from one new moon to another called8 ,it is called a ,lunar month4 ,are the lunar months all of the same length8 ,yes2 they are all of the same length4 ,is there any other kind of month8 ,yes2 the ,calendar month1 as it stands in almanacs4 ,how many calendar months in a year8 ,there are twelve calendar months in a year4 ,are the calendar months all of the same length8 ,no2 some are thirty-one days long1 some thirty days long1 and one only twenty-eight days long4 ,when can we see the moon and stars best8 ,we can see them best when it is night4 ,from what do the moon and the other planets get their light8 ,they get their light from the sun4 ,what do they do with this light8 ,they reflect it4 ,how do we see them8 ,we see them by the light which they reflect4 ,why cannot we see the moon and stars in the day-time8 ,because the bright light of the sun hides their light4 ,are there stars in every direction around the earth8 ,there are stars in every direction around the earth4 ,how do we know this8 ,because stars may be seen from every part of the earth1 when it is night4 ,stars are in every direction around the earth1 just as we may imagine the apples to be in every direction around a boy who has climbed into a tree full of that fruit4 ,what planet moves around the earth8 ,the moon moves around the earth4 ,upon what part of the moon does the sun shine8 ,it shines upon the part towards the sun4 ,what does the moon do with the light which it receives from the sun8 ,the moon reflects the light received from the sun4 ,what is this reflected light called8 ,it is called moonlight when reflected from the moon4 ,is that part of the moon on which the sun shines always towards the earth8 ,it is not always towards the earth4 ,when all of the moon on which the sun shines is towards the earth1 how does the moon appear8 ,the moon appears to be round1 and the whole of it seems to shine4 ,what is the moon then called8 ,it is called the ,full ,moon4 ,when no part of the moon on which the sun shines is towards the earth1 how does the moon appear8 ,we do not see the moon at all1 and we say there is no moon4 ,when a small part of the moon on which the sun shines is first turned towards the earth1 what is it called8 ,it is called the ,new ,moon4 ,does the lighted part of the moon grow8 ,it seems to grow larger and larger1 until the whole of the moon is lighted4 ,what is it then called8 ,it is then called the ,full ,moon4 ,what then takes place8 ,it seems to grow smaller and smaller1 until the whole of the lighted part is gone4 ,just before the last part is gone1 what is it called8 ,it is called the ,old ,moon4 ,how long is it from one full moon to another full moon8 ,it is a lunar month4 ,how many full moons are there in a year8 ,there are thirteen full moons in a year4 ,is the sun much larger than the moon8 ,the sun is many thousand times larger than the moon4 ,why does the moon appear nearly as large as the sun8 ,because it is so much nearer to us4 ,how far is the moon from the earth8 ,the moon is nearly #bdj1jjj miles from the earth4 ,how far is the sun from the earth8 ,the sun is nearly #ib1jjj1jjj miles from the earth4 ,how long does it take the light of the sun to reach the earth8 ,it takes about eight minutes2 therefore1 the light of the sun must travel about twelve millions of miles in a minute1 or two hundred thousand miles in a second of time4 ,at this rate1 the light would come from the moon to the earth in a little more than one second of time4 ,it would take no longer for it to come than it does for the pulse to beat once1 or the clock to make one tick4 ,eclipses4 ,how do we know that the earth is round1 like a ball8 ,we know that the earth is round like a ball1 because its shadow is similar to the shadow of a ball4 ,how else do we know that the earth is round8 ,we also know that the earth is round1 because we can circumnavigate or sail around it4 ,where can we see the shadow of the earth8 ,we can see the shadow on the moon1 when the moon is eclipsed4 ,what is the shadow on the moon like8 ,it is round1 like the shadow of a ball4 ,when the ,earth comes between the sun and the moon1 where does the shadow of the earth fall8 ,the shadow of the earth falls on the moon1 as is represented in ,fig4 #d4 ,illustration3 ,fig4 #d4 ,what is this shadow on the moon called8 ,it is called an ,eclipse of the moon4 ,how do we know that the moon is round8 ,we know that the moon is round1 because its shadow is similar to the shadow of the earth4 ,when is the moon eclipsed8 ,when it comes into the earth's shadow4 ,when the moon comes fully into the earth's shadow1 what is it called8 ,it is called a total eclipse of the moon4 ,when it comes partly into the earths shadow1 what is it called8 ,it is called a partial eclipse of the moon4 ,when the moon comes between the sun and the earth1 where does the shadow of the moon fall8 ,the shadow of the moon falls on the earth1 as is represented in ,fig4 #e4 ,illustration3 ,fig4 #e4 ,what does this produce8 ,it produces an eclipse of the sun4 ,when the moon is between the sun and the earth1 can we see the sun8 ,no2 we cannot see the sun1 because the moon prevents the rays of the sun from coming to us4 ,when the moon prevents the sun's rays from falling on us1 what is it called8 ,it is called an eclipse of the sun4 ,when the moon prevents all the sun's rays from falling on us1 what is it called8 ,it is called a total eclipse of the sun4 ,when the moon prevents only a part of the sun's rays from falling on us1 what is it called8 ,it is called a partial eclipse of the sun4 ,when will the sun be eclipsed8 ,whenever the moon comes between the sun and the earth4 ,when will the moon be eclipsed8 ,whenever the earth comes between the sun and the moon4 ,who made the sun1 the moon1 and the stars8 ,god1 the creator of all things1 made the sun1 the moon1 and the stars4 ,he placed them in the heavens1 where they remain in obedience to ,his will4 ,he made the bright rays from the sun to light up the day1 and give beauty to the world2 but the feebler rays of the moon and the stars are seen best at night1 when the sun is hid4 ,illustration3 ,paddlewheel steamboat4 ,illustration3 ,decoration4 ,,chapter ,,ii4 ,light4 ,color4 ,illustration3 ,illustrated ,capital ,i ,in what way is the sun useful to us8 ,it gives heat1 which makes us warm1 and it gives light1 so that we can see4 ,is it useful in any other way8 ,it gives light and warmth to all animals as well as to all plants4 ,what make the flowers and leaves so beautiful8 ,the light and heat from the sun make them beautiful4 ,what do the light and heat from the sun ripen8 ,they ripen the apples1 cherries1 and other fruits2 also1 the wheat1 corn1 and other grains1 and make them fit for food4 ,when it is night-time or dark1 can we distinguish objects8 ,no2 because all things are then without color1 and they cannot be seen4 ,as it grows light in the morning1 what takes place8 ,at first1 we see the objects around us faintly2 but as it grows lighter1 we see them more distinctly4 ,do they all show the same color in the light8 ,they do not2 they show different colors4 ,what enables us to see the color of different things8 ,light enables us to see the color of everything4 ,what kinds of light have we8 ,we have the light of the sun1 moon1 and stars2 also1 the light from the burning of any substance4 ,does the light show many colors8 ,it does show many colors or shades of color4 ,how may some colors be made8 ,they may be made by mixing other colors together4 ,how can we make a purple color8 ,by mixing a red and a blue color together4 ,how can a green color be made8 ,by mixing a blue and a yellow color together4 ,how can an orange color be made8 ,by mixing a red and a yellow color together4 ,how does the light come from the sun8 ,it comes in rays or straight lines4 ,what may be done with a ray of light8 ,it may be separated into different colors4 ,into how many colors may a ray of light be separated8 ,into seven colors1 like the colors of the rainbow4 ,what names are given to these colors8 ,red1 orange1 yellow1 green1 blue1 indigo1 violet4 ,how may these colors be separated8 ,by a prism1 or three-sided piece of glass4 ,how may this be done8 ,if a sunbeam1 shining through a hole in the window-shutter of a dark room1 should fall upon a prism1 it will be broken up as it passes through the prism1 and be shown on the opposite wall1 in the seven rainbow colors4 ,illustration3 ,fig4 #f4 ,in ,fig4 #f1 ,d is a sunbeam passing through a shutter4 ,when it passes through the prism1 at ,e1 it is separated into the seven rainbow colors1 as is shown on the opposite wall4 ,in what order will these colors appear8 ,they will always appear one above the other1 in the order named4 ,how may this order be remembered8 ,by the word ,roy-g-biv1 made from their initial letters1 beginning at the bottom4 ,from what are the colors of the rainbow made8 ,from the rays of light coming from the sun4 ,when is a rainbow seen8 ,a rainbow is seen when the sun shines through the drops of water as they fall through the air4 ,how do the drops of water help to make a rainbow8 ,the drops of water act like little prisms1 and separate the rays of light passing through them into the colors of the rainbow4 ,what two things1 then1 are needed to make a rainbow8 ,a shower of water1 and a bright sunshine4 ,in what part of the sky does the rainbow appear8 ,in the part opposite to that in which the sun is1 at the time of the shower4 ,how does the rainbow appear8 ,it appears like a great arch1 spanning the sky1 and its splendid bright colors are very beautiful4 ,what may we remember in reference to the rainbow8 ,we may remember that ,god set his 8bow0 in the cloud1 as a token that the world should no more be destroyed by a flood of waters4 ,where else may we see a variety of colors8 ,in the soap-bubble4 ,why are these colors constantly changing8 ,because the walls of the bubble are constantly growing thinner1 and different colors are1 therefore1 reflected from them4 ,why do the walls of the soap-bubble grow thinner8 ,because the water runs to the bottom of the bubble until its top becomes so thin as to burst4 ,can we tell the color of any object by touching it8 ,no2 we must see it in order to tell its color4 ,how do we know this8 ,if there are two coats1 one blue and the other black1 we cannot tell which is the blue one or which is the black one1 by feeling them4 ,what is necessary in order to see the colors8 ,light is necessary2 because all colors come from the rays of light4 ,can we see the different colors in the ray itself8 ,we cannot2 because ,god has so blended them together that they cannot be seen by us4 ,when most of the rays of light pass through a substance1 what is said of it8 ,the substance is said to be transparent4 ,name some transparent substances4 ,glass1 ice1 diamonds1 air1 and clear water4 ,when only a few rays of light pass through a substance1 what is said of it8 ,the substance is said to be translucent4 ,name some translucent substances4 ,flint1 isinglass1 scraped-horn1 and china-ware4 ,when no rays of light pass through a substance1 what is said of it8 ,the substance is said to be opaque4 ,name some opaque substances4 ,wood1 iron1 coal1 and granite4 ,can we see through a glass window8 ,yes2 because the glass is transparent1 and the light passes through it4 ,can we see through a looking-glass8 ,no2 because the back of the looking-glass is covered with quicksilver1 which prevents the rays of light from passing through it4 ,what becomes of the light falling on the looking-glass8 ,it is thrown back from the glass4 ,what is this called8 ,it is called reflection4 ,what objects are good reflectors of light8 ,those having smooth and polished surfaces2 such as tin1 silver1 gold1 and quicksilver4 ,what objects are poor reflectors of light8 ,those having dull1 uneven surfaces2 such as iron1 wood1 cloth1 leather1 and calico4 ,of what is every ray of sunlight composed8 ,it is composed of the seven colors of the rainbow4 ,what does a looking-glass do with these colors8 ,a looking-glass throws them all back from its surface4 ,what does a glass window do with these colors8 ,a glass window permits all these colors to pass through it4 ,what do opaque substances do with these colors8 ,they throw back or reflect some of them4 ,do they all reflect the same color8 ,no2 some reflect one color1 and some another color4 ,what color does the grass reflect8 ,it reflects the green color2 therefore1 the grass is green4 ,what does the grass do with the other colors8 ,it absorbs or hides them in itself4 ,how do we know the color of anything8 ,we know it by the color which it reflects4 ,why is the rose red8 ,because it reflects the red color1 and absorbs or hides the other colors in itself4 ,when anything absorbs all the colors of a ray of light1 what color is it8 ,it is black4 ,when it reflects all the colors of light1 what color is it8 ,it is white4 ,why are the letters on this page black8 ,because they absorb all the colors of light1 and reflect none4 ,why is the paper white8 ,because it reflects all the colors of light1 and absorbs none4 ,why are all things black in the dark8 ,because there are no rays of light falling on them2 hence1 there is no color for them to reflect4 ,does an object reflect its color in every direction8 ,it does reflect its color in every direction4 ,how do we know this8 ,because thousands of persons1 in different directions from the same object1 can see it at the same time4 ,how are the rays of color reflected from an object8 ,they are reflected in straight lines4 ,where must a person be so as to see an object8 ,he must be in a position so that there is nothing to prevent the rays of light passing in a straight line from the object to his eyes4 ,what color does a red ribbon reflect8 ,it reflects a red color4 ,why are some red ribbons of a brighter red than others8 ,when they reflect a great many red rays1 they are of a bright red color2 but when they reflect only a few red rays1 they are of a dull red color4 ,upon what does the brightness or dullness of a color depend8 ,it depends upon the number of rays of that color reflected4 ,what variety does this produce8 ,it produces a great variety in the shades and tints of color4 ,where may many of these shades and tints be seen8 ,in the pretty flowers that grow in the woods1 fields1 and gardens2 in the beautiful tints of the leaves in autumn2 and in the plumage of the birds that visit us every spring1 and cheer us with their songs4 ,what may these things teach us8 ,they may teach us the goodness of ,god1 in giving us a world so full of beauty2 and we should feel ever thankful to ,him for the great pleasure that we have in seeing them4 ,why cannot we see the light of a lamp or candle distinctly1 in the day-time8 ,because the strong rays from the sun hide the more feeble rays from the lamp4 ,why cannot we see the stars in the day-time8 ,because the bright light from the sun hides their more feeble light4 ,when can we see the glow-worms or fire-flies best8 ,at night1 when it is dark2 because1 at other times1 the light of the sun hides their feeble light4 ,where may we see them at night8 ,flying about in all directions1 looking like bits of fire moving in the air4 ,does a looking-glass reflect all the colors of light falling upon it8 ,it does2 hence1 the ray of light is not changed4 ,when the object is of a blue color1 why is blue only reflected8 ,because it is the only color falling upon the glass1 and there is no other color to reflect4 ,is the color of any object changed by falling upon a looking-glass8 ,no2 the color of every object is reflected from a looking-glass without change4 ,do other objects generally reflect the colors falling upon them8 ,they do not2 they absorb or hide the color of all other objects1 and reflect only their own color4 ,if every object was a good reflector of color1 like a looking-glass1 what would result8 ,then every object would reflect the color of every other object around it1 and there would be an endless confusion of colors4 ,what objects reflect the most light8 ,those of a white or light color4 ,what objects reflect the least light8 ,those of a darker color2 and the nearer the color approaches to black1 the less light it reflects4 ,why is it darker when the sky is covered by dark-colored1 than by light-colored1 clouds8 ,because the dark-colored clouds reflect less light1 than the light-colored clouds do4 ,what advantage do we derive from the green color of the grass and the leaves8 ,they reflect a soft1 pleasant light1 which does not dazzle or hurt our eyes4 ,how would it be if those objects were white8 ,they would dazzle us by the amount of light reflected4 ,if we wish to make a room light1 of what color should the walls be8 ,they should be white2 and when papered1 it should be with light-colored paper4 ,why does dark-colored paper darken a room8 ,because it absorbs some of the rays of light which come in at the windows2 hence1 there is less light in the room4 ,dark-colored carpets1 or dark furniture1 darken the room for the same reason4 ,does the light from a burning body differ from sun-light8 ,yes2 it differs in intensity1 in color1 and in many other ways4 ,what effect does the lamp-light have upon the color of some substances8 ,it changes their color4 ,where may we find an example of this8 ,in trying to match the colors of thread or silk at night4 ,why is the color different by lamp-light from what it is by daylight8 ,because the yellow color of the lamp's rays acts upon the color of the silk1 forming a third color4 ,blue silk becomes green by lamp-light1 and red silk becomes orange4 ,are all persons able to distinguish one color from another8 ,no2 some are color-blind4 ,to such persons all colors appear to be alike4 ,what curious instances of color-blindness may be mentioned8 ,dr4 ,mitchell tells of an officer who bought a blue coat and a red waistcoat1 thinking them to be of the same color4 ,he also tells of a tailor who patched a black waistcoat with a piece of crimson2 and of another1 who put a red collar on a blue coat4 ,dr4 ,dalton lost a piece of red sealing-wax in the grass1 and he could not find it because it and the grass seemed of the same color to him4 ,refraction of ,light4 ,how do the rays of light from the sun come to us8 ,they come to us in straight lines4 ,when the rays of light pass from one substance to another more dense1 what takes place8 ,they are bent or turned from a straight course4 ,what is said of these bent rays8 ,they are said to be refracted4 ,what is meant by refraction8 ,bending a ray of light1 as it passes from one substance to another of different density2 as from air to water1 or from water to air4 ,where may we see an example of refraction8 ,in the rays of light from a rod which has one end in the water4 ,illustration3 ,fig4 #g4 ,why does the rod appear to be bent8 ,because light coming from the part of the rod under the water1 is refracted or bent at the surface of the water1 while the light from the part above the surface1 comes in straight lines to the eye2 hence1 the rod appears to be bent at the surface1 as is represented in ,fig4 #g4 ,how does a pole appear when one end is placed in the water8 ,it appears to be bent where it meets the surface of the water4 ,how does the part of the rod under water appear8 ,the part under the water appears to be raised up1 as may be seen in ,fig4 #g4 ,how does the bottom of a pond or stream of water appear8 ,it appears to be raised up1 and the water does not seem so deep as it really is4 ,why is this the case8 ,because the light from the bottom of the pond is refracted or bent at the surface of the water2 hence1 the bottom appears to be raised up4 ,how much does the bottom of a pond or stream of water seem to be raised up8 ,about one-third of the depth of the water4 ,if the water is really six feet deep1 how deep does it appear8 ,it appears to be only four feet deep4 ,what has frequently happened from not knowing this fact8 ,people have been drowned from getting into water deeper than it appeared to be4 ,do the fish and other things floating in the water appear to be raised up8 ,yes2 like the bottom of the stream1 they also appear to be only two-thirds as far from the surface as they really are4 ,if we wish to spear the fish1 what must we do8 ,we must aim below the place where they seem to be1 or we must strike perpendicularly at them4 ,reflection of ,light4 ,when a ball is thrown against a wall1 what is the path through which it goes called8 ,the line of incidence4 ,when the ball bounds back1 what is its path called8 ,the line of reflection4 ,what is the angle at which a ball strikes the wall called8 ,the angle of incidence4 ,what is the angle at which the ball rebounds called8 ,the angle of reflection4 ,when a ray of light falls upon a looking-glass1 what is the path through which it goes called8 ,the line of incidence4 ,when the ray is reflected1 what is its path called8 ,the line of reflection4 ,the angle of incidence is the angle between a perpendicular and the line of incidence2 and the angle of reflection is the angle between the perpendicular and the line of reflection4 ,the two angles are always equal to each other1 as is represented in ,fig4 #h4 ,illustration3 ,fig4 #h4 ,when a ray of light strikes a looking-glass obliquely or slantingly1 what is done with it8 ,the ray is reflected as obliquely from the glass as it strikes or falls upon it4 ,why is the reflection of the sun in a pond of water seen near the edge at noon8 ,because the angle of reflection is equal to the angle of incidence2 and the observer must be nearly over the place where the rays strike1 so that1 when reflected1 they may meet his eye4 ,where is the reflection seen in the morning or in the evening8 ,it is seen nearer the middle of the pond2 because the sun's rays then fell more obliquely on the pond1 and are reflected more obliquely to the eye4 ,when an opaque object is placed between a candle and a wall1 why will there be a shadow8 ,because the opaque object prevents the rays of light from falling on the wall4 ,why will the shadow be larger1 the nearer the object is to the candle8 ,because the rays of light diverge1 in every direction from the candle1 in straight lines1 and the nearer the object1 the more rays will it intercept1 as is represented in ,fig4 #i4 ,illustration3 ,fig4 #i4 ,in ,fig4 #i1 let ,l represent the flame of a candle4 ,when the object is placed at ,a1 the shadow on the wall will extend from ,c to ,d2 but when the object is moved nearer1 as at ,b1 the shadow will extend from ,e to ,f4 ,why does an object seem to be smaller1 the farther it is from us8 ,because the angle at which the light from it strikes the eye1 is less when at a distance1 than when near to the eye4 ,illustration3 ,fig4 #aj4 ,in ,fig4 #aj1 the diameter of the near circle is from ,a to ,b2 but the diameter of the more distant circle1 although just as large1 seems only to be from ,c to ,d4 ,why does an object grow more dim the farther it is from us8 ,because the rays of light from it spread out in every direction2 and fewer rays enter the eye when it is at a distance than when it is near by4 ,what is the use of the telescope8 ,it is used to view distant objects4 ,why can we see a distant object more distinctly with a telescope1 than without one8 ,because the telescope enlarges the image of the object1 and it also collects more light from that object than is collected by the unaided eye2 thus1 making the image distinctly visible4 ,what class of objects do we view with a telescope8 ,we view the heavenly bodies2 the sun1 moon1 and stars4 ,what is a spy-glass8 ,it is a glass mostly used to view distant objects on the earth4 ,is the spy-glass like the telescope8 ,the spy-glass is much like the telescope1 only it is smaller4 ,when looking through a spy-glass1 how do objects appear8 ,they seem to be brought nearer to us1 and they appear larger4 ,by whom are spy-glasses much used8 ,spy-glasses are much used by persons on board of vessels1 while at sea4 ,what instruments have we for magnifying small objects8 ,we have magnifying glasses and microscopes4 ,what are magnifying glasses8 ,they are single glasses or lenses1 used for magnifying small objects4 ,by whom are magnifying glasses used8 ,they are used by jewellers1 watchmakers1 engravers1 and others who examine small objects4 ,what are microscopes8 ,they are instruments used for examining very small objects4 ,how does a drop of rain-water or vinegar appear under the microscope8 ,it appears to be full of strange-looking creatures1 which are always in motion4 ,how do the smallest insects appear8 ,they appear to be as perfectly formed as the larger ones which are seen with the naked eye4 ,what may be seen with a microscope8 ,thousands of things too small to be seen by us unless they are magnified4 ,what kind of spectacles do near-sighted people use8 ,near-sighted people use glasses1 thickest at the edge and thinnest at the centre4 ,what kind of spectacles do we use as we grow old8 ,as we grow old we use glasses1 thinnest at the edge and thickest at the centre4 ,of what use are spectacles8 ,when the vision is defective1 spectacles enable us to see objects more clearly4 ,how should spectacles be made8 ,they should be so made as to render objects distinct1 but neither to magnify nor diminish them4 ,as people grow old1 how do their eyes change8 ,their eyes change so that they see objects at a distance better than those which are nearer1 hence1 in reading they hold a book farther from the eye4 ,the ,eye4 ,what is that part of the eye called1 which is blue1 gray1 or brown1 in different persons8 ,it is called the iris4 ,what is the pupil of the eye8 ,the pupil is the black spot or hole in the centre of the iris4 ,illustration3 ,fig4 #aa4 ,what is the use of the pupil8 ,the pupil is the window of the eye1 and the rays of light which enter the eye must pass through it4 ,what power has the iris over the pupil8 ,the iris has the power of making the pupil larger or smaller1 according to the amount of light which it receives4 ,how does a bright light affect the iris8 ,it causes the iris to contract1 so that the pupil becomes smaller4 ,how does a faint light affect the iris8 ,it causes the iris to dilate1 so that the pupil becomes larger4 ,of what advantage is the iris to the eye8 ,the iris acts like a sentinel to protect the eye from any sudden light4 ,how does a sudden light affect the eye8 ,a sudden light causes pain to the eye4 ,of what shape is the pupil of the eye8 ,in man1 the pupil of the eye is circular4 ,what is the size of the pupil of the eye8 ,the pupil varies from the one-twentieth to the one-third of an inch in diameter1 depending upon the brightness of the light entering the eye4 ,how else are our eyes protected from any sudden light8 ,by means of our eyelids1 which may be closed1 and thus shut out all the light4 ,when we pass from a well-lighted room into the open air1 at night1 why does it seem darker at first than it does afterwards8 ,because the pupil is contracted at first2 but it soon dilates1 and allows more rays of light to pass into the eye1 so that the night seems less dark4 ,why does the pupil become larger in the twilight8 ,so that more rays of light may enter the eye1 whereby objects may be more distinctly seen4 ,why can an owl or a bat see at night8 ,because the pupil of the eye in them is quite large1 and admits much light4 ,why do they stay in dark places through the day8 ,because the bright light of day hurts their eyes4 ,may the image of an object be retained in the eye after the eyelids are closed8 ,it may for a very short time1 as any one can prove by first looking at some bright object1 and then closing the eyelids4 ,why does a burning coal moved rapidly around1 seem like a circle of fire8 ,because the light from it is retained a short time by the eye1 thus seeming to form a complete circle4 ,why cannot we count the posts in a fence1 when riding rapidly in a car8 ,because the light from each post falls in such quick succession upon the eye1 that it cannot distinguish one post from another4 ,can objects be seen distinctly when placed near the eye8 ,no2 when objects are within six inches of the eye they cannot be seen distinctly4 ,can objects be seen when at a great distance from the eye8 ,yes2 objects may be seen even when millions of miles away from us2 thus1 the sun is seen although ninety-five millions of miles from the earth1 and some of the stars which we behold in the heavens1 are still farther away than the sun4 ,of what use is the eye to us8 ,the eye gives us ideas of the size1 the shape1 the color1 the place1 the distance1 and the movements of things around us1 so that we can use them the better to promote our comfort and our happiness4 ,what may we remember about the light8 ,and ,god said1 8,let there be light20 and there was light4 ,thus the day was separated from the night1 and the sun was made to send forth his silvery rays upon hill and valley1 field and forest1 causing the rarest buds and most beautiful blossoms to come forth from the lifeless earth1 although no eye1 save the ,all-,seeing ,one1 was there to behold them6 ,illustration3 ,locomotive4 ,illustration3 ,decoration4 ,,chapter ,,iii4 ,heat4 ,sources of ,heat4 ,illustration3 ,illustrated ,capital ,w ,what is heat8 ,heat is that agent which causes the feeling of warmth4 ,can heat be seen8 ,no2 heat cannot be seen1 it can only be felt4 ,when we touch a substance hotter than we are1 what takes place8 ,a part of the heat from that substance comes to us and causes a feeling of warmth4 ,when we touch a substance colder than we are1 what takes place8 ,a part of the heat from us goes to that substance1 and we experience a feeling of cold4 ,does the amount of heat in any substance vary8 ,yes2 water may be heated until it is scalding hot1 or the heat may be taken from it until it is frozen into ice4 ,what causes a substance to become cold8 ,taking away heat from a substance causes it to become cold4 ,then what is cold8 ,cold is only the absence or want of heat4 ,when we pass from a very hot room to one moderately warm1 how do we feel8 ,we experience a feeling of cold4 ,when we pass from a very cold room to one moderately warm1 how do we feel8 ,we have a feeling of warmth1 although the room is no warmer than in the first instance4 ,how else can we prove that we judge of heat and cold by our feelings8 ,if one hand be held in quite warm water1 and the other in quite cold water1 for a few moments1 and then both hands be plunged into tepid water1 the tepid water will feel cold to the hand that was in the warm water1 and warm to the hand that was in the cold water4 ,is there anything without heat8 ,no2 the coldest substance known still contains some heat4 ,how many kinds of heat are there8 ,there are two kinds of heat4 ,what are the two kinds of heat8 ,heat accompanied by light1 as the heat from the sun1 or a lamp2 and heat without light1 as the heat from boiling water4 ,from what source does heat mostly come8 ,heat mostly comes from the sun1 which is also the source of light4 ,what is said of the heat and light from the sun8 ,heat and light from the sun come together in the sunbeam4 ,from what other source is heat obtained8 ,heat is obtained from the burning of any substance4 ,what else does the burning of any substance produce8 ,it often produces light4 ,can the light and heat from the sun easily be separated8 ,they cannot easily be separated4 ,what does a glass window do with the light and heat of the sunbeam8 ,it permits both the light and the heat to pass into the room1 so that we can see the one and feel the other4 ,are the light and heat from a fire united1 as they are in the sunbeam8 ,they are not2 but they seem to be separated from each other4 ,what does a glass window do with the light and heat from a fire8 ,it permits the light to pass through2 but it stops the heat4 ,how may this be proved8 ,when a pane of glass is held between the face and a fire1 it will protect the face from the heat4 ,is there any heat without light8 ,yes2 many substances contain heat1 but do not emit light4 ,does light change the amount of heat in a substance8 ,no2 boiling water is as hot in the dark as it is in the light2 and ice is as cold in the daytime as it is at night4 ,is there any other source of heat8 ,yes2 heat is produced by rubbing or striking substances together4 ,what will result from rubbing two pieces of wood together8 ,they may be rubbed until they take fire4 ,how do ,indians kindle fires8 ,by rubbing two pieces of wood together until they take fire4 ,how is heat produced by the brakes on railroad cars8 ,it is produced by the car-wheels rubbing against the brakes4 ,what may be seen when a horse strikes his shoes against a stone8 ,small sparks of fire1 which contain heat1 may be seen4 ,if a piece of iron be hammered1 will its heat be increased8 ,its heat will be increased4 ,how can this be proved8 ,a person can1 by hammering a piece of cold iron1 make it red-hot4 ,could we live without heat8 ,no2 our bodies must be kept warm1 and this can be done only by heat4 ,is this true of other living things8 ,yes2 all the animals and all the plants would die if heat were taken away4 ,how should we feel in regard to these things8 ,we should feel thankful to an ,all-wise ,creator1 for having provided us with both heat and light from a never-failing source--the sun4 ,expansion by ,heat4 ,how does heat generally affect substances8 ,heat expands them or makes them larger4 ,does heat expand all metals8 ,yes2 all metals are expanded by heat4 ,when a rod of iron is heated1 is it longer or shorter than when cold8 ,it is longer than when it is cold4 ,how do we know this8 ,we know it by measuring the rod when it is cold1 and again when it is heated4 ,will the rod be larger1 as well as longer8 ,the rod will be larger4 ,how can we prove this8 ,the rod1 when red-hot1 will not go through as small a hole as when it is cold4 ,how do heat and cold affect most substances8 ,heat expands most substances1 and cold contracts them4 ,do all metals expand alike by heat8 ,no2 some metals expand much more than others4 ,how does heat expand substances8 ,heat pushes the parts or atoms of an object farther from each other1 and thus its size is increased4 ,what does a blacksmith do with a tire before putting it on a wheel8 ,he heats the tire red-hot4 ,why does he heat the tire red-hot8 ,so that it will be increased in size1 and will go on the wheel more easily4 ,what takes place as the tire cools8 ,it becomes smaller1 and thus binds the parts of the wheel tightly together4 ,when a fire is made in a room1 why does the furniture often make a snapping noise8 ,because heat expands the wood1 and the particles make a snapping noise upon separating4 ,why does a stove make a crackling noise as it grows hot8 ,the particles of the iron make the noise in expanding4 ,if a piece of glass be held in the hand1 will the glass become warm8 ,the glass will become as warm as the hand4 ,what part of the glass will be warmed first8 ,the part touching the hand will be warmed first4 ,what part of the glass will be warmed last8 ,the part farthest from the hand will be warmed last4 ,which part of the glass will be expanded first8 ,the part touching the hand1 because it is first warmed4 ,which part will be expanded last8 ,the part farthest from the hand1 because it is the last part warmed4 ,if any other warm substance touch the glass1 will the glass be heated in the same manner8 ,the glass will be heated in the same manner4 ,what often results from this unequal heating8 ,the glass is broken4 ,why are glass plates or tumblers broken when placed in hot water8 ,they are broken because the part next to the hot water is expanded more than that farther away4 ,why will a cloth dipped in hot water and wrapped around the neck of a bottle loosen its stopper8 ,because the heat from the cloth expands the neck of the bottle before it does the stopper1 so that the stopper is loosened4 ,why do stove-plates often break8 ,because they are fitted together in the stove so that they have not room to expand without breaking4 ,what effect has cold upon substances8 ,cold causes them to contract or grow smaller4 ,things expand unequally2 do they also contract unequally8 ,they do contract unequally1 and in this way may be broken4 ,why are lamp chimneys often broken while the lamp is burning8 ,because the heat of the flame causes them to expand unequally4 ,in what other way are they broken8 ,by a draught of cold air1 or a drop of cold water1 touching them1 thus causing them to contract unequally4 ,why are they sometimes broken when the lamp is not burning8 ,because a current of cold air from a window or a door1 blows upon them4 ,does quicksilver expand when heated8 ,like other metals1 quicksilver expands as it grows warmer1 and contracts as it grows cooler4 ,is quicksilver in the form of a solid or a fluid8 ,it is a fluid as we usually see it4 ,for what is quicksilver used8 ,it is used for filling the tubes of thermometers4 ,what is a ,thermometer8 ,it is an instrument used for measuring the degree or quantity of heat in any substance4 ,how does heat affect the quicksilver8 ,heat expands the quicksilver1 and causes it to rise in the tube4 ,how does cold affect the quicksilver8 ,cold contracts the quicksilver1 and causes it to fall in the tube4 ,does heat expand liquids more than solids8 ,heat does expand liquids more than solids4 ,why are liquids expanded more than solids8 ,because the particles of which they are formed are more easily separated or pushed apart by the heat4 ,if we continue to apply heat to a liquid1 what becomes of it8 ,the liquid is changed into a gas or vapor4 ,what common example have we of vapor8 ,water1 when heated1 is turned into steam4 ,mention some gas4 ,the air we breathe is a gas4 ,how does heat affect the air8 ,heat warms the air and causes it to expand4 ,do solids all expand equally when heated8 ,no2 some solids expand more than others2 thus1 zinc expands more than iron1 and iron more than glass4 ,do liquids all expand equally when heated8 ,no2 liquids1 although more sensitive to heat1 do not expand as equally as solids4 ,do gases expand equally when heated8 ,yes2 gases expand uniformly2 thus1 #dia cubic inches of any gas1 if heated one degree1 will become #dib cubic inches4 ,if one cup be filled with lead1 and another cup of the same size with water1 which will weigh the more1 the lead or the water8 ,the lead will weigh more than the water4 ,which is the heavier substance1 lead or water8 ,lead is heavier than water4 ,why do we say lead is heavier than water8 ,because a cup full of lead will weigh more than the same cup fall of water1 or any bulk of lead will weigh more than an equal bulk of water4 ,why is cork lighter than water8 ,because any bulk of cork is lighter than an equal bulk of water2 a cup filled with cork will weigh less than when it is filled with water4 ,when lead is put in water1 why does it sink to the bottom8 ,because the lead is heavier than an equal bulk of water4 ,when cork is put in water1 why does it rise to the surface8 ,because the cork is lighter than an equal bulk of water4 ,does heat increase the weight of any substance8 ,heat does not increase the weight of any substance4 ,how do we know this8 ,because a piece of iron when cold will weigh as much as when heated red-hot4 ,when a liquid is heated1 does it become lighter or heavier8 ,it becomes lighter1 bulk for bulk1 when heated4 ,why does a liquid become lighter when heated8 ,because the same liquid is expanded and takes up more room1 although it has no more weight4 ,why will a gallon of cold water weigh more than a gallon of hot water8 ,because a gallon of cold water1 when heated1 will make more than a gallon of hot water4 ,when do we get the most molasses1 by buying it in hot or in cold weather8 ,we get the most by buying it in cold weather1 because a gallon bought then will make more than a gallon when the weather becomes warmer4 ,does heat expand the air and make it lighter8 ,heat does expand the air and make it lighter4 ,what does the air do when heated8 ,it ascends or rises up1 because it is lighter1 and the cold or heavier air falls to take its place4 ,what part of a room1 in which there is fire1 is the warmest8 ,the part next to the ceiling is the warmest1 because the heated air always ascends4 ,why does a soap-bubble ascend8 ,because it is filled with heated air from the lungs1 and is1 therefore1 lighter than the air around it4 ,why do balloons ascend8 ,because they are filled with a gas lighter than the air around them4 ,why does a chestnut split open when roasting8 ,because the air in it is expanded by the heat1 so that it bursts the shell4 ,why does the chestnut not split open when a hole is made in the shell8 ,because the air can then escape as it expands1 without bursting the shell4 ,what becomes of the air in an apple1 when the apple is roasted8 ,the air1 upon being heated1 bursts through the peel of the apple1 carrying the juice with it4 ,why does an apple become soft when roasted8 ,because the air in the cells of the apple expands1 and breaks those cells1 so that the apple becomes soft4 ,what part of the apple first becomes soft8 ,the outside1 because it is first heated4 ,why do all fruits and vegetables become soft when cooked8 ,because the heat expands the air in them1 and thus breaks up their cells1 so that they become soft4 ,why does wood make a snapping noise when burning8 ,because the air in the cells of the wood bursts them apart1 thus making the noise4 ,why are sparks of fire thrown out8 ,because the heated air bursts the cells with such force as to throw off small pieces of the burning wood4 ,what kinds of wood snap the most8 ,the coarse-grained kinds1 like chestnut2 while the finer-grained kinds1 like walnut1 seldom snap much4 ,why does dry wood snap more than green wood8 ,because the sap in the pores of the green wood dries up as the wood becomes dry1 and its place is filled with air1 so that there is more air in dry wood than in green wood4 ,why does smoke rise in a chimney8 ,because the air in the chimney is heated by the fire1 and as the air rises1 it carries the smoke with it4 ,why does a chimney smoke when the fire is first kindled8 ,because the cold walls of the chimney cool the heated air so rapidly as to prevent its rising to the top1 and the smoke then sinks back into the room4 ,how are houses heated with hot air8 ,by having the fires made in the cellar1 so that the air when heated1 may ascend through pipes to the different parts of the building4 ,is there any substance that does not contract by cold8 ,yes2 water1 when near freezing1 does not contract by cold4 ,what takes place with the water8 ,when it is reduced nearly to the freezing point1 it begins to expand1 and when it freezes1 it expands still more4 ,how much does water expand by freezing8 ,it expands about one-seventh of its bulk4 ,that is1 seven gallons of water will make eight gallons of ice4 ,does freezing water expand with much force8 ,yes2 it expands with great force4 ,why are vessels containing water often broken during a cold night8 ,as the water in them freezes1 it expands and breaks the vessels4 ,why do lead pipes and iron pipes often burst during the winter8 ,because the water in them is permitted to freeze1 and as there is not room for it to expand1 the pipes are burst4 ,is ice heavier or lighter than water8 ,ice is lighter than the same bulk of water4 ,how much lighter is ice than water8 ,eight gallons of ice weigh no more than seven gallons of water4 ,does the ice protect the water beneath it from freezing8 ,ice does protect the water from freezing1 to a very great extent4 ,if ice were heavier than water1 what would result8 ,the ice would sink as rapidly as formed1 and our streams would1 every winter1 freeze to the bottom1 thus destroying the fish and other creatures living in them4 ,in this1 as in many other ways1 we may learn the lesson1 that in the creation of the world1 ,god wisely made all things to serve some useful purpose4 ,conduction of ,heat4 ,why does iron feel cold to the touch on a cold morning8 ,because heat goes from the hand to the iron1 thus giving the sensation of cold4 ,what is the passage of heat from the hand to the iron called8 ,it is called conduction4 ,when one end of a rod of iron is placed in a fire1 does the whole rod become heated8 ,the whole rod does become heated4 ,how does this take place8 ,the heat of the fire passes from one particle to another throughout the rod4 ,what is this called8 ,it is called conduction4 ,what then is conduction of heat8 ,it is the passage of heat from one body to another which it touches1 or from one particle of a body to another particle of the same body4 ,what bodies are good conductors of heat8 ,such bodies as gold1 platinum1 copper1 silver1 iron1 zinc1 tin1 and lead1 in the order named1 are the best conductors of heat4 ,what bodies are poor conductors of heat8 ,such bodies as glass1 wood1 charcoal1 wool1 hair1 and fur4 ,fur is the poorest conductor of heat known4 ,why does a piece of wood blazing at one end not feel hot at the other end8 ,because wood is a poor conductor1 and the heat goes slowly through it4 ,why does a piece of iron feel cold in winter8 ,because the iron is a good conductor1 and carries the heat away from our hands very rapidly4 ,why does fur feel warmer than iron in the winter8 ,because the fur is a poor conductor1 and carries the heat away from our hands very slowly4 ,why does a wooden pump-handle seem less cold than one of iron8 ,because wood is not so good a conductor as iron2 hence1 it does not carry the heat of our hands away so rapidly4 ,why does carpet seem warmer than the bare floor8 ,because the carpet is a poorer conductor than the wood of the floor1 and does not carry away the heat of our bodies so rapidly4 ,why does a stone pavement make our feet cold in winter8 ,because the stone is a good conductor1 and rapidly carries the heat away from our feet4 ,why does heated iron feel hot to us8 ,because the iron is a good conductor1 and gives off its heat rapidly to our bodies4 ,why does a piece of cloth1 when heated1 not feel hot8 ,because the cloth is a poor conductor1 and gives off its heat very slowly4 ,why will a block of wood1 when heated1 remain hot longer than a heated brick8 ,because wood is a poorer conductor than brick1 and does not give off its heat so rapidly4 ,why is a block of wood better than iron or brick1 to keep our feet warm while on a journey8 ,because it does not give off its heat so rapidly1 and therefore remains warm longer than iron or brick4 ,why should the wood or brick be wrapped in cloth8 ,because the cloth1 being a poor conductor1 helps to keep the heat from passing off so rapidly4 ,why does iron feel colder than water when both are at the same temperature8 ,because iron is a better conductor than water1 and carries away the heat from our hands more rapidly4 ,are liquids good conductors of heat8 ,no2 liquids are poor conductors of heat4 ,is air a good conductor of heat8 ,no2 air is a poor conductor of heat4 ,are gases as good conductors as liquids8 ,no2 gases are poorer conductors than liquids4 ,why is water a better conductor than air8 ,because the particles of water are closer together than the particles of air4 ,why is iron a better conductor than water8 ,because the particles of iron are closer together than the particles of water4 ,how do we know that water is a poor conductor of heat8 ,because water may be made to boil at its surface without melting ice a short distance below the surface4 ,how do we know that air is a poor conductor of heat8 ,because the air at the ceiling of a room may be made very warm without melting ice near the floor4 ,why does a linen shirt feel cool8 ,because linen is a good conductor1 and there is but little air among its fibres4 ,why is a cotton shirt warmer than one made of linen8 ,because the cotton contains more air among its fibres1 and air is a poor conductor of heat4 ,why is a woollen shirt warmer than one made of cotton8 ,because wool contains more air among its fibres1 and is1 therefore1 a poorer conductor of heat4 ,why is fur warmer than wool8 ,because there is more air among the hairs of the fur1 and it is1 therefore1 a poorer conductor of heat4 ,what fur is the warmest8 ,fur with very fine hairs1 like that of the rabbit1 because it contains the most air4 ,why is fur warmer when the hair is next to our bodies8 ,because the fur and the air in it both help to keep the heat of our bodies from passing off rapidly4 ,is the earth a good conductor of heat8 ,no2 the earth is a poor conductor of heat4 ,how do we know that the earth is a poor conductor of heat8 ,because the heat of summer warms the earth only a few inches below the surface4 ,how is it with the earth in winter8 ,in this latitude1 the frost of winter reaches only a few inches below the surface of the earth4 ,in all parts of the earth1 except in the ,frigid ,zones1 the heat of the summer takes away the frost and ice of the winter1 and the earth is warmed so that plants may grow4 ,why is spring-water generally cool1 even in summer8 ,because the springs are mostly so far below the surface of the earth1 that they are not warmed by the sun's rays4 ,why is snow a warm covering for the earth8 ,because the air among the particles of snow prevents the heat of the earth from passing off rapidly4 ,why does wrapping straw around a pump in winter1 prevent the water in it from freezing8 ,because the stalks of straw are hollow1 and the air in the stalks makes them poor conductors of heat4 ,will straw1 wrapped around shrubbery1 prevent it from freezing8 ,it will2 because it keeps the heat of the shrubbery from passing off into the air4 ,why are rooms warmer from having double windows8 ,because the air which is confined between the double windows1 being a poor conductor1 keeps the warmth of the room from escaping4 ,why is the space between the double walls of ice-coolers filled with charcoal8 ,because charcoal is a poor conductor1 and keeps the heat of the air from the ice4 ,why do ice-houses have double walls1 with saw-dust or straw between them8 ,because the saw-dust and the straw are both poor conductors1 and keep the heat of the air from the ice4 ,why does ice melt more slowly when wrapped in flannel8 ,because the flannel is a poor conductor1 and keeps the heat of the air from the ice4 ,why are woollen holders used about the stove8 ,because wool is a poor conductor1 and thus keeps the heat of the iron from burning the hand4 ,convection of ,heat4 ,when air near the floor of a room is heated1 what becomes of it8 ,it ascends to the ceiling of the room4 ,what is done with the cold air at the ceiling8 ,it descends to the floor1 to take the place of the warm air4 ,when the air ascends to the ceiling1 does it carry the heat with it8 ,yes2 it carries the heat with it4 ,what is this mode of carrying heat called8 ,it is called ,convection4 ,what is needed so as to heat a substance by convection8 ,its particles must be able to move about freely4 ,why is the air easily heated by convection8 ,because the particles of the air move about freely4 ,why is a liquid easily heated by convection8 ,because its particles move about freely4 ,why cannot a solid be heated by convection8 ,because its particles cannot move4 ,when water near the bottom of a vessel is heated1 what becomes of it8 ,it rises to the surface4 ,what becomes of the cold water at the surface8 ,it falls to the bottom of the vessel1 to take the place of the warm water4 ,how long will this circulation continue8 ,it will continue so long as heat is applied to the bottom of the vessel4 ,when heat is applied to the surface of the water1 what is the result8 ,the water near the surface only is heated4 ,why does it not heat all the water in the vessel8 ,because the water when heated1 becomes lighter1 and stays at the surface1 while the cold water is heavier and remains at the bottom of the vessel4 ,where must heat be applied to warm a liquid or a gas8 ,it must be applied to the bottom of the vessel containing the liquid or the gas4 ,where must a fire be1 so as to warm a room8 ,the fire must be near the floor of the room4 ,why does a hot substance cool quickly in the air8 ,because the air touching a substance ascends as soon as heated1 and cold air takes its place2 as this process goes on rapidly1 the substance is quickly cooled4 ,how is water cooled by convection8 ,the water at the surface is cooled by giving off its heat to the air2 it then falls to the bottom1 and the warm water rises to take its place at the surface4 ,why does stirring hot coffee cool it quickly8 ,because the hot coffee at the bottom of the vessel1 is brought more rapidly in contact with the air1 and1 therefore1 gives off its heat more rapidly4 ,why does blowing hot coffee cool it quickly8 ,because the hot air over the coffee is removed by blowing1 and the cold air is brought more rapidly in contact with the coffee4 ,liquefaction4 ,is ice a solid or a liquid8 ,ice is a solid4 ,when heat is applied to ice1 what becomes of the ice8 ,the ice is changed into water4 ,is water a liquid8 ,water is a liquid4 ,how then can a solid be changed to a liquid8 ,by applying heat to a solid1 it may be changed to a liquid4 ,what is meant by liquefaction8 ,liquefaction is the changing of a solid to a liquid1 by heat4 ,how may tallow be melted8 ,by heating the tallow1 it may be melted4 ,will the tallow become hard again when cold8 ,it will be hard again when cold4 ,can lead and other metals be melted8 ,they can be melted or changed to a liquid state by heat4 ,can all solids be changed to liquids8 ,no2 there are many solids1 such as wood1 coal1 paper1 and leather1 that cannot be changed to liquids4 ,how can a liquid be changed to a solid8 ,by taking heat away from the liquid1 it may be changed to a solid4 ,why is a solid melted by heat8 ,because heat forces the particles of the solid apart1 until it is changed to a liquid4 ,illustration3 ,decoration4 ,latent ,heat4 ,why does warm iron feel warm to the hand8 ,because it gives off some of its heat to the hand4 ,is the hand sensible of the heat coming from the iron8 ,the hand is sensible of the heat4 ,what then may this heat be called8 ,it may be called sensible heat1 because it can be felt4 ,how do we measure heat8 ,we measure heat by degrees4 ,how many degrees of heat in ice when at the melting point8 ,thirty-two degrees of heat1 as measured by the thermometer4 ,how can we change ice into water8 ,by applying heat to the ice it will be changed into water4 ,how many degrees of heat are necessary to change the ice into water8 ,one hundred and forty degrees of heat are necessary4 ,how many degrees of heat are in the water when the ice is all melted8 ,only thirty-two degrees of heat1 by the thermometer4 ,does the water feel any warmer than the ice to the hand8 ,no2 the water does not feel any warmer than the ice4 ,what has become of the one hundred and forty degrees of heat8 ,they have been hidden in the water4 ,what is this hidden heat called8 ,it is called latent heat4 ,what is latent heat8 ,it is heat that is not sensible to the touch1 or to the thermometer4 ,when water is made to boil1 what change takes place8 ,the water is changed into steam4 ,how many degrees of heat are necessary to change water into steam8 ,more than nine hundred degrees of heat are necessary4 ,how many degrees of latent heat in steam8 ,more than nine hundred degrees of latent heat4 ,when steam is changed back again to water1 what becomes of the latent heat8 ,it passes off to the air and the surrounding objects1 and makes them warmer4 ,when water is changed into ice1 what becomes of the latent heat8 ,it passes off to the surrounding objects and makes them warmer4 ,is freezing a warming process8 ,yes2 because the water gives off its latent heat while freezing2 hence1 the surrounding objects are made warmer4 ,is thawing a cooling process8 ,yes2 because the ice absorbs so much heat while thawing that it cools the surrounding objects4 ,where does the ice obtain its heat1 while thawing8 ,the ice obtains its heat from the surrounding objects4 ,are these objects made cooler by the melting of the ice8 ,they are made cooler by the melting of the ice4 ,what effect does salt have upon ice8 ,salt makes the ice melt more rapidly4 ,when salt and ice are placed around a vessel of cream1 what takes place8 ,the salt causes the ice to melt quickly1 and the ice in melting takes so much heat from the cream as to freeze it1 thus making it ice-cream4 ,ebullition4 ,what is meant by ebullition8 ,ebullition means boiling4 ,when is a liquid in a state of ebullition8 ,when it has been heated so as to boil4 ,can solids be made to boil8 ,no2 liquids only can be made to boil4 ,what change takes place when a liquid boils8 ,the liquid is changed into a vapor or gas4 ,what becomes of water when it is boiled8 ,water when boiled passes off into steam4 ,what is necessary to make water boil8 ,heat is necessary to boil water or any other liquid4 ,how much heat is contained in boiling water8 ,two hundred and twelve degrees of heat4 ,when water passes into steam1 how much is its bulk increased8 ,about seventeen hundred times4 ,how much steam will a pint of water make8 ,a pint of water will make about seventeen hundred pints of steam4 ,what do bubbles of boiling water contain8 ,they contain steam4 ,why are these bubbles formed8 ,because the water at the bottom of the vessel is heated and changed into steam1 which expands and forms the bubbles4 ,why do these bubbles rise to the surface8 ,because steam is lighter than water4 ,when does water simmer8 ,when water is heated1 the steam at first forms in very small bubbles at the bottom of the vessel1 and as these bubbles rise through the colder water1 the steam in them is condensed to water1 so that they break before reaching the surface1 thus producing what is called 8simmering40 ,when does water boil8 ,water boils when it becomes heated so that the bubbles rise to the surface of the water before breaking4 ,why will a vessel full of water run over when heated8 ,because the water is expanded by heat1 and some of it must run over4 ,why will the water boil over when the vessel is not full8 ,because the steam1 in trying to escape1 throws some of the water over the edge of the vessel4 ,vaporization4 ,when water is boiled1 what change does it undergo8 ,it is changed into a vapor1 called steam4 ,what is this process called8 ,it is called ,vaporization4 ,what is meant by vaporization8 ,vaporization is the changing of a liquid into a vapor1 by boiling4 ,what is necessary to change a liquid into a vapor8 ,heat is necessary to change a liquid into a vapor4 ,at what temperature is water changed into steam8 ,at the temperature of two hundred and twelve degrees4 ,are all liquids changed to vapor at the same temperature8 ,no2 they vary very much in the amount of heat required4 ,ether boils at #if degrees1 alcohol at #agf degrees1 and quicksilver at a temperature of #ffb degrees4 ,when water is changed into steam1 what becomes of the steam8 ,the steam passes off into the air4 ,what does the air do with the steam8 ,the air condenses or changes it into very small particles of water1 so that it is seen like a fog or a cloud4 ,can steam be seen8 ,no2 steam is like the air in this respect1 and cannot be seen4 ,how can we prove this8 ,when water is boiled in a glass vessel1 no steam is visible1 although it is there4 ,cannot we see the steam coming from the spout of a tea-kettle8 ,no2 we do not see anything for half an inch or more from the spout4 ,why does it become visible farther away8 ,because the air condenses it1 and then we see it in its cloud-like state4 ,how much steam will one gallon of water make8 ,one gallon of water will make seventeen hundred gallons of steam4 ,when this steam is confined in a vessel1 what does it try to do8 ,it tries to expand or spread out in every direction4 ,does it expand with much force8 ,yes2 it expands with so much force as frequently to burst the vessel containing it4 ,why is the lid of the tea-kettle lifted up when the water boils8 ,because the steam expands and raises the lid1 so that it can escape4 ,if the lid were fastened down1 what would result8 ,the steam1 in trying to escape1 would burst the tea-kettle4 ,why does water run out of the spout of the tea-kettle8 ,because the steam in the tea-kettle presses on the water with force enough to cause it to run out4 ,why does steam burst vessels in which it is confined8 ,because the vessels are not strong enough to keep the steam from expanding4 ,how is the boiler of a steam-engine kept from bursting8 ,by means of a safety-valve4 ,what is a safety-valve8 ,it is a valve or opening through which steam may escape4 ,what prevents all of the steam from escaping through the valve8 ,the valve is kept closed by a weight1 which prevents the escape of the steam until a certain quantity of it is formed in the boiler2 it then lifts up the valve1 and a portion of it escapes1 the same as it does with the lid of the tea-kettle4 ,evaporation4 ,does a wet blanket1 when hung in the air1 remain wet8 ,no2 it soon becomes dry4 ,what becomes of the water in the blanket8 ,the water passes off into the air4 ,what is this process called8 ,it is called ,evaporation4 ,what is meant by evaporation8 ,it is the gradual change of a liquid into a vapor4 ,when water is left in a shallow vessel1 what becomes of it8 ,the water evaporates or passes off into the air4 ,do liquids generally evaporate8 ,yes2 when exposed to the air1 nearly all liquids evaporate4 ,does water change into steam when it evaporates8 ,water does not change into steam when it evaporates4 ,how1 then1 does water evaporate8 ,it passes off into the air in particles or drops so very small as not to be visible4 ,is evaporation always going on around us8 ,yes2 wherever there is water exposed to the air1 evaporation is taking place4 ,where does the most evaporation take place8 ,from the surface of the rivers1 the lakes1 and the ocean4 ,what becomes of the water when evaporated8 ,it is formed into fogs and clouds4 ,in what kind of air does evaporation go on most rapidly8 ,in air that is warm and dry4 ,does evaporation take place in cool air8 ,it does2 because clothing will dry during the coldest weather of winter4 ,why does water evaporate more in warm air than in cold air8 ,because the warm air can hold more of the fine particles of water1 and1 therefore1 can absorb more4 ,why does water evaporate more slowly in damp weather than in dry weather8 ,because the damp air contains so much moisture that but little more can pass off into it4 ,what example have we of this8 ,wet clothes dry much more slowly when the air is damp than when it is dry4 ,why do clothes dry more rapidly in windy weather8 ,because the damp air in contact with them is blown away1 and the dry air is constantly taking its place4 ,is heat necessary in evaporation8 ,heat is necessary to produce evaporation4 ,why do our hands feel cold when wet8 ,because the water on our hands evaporates1 and thus heat is taken from them4 ,why is the air cooler after a rain8 ,because evaporation then takes place from every wet object1 and this absorbs heat from the air4 ,why does watering streets and roads cool the air8 ,because the water evaporates and absorbs heat from the air1 making it cooler4 ,why do we feel cold when our clothes are wet8 ,because the moisture in them evaporates and absorbs heat from our bodies4 ,why is wet land always cold8 ,because so much heat is absorbed from the land in the evaporation which is constantly taking place4 ,what becomes of the dew that collects on plants and other objects at night8 ,it is evaporated4 ,how does the sun hasten the evaporation of the dew8 ,by supplying the heat needed to change the dew into a vapor1 the sun hastens its evaporation4 ,why do bread and biscuit become hard when kept a few days8 ,because the moisture in them passes off into the air1 and thus they become dry and hard4 ,how can they be kept moist and soft for a longer time8 ,by keeping them in a covered vessel1 so that evaporation will take place more slowly1 they may be kept moist for a longer time4 ,radiation4 ,when we stand near the fire1 why do we feel warm8 ,because the fire gives off heat which makes us feel warm4 ,how does the fire give off heat8 ,it gives off heat in straight lines1 and in every direction4 ,what is this giving off of heat called8 ,it is called ,radiation of heat4 ,does the sun radiate heat8 ,the sun does radiate or give off both heat and light4 ,how do heat and light from the sun come to us8 ,they come together in the sunbeam4 ,does heat travel as rapidly as light8 ,yes2 heat and light travel together at the rate of #bjj1jjj miles in a second of time4 ,do all substances radiate heat equally well8 ,no2 some substances are much better radiators than others4 ,what kind of objects are the best radiators8 ,those with rough and dark surfaces4 ,what kind of objects are the poorest radiators8 ,those with smooth and bright surfaces4 ,why does water keep hot a long time in a bright tin vessel8 ,because the tin is a poor radiator1 and prevents the heat of the water from passing off into the air4 ,why does water soon cool in a dull earthen vessel8 ,because the earthen vessel is a good radiator1 and gives off the heat of the water rapidly4 ,if the bright tin vessel be painted1 will the water keep hot so long8 ,no2 the tin becomes a good radiator when painted1 and the water is soon cooled4 ,why does a stove cool so quickly8 ,because the iron is a good radiator1 and gives off its heat rapidly4 ,do the rays from the sun give off much heat while passing through the air8 ,the rays from the sun give off about one-fourth of their heat while passing through the air4 ,what becomes of the remaining heat from the sun8 ,it is absorbed or reflected at the earth's surface4 ,what does the earth do with the heat8 ,the earth radiates the heat1 and thus warms the air4 ,reflection4 ,when a piece of bright tin is held near the fire1 does the tin become hot8 ,no2 the tin is scarcely warmed4 ,what does the tin do with the rays of heat from the fire8 ,the tin throws them back from its surface4 ,what is this called8 ,it is called ,reflection of heat4 ,do all substances reflect heat equally well8 ,no2 some reflect much more heat than others4 ,what kind of objects reflect heat the best8 ,those with bright and smooth surfaces4 ,what kind of objects reflect heat the least8 ,those with rough and dark surfaces4 ,does bright tin reflect heat better than glass8 ,yes2 bright tin reflects about eight times as much heat as glass does4 ,why does it take so long to heat water in a new tin cup8 ,because the bright tin is a good reflector1 and throws off the greater part of the rays of heat that come to it from the fire4 ,why does a piece of tin or other bright metal1 placed under a stove1 protect the carpet from burning8 ,because the tin being a good reflector1 remains cool1 and cannot burn the carpet under it4 ,why will not a piece of iron protect the carpet from burning8 ,because the iron1 being a poor reflector1 soon becomes heated1 so as to burn the carpet under it4 ,absorption4 ,when a piece of iron is held near a fire1 does the iron become hot8 ,yes2 the iron soon becomes hot4 ,how is the iron heated8 ,the iron absorbs or takes in the heat from the fire4 ,what is this power to take in the heat called8 ,it is called ,absorption of heat4 ,what is this process like8 ,it is somewhat like a sponge1 that absorbs or sucks up moisture4 ,do all substances absorb heat equally well8 ,no2 some substances absorb more heat than others4 ,what kind of objects absorb heat the best8 ,those with rough surfaces absorb heat the best4 ,what kind of objects absorb heat the least8 ,those with bright and smooth surfaces4 ,what colored objects absorb heat the best8 ,objects of a dark or black color4 ,do objects that absorb heat well1 radiate well8 ,yes2 good absorbers are good radiators4 ,why is this8 ,because every substance must absorb heat before it can have heat to give off4 ,do objects that absorb heat well1 reflect it well8 ,no2 objects that absorb heat well1 cannot reflect it well4 ,why is this8 ,because a ray of heat cannot be reflected from an object1 and be absorbed by that object1 both at the same time4 ,why is water rapidly heated in a tea-kettle8 ,because the rough1 dark iron of the tea-kettle absorbs the heat from the fire1 and gives it off rapidly to the water contained in the kettle4 ,the iron is also a good conductor of heat2 therefore1 the heat from the fire passes rapidly through it to the water4 ,why does black cloth1 when spread on the snow1 cause the snow to melt more rapidly8 ,because the cloth absorbs heat from the rays of the sun1 and1 therefore1 melts the snow beneath it4 ,why does not white muslin1 when spread on the snow1 hasten its melting8 ,because the white muslin reflects the heat from the rays of the sun1 so that but little of it enters the snow4 ,does the snow receive much heat from the sun8 ,snow is a good reflector1 and throws back most of the heat from the sun4 ,what causes the snow to melt8 ,the heat it receives from touching the earth1 causes the most of it to melt4 ,why does snow melt first on dark earth8 ,because dark earth is a good radiator1 and gives off much heat to the snow4 ,why does snow remain longest on light-colored earth8 ,because the light-colored earth is a poor radiator1 and gives off but little heat to the snow4 ,why does the air feel cold in winter time8 ,because it is so much cooler than our bodies that it absorbs heat from them rapidly1 and thus makes them feel cold4 ,why does the air feel warm in summer time8 ,because it is then nearly as warm as our bodies1 and1 therefore1 absorbs heat from them slowly4 ,why are greasy shoes warmer than those polished with blacking8 ,because the greasy shoes absorb heat from the sun1 but the polished shoes throw off the heat of the sun by reflection4 ,what may we remember about heat8 ,and ,god said1 ,let there be light2 and there was light4 ,but along with the light1 came its companion--heat2 for when the sunbeam first came forth at ,his command1 the twin sisters1 light and heat1 together touched the earth1 causing it to bloom with life and beauty4 ,and the earth brought forth grass1 the herb yielded its seed1 and the tree its fruit3 ,and ,god saw that it was all good4 ,illustration3 ,an outdoor walk4 ,illustration3 ,decoration4 ,,chapter ,,iv4 ,the ,air4 ,illustration3 ,illustrated ,capital ,w ,where do we find air8 ,we find air everywhere around the earth4 ,does the air fill every place8 ,the air fills every place not filled by some other substance4 ,when we say a bottle is empty1 what do we mean8 ,we mean that it does not contain anything but air4 ,what do all vessels contain when empty8 ,all vessels contain air when seemingly empty4 ,do all liquids contain air8 ,yes2 all liquids contain air4 ,where is the air in a liquid8 ,the air is among the particles which compose the liquid4 ,is there air in water8 ,yes2 there is air in water4 ,of what use is the air in the water8 ,it is used by the fish and other creatures that live in the water4 ,how do the fish and other creatures use it8 ,they breathe it into their lungs1 and it supports life in them1 the same as the air which we breathe supports life in us4 ,do solids contain air8 ,yes2 solids contain more or less air4 ,where is the air in fur and in wool8 ,it is among the hairs of the fur and the wool4 ,where is the air in cotton and linen goods8 ,it is among the fibres of the cotton and the linen4 ,where is the air in fruit8 ,it is among the particles composing the fruit4 ,where is the air in wood8 ,it is in the pores or small spaces in the wood4 ,is there air in the earth8 ,yes2 there is air among the particles of the earth4 ,how deep in the earth does the air extend8 ,we cannot tell2 but both air and water have been found several hundred feet below the earth's surface4 ,of what use is the air in the earth8 ,it is breathed by the worms and other creatures that live in the earth4 ,when part of the air is taken from a room1 what becomes of the air left in the room8 ,it expands so as to fill the whole room4 ,are the particles of air so close together after it expands as they were before8 ,they are not so close together4 ,when air is thus expanded1 what is said of it8 ,it is said to be rare4 ,when pressure is put upon air in a vessel1 what becomes of the air8 ,it is forced or pressed into a smaller space1 and1 therefore1 occupies less room4 ,when pressure is put upon air1 are its particles closer together8 ,they are closer together4 ,when air is thus compressed1 what is said of it8 ,it is said to be dense4 ,can air be much condensed by pressure8 ,it has been condensed so much that #ajj cubic feet of air was reduced to the bulk of only one cubic foot4 ,what makes the air so dense as it is at the surface of the earth8 ,the pressure of the air above the surface4 ,does the air then become less dense the higher we ascend8 ,yes2 because there is less air above to press upon it4 ,does the air become more dense the deeper we go in the earth8 ,it does2 because there is more air above to press upon it4 ,how can we understand this8 ,in a large heap of wool1 the hairs of the wool at the bottom of the heap are pressed closely together1 but they are farther and farther apart the nearer they are to the top of the heap4 ,how high does the air extend above the earth8 ,it is supposed to extend to the height of fifty miles4 ,do these fifty miles of air press upon the earth8 ,they do press upon the earth4 ,with how much force does the air press on the earth8 ,with a force of fifteen pounds on every square inch of surface4 ,then has the air weight8 ,the air has weight4 ,why do we not feel the weight of the air8 ,because it presses with equal force1 in every direction2 up1 down1 and on every side4 ,how can we show that the air presses upwards8 ,fill a tumbler with water and put a piece of writing-paper over the top4 ,hold the hand on the paper and quickly invert the tumbler1 or turn it bottom upwards2 then remove the hand1 and the pressure of the air against the paper will keep the water in the tumbler4 ,this is represented in ,fig4 #ab4 ,illustration3 ,fig4 #ab4 ,if a tumbler be filled with water in a bucket1 and then raised bottom upwards until its edge is just below the surface of the water1 it will remain full of water2 why is this8 ,the pressure of the air on the water in the bucket1 keeps the water in the tumbler4 ,if we use an iron pipe or a lead pipe1 instead of a tumbler1 will the pressure of the air keep the water in the pipe8 ,it will1 the same as it keeps it in the tumbler4 ,how high will the air keep the water in the pipe8 ,it will keep the water to the height of thirty-four feet4 ,why does the air keep the water up thirty-four feet8 ,because the air presses down with a force of fifteen pounds on every square inch of surface1 and a column of water thirty-four feet high presses down with a force of fifteen pounds on every square inch of surface4 ,does the weight of the air exactly balance the weight of the column of water8 ,it does2 they balance each other4 ,is water heavier than air8 ,water is heavier than air2 because a column of water thirty-four feet high weighs as much as a column of air fifty miles high4 ,is quicksilver heavier than water8 ,yes2 quicksilver is about thirteen times heavier than water4 ,how high a column of quicksilver can the air keep up8 ,the air can keep up a column of quicksilver only thirty inches high4 ,why is this8 ,because a column of quicksilver thirty inches high1 weighs exactly the same as a column of air fifty miles high1 or a column of water thirty-four feet high4 ,how can this be shown8 ,take a glass tube about thirty-three inches long1 cork up one end1 and fill the tube with quicksilver2 then put the open end of the tube beneath the surface of some quicksilver1 in a basin1 and the quicksilver in the tube will fall to the height of thirty inches1 as is shown in ,fig4 #ac4 ,illustration3 ,fig4 #ac4 ,if the cork be removed from the glass tube1 what will become of the quicksilver8 ,it will immediately sink into the basin below4 ,why will the quicksilver sink into the basin8 ,because the air will then press upon the quicksilver in the tube1 the same as it does on that in the basin2 hence1 all the quicksilver will fall to the same level4 ,does the weight of the air vary at different times8 ,yes2 the air does vary in weight at different times4 ,how can we tell when the air changes in weight8 ,by means of a ,barometer4 ,what is a barometer8 ,it is an instrument having a tube filled with quicksilver4 ,when the air is heavier1 how does it affect the quicksilver8 ,the quicksilver rises in the tube4 ,when the air is lighter1 how does it affect the quicksilver8 ,the quicksilver sinks in the tube4 ,what is the use of the barometer8 ,it shows the changes about to take place in the weather4 ,when the quicksilver rises1 what kind of weather is indicated8 ,it indicates fair weather4 ,when the quicksilver sinks1 what kind of weather is indicated8 ,it indicates cloudy or stormy weather4 ,where is the barometer most useful8 ,it is most useful at sea1 to warn the sailors of coming storms4 ,what use is it to farmers8 ,they can use it as a guide when planting and gathering their crops1 and thus be better prepared for stormy weather4 ,for what else may the barometer be used8 ,it may be used to tell the height or depth of any place4 ,does the air become lighter as we ascend8 ,the air does become lighter as we ascend4 ,how does this affect the barometer8 ,as the air becomes lighter1 the quicksilver in the barometer sinks lower4 ,at what height does the quicksilver stand at the level of the sea8 ,it stands at the height of thirty inches4 ,when we ascend a mountain #aj1jjj feet high1 how much does the quicksilver sink8 ,it sinks ten inches1 and1 therefore1 stands at the height of only twenty inches4 ,does the same thing take place when we ascend in a balloon8 ,yes2 the higher the balloon ascends1 the lower the quicksilver in the barometer sinks4 ,when we descend into the mines dug in the earth1 does the air become heavier8 ,it does2 and the quicksilver in the barometer rises4 ,at what temperature does water boil8 ,water boils at a temperature of two hundred and twelve degrees4 ,when the weight of the air is taken off1 will the water boil at a lower temperature8 ,water will then boil at a lower temperature4 ,where will water boil at the lowest temperature1 on a mountain1 or in a valley8 ,it will boil at the lowest temperature on a mountain4 ,at how much lower temperature will water boil1 as we ascend8 ,water will boil at one degree less for every five hundred feet we ascend4 ,how high is the city of ,quito1 in ,south ,america8 ,quito is nine thousand feet above the level of the sea4 ,at what temperature does water boil there8 ,water boils1 in ,quito1 at a temperature of one hundred and ninety-four degrees4 ,will an egg boil hard at ,quito8 ,no2 because the water passes off into steam at one hundred and ninety-four degrees1 and it requires more than one hundred and ninety-four degrees of heat to boil an egg hard4 ,do persons1 while ascending mountains1 often have difficulty in cooking their food8 ,they do1 on account of water boiling there at a temperature below two hundred and twelve degrees4 ,what is a vacuum8 ,a vacuum is a place that does not contain anything1 not even air4 ,when a vessel contains water and we pour the water out1 does that produce a vacuum8 ,no2 because air passes in and fills the vessel4 ,how then can a vacuum be produced8 ,a vacuum in any place1 can be produced only by drawing the air out of it4 ,when a vacuum is produced1 what does the surrounding air try to do8 ,it tries to get in so as to fill the vacuum4 ,with what force does the air try to fill a vacuum8 ,with a force of fifteen pounds on every square inch of surface4 ,when a vacuum is produced in contact with a liquid1 what does the liquid do8 ,the liquid tries to pass in to fill the vacuum4 ,can there be a vacuum in contact with a gas or a liquid8 ,no2 because the gas or the liquid will instantly fill the vacant space4 ,why does water make a gurgling noise when poured out of a bottle8 ,because air is passing into the bottle at the same time that the water is coming out1 and the air makes the noise in passing through the water4 ,why does water make a gurgling noise when running out of a barrel8 ,because the air passes into the barrel at the opening where the water passes out1 and thus the noise is made4 ,how can the gurgling noise be prevented8 ,by making an opening at the top of the barrel1 so as to admit the air4 ,does water flow freely from a vessel that has but one opening8 ,no2 because part of this opening is needed to admit air into the vessel4 ,why does the water flow freely1 when there is an opening at the top as well as at the bottom of the vessel8 ,because air is admitted at the top1 and there is then nothing to obstruct the flow of water from the opening at the bottom4 ,what causes fruit1 vegetables1 and meat to spoil8 ,the air causes them to spoil4 ,how do we know this8 ,because when kept from the air they remain good for a long time4 ,what is this process of keeping fruit called8 ,it is called canning4 ,how is fruit canned8 ,the fruit is put into a glass jar1 or into a tin can1 along with some water1 and then heated until the jar or can is filled with steam and the air is all forced out2 it is then sealed so as to be air-tight1 and1 in this condition1 may be kept for many months4 ,what becomes of the steam in the jar or can8 ,as the fruit cools1 the steam is condensed to water1 and a vacuum is produced1 so that the fruit is kept from the air4 ,what is the plaything which boys call a sucker8 ,a sucker is a round piece of leather1 with a string fastened to its centre4 ,how is the sucker used8 ,the leather is made very soft and wet1 so that when pressed against a stone or brick1 all the air under the leather is forced out2 and when the leather is lifted up1 the stone or brick is lifted with it1 as is represented by ,fig4 #ad4 ,illustration3 ,fig4 #ad4 ,what keeps the leather against the stone8 ,the pressure of the air upon the leather keeps it against the stone4 ,with how much force does the air press the leather against the stone8 ,with a force of fifteen pounds on every square inch4 ,when there is air between the stone and the leather1 can the stone be lifted with the sucker8 ,it cannot2 because the air under the leather will press it up as much as the air above will press it down4 ,how does a fly walk upon the ceiling8 ,the fly's feet are much like the sucker1 and are kept against the ceiling by the pressure of the air4 ,how do snails cling to objects8 ,they force out all the air between the object and their bodies1 and are then held against the object1 as the sucker is held against the stone4 ,what is a siphon8 ,a siphon is a bent tube1 having one branch longer than the other1 as is represented in ,fig4 #ae4 ,illustration3 ,fig4 #ae4 ,for what is the siphon used8 ,the siphon is used to draw liquids from one vessel into another4 ,how can water be drawn from a vessel by means of a siphon8 ,put the short branch in the water1 then1 by means of the mouth applied to the long branch1 suck the air from it1 and the water will begin immediately to flow from the long branch4 ,where must the open end of the short branch be kept8 ,it must be kept beneath the surface of the water1 so as to prevent air from entering the tube4 ,where must the open end of the long branch be kept8 ,it must be kept lower than the open end of the short branch4 ,while the water is running out of the long branch1 what is produced at the bend of the tube8 ,the tendency is to produce a vacuum at the bend of the tube4 ,what is the result of this8 ,the water is continually forced up the short branch to fill this vacuum1 so that it runs out of the long branch in a steady stream4 ,how do boys often suck cider from a barrel8 ,by means of a straw4 ,how is this done8 ,one end of the straw is placed in the cider1 and the other end in the mouth2 then the air is sucked out of the straw1 and the cider is forced up to fill the vacuum4 ,when the cider is sucked out1 more cider is forced up1 so that the straw is kept full4 ,what makes the cider rise to fill the vacuum in the straw8 ,the pressure of the air on the cider in the barrel4 ,to what height will water rise in a tube to fill a vacuum8 ,the water will rise to the height of thirty-four feet4 ,to what useful purpose is this applied8 ,it is applied to making pumps4 ,of what material are pumps made8 ,either of wood1 or of metal1 such as lead or iron4 ,what is necessary in regard to the tube or pump-tree8 ,it must always be air-tight4 ,why must the tube or pump-tree be air-tight8 ,so that a vacuum may be produced in it4 ,how is this accomplished8 ,by means of two valves in the pump-tree4 ,what is a valve like8 ,a valve is like the lid on a tea-kettle1 or the cover on an inkstand2 and it is kept in its place by a hinge on one side4 ,where is one valve placed8 ,one valve is placed in the lower part of the pump-tube4 ,how near the water must this valve be8 ,it must be within thirty-four feet of the water4 ,why must the lower valve be within thirty-four feet of the water in the well8 ,because the air can force water up a tube only to the height of thirty-four feet4 ,does this valve move about in the pump-tube8 ,no2 it remains fixed in one place4 ,is this valve air-tight8 ,yes2 the lower valve or bucket in a pump must always be air-tight4 ,where is the upper valve8 ,it is fastened on the end of a rod1 which is attached to the pump-handle4 ,does this valve remain fixed in one place8 ,no2 it moves up and down when the pump-handle is moved4 ,is the upper valve air-tight8 ,no2 the upper valve is not air-tight4 ,illustration3 ,fig4 #af4 ,illustration3 ,fig4 #ag4 ,illustration3 ,fig4 #ah4 ,explain the working of a pump4 ,when the pump-handle is lowered1 the water1 above the valve or bucket attached to the end of the rod1 is raised so that it runs out at the spout2 and the vacuum1 thus produced by raising the water1 is filled by the water in the well1 which is forced up the pump-tube by the pressure of the air4 ,when the pump is at rest1 the lower valve1 which is air-tight1 prevents the water from sinking back into the well1 so that the pump-tube is always full of water1 whether we are pumping or not4 ,what does ,fig4 #af represent8 ,it represents a pump1 when it is not working4 ,how are the valves8 ,the valves are both closed4 ,what keeps the water above the lower valve8 ,the lower valve is air-tight1 and1 therefore1 water-tight1 so that it keeps the water above it4 ,what keeps the water in the tube below the lower valve8 ,the pressure of the air on the water in the well1 forces it up the tube to the lower valve4 ,what does ,fig4 #ag represent8 ,it represents a pump1 when the handle is being raised4 ,how is the lower valve8 ,the lower valve is closed4 ,why is the lower valve closed8 ,so as to prevent the water from being forced back again into the well4 ,how is the upper valve8 ,the upper valve is open4 ,why is the upper valve open8 ,so that the water may pass up through the valve1 while the valve is descending4 ,what does ,fig4 #ah represent8 ,it represents a pump when the handle is being lowered4 ,how is the upper valve8 ,the upper valve is closed4 ,why is the upper valve closed8 ,so as to lift up the water which is above it4 ,what becomes of the water which is lifted up8 ,it runs out of the spout of the pump4 ,as the upper valve is raised up1 what is produced under it8 ,a vacuum is produced under it4 ,how is this vacuum filled8 ,the water below the lower valve is forced up1 so as to fill the vacuum4 ,how is the lower valve8 ,the lower valve is open4 ,why is the lower valve open8 ,so that the water may pass through and fill the vacuum above the valve4 ,where are pumps mostly used8 ,pumps are mostly used by people in the country1 for the purpose of obtaining water from the wells which have been sunk in the earth4 ,when does smoke ascend through the air8 ,when smoke is lighter than the air1 it ascends through it4 ,when does smoke descend through the air8 ,when smoke is heavier than the air1 it descends through it4 ,why does a cork rise to the surface of the water8 ,because the cork is lighter than the same bulk of water2 hence1 it ascends to the surface4 ,why does heated air ascend8 ,because it is lighter than the cold air4 ,if a feather be put in the heated air1 will it be carried up with the air8 ,the feather will be carried up with the air4 ,if warm air be confined in a bag1 will it rise up and carry the bag with it8 ,it will rise up and carry the bag with it4 ,what might this bag be called8 ,it might be called a balloon4 ,what is a balloon8 ,it is a bag filled with gas1 and used for sailing in the air4 ,illustration3 ,fig4 #ai4 ,what is placed over this bag8 ,a network of ropes is placed over it1 and they are so arranged as to extend beneath the bag1 as is represented in ,fig4 #ai4 ,what is fastened to these ropes8 ,a car or basket is fastened to these ropes4 ,what is the car or basket for8 ,it is to carry up those who wish to ascend with the balloon4 ,how large are balloons usually made8 ,they are from twenty to thirty feet in diameter4 ,with what are balloons filled8 ,balloons are filled with a gas lighter than air4 ,what gas is often used for filling balloons8 ,the coal gas1 such as is used to light our cities at night4 ,what lighter kind of gas is sometimes used8 ,hydrogen gas is sometimes used4 ,is hydrogen gas much lighter than the air8 ,it is so much lighter than the air1 that fifteen cubic feet of hydrogen gas weigh no more than one cubic foot of air4 ,how much less will a balloon thirty feet in diameter weigh1 when filled with hydrogen gas1 than when filled with air8 ,it will weigh about ten thousand pounds less4 ,how much less1 when filled with coal gas than when filled with air8 ,about two thousand pounds less4 ,how much force then is necessary to hold the balloon filled with coal gas to the earth8 ,a force of two thousand pounds1 because the balloon is two thousand pounds lighter than the same bulk of air4 ,if a weight of only one thousand pounds were fastened to the balloon1 what would result8 ,the balloon would rise in the air and carry the weight of one thousand pounds with it4 ,how high will the balloon ascend8 ,it will ascend until the air displaced is of the same weight as the balloon4 ,what will then become of the balloon8 ,it will be carried about in the currents of air4 ,with what is the car attached to the balloon loaded8 ,it is usually loaded with bags of sand1 which serve as a weight to keep it from rising too high4 ,when those in the car wish to go higher1 what do they do8 ,they throw the sand out1 so as to lighten the car2 then it will rise higher4 ,when they wish to descend1 what do they do8 ,they open a valve at the top of the balloon1 which permits some of the gas to escape2 then it will sink towards the earth4 ,how is the valve at the top of the balloon opened and closed8 ,it is opened and closed by means of small ropes1 reaching from the valve to the car beneath4 ,can the balloon be made to go in any one direction8 ,no2 it is carried about by the currents of air1 and those in the car cannot control its course2 therefore1 it has never been of much use to man4 ,winds4 ,what is wind8 ,wind is air moving from one place to another4 ,does the air move in every direction8 ,it does move in every direction1 upward1 downward1 and to every side4 ,when the wind blows from the north towards the south1 what is it called8 ,it is called a north wind4 ,what is it called1 when it blows from other directions8 ,when it blows from the east1 it is called an east wind2 from the south1 a south wind2 and from the west1 a west wind4 ,what causes the air to move from place to place8 ,heat causes the air to move from place to place4 ,when air is heated1 what change takes place8 ,the heated air ascends1 and colder air moves in to fill its place2 thus causing the wind to blow4 ,what illustration have we of this8 ,when a candle is held in the open door of a heated room1 its flame is blown outwards if placed at the top of the door1 and inwards if placed at the bottom of the door2 thus showing two currents of air4 ,why is this8 ,the heated air escapes from the top of the room1 so as to ascend higher1 while the colder air comes in at the bottom1 to fill its place4 ,why does the wind blow towards a fire in the open air8 ,because the air near the fire becomes heated1 and ascends rapidly1 so that the air rushes in from every direction to fill its place4 ,what does the earth do with the heat it receives from the sun8 ,the earth gives off its heat to the air nearest to it4 ,what becomes of this heated air8 ,this heated air ascends1 and colder air comes to take its place2 thus producing winds4 ,are all parts of the earth heated alike by the sun8 ,no2 they are not all heated alike4 ,how does this unequal heating affect the air8 ,it causes currents in the air all over the world4 ,does water give off heat as rapidly as the earth does8 ,no2 water is a poorer radiator of heat than the earth is4 ,on which will the air be the cooler when the sun shines1 on the earth1 or on the water8 ,it will be cooler on the water than on the earth4 ,why does a sea-breeze feel cool in the daytime8 ,because the air over the water1 in the daytime1 is less heated than the air over the land2 hence1 the sea-breeze feels cool4 ,why does the earth become colder than the water at night8 ,because the earth gives off its heat more rapidly than the water1 and as it receives no heat from the sun at night1 it soon becomes colder than the water4 ,why does a land-breeze feel cool at night8 ,because the air over the land at night is less heated than the air over the water2 hence1 the land-breeze feels cool4 ,how rapidly does the wind move8 ,a gentle breeze goes four or five miles in an hour2 a high wind goes from twenty to fifty miles in an hour1 and a hurricane goes from sixty to one hundred miles in an hour4 ,of what use is the wind8 ,the wind carries away the impure air and injurious gases from cities and other places1 so that they are the more healthy2 it dries up the water on the surface of the earth1 and thus promotes vegetation2 it sweeps the clouds filled with moisture from the lakes and the oceans1 over every part of the world1 so that the water in them may fall in refreshing showers1 to fill the springs1 to purify the air1 and in many other ways to make the earth a fitting place of abode for man4 ,but these are only a few of the many blessings that an all-wise ,creator has given us2 and1 for them all1 we should ever remember to offer up to ,him the homage of a grateful heart4 ,illustration3 ,paddlewheel steamboat4 ,illustration3 ,decoration4 ,,chapter ,v4 ,water4 ,illustration3 ,illustrated ,capital ,w ,where do we find water8 ,we find water almost everywhere2 above the earth1 on the earth1 and beneath the earth's surface4 ,where do we find water above the earth8 ,we find it in the air1 in the form of vapor4 ,where do we find water on the earth8 ,we find it in springs1 in streams of water1 and in lakes and oceans4 ,where else is water on the earth8 ,it is in the sap of plants1 the juice of fruits1 and the blood of animals4 ,where do we find water beneath the earth's surface8 ,we find it in streams running in every direction4 ,has water any influence on climate8 ,yes2 water causes many changes in climate4 ,what changes does water produce in climate8 ,it makes spring and summer cooler1 and autumn and winter warmer4 ,how does water make the ,spring of the year cooler8 ,the ice and snow while melting1 take up a large amount of heat1 which passes into the water as latent heat4 ,where does the melting ice and snow obtain this heat8 ,they obtain it from the air1 and from objects near the surface of the earth4 ,what advantage is derived from this8 ,the tender buds and blossoms are kept back in the spring until the ice and the snow are melted1 and the earth becomes warmed1 so that they are seldom injured by the cold4 ,how does water make ,summer cooler8 ,by the streams1 lakes1 and oceans1 which absorb heat from the sun2 and1 as the water is a poor radiator1 but little of this heat is given off to the air4 ,what effect does this heat produce upon the water8 ,the temperature of the water is gradually increased by it during the hot weather of summer4 ,how is this useful8 ,it gives heat to the plants in the water1 so that they may grow2 and it rouses into active life1 the fish and other breathing things1 from the torpid state in which they are during winter4 ,does water store away a large amount of heat8 ,it does2 and thus the summer is made much cooler4 ,how does water make ,autumn warmer8 ,in the autumn the heat in the water is given off1 so that the air is kept warmer than it would otherwise be4 ,how does this affect autumn weather8 ,it makes that season of the year mild and pleasant4 ,what advantage is derived from this8 ,it gives the late fruits and seeds a chance to ripen2 and it affords time for the sap of plants to return to the roots1 and to become prepared for the frosts of winter4 ,how does water make ,winter warmer8 ,by being changed into ice and snow4 ,when water is changed into ice or snow1 what takes place8 ,the latent heat in the water is given off1 and thus the winter air is made warmer4 ,can water be compressed into a smaller bulk8 ,yes2 it can be compressed1 but not so much as air4 ,what is said of water that is compressed8 ,its particles are pressed closer together1 and it is said to be more dense4 ,why is the water at the bottom of a pond more dense than that at the surface8 ,because the water at the bottom of the pond has to bear the weight of all the water above it4 ,is the weight of the water very great8 ,the weight of the water is very great4 ,what is its weight at the depth of one hundred feet8 ,at the depth of one hundred feet1 it presses in every direction1 with a force of forty-three pounds on every square inch of surface4 ,what is its weight in the ocean at the depth of one mile8 ,at the depth of one mile it presses in every direction1 with a force of two thousand three hundred pounds on each square inch of surface4 ,when one opening is made near the top1 and another near the bottom of a vessel full of water1 from which will the water flow with the most force8 ,from the opening near the bottom of the vessel4 ,why is this8 ,because there is more weight of water to press it out from the opening near the bottom4 ,when water is poured into a vessel1 what becomes of it8 ,it spreads out so that its surface is level4 ,when different vessels are connected together1 what does the water do8 ,it falls to the same level in all of them4 ,how high will the tea stand in the spout of a tea-pot8 ,just as high as the tea is in the tea-pot4 ,illustration3 ,fig4 #bj4 ,will the tea in the spout balance that in the tea-pot8 ,the tea in the spout will balance that in the tea-pot1 as is shown in ,fig4 #bj4 ,how else can it be shown that water will rise to the same level in different vessels8 ,by a reference to ,fig4 #ba1 this may be seen4 ,illustration3 ,fig4 #ba4 ,let these vessels be made so as to connect with each other by the tube at the bottom2 then1 when water is poured into one of them1 it will rise up in each of the others1 so as to be the same height in all4 ,where is this principle used to benefit mankind8 ,it is used in supplying the inhabitants of cities with water4 ,what must be built in order to supply a city with water8 ,a reservoir must be built4 ,what is a reservoir8 ,it is a large basin made so as to hold water4 ,how high is the water in the basin8 ,it is usually as high as the tops of the houses in the city4 ,how is the water raised into the basin8 ,it is raised into the basin by means of pumps4 ,how is the water conveyed from the basin to the houses in the city8 ,by means of pipes laid under the surface of the earth1 and extending to all parts of the city4 ,how high will the water rise in these pipes8 ,nearly as high as it is in the basin4 ,if an opening be made in a pipe1 how high will the water be forced up8 ,nearly as high as the water in the basin4 ,what is the water flowing from such an opening called8 ,it is called a fountain4 ,what makes the water shoot up in a fountain8 ,the pressure of the water in the basin forces it to shoot up in the fountain4 ,to what does water always tend8 ,water always tends to fall to a level4 ,what instrument is constructed on this principle8 ,the water-level4 ,what is a water-level8 ,it is a glass tube so nearly filled with water that it contains only a bubble of air4 ,this tube is fastened in a piece of wood1 as shown in ,fig4 #bb4 ,illustration3 ,fig4 #bb4 ,how can we tell when the instrument is level8 ,by the bubble of air1 which will always be at the centre of the tube when it is level4 ,what other liquid may be used to fill the tube8 ,alcohol may be used to fill the tube1 and it is then called a spirit-level4 ,of what use is the spirit-level8 ,it is used for levelling the walls and wood-work of houses1 bridges1 and other structures4 ,springs and ,streams4 ,when we dig into the earth1 can we always find water8 ,yes2 we can always find water4 ,what reason may be given for believing this8 ,because thousands of wells have been dug in different parts of the country1 and water is obtained from them4 ,are these wells all of the same depth8 ,no2 they vary in depth from four or five feet to eighty or ninety feet4 ,what makes the water hard in some wells8 ,when the stream of water passes through iron ore1 before reaching the well1 it absorbs some of the iron1 which makes it hard4 ,how else may it become hard8 ,by passing through other mineral substances1 such as limestone and sulphur1 it will become hard4 ,why is the water in some wells much warmer than in others8 ,in wells where the water is warm1 the streams flowing into them are near the surface of the earth1 and are heated by the sun2 but in the wells of cold water1 the streams are much deeper in the earth4 ,when these streams flow out at the surface of the earth1 what are they called8 ,they are called springs4 ,where are springs found8 ,they are mostly found on hill-sides1 or in valleys2 but they are sometimes found on the top of the hills4 ,why is the water in some springs warmer than in others8 ,in springs where the water is warm1 the streams flowing into them are so near the surface of the earth as to be warmed by the sun1 while in springs where the water is colder1 the streams are much deeper in the earth4 ,what becomes of the water in the springs8 ,it runs away down the valleys1 forming brooks and creeks4 ,when these brooks and creeks flow into other brooks and creeks1 what do they form8 ,they form lakes and rivers4 ,into what do the rivers flow8 ,the rivers flow into the ocean4 ,how are waves produced8 ,waves are produced by the winds blowing against the surface of the water4 ,what does a light wind produce8 ,a light wind produces only ripples on the surface of the water4 ,what does a stronger wind produce8 ,a stronger wind produces waves in the water4 ,why is the water of the ocean and the larger lakes seldom at rest8 ,because the wind touching the water seldom ceases to blow4 ,to what depth does the wind disturb the water of the ocean8 ,wind seldom disturbs the ocean to a greater depth than thirty feet below its surface4 ,fogs and ,clouds4 ,what is always taking place from the surface of the water in the rivers1 lakes1 and oceans8 ,the water is always passing off in the form of vapor4 ,where does this vapor go8 ,it goes into the air so that the air becomes filled with moisture4 ,what kind of air will hold the most vapor8 ,warm air will hold the most vapor4 ,when warm air becomes colder1 what is done with the vapor8 ,the vapor is condensed into small particles of water4 ,when this takes place near the earth1 what does it produce8 ,it produces a fog4 ,where do fogs mostly occur8 ,fogs mostly occur over low grounds and along the course of streams4 ,when the vapor is condensed higher up in the air1 what does it produce8 ,it produces a cloud4 ,what is a cloud8 ,a cloud is only a fog1 higher up in the air4 ,do fogs ever ascend in the air8 ,yes2 they often ascend1 and thus produce clouds4 ,what causes the vapor of the air to be condensed into clouds8 ,cold causes it to be condensed into clouds4 ,does the air grow colder as we ascend8 ,yes2 the higher we ascend1 the colder we find the atmosphere4 ,what becomes of the vapor in the air1 as it ascends from the earth8 ,the vapor is condensed into clouds in the upper regions of the air4 ,why do we mostly see clouds at the top of a mountain8 ,because the vapor in the air is condensed into clouds by the cold at the top of the mountain4 ,when is a cloud formed in the air8 ,when a warm1 damp wind meets with a cold wind1 its vapor is condensed and a cloud is formed4 ,are clouds often formed in this way8 ,yes2 clouds are often quickly formed in this way4 ,when the cloud passes into a warmer current of air1 what becomes of it8 ,it is changed back into vapor1 so that it cannot be seen4 ,how then can a cloud in the sky disappear very quickly8 ,by passing into a warmer current of air the cloud is changed into a vapor1 and may thus quickly disappear4 ,are clouds of different heights8 ,yes2 some clouds touch the earth1 while other clouds are high up in the air4 ,why are clouds higher on a fine day8 ,because there is not so much moisture in the air1 and1 therefore1 it rises higher before its vapor is condensed into clouds4 ,why are clouds lower on a rainy day8 ,because there is so much moisture in the air1 that it is condensed into clouds near the earth4 ,are the clouds high during a thunder-storm8 ,no2 during a thunder-storm the clouds are seldom more than one-third of a mile high1 and very often are much nearer the surface of the earth4 ,is there any difference in the thickness of the clouds8 ,yes2 some are only a few inches thick1 while others are a mile or more in thickness4 ,when the sun is about to rise1 which of the seven colors of light is the first to appear8 ,the red color appears first4 ,when the sun sets1 which of the seven colors is the last to fade away8 ,the red color is the last to fade away4 ,why are the clouds red just before sunrise8 ,because they are tinged by the red ray of light1 before the other rays appear4 ,why are the clouds red after sunset8 ,because they are tinged by the red ray of light1 after the other rays have faded away4 ,dew4 ,what is dew8 ,dew is the moisture that collects on plants and other objects1 during the night4 ,what causes dew upon any object8 ,the air in contact with that object has its vapor condensed1 so that the water is deposited on it in the form of dew4 ,does the same quantity of dew collect upon all objects8 ,no2 it collects much more upon some objects than upon others4 ,upon what objects does it collect the most8 ,upon those which radiate or give off heat the best4 ,why do objects that are good radiators1 collect the most dew8 ,because they give off their heat rapidly after sunset1 and before morning1 become so cold that they condense the vapor in the air touching them1 and cause the dew to be deposited on their surfaces4 ,what objects are the best radiators of heat8 ,grass1 wood1 the leaves of plants1 and1 in fact1 all things of a vegetable nature4 ,what objects then collect the most dew8 ,plants collect the most dew4 ,of what use is the dew to plants8 ,it supplies them with moisture1 and answers in the place of rain4 ,when do we have the heaviest dew8 ,when the air is still and the sky is free from clouds4 ,why does wind prevent the deposit of dew8 ,because the air in contact with the grass and other objects1 is removed so quickly that it does not get cool enough to deposit dew4 ,why are dews heaviest when the air is still8 ,because the air remains in contact with the grass and other objects1 until it is cool enough to deposit the dew4 ,why is there but little dew on a cloudy night8 ,because the clouds prevent radiation of heat from the earth2 hence1 the earth and the objects near it1 remain too warm to cause any dew4 ,why is there a heavy dew on a clear night8 ,because there is nothing then to prevent free radiation of heat from the earth2 hence1 it soon cools so as to cause a heavy dew4 ,how may dew be prevented from forming on any object8 ,by placing a cover over that object4 ,how does a cover prevent the formation of dew8 ,it prevents the object that is covered from giving off its heat1 so that it does not get cool enough to cause a deposit of dew4 ,why is there but little dew under trees8 ,because trees prevent the free radiation of heat from the objects beneath them2 hence1 but little dew is formed under trees4 ,why do stone walls sweat8 ,because the walls cool the air in contact with them1 so that its vapor is condensed into water1 and deposited on the walls4 ,why does the sweating of stones indicate rain8 ,because it shows that the air contains a large amount of moisture4 ,when is a vessel of water said to sweat8 ,when drops of water collect on the outside of the vessel1 it is said to sweat4 ,why does a pitcher of cold water sweat8 ,because the vapor in the air in contact with the cold pitcher is condensed into moisture1 and deposited on the pitcher4 ,why does the pitcher sweat most before a rain8 ,because the air then contains a large quantity of moisture4 ,why will not the pitcher sweat in fine weather8 ,because the air contains only a small quantity of moisture in fine weather4 ,why does moisture sometimes collect on a glass window in a warm room8 ,because the glass cools the air1 and causes its moisture to collect in small drops on the glass4 ,what makes the glass cold enough to condense the vapor in the air8 ,the cold air1 outside of the room1 in contact with the glass4 ,where does the moisture in the air of the warm room come from8 ,it comes from the breath of persons1 and from the steam of the tea-kettle4 ,when the breath is blown on a cold object1 like a piece of glass or metal1 what is the result8 ,the moisture in the breath is condensed by the cold object1 and is collected in small drops of water on its surface4 ,frost4 ,when the temperature of the air is reduced below thirty-two degrees1 what becomes of the moisture collected on plants and other things8 ,the moisture is frozen4 ,what is this frozen moisture called8 ,it is called frost4 ,what then is frost8 ,frost is the frozen moisture on the walls and window panes1 and the frozen dew on plants and other objects4 ,on what objects do we find the most frost8 ,the most frost is found on objects having the most dew4 ,what is a heavy dew when frozen called8 ,it is called a hoar-frost4 ,when do we have a hoar-frost8 ,we have heavy frosts when the air is full of moisture4 ,why does a heavy frost indicate rain or snow8 ,because it shows that the air contains much moisture4 ,are heavy frosts usually followed by rain or snow8 ,yes2 a heavy frost1 on two successive mornings1 is mostly followed by rain or snow within a few hours4 ,rain1 ,snow1 and ,hail4 ,what is a mist8 ,a mist is very small drops of water falling through the air4 ,when these drops are larger1 what is it called8 ,it is called rain4 ,what causes rain8 ,rain is caused by the sudden cooling of the air above the earth4 ,how does cooling the air cause rain8 ,the cold condenses the vapor in the air1 so that its moisture is forced out in drops1 which fall to the earth4 ,what becomes of the rain falling upon the earth8 ,a part of it remains on the surface of the earth1 and is either absorbed again by the air1 or is carried away to the ocean by the creeks and rivers4 ,what becomes of the remaining part8 ,it sinks into the earth1 to furnish moisture to the roots of plants1 and to supply the streams beneath the earth's surface with water4 ,how does rain purify the air8 ,by washing away many things that would1 if left1 decay and make the air impure and unhealthy4 ,when the air is cooled below thirty-two degrees1 what becomes of the moisture in it8 ,the moisture in it is frozen4 ,what is this frozen moisture in the air called8 ,it is called snow4 ,what are the particles of snow called8 ,they are called snow-flakes4 ,are these snow-flakes all alike8 ,no2 they vary very much in size and shape4 ,what does ,fig4 #bc represent8 ,it represents a few of the various and beautiful forms of the snow-flake or snow-crystals4 ,illustration3 ,fig4 #bc4 ,at what temperature of the air does snow usually fall8 ,at a temperature of about thirty-two degrees4 ,is there any reason for the remark that it is 8too cold to snow08 ,yes2 for it seldom snows when the temperature of the air is much below thirty-two degrees4 ,of what use is snow8 ,the snow is a warm covering for the earth4 ,why is snow a warm covering for the earth8 ,because the air in the snow makes it a poor conductor of heat1 so that it prevents the warmth of the earth from passing off into the air4 ,snow is1 therefore1 a protection to the plants1 and prevents their being frozen by the cold weather of winter4 ,what is hail8 ,drops of rain1 when frozen1 are called hail4 ,how is hail formed8 ,the rain-drops are frozen as they fall through the air2 hence1 the hail-stones of winter are no larger than the rain-drops4 ,when have we dew8 ,when the air in contact with the earth or the plants is cooled1 its vapor is condensed into dew4 ,when have we frost8 ,when the air in contact with the earth or the plants is cooled below thirty-two degrees1 its vapor is condensed into dew1 and the dew is frozen into frost4 ,when have we fog8 ,when the air near the earth is slightly cooled1 its vapor is condensed into fog4 ,when have we clouds8 ,when the air higher above the earth is slightly cooled1 its vapor is condensed into clouds4 ,when have we mist8 ,when the air is a little more cooled1 its vapor is condensed and mist falls4 ,when have we rain8 ,when the air is still more cooled1 its vapor is condensed and rain falls4 ,when have we snow8 ,when the air is cooled below thirty-two degrees1 its vapor is condensed and frozen into snow4 ,when have we hail8 ,when the rain-drops1 while falling1 pass through a current of air cold enough to freeze them1 hail is produced4 ,ice4 ,what is ice8 ,ice is frozen water4 ,when does water freeze8 ,water freezes when its temperature is reduced to thirty-two degrees4 ,is water increased in bulk by freezing8 ,water is increased in bulk by freezing4 ,why do water-pipes often burst in cold weather8 ,the water in them freezes1 and as it increases in bulk1 the pipes burst4 ,why are some springs never frozen8 ,because water1 much above the freezing-point1 is always flowing into them from the earth1 and thus they are kept too warm to freeze4 ,why are some other springs frozen8 ,because the water flowing into them comes from near the surface of the earth1 and is soon made cold enough to freeze4 ,does salt water freeze at the same temperature as fresh water8 ,no2 fresh water freezes at thirty-two degrees1 but salt water requires a lower temperature depending upon the amount of salt it contains4 ,how is this useful8 ,the surface of the ocean is never frozen over except in very cold latitudes2 hence1 vessels may sail on it at all seasons of the year1 and carry the products of one country to another2 thus adding much to our comfort and our enjoyment4 ,illustration3 ,horse4 ,illustration3 ,decoration4 ,,chapter ,,vi4 ,sound4 ,illustration3 ,illustrated ,capital ,w ,when the hands are brought quickly together1 what is produced8 ,they produce a shaking or vibration in the air4 ,what is this vibration in the air called8 ,it is called a wave in the air4 ,what is this wave in the air like8 ,it is like a wave in the water4 ,when this wave in the air reaches the ear1 what does it produce8 ,it produces a sensation which is called sound4 ,when a stone is dropped into the water1 what does it produce8 ,it produces waves in the water4 ,how do these waves move8 ,they move in every direction from the stone4 ,do they get smaller the farther they go8 ,they do get smaller and smaller1 until at last they disappear4 ,do the waves of sound in the air act in the same way as the waves in the water8 ,they do act in the same way4 ,what then becomes of the waves of sound8 ,they get smaller and smaller the farther they go1 until at last there is no wave left4 ,when the wave in the air is large1 what kind of sound is made8 ,it makes a loud sound4 ,as the wave gets smaller1 does the sound grow fainter8 ,yes2 the smaller the wave the fainter the sound1 until at last both the wave and the sound die away4 ,where must we be to hear a loud sound8 ,we must be near the place in which the sound is made4 ,what kind of waves will make a faint sound8 ,small waves in the air make a faint sound4 ,will these waves extend as far away as larger ones8 ,no2 as all waves of sound decrease in size as they recede1 the smallest ones will soonest disappear4 ,why will a loud sound be heard farther than a fainter sound8 ,because the waves in the air from the loud sound will extend farther away than those from the fainter one4 ,how are sounds produced8 ,sounds are produced by striking solid bodies together4 ,how else may sound be produced8 ,by striking a solid body against a liquid1 as a stick struck against the water4 ,in what other way may sound be made8 ,sound may be made by causing a substance to move rapidly through the air4 ,when a piece of wood attached to a string is swung rapidly around1 what kind of a noise is made8 ,it makes a humming noise4 ,when lightning passes through the air1 what noise is made8 ,a noise which we call thunder4 ,how can a murmur be produced8 ,when sounds1 too faint to be heard separately1 are united1 they produce a murmur4 ,where may we hear a murmur8 ,we may hear a murmur from the brook1 as its waves flow over the pebbles1 and from the wind1 as it passes through the trees4 ,when a sound is heard but once1 what is it called8 ,it is called a noise4 ,when sounds are made at irregular intervals1 what are they called8 ,they are called noises4 ,when sounds are repeated at regular intervals1 what do they become8 ,they become musical sounds4 ,upon what do the high and low sounds in music depend8 ,they depend upon the rapidity with which the waves are produced in the air4 ,when the waves are repeated rapidly1 what sound is made8 ,they make a high or acute sound4 ,when they are repeated more slowly1 what sound is made8 ,they make a low or grave sound4 ,how small a number of vibrations or waves in the air can be heard8 ,sixteen vibrations in a second of time1 will produce the gravest sound that can be heard4 ,how large a number of vibrations in the air can be heard8 ,twenty-four thousand vibrations in a second of time1 make the most acute sound that can be heard4 ,how is the human voice made8 ,it is made by means of the vocal chords at the upper part of the larynx4 ,what is the larynx8 ,the upper part of the windpipe is called the larynx4 ,how do these chords produce the voice8 ,when the air is forced out of the lungs1 it causes these chords to vibrate1 so as to produce the voice4 ,are these chords the same in all persons8 ,no2 they are larger and coarser in some persons than in others4 ,in whom are they larger and coarser8 ,they are usually larger and coarser in men1 and they are smaller and finer in women4 ,what kind of a voice is made by the large and coarse chords8 ,they make a rough1 coarse voice4 ,what kind of voice is made by the finer chords8 ,they make a finer and more delicate voice4 ,do these chords vibrate so rapidly in man as in woman8 ,no2 they do not vibrate so rapidly in man as in woman4 ,what kind of voice do rapid vibrations make8 ,they make an acute voice2 hence1 woman can1 when singing1 raise her voice to a very high pitch4 ,where is the sensation of sound produced8 ,the sensation of sound is produced on the ear4 ,do people vary in their ability to hear8 ,yes2 they vary very much in their ability to hear4 ,is every person able to distinguish musical sounds8 ,no2 some persons cannot tell one musical note from another1 and some cannot even tell one bird from another by its notes4 ,is the hearing of all animals alike8 ,no2 some can hear more acutely than others2 a lion has more acute hearing than a man4 ,what other animals have acute hearing8 ,all such animals as hares1 rabbits1 and deer4 ,of what use is the acute hearing to these animals8 ,it enables them quickly to hear the approach of their enemies1 so that they may run away in time to escape the danger4 ,conduction of ,sound4 ,how does sound come to our ears8 ,sound is carried to our ears by the air4 ,is the air a conductor of sound8 ,yes2 the air is a conductor of sound4 ,is there any sound where there is no air8 ,no2 there is not any sound where there is no air4 ,how do we know this8 ,when a bell is rung in a vacuum1 no sound is heard4 ,can sounds be distinctly heard when the air is rare8 ,no2 the rarer the air the more poorly it conducts sound4 ,what proof have we of this8 ,on the top of a high mountain the human voice is heard only at a distance of a few yards2 and a pistol when exploded sounds as faintly as the breaking of a stick4 ,can sounds be heard better when the air is dense8 ,yes2 the denser the air1 the better it conducts sound4 ,what proof have we of this8 ,the human voice sounds so distinctly in the dense air of deep mines1 that conversation may be carried on in a whisper4 ,why are sounds heard better at night than in the day8 ,because the air at night is condensed by cold1 and becomes a better conductor of sound2 also1 because the nights are stiller1 and fewer sounds take our attention4 ,why is moist or damp air a better conductor of sound than dry air8 ,because the particles of water in the damp air increase its power of conduction4 ,why is sound heard farther when over the water8 ,because the damp air over the water is a better conductor1 and because it contains fewer objects to obstruct the waves of sound4 ,how far has the human voice been heard over the water8 ,the words 8all's well0 have been heard across the ,strait of ,gibraltar1 a distance of ten miles4 ,how far has the human voice been heard over the land8 ,it has been heard at the distance of four miles4 ,how does the wind affect sound8 ,the wind carries the sound the way in which it is blowing1 so that a noise may be heard much farther with the wind than against it4 ,why does water conduct sound faster than air8 ,because the particles of water are closer together than the particles of air4 ,how can we prove that water is a conductor of sound8 ,when a bell is rung under water1 the sound may be heard by any person whose head is beneath the surface of the water4 ,does a solid substance conduct sound more rapidly than air8 ,it does1 much more rapidly4 ,how can we prove this8 ,when the ear is placed at one end of a log of wood and the other end is struck with a hammer1 two sounds will be heard2 first1 the one coming through the log1 and1 afterwards1 the one coming through the air4 ,what use is made of this fact8 ,the tramping of horses or the rumbling of cars and wagons1 when at a distance1 may be heard by placing the ear near the ground4 ,do all solid substances produce the same amount of sound when struck8 ,no2 soft substances1 such as lead and wood1 produce but little sound2 while hard substances1 such as copper1 bell-metal1 and glass1 produce much more sound4 ,what are hard bodies1 producing much sound1 called8 ,they are called sonorous bodies4 ,is a bell a very sonorous body8 ,yes2 a bell is one of the most sonorous bodies that we have4 ,why does a bell ring when struck8 ,because the stroke causes the particles of the bell to vibrate4 ,when we touch a bell while ringing1 why does the sound stop8 ,because we stop its vibrations when we touch it4 ,why does a crack in a bell check its ringing8 ,because the crack stops the vibrations in the metal4 ,what other substances ring when struck8 ,all vessels made of glass1 earth1 stone1 iron1 etc41 ring when struck4 ,how may we detect a crack in any such vessel8 ,by striking the vessel2 if it is cracked there will be no ringing sound4 ,trumpets and ,speaking-,tubes4 ,how do the waves of sound move8 ,the waves of sound move in every direction from the place where the noise is made4 ,why do we put both hands around the mouth when we call to a person at a distance from us8 ,we do so to keep the waves of sound more together4 ,does it make the voice louder8 ,it does make the voice louder4 ,what instrument has been made so as to operate in the same way8 ,the speaking-trumpet1 as is shown in ,fig4 #bd4 ,illustration3 ,fig4 #bd4 ,of what use are speaking-trumpets8 ,they are of much use to firemen when giving orders at a fire1 and to those on board of vessels when giving orders to the sailors4 ,why do we hold the hand behind the ear when we wish to hear more distinctly8 ,because the hand catches more of the waves of sound1 and conducts them to the ear4 ,what instrument has been made to serve the same purpose8 ,the ear-trumpet1 as is shown in ,fig4 #be4 ,illustration3 ,fig4 #be4 ,how does the ear-trumpet aid the hearing8 ,the large end of the trumpet collects more of the waves of sound than the ear can2 hence1 more waves reach the ear4 ,why do such animals as the horse1 the rabbit1 and the deer1 hear better than we do8 ,because their large ears act like ear-trumpets to collect the waves of sound1 and thus increase their faculty of hearing4 ,how can these animals still farther increase their sense of hearing8 ,by being able to turn their ears1 just as we do the ear-trumpet1 in the direction whence the sound comes4 ,what are speaking-tubes8 ,they are metal pipes extending from one part of a building to another part4 ,of what use are speaking-tubes8 ,they are used to convey the voice to the more distant parts of a building4 ,do they require loud talking8 ,no2 even a whisper has been heard through a metal pipe over three thousand feet long4 ,velocity of ,sound4 ,how fast do the waves of sound move through the air8 ,they move at the rate of ten hundred and ninety feet in a second of time1 when the temperature of the air is thirty-two degrees4 ,what effect does warm air have on sound8 ,sound travels more rapidly in warm air4 ,how much does heat increase the velocity of sound8 ,the velocity of sound is increased one foot in a second of time1 for every degree of heat added to the air2 so that sound travels eleven hundred and twenty feet in a second1 when the temperature is at sixty-two degrees1 which is nearly one mile in five seconds4 ,does light travel more rapidly than sound8 ,yes2 light comes from the moon to the earth1 a distance of two hundred and forty thousand miles1 while sound moves eleven hundred and twenty feet4 ,what familiar examples of this difference may be given8 ,a wood-chopper's axe is seen to descend before we hear the stroke1 and the smoke from a gun is seen before we hear the report4 ,how can we tell the distance of the wood-chopper from us8 ,if we count the number of seconds between the stroke of the axe and the time when the sound reaches our ear1 and multiply eleven hundred and twenty by this number1 it will give us the distance in feet2 because sound travels eleven hundred and twenty feet in a second4 ,how can we tell the distance of lightning from us8 ,if we count the number of seconds between the lightning and the thunder1 and divide this number by five1 it will give the distance in miles2 because sound travels one mile in every five seconds4 ,how rapidly does sound travel through water8 ,sound travels about four times as rapidly through water as it does through air4 ,how rapidly does sound travel through a solid8 ,sound travels ten times as rapidly through wood1 and sixteen times as rapidly through glass1 as it does through air4 ,does a loud sound travel more rapidly than a faint one8 ,no2 it does not4 ,how do we know this8 ,because the notes from a band of music come to us in the order in which they are played1 whether they are loud or faint4 ,reflection of ,sound4 ,what becomes of the waves of sound when they strike a solid substance8 ,they are thrown back1 as light from a looking-glass1 or a ball from a stone wall4 ,what is this called8 ,it is called reflection of sound4 ,in what direction is sound reflected8 ,sound1 like light1 is reflected so that the angles of incidence and reflection are always equal4 ,when the reflected sound comes back to the ear1 what does it make8 ,it makes an echo4 ,when the sound comes back several times1 what does it make8 ,it makes several echoes4 ,where are echoes always to be heard8 ,echoes may be heard in the deep caves of the earth2 because the walls of the caves reflect sounds striking against them4 ,what curious echo may be mentioned8 ,there is an echo in ,fairfax ,county1 ,virginia1 which sends back twenty notes played on a flute4 ,does every reflection of sound produce an echo8 ,no2 it does not4 ,why is there no echo from the walls of a small room8 ,because the walls are too close together to make an echo4 ,how far away must the reflection of a sound be made1 so as to produce a perfect echo8 ,sound must be made not less than one hundred and twelve feet distant to produce a perfect echo4 ,how many syllables can be heard from an echo one hundred and twelve feet distant8 ,only one syllable can be heard4 ,how far must the echo be to hear two syllables8 ,it must be twice the one hundred and twelve feet1 or two hundred and twenty-four feet1 to hear two syllables2 and three times that distance to hear three syllables1 and so on4 ,why can a person when speaking1 be heard better in a room than in the open air8 ,because the walls of the building reflect his voice to the hearers1 so that more waves of sound reach their ears4 ,why are noises heard so distinctly in an unfurnished dwelling8 ,because there is then nothing but the walls to obstruct the waves of sound2 but when the dwelling is furnished1 each article of furniture helps to obstruct the sound and to make it less distinct4 ,what may be said of the harmony of sounds8 ,the babbling of the brook1 the roaring of the cataract1 the wailing of the wind1 and the singing of the birds1 everywhere show the ,divine love of harmony2 for where there is no human ear to listen1 they still sing their heavenly anthems of praise to ,his ear alone4 ,illustration3 ,horse-drawn trolley car4 ,illustration3 ,decoration4 ,,chapter ,,vii4 ,matter4 ,illustration3 ,illustrated ,capital ,i ,in what form is all matter found8 ,in the form of a solid1 a liquid1 or a gas4 ,what is true of all solids8 ,all solids must have length1 breadth1 and thickness4 ,do solids vary much in length1 breadth1 and thickness8 ,yes2 they vary so much that we can scarcely find two things exactly alike in shape and size4 ,can the shape of any substance be changed8 ,yes2 its shape may be changed in many ways4 ,what takes place in india-rubber when it is stretched8 ,its particles are drawn farther apart1 and its shape is altered4 ,when the force is removed1 what does the india-rubber do8 ,it springs back into its former shape4 ,what is this property of the india-rubber called8 ,it is called ,elasticity4 ,can air be pressed into a smaller bulk8 ,it can1 by means of a weight4 ,when the weight is removed1 what does the air do8 ,the air goes back to its former bulk4 ,is air very elastic8 ,yes2 air is one of the most elastic substances known4 ,why does a ball rebound when thrown against the floor8 ,because the substance of the ball is pressed out of shape when it strikes the floor1 and1 in its effort to spring back to its former shape1 it is forced to rebound4 ,why does the ball rebound from the floor8 ,because the floor is firm1 and will not move from the ball4 ,does a ball rebound when it strikes a soft substance8 ,no2 it does not rebound when it strikes a soft substance1 like a heap of wool or feathers4 ,are solids ever elastic8 ,yes2 many solids are elastic4 ,name some articles useful from their elastic properties4 ,watch-springs1 wagon-springs1 steel pens1 and spring seats are very useful4 ,why does a wooden bow throw an arrow from it8 ,when the force that bends the bow is removed1 it springs back to its former shape1 and in so doing throws the arrow from it4 ,can metals be bent8 ,yes2 nearly all metals can be bent4 ,what is this property of being bent called8 ,it is called ,flexibility4 ,do substances usually spring back after being bent8 ,no2 they usually remain in the bent form4 ,can glass be bent8 ,glass can be bent only a very little without being broken4 ,what is this property of being easily broken called8 ,it is called ,brittleness4 ,what may be said of brittle substances8 ,brittle substances are generally hard1 while flexible substances are much softer4 ,what metal may be made either flexible or brittle8 ,steel1 when heated and cooled slowly1 becomes flexible1 but when cooled quickly1 it becomes brittle4 ,for what is brittle steel used8 ,it is used for making knives1 razors1 axes1 and other cutting instruments4 ,what may be done with metals that are flexible8 ,they may be hammered into thin plates4 ,what is this property in metals called8 ,it is called ,malleability4 ,which is the most malleable of all metals8 ,gold is the most malleable2 and it can be made into leaves so thin that three hundred and sixty thousand of them1 when placed together1 make a bulk only one inch in thickness4 ,name some other metals that are malleable4 ,silver1 copper1 tin1 zinc1 iron1 and lead4 ,can the particles of a piece of iron easily be separated8 ,no2 its particles cannot easily be separated4 ,what is this property of iron called8 ,it is called ,tenacity4 ,can the particles of a brittle substance1 like glass1 easily be separated8 ,yes2 its particles can easily be separated4 ,is there much tenacity in brittle substances8 ,no2 there is very little tenacity in brittle substances4 ,is there any tenacity in air8 ,no2 because its particles are always trying to separate from each other4 ,is there any tenacity in water8 ,only a little1 just enough to hold its particles together in the form of drops4 ,upon what does the strength of substances depend8 ,their strength depends upon their tenacity4 ,do the different kinds of wood vary much in strength8 ,yes2 hickory and oak are much stronger than pine or cedar4 ,when is a knowledge of the strength of wood necessary8 ,it is necessary to know the strength of wood used in the construction of stores1 bridges1 houses1 etc4 ,which is the most tenacious of metals8 ,iron is the most tenacious of metals4 ,how is this principle in iron made useful8 ,it is useful in the construction of suspension bridges1 and in very many other ways4 ,can iron be drawn into wire8 ,yes2 iron can be drawn into wire4 ,what is this property of being drawn into wire called8 ,it is called ,ductility4 ,which are the most ductile of metals8 ,platinum1 silver1 iron1 copper1 and gold1 are the most ductile1 in the order named4 ,when is glass ductile8 ,when glass is melted it becomes ductile1 and may be drawn into very fine threads4 ,if we take half the air out of a room1 what will the remaining half do8 ,its particles will separate until they fill the whole room4 ,what is said of air when its particles are thus separated8 ,the air is in a state of rarity4 ,what is said of it when the particles are pressed closer together8 ,the air is then said to be in a state of density4 ,are the particles of water closer together than those of air8 ,yes2 therefore water is denser than air4 ,upon what does the weight of a substance depend8 ,its weight depends upon its density4 ,how much heavier is steel than water8 ,steel is seven times as heavy as water1 and is1 therefore1 seven times as dense4 ,how much denser is mercury than water8 ,mercury is thirteen times as dense as water1 and is1 therefore1 thirteen times as heavy4 ,why can a bird move through the air8 ,because the particles of air can be separated by the bird4 ,why can a fish swim through the water8 ,because the particles of water can be separated by the fish4 ,why can a needle be passed through cloth8 ,because the fibres of the cloth can be separated by the needle4 ,why can a nail be driven through a board8 ,because the fibres of wood can be separated by the nail4 ,what name given to this property in these substances8 ,this property is called ,penetrability4 ,what is necessary in order to penetrate a substance8 ,we must use a substance harder than the one which we wish to penetrate4 ,why will iron penetrate wood8 ,because iron is harder than wood4 ,why cannot our bodies penetrate the wood8 ,because our bodies are softer than the wood4 ,why can our bodies move more easily through air than through water8 ,because air is more easily penetrated than water4 ,why can a nail be driven into a pine board more easily than into an oak board8 ,because the fibres of pine are more easily separated than the fibres of oak2 hence1 pine wood is more penetrable than oak wood4 ,illustration3 ,decoration4 ,illustration3 ,decoration4 ,,chapter ,,viii4 ,attraction4 ,cohesion and ,adhesion4 ,illustration3 ,illustrated ,capital ,w ,why can a cup be lifted by taking hold of the handle8 ,because the particles of the cup do not separate from each other4 ,what is the power which holds these particles together called8 ,it is called ,cohesion4 ,in what bodies is cohesion the strongest8 ,cohesion is strongest in solid bodies4 ,is the cohesion alike in all solids8 ,no2 the cohesion in iron is much greater than the cohesion in wood4 ,upon what does the strength of a substance depend8 ,the strength of a substance depends upon the amount of cohesion among its particles4 ,what effect does heat have upon the cohesion of bodies8 ,heat tends to destroy the cohesion of bodies by separating their particles4 ,how does heat affect ice8 ,heat destroys the cohesion between the particles of ice1 and thus it is changed into water4 ,how does heat affect water8 ,when still more heat is applied1 the cohesion in the water is destroyed1 and thus it is changed into steam4 ,is there any cohesion in steam8 ,no2 there is not any cohesion in steam4 ,is there any cohesion in air8 ,no2 because the particles of air are always trying to separate from each other4 ,is there any cohesion in liquids8 ,yes2 there is some cohesion in liquids1 but it is only strong enough to hold them together in drops4 ,does the cohesion in liquids vary8 ,yes2 the cohesion in mercury is stronger than it is in water2 therefore1 a drop of mercury is larger than a drop of water4 ,how is it in chloroform8 ,the cohesion in chloroform is weaker than it is in water2 therefore1 a drop of chloroform is smaller than a drop of water4 ,how is shot made8 ,when lead is melted and poured through a sieve at the top of a high tower1 the attraction of cohesion forms it into round drops or globules2 these cool1 while falling1 thus forming the grains of shot4 ,how high must a shot-tower be8 ,a shot-tower must be not less than two hundred feet high1 so that the lead may harden while falling4 ,why does putty stick to a pane of glass8 ,because there is an attraction between the putty and the glass4 ,what is this attraction called8 ,it is called ,adhesion4 ,upon what does adhesion depend8 ,adhesion depends upon the attraction which substances have for each other4 ,has water any attraction for oil8 ,no2 therefore1 there is no adhesion between oil and water4 ,has glass any attraction for water8 ,yes2 therefore1 the water collects on the glass in drops4 ,what other examples of adhesion may be given8 ,paint adheres to wood1 dust to furniture1 and tin and mercury to the back of a looking-glass4 ,will you name a few of the most adhesive substances8 ,glue1 mortar1 paste1 and putty4 ,of what use is glue8 ,glue fastens pieces of wood together4 ,of what use is mortar8 ,mortar fastens together the bricks and stones used in the construction of houses and other buildings4 ,of what use is paste8 ,paste fastens pieces of paper together1 and it fastens paper to the walls and ceilings of rooms4 ,of what use is putty8 ,putty fastens the glass to the wood-work of our windows4 ,capillary ,attraction4 ,why does a sponge suck up water8 ,because the particles of the sponge have an attraction for the water4 ,what is this attraction called8 ,it is called ,capillary attraction4 ,in what bodies do we find the most capillary attraction8 ,in those that are of a porous or spongy nature4 ,why does a lump of sugar or salt1 when partly dipped into water1 soon become entirely wet8 ,because sugar and salt are porous substances1 and the water rises in them by capillary attraction4 ,why does a heap of dry sand soon become damp when one edge touches the water8 ,because the water is drawn through the sand by capillary attraction4 ,why does water poured into the saucer of a flower-pot soon wet the earth in the flower-pot8 ,because the earth is porous1 and the water is drawn up through it by capillary attraction4 ,how does the oil in a lamp rise so as to be burned8 ,the oil is drawn up through the wick by capillary attraction4 ,where may examples of capillary attraction be noticed8 ,in blotting-paper when it takes up the ink1 and in bread when it soaks up the juice of meats4 ,what other examples may be given8 ,when one end of a towel is placed in a basin of water1 and the other end is left hanging outside the basin1 the water will pass through the towel by capillary attraction1 until the basin is entirely dry4 ,why is water in a glass tumbler a little elevated at the edges8 ,because the glass has a slight attraction for the water near it1 and thus lifts it up a little4 ,why will water rise in a small glass tube higher than in the surrounding vessel8 ,because the glass has an attraction for the water1 and elevates it at the edges1 as is shown in ,fig4 #bf4 ,illustration3 ,fig4 #bf4 ,why do salt and other substances dissolve in water8 ,because water overcomes the force of cohesion in the salt1 and thus separates its particles4 ,the capillary attraction between the salt and the water is greater than the cohesion between the particles of salt2 hence1 the salt is dissolved by the water4 ,gravitation4 ,when a ball is thrown into the air1 why does it fall back to the earth8 ,because the earth attracts the ball4 ,why do rain and snow fall to the earth8 ,because the earth attracts them4 ,what is this kind of attraction called8 ,it is called attraction of ,gravitation4 ,does the attraction of gravitation exist in all things8 ,yes2 every substance attracts every other substance4 ,upon what does the attraction of gravitation in a body depend8 ,it depends upon the size and weight of that body4 ,do larger bodies attract with more force than smaller ones8 ,yes2 larger bodies do attract more than smaller ones4 ,do heavy bodies attract with more force than light ones8 ,yes2 heavy bodies do attract more than light ones1 although they may be of the same size4 ,where are all substances drawn by the attraction of gravitation8 ,they are all drawn towards the centre of the earth4 ,why are substances drawn towards the centre of the earth8 ,because the earth is larger than any substance on or near its surface4 ,in what direction do all objects fall through the air8 ,they all fall towards the centre of the earth4 ,which way then do we call 8down08 ,down is always towards the centre of the earth4 ,which way do we call 8up08 ,up is always away from the centre of the earth4 ,where must all plumb lines or perpendicular lines point8 ,they must all point with one end towards the centre of the earth4 ,when the earth turns over1 can any substance fall away from its surface8 ,no2 all things are drawn to the earth with so much force that they cannot fall away4 ,upon what does the weight of a body depend8 ,the weight of a body depends upon the force with which it is drawn towards the earth4 ,what kind of substances are attracted with the most force8 ,those that are the most dense1 like the metals2 hence1 they are the heaviest4 ,what causes a liquid to form into a drop at the mouth of a bottle8 ,the attraction of cohesion causes the drop to be formed4 ,what causes the drop to fall to the earth8 ,the attraction of gravitation causes the drop to fall to the earth4 ,when water is poured from a tumbler1 why does it run down the side of the tumbler8 ,because the attraction of cohesion draws the water to the side of the tumbler1 as is shown in ,fig4 #bg4 ,illustration3 ,fig4 #bg4 ,why does a spout prevent the water from running down the side of the vessel8 ,because the spout is curved so that its lowest point is where the water falls from it2 hence1 gravitation causes the water to fall directly to the earth1 as is shown in ,fig4 #bh4 ,illustration3 ,fig4 #bh4 ,does the air obstruct bodies when falling through it8 ,yes2 air obstructs all bodies when falling through it2 but it obstructs light bodies more than heavy ones4 ,do all bodies fall with equal rapidity in a vacuum8 ,yes2 all bodies fall with equal rapidity in a vacuum4 ,what bodies fall through the air most rapidly8 ,those that are the heaviest or most dense2 because they are the smallest in bulk4 ,do heavy bodies increase in velocity as they descend8 ,they do increase rapidly in velocity as they descend4 ,how far does a heavy body like lead fall in one second8 ,it falls sixteen feet in one second4 ,a falling body increases thirty-two feet in velocity for every second of time it is in falling4 ,during the first second it falls sixteen feet4 ,during the second second1 it falls sixteen feet plus thirty-two feet1 or forty-eight feet4 ,during the third second1 it falls forty-eight feet plus thirty-two feet1 or eighty feet1 etc4 ,a rising body decreases thirty-two feet in velocity for every second of time it is in rising4 ,if it be three seconds in rising1 its velocity will be eighty feet the first second1 forty-eight feet the second second1 and sixteen feet the third second1 being just the reverse of the same body when falling1 as is shown in ,fig4 #bi4 ,illustration3 ,fig4 #bi4 ,how may the distance a body falls in a given time be found8 ,it may be found by multiplying the number of seconds it is in falling1 by the same number1 and this product by sixteen feet4 ,thus1 when it is three seconds in falling1 multiply three by three1 and this product by sixteen feet1 which gives one hundred and forty-four feet1 the distance it falls in three seconds4 ,what familiar example have we of the force of falling bodies8 ,we have an example in the large hail-stones which fall to the earth in summer-time1 breaking the glass in our windows and doing much injury to the crops4 ,centre of ,gravity4 ,what is the centre of gravity in a body8 ,the centre of gravity in a body1 is the point on which the body may be balanced1 as is shown in ,fig4 #cj4 ,illustration3 ,fig4 #cj4 ,where is the centre of gravity in a circle8 ,it is the centre of the circle4 ,where is the centre of gravity in a ball8 ,it is the centre of the ball4 ,what influence does the earth have on the centre of gravity8 ,the earth draws the centre of gravity in a body as near to itself as possible4 ,why will an egg1 when placed on either end1 fall over on its side8 ,because the centre of gravity is nearer the earth when the egg is placed upon its side than when upon either end1 as is shown in ,fig4 #ca and ,fig4 #cb4 ,illustration3 ,fig4 #ca4 ,illustration3 ,fig4 #cb4 ,why will a ball remain in any position when placed on the earth8 ,because its centre of gravity is always the same distance from the earth1 whatever may be its position4 ,when will a body change its position if left unsupported8 ,a body will change its position whenever by so doing its centre of gravity will be lowered4 ,when may a body be readily moved about8 ,when its centre of gravity always remains at the same distance from the earth while being moved4 ,why is a round body1 like a ball1 easily rolled about the floor8 ,because its centre of gravity remains at the same distance from the floor4 ,when is the position of a body difficult to change8 ,whenever the centre of gravity in it has to be lifted up in order to make the change1 as is shown in ,fig4 #ce4 ,illustration3 ,fig4 #cc4 ,illustration3 ,fig4 #cd4 ,illustration3 ,fig4 #ce4 ,the centre of gravity1 in ,fig4 #cc1 may be lowered2 hence1 it will change its position if unsupported4 ,the centre of gravity1 in ,fig4 #cd1 can neither be lowered nor lifted up2 hence1 it may be readily rolled about4 ,the centre of gravity1 in ,fig4 #ce1 must be lifted up2 hence1 it remains firm in its place4 ,when does an object stand firm8 ,it stands firm when it has a broad base1 and its centre of gravity is near the earth4 ,what effect is produced by elevating the centre of gravity8 ,the higher the centre of gravity in any body is raised above the earth1 the greater is its tendency to fall4 ,why is a load of hay more easily overturned than a load of iron1 when upon the same wagon8 ,because the centre of gravity in the load of hay is much higher than it is in the load of iron4 ,why do passengers on top of a stage cause it to overturn more easily8 ,because their weight on the top raises the centre of gravity in the stage1 and it is more readily overturned4 ,why is a person more likely to fall when standing up than when sitting down8 ,because the centre of gravity is higher in a person when standing than when sitting4 ,why is a boy more likely to fall when raised on stilts8 ,because the centre of gravity in the boy is farther from the earth when he is raised on stilts4 ,when will a load of hay be overturned8 ,it will be overturned whenever the line from the centre of gravity to the earth falls outside of the wheels1 as is shown in ,fig4 #cf4 ,illustration3 ,fig4 #cf4 ,why should lamps have large bottoms8 ,lamps should have large bottoms so that the line of gravity may not fall outside of the bottom4 ,where must the line of gravity in a body always fall8 ,it must always fall within the base of that body1 or the body will be overturned4 ,how must a leaning tower be built so as not to fall8 ,it must be built so that the line of gravity will fall within its base4 ,why do we lean back when carrying a load in front of us8 ,we lean back so that the line of gravity may be kept directly over our feet4 ,why does a person standing up in a wagon fall when the wagon is suddenly moved8 ,because the feet1 being in contact with the wagon1 move with it before the motion extends to the rest of the body1 thus throwing the line of gravity behind the feet2 hence1 the person must fall1 unless supported4 ,why does a person standing up in a wagon fall when the wagon is suddenly stopped8 ,because the feet1 being in contact with the wagon1 are suddenly stopped1 while the body still moves forward1 thus throwing the line of gravity ahead of the feet2 hence1 the person must fall1 unless supported4 ,why do animals with four feet stand firmer than those with only two feet8 ,because the four feet afford a larger base to stand upon than the two feet do1 and1 therefore1 support the centre of gravity better4 ,why can a horse or a cow remain standing for many hours without seeming to be weary8 ,because their four feet afford a good support to the centre of gravity4 ,why does a person who is standing soon become weary8 ,because it requires a constant effort to keep the line of gravity over the feet1 and this soon produces weariness4 ,why can a person sit longer than he can stand8 ,because the centre of gravity is lower1 when he is sitting1 than when he is standing2 hence1 it requires less strength to support the body in a sitting position4 ,why can a person lie down longer than he can sit or stand8 ,because the centre of gravity is nearest the earth when he is lying down1 and it requires no effort to remain in that position4 ,how do we measure time8 ,we measure time by means of a pendulum1 such as is used in a common clock4 ,how does the pendulum move8 ,the pendulum moves regularly to and fro1 from the line of gravity4 ,does the pendulum vary any in its vibrations1 or the time of moving to and fro8 ,the pendulum does not vary any in its vibrations4 ,illustration3 ,fig4 #cg4 ,why does the pendulum keep moving8 ,when the pendulum is at ,a1 in ,fig4 #cg1 gravity causes it to descend to ,c1 and the motion it gains while falling to ,c carries it up to ,b2 gravity then causes it to descend to ,c1 and the motion it gains while falling to ,c carries it back to ,a again4 ,what helps to keep the pendulum in motion8 ,the works inside of the clock help to keep the pendulum in motion4 ,how long must the pendulum be1 so as to tick once in every second8 ,the pendulum must be thirty-nine inches long4 ,how does it tick when the pendulum is shortened8 ,it ticks more rapidly4 ,how does it tick when the pendulum is lengthened8 ,it ticks more slowly4 ,how then does cold affect a clock8 ,cold makes the clock go faster by shortening the pendulum4 ,how does heat affect a clock8 ,heat makes the clock go more slowly by lengthening the pendulum4 ,how may the pendulum always be kept of the same length8 ,by having the weight at the bottom of the pendulum1 so that it may be raised or lowered by means of a screw4 ,specific ,gravity4 ,upon what does the weight of a body1 when in the air1 depend8 ,the weight of a body depends upon the force with which it is drawn towards the earth4 ,what is this attractive force called8 ,it is called gravitation or gravity4 ,what is gravity8 ,gravity is the weight of any body4 ,what is specific gravity8 ,specific ,gravity is the weight of any body1 compared with an equal bulk of water4 ,do substances weigh as much in water as they do in air8 ,no2 they do not weigh so much4 ,when we drop lead in a vessel full of water1 what becomes of the water8 ,the water is forced over the sides of the vessel4 ,how much water is thus forced over the sides of the vessel8 ,a quantity equal in bulk to the lead dropped into the vessel4 ,when the water thus displaced weighs just one pound1 how much less will the lead weigh while in the water than it did in the air8 ,it will weigh one pound less4 ,then how much less is the weight of a body in water than it is in air8 ,its weight in the water is as much less as the weight of the water which it displaces4 ,when a body has greater specific gravity than water1 what will it do8 ,it will sink in the water4 ,when it has less specific gravity than water1 what will it do8 ,it will float on the surface of the water4 ,will all parts of the body be above the surface of the water8 ,no2 a part of it will sink into the water4 ,how much of it will sink into the water8 ,it will sink so as to displace water enough to balance its own weight4 ,why does a boat float on the water8 ,because it weighs less than a bulk of water of the same size as the boat4 ,when a cargo is placed on the boat1 why does it still float8 ,because it still weighs less than a bulk of water of the same size as the boat4 ,how do we make use of this principle8 ,we make use of it in the construction of vessels1 so as to carry on trade with other parts of the world4 ,why can ducks and geese float on the water8 ,because their light1 downy feathers make their specific gravity less than that of the water2 hence1 they must float on its surface4 ,what may be said of the specific gravity of the human body8 ,when the lungs are filled with air1 the specific gravity of the human body is rather less than that of water4 ,can a person float in the water8 ,yes2 if a person1 who cannot swim1 will throw his head back so that his mouth and nose only remain above the water1 he may float in this position for some time4 ,what is the specific gravity of fish8 ,the specific gravity of fish is so nearly equal to that of water1 that they can move about anywhere beneath its surface4 ,how do fish rise and sink in the water8 ,fish rise and sink in the water by means of an air-bladder in their bodies4 ,how does the air-bladder help the fish to rise or sink8 ,when the bladder is filled with air1 the specific gravity of the fish becomes lighter1 and it rises towards the surface2 and when the air is forced out1 the specific gravity becomes heavier1 and the fish sinks towards the bottom4 ,why does cream rise to the surface of milk8 ,because the specific gravity of the cream is less than that of the milk4 ,why does oil float on water8 ,because the specific gravity of the oil is less than that of the water4 ,why can a fat person float more easily in the water than a lean person8 ,because the fat reduces the specific gravity of the body1 so that it floats more easily4 ,why can a person float more easily in salt water than in fresh water8 ,because salt increases the weight of the water1 and1 therefore1 it buoys up with more force4 ,what familiar example have we of this8 ,an egg will sink when placed in fresh water2 but if salt be dissolved in the water1 the egg will float near the surface4 ,illustration3 ,decoration4 ,illustration3 ,decoration4 ,,chapter ,,ix4 ,motion4 ,illustration3 ,illustrated ,capital ,w ,when is a body said to be in motion8 ,a body is in motion when it is moving from one place to another4 ,when is a body said to be at rest8 ,a body is at rest when it is not moving from one place to another4 ,what is necessary to give motion to a body8 ,force of some kind is necessary to give motion to a body4 ,how long will the motion given to a body continue8 ,the motion will continue until it is checked4 ,what is necessary to check the motion of a body8 ,force of some kind is necessary to check its motion4 ,what force is always acting so as to bring bodies to a state of rest8 ,the force of gravity1 which is constantly drawing all bodies to the earth4 ,what else may check the motion of a body8 ,the air1 the water1 and solids of all kinds may check the motion of a body4 ,in what direction will a body move when its course is not obstructed8 ,it will move in a straight line4 ,why does a ball struck by a bat make a curve to the earth8 ,because the force of gravity gradually overcomes the force given by the bat1 so that the ball moves in a curve4 ,why does a bullet make a curve to the earth8 ,because the force of gravity gradually overcomes the force given by the powder1 so that the bullet moves in a curve to the earth4 ,when a person aims directly at a mark some distance from him1 where will the bullet strike8 ,the bullet will strike below the mark4 ,why will the bullet strike below the mark8 ,because the force of gravity draws it towards the earth1 while it is going from the gun to the mark4 ,when a ball attached to a string is whirled around1 as in ,fig4 #ch1 what is the tendency of the ball8 ,the tendency of the ball is to fly off in a straight line4 ,illustration3 ,fig4 #ch4 ,what is the force tending to make the ball fly off called8 ,it is called centrifugal force4 ,what keeps the ball from flying off8 ,the string keeps the ball from flying off4 ,what is the force exerted by the string called8 ,it is called centripetal force4 ,what then is centrifugal force8 ,it is the force tending to fly off from the centre4 ,what is centripetal force8 ,it is the force tending to draw towards the centre4 ,why does mud fly off from the wheel of a wagon when in motion8 ,because the motion of the wheel gives centrifugal force to the mud1 and causes it to fly off4 ,what does the rim of a wheel when in motion1 tend to do8 ,the rim tends to fly off from the centre of the wheel4 ,how is it prevented from flying off8 ,it is prevented by making the wheel very strong1 so that all parts of it are held firmly together4 ,what does this centrifugal force sometimes cause8 ,the centrifugal force is so great that it sometimes causes grind-stones and mill-stones1 when revolving rapidly1 to burst into pieces4 ,what becomes of these stones when they burst8 ,when they burst1 their pieces fly off in different directions1 doing more or less injury to whatever obstructs their course4 ,when a horse turns a corner1 why does the rider lean in the direction in which the horse is turning8 ,he leans so as to overcome the centrifugal force1 and is thus prevented from falling off the horse4 ,how are cars prevented from running off the track1 while turning a curve8 ,the outer rail is made higher than the inner rail1 so as to overcome the tendency of the cars to run off the track4 ,what grand example have we of the action of these two forces8 ,the earth and other planets that move around the sun1 are kept in their places by the action of these two forces4 ,when a ball strikes a solid body and bounds back1 what is that motion called8 ,it is called reflected motion4 ,at what angle does the ball leave the solid body8 ,it bounds off from the solid body1 so that the angle of reflection is always equal to the angle of incidence1 as is shown in ,fig4 #ci4 ,illustration3 ,fig4 #ci4 ,how may a stone be skipped on a smooth pond8 ,a stone may be skipped1 by throwing it so obliquely that the water will cause it to bound off from its surface4 ,when a boat moves across a river at the rate of four miles an hour1 and the current runs four miles an hour1 in what direction will the boat go8 ,the boat will go diagonally across the river4 ,why will the boat go diagonally across the river8 ,because the boat will be carried as far down the river as the river is wide4 ,if the river be one mile wide1 then the boat1 while crossing1 will be carried down it one mile4 ,how do boatmen overcome this difficulty8 ,they overcome this by rowing the boat towards a point higher up the stream4 ,does it take longer to cross a stream when the current is strong8 ,yes2 because the boat is carried farther down the stream by the current1 and it must1 therefore1 go a greater distance in crossing4 ,why is a person apt to fall when he jumps from a wagon that is moving8 ,because his body partakes of the motion of the wagon and moves on after his feet are stopped by the ground1 so that he falls forwards4 ,how can he prevent falling8 ,he can prevent falling by jumping in the same direction as that in which the wagon is moving4 ,when a stone is dropped from the top of a mast of a vessel1 where does it fall8 ,the stone falls at the bottom of the mast4 ,why does the stone fall at the bottom of the mast8 ,because it partakes of the motion of the vessel1 and is carried forward while falling4 ,when a ball is thrown perpendicularly into the air by a person on a boat1 where does the ball fall8 ,the ball falls back into the person's hand1 although the boat may have carried him several feet while the ball was in the air4 ,why does the ball fall back into his hand8 ,because it partakes of the motion of the boat1 and moves as far as the boat moves4 ,when a stone thrown from a car is aimed at a post1 where will it strike8 ,the stone will strike ahead of the post4 ,how far ahead of the post will the stone strike8 ,it will strike as far ahead as the car moves while the stone is going to the post4 ,where must we aim so as to hit a bird that is flying8 ,we must aim ahead of the bird4 ,why must we aim ahead of the bird8 ,because the bird will move a short distance through the air while the shot is reaching it4 ,when a body in motion strikes one at rest1 is the force felt alike by both bodies8 ,the force is felt alike by both bodies2 thus1 when one head is struck against another1 both are equally hurt4 ,do bodies1 when moving rapidly1 strike with more force than when moving slowly8 ,yes2 the force with which they strike depends upon their velocity4 ,what examples of this force may be given8 ,a nail may be driven into a board by a hammer1 when it falls rapidly upon the nail2 a bullet may be shot through a plank2 and even a tallow candle1 when shot from a gun1 may move with velocity enough to pass through a pine board4 ,why do large bodies start slowly8 ,because it takes some time for the force to reach all parts of them4 ,why is it difficult for horses to start a loaded wagon8 ,because they must pull some time before the force reaches all parts of the wagon1 causing it to move4 ,why is machinery slow at starting8 ,because it requires time for the force applied to reach all parts of the machinery4 ,when two solid bodies1 moving slowly1 strike against each other1 what takes place8 ,they are pushed off from each other in opposite directions4 ,which body is pushed off the more rapidly8 ,the one having the less weight1 is pushed off the more rapidly4 ,when the oars of a boat push against the water1 what takes place8 ,the boat and the water move in opposite directions4 ,when the wings of a bird strike the air1 what takes place8 ,the bird and the air move in opposite directions4 ,how can a duck or a goose swim in the water8 ,the toes of a duck or a goose are joined together by a web which makes the foot broad1 like a paddle2 and when these broad feet are pressed against the water1 the duck or the goose moves forward4 ,can all birds swim in the water8 ,no2 only those birds can swim whose toes are joined together by a web1 thus giving them a broad foot to be pushed against the water4 ,what is produced by the rubbing of bodies together8 ,friction is produced by rubbing bodies together4 ,what does friction tend to do8 ,friction tends to check the motion of bodies4 ,how do we lessen the friction in machinery8 ,we lessen the friction in machinery by oiling the parts where they rub together4 ,how are waves produced in the water8 ,waves are produced by the friction of the air upon the water4 ,what causes the water to flow in creeks and rivers8 ,the attraction of gravitation1 which causes water always to fall to its lowest level4 ,what retards the current of water in streams8 ,the friction1 caused by the water rubbing against the banks and bottoms of the streams1 retards their current4 ,in what part of a stream is the current the strongest8 ,it is strongest in the middle of a stream1 because there is less friction there4 ,what retards the flow of water through a pipe8 ,the friction of the water against the sides of the pipe1 retards its flow very much4 ,why do sudden turns in a pipe check the flow of water through it8 ,because every turn in the pipe increases the friction made by the water4 ,why does a wagon-wheel turn around when the wagon moves8 ,because the friction between the wheel and the earth1 prevents the wheel from sliding along4 ,why can a steam-engine draw a train of heavy cars8 ,because the friction1 between the wheels and the rails1 causes the wheels to turn around instead of sliding2 and thus the engine moves forward drawing the cars with it4 ,why is sand sometimes put on the rails8 ,sand is put on the rails to increase the friction between the wheels and the rails1 so that the engine may start a heavier train4 ,why do we use sleighs when there is snow on the ground8 ,because sleighs slip easily on the snow4 ,why do sleighs slip easily on the snow8 ,because there is but little friction between the sleigh and the snow4 ,why do wagons run more heavily when the ground is soft8 ,because their wheels then sink farther into the earth1 and thus the friction is increased4 ,why do wagons run more heavily when the ground is covered with snow8 ,because their wheels sink into the snow1 and thus the friction is increased4 ,why will a person slip down upon the ice more easily than upon the earth8 ,because there is less friction between his feet and the ice than there is between his feet and the earth4 ,why do we put ashes on our walks when they are covered with ice8 ,we put ashes on our walks to increase the friction between the ice and our feet1 so that we may not slip down when walking on them4 ,why is a lock or a brake used on a wagon8 ,it is used to check the motion of the wagon4 ,how does a lock check the motion of the wagon8 ,the lock is pressed against the wheels1 so that enough friction is produced to check the motion of the wagon4 ,why does it require more force to draw a rusty plough through the ground1 than to draw one that is bright and smooth8 ,because the rust increases the friction between the plough and the ground1 and this makes more force necessary in order to move it4 ,why cannot we hold a live eel in our hand1 as easily as we can a live fish8 ,because the skin of the eel is so smooth1 that there is much less friction between it and our hand1 than there is between the fish and our hand4 ,dry sand or dry ashes sprinkled on the eel will increase the friction so that it can be held4 ,illustration3 ,explorer4 ,illustration3 ,decoration4 ,,chapter ,x4 ,mechanical ,powers4 ,lever4 ,illustration3 ,illustrated ,capital ,w ,what is a lever8 ,a ,lever is a rod or bar of some kind used for raising weights4 ,of what are levers made8 ,levers are made of any solid substance1 such as wood and iron4 ,when a spoon is balanced on a cup1 as in ,fig4 #dj1 what may the spoon be called8 ,the spoon may then be called a lever4 ,upon what does the spoon rest8 ,it rests upon the edge of the cup4 ,illustration3 ,fig4 #dj4 ,what is the cup on which the spoon rests called8 ,it is called a ,fulcrum4 ,what is a fulcrum8 ,a fulcrum is any solid body against which a lever rests4 ,when the spoon is called a lever1 what are the parts on each side of the fulcrum called8 ,they are called the arms of the lever4 ,what is necessary1 so that a lever may balance8 ,the arms of the lever must be of equal weight1 or they will not balance4 ,if the bowl of the spoon be filled with water1 what will result8 ,the bowl will sink1 and the handle of the spoon will rise4 ,what will cause the bowl of the spoon to sink8 ,the weight of the water in it will cause it to sink4 ,how can the bowl of the spoon be prevented from sinking8 ,by applying a force to the handle of the spoon1 equal to the weight of the water put in the bowl4 ,what is the force applied to the handle called8 ,it is called the ,power4 ,what three things are always necessary when the lever is used8 ,the power1 the fulcrum1 and the weight1 are always necessary when the lever is used4 ,which of these three things are movable8 ,the power and the weight are movable4 ,which one does not move8 ,the fulcrum does not move4 ,how many kinds of levers are there8 ,there are three kinds of levers4 ,what is the first kind of lever8 ,it is where the fulcrum is between the power and the weight1 as is shown in ,fig4 #da4 ,illustration3 ,fig4 #da4 ,when the fulcrum is under the middle of the lever1 how can the lever be kept balanced8 ,the lever will remain balanced1 so long as the power and the weight used are equal to each other4 ,when the lever is moved1 so that the fulcrum is nearer the weight1 which arm of the lever is the heavier8 ,the arm towards the power1 because it is the longer arm4 ,will the power applied to the long arm of the lever be as heavy as the weight8 ,no2 the nearer the fulcrum is to the weight1 the less will be the power needed to balance that weight4 ,how will it be when the fulcrum is nearer to the power than it is to the weight8 ,then the power must be heavier than the weight4 ,when the long arm of the lever is twice the length of the short arm1 what will be the difference in the weights8 ,one pound applied to the long arm will then balance two pounds applied to the short arm4 ,upon what does the power of a lever depend8 ,it depends upon how much nearer the fulcrum is placed to one end of the lever1 than to the other end4 ,of what use is the lever8 ,it is very useful in raising heavy bodies4 ,illustration3 ,fig4 #db4 ,what is the weight to be lifted in ,fig4 #db8 ,the stone is the weight to be lifted4 ,where is the fulcrum placed8 ,the fulcrum is placed near the stone4 ,where is the power applied8 ,the power is applied by the hand to the long arm of the lever4 ,how may a see-saw be made8 ,a see-saw may be made by placing a plank or a board across a rail in a fence1 so that it will balance4 ,is the see-saw1 as shown in ,fig4 #dc1 an example of the lever8 ,yes2 the see-saw is an example of the lever4 ,illustration3 ,fig4 #dc4 ,what are the parts of the plank on each side of the fence-rail called8 ,they are called the arms of the lever4 ,what is the fulcrum in the see-saw8 ,the fence-rail on which it rests1 is the fulcrum4 ,what is the power in the see-saw8 ,the power is the boy on one end of the lever4 ,what is the weight in the see-saw8 ,the weight is the boy on the other end of the lever4 ,how do children play at see-saw8 ,by pushing against the earth with their feet1 the arms of the lever are alternately forced to rise and fall in the air1 thus making a see-saw4 ,where must the fulcrum be when the two boys are of the same weight8 ,the fulcrum must be under the middle of the lever4 ,where must the fulcrum be when one boy is heavier than the other8 ,the fulcrum must then be nearest to the heavier boy1 so that they may balance4 ,does it require much force to play at see-saw8 ,no2 when the see-saw is balanced1 a very little force will cause it to move up and down4 ,of what use is a pair of scales8 ,a pair of scales is very useful in weighing different substances4 ,illustration3 ,fig4 #dd4 ,are the scales1 as shown in ,fig4 #dd1 an example of the lever8 ,the scales are an example of the lever4 ,where is the fulcrum of the scales8 ,the fulcrum is the point on which the lever rests4 ,what is the weight8 ,the weight is the lead put in one scale4 ,what is the power8 ,the power is the substance put in the other scale1 so as to balance the weight4 ,when the lead put in one scale weighs exactly a pound1 how much sugar must be put in the other scale to balance the lead8 ,exactly one pound of sugar must be put in to balance the lead4 ,for what is a balance mostly used8 ,a balance is mostly used for weighing heavy bodies4 ,is the balance a lever8 ,yes2 the balance is a lever4 ,which is the fulcrum in the balance8 ,the fulcrum is the hook that holds the balance up4 ,illustration3 ,fig4 #de4 ,what is the weight8 ,the weight is the large body hanging from the short arm of the lever4 ,what is the power8 ,the power is the smaller body hanging from the long arm of the lever4 ,in ,fig4 #de1 the distance from the fulcrum to the power is ten times the distance from the fulcrum to the weight2 now1 if the small body weighs one pound1 how much must the large body weigh1 so as to balance it8 ,the large body must weigh ten pounds4 ,when the small body weighs ten pounds1 how much must the large body weigh1 so as to balance it8 ,the large body must weigh ten times as much1 or one hundred pounds4 ,if the smaller body be moved half-way to the fulcrum1 how much weight will then balance it8 ,it will then take only half the weight1 or fifty pounds to balance it4 ,what other familiar example of this kind of lever may be mentioned8 ,the pump-handle is a lever of this kind4 ,illustration3 ,fig4 #df4 ,what is the power8 ,the power is the force applied to the pump-handle4 ,what is the fulcrum8 ,the fulcrum is the screw that fastens the handle to the pump4 ,what is the weight8 ,the weight is the water raised by the bucket4 ,are scissors an example of the lever8 ,yes2 scissors are a double lever4 ,what is the fulcrum in the scissors8 ,the fulcrum is the rivet which holds the two levers together4 ,what is the power8 ,the power is the force applied by the fingers4 ,what is the weight8 ,the weight is the paper1 or other substance1 to be cut by the scissors4 ,can scissors be made very strong8 ,yes2 some scissors are made so strong that they are used for cutting iron1 tin1 and zinc4 ,what other useful instruments are made upon the same principle as the scissors8 ,such instruments as nippers1 pincers1 tweezers1 and blacksmith's tongs4 ,what is the second kind of lever8 ,it is where the weight is between the power and the fulcrum1 as is shown in ,fig4 #dg4 ,illustration3 ,fig4 #dg4 ,of what use is this kind of lever8 ,it is very useful in lifting heavy weights a short distance from the earth4 ,what example is there of this kind of lever8 ,the door on its hinges is a lever of this kind4 ,what is the fulcrum8 ,the hinges are the fulcrum4 ,what is the weight8 ,the door is the weight4 ,what is the power8 ,the force that opens or shuts the door is the power4 ,what other examples of this kind of lever have we8 ,we have an example in the lid of the tea-kettle1 and in the cover of the ink-stand1 when they are fastened on by hinges4 ,what is the third kind of lever8 ,it is where the power is between the fulcrum and the weight1 as is shown in ,fig4 #dh4 ,illustration3 ,fig4 #dh4 ,what examples of this kind of lever have we in common use8 ,the shovel1 the spade1 and the pitch-fork1 are levers of this kind4 ,what is the fulcrum8 ,one hand is the fulcrum4 ,what is the power8 ,the other hand is the power4 ,what is the weight8 ,the earth raised on the shovel is the weight4 ,what other familiar example have we of this kind of lever8 ,the fishing-rod is an example of this kind4 ,one hand is the fulcrum1 the other hand is the power1 and the line1 with the fish1 is the weight4 ,this is made plain by ,fig4 #di1 representing a lad just drawing a fish out of the water4 ,illustration3 ,fig4 #di4 ,there are several other examples of this kind of lever2 will you name some of them8 ,yes2 brooms1 hoes1 rakes1 and axes are all levers of this kind4 ,what is the first kind of lever mentioned8 ,it is where the fulcrum is between the power and the weight1 as in ,fig4 #ej4 ,illustration3 ,fig4 #ej4 ,what is the second kind of lever mentioned8 ,it is where the weight is between the power and the fulcrum1 as in ,fig4 #ea4 ,illustration3 ,fig4 #ea4 ,what is the third kind of lever mentioned8 ,it is where the power is between the fulcrum and the weight1 as in ,fig4 #eb4 ,illustration3 ,fig4 #eb4 ,wheel and ,axle4 ,what other way have we for raising weights8 ,we have the wheel and axle1 as is shown in ,fig4 #ec4 ,illustration3 ,fig4 #ec4 ,what is the wheel and axle8 ,the wheel and axle is only another form of the lever4 ,where is the power applied8 ,the power is applied to the rope which passes around the wheel4 ,where is the weight8 ,the weight is the bucket attached to the rope which passes around the axle4 ,where is the fulcrum8 ,the fulcrum is the frame on which the ends of the axle rest4 ,is the power applied to the wheel equal to the weight to be raised8 ,no2 the power is always less than the weight to be raised4 ,upon what do the power and the weight depend8 ,they depend upon the size of the wheel and the axle4 ,when the diameter of the wheel is ten times the diameter of the axle1 how much will one pound raise8 ,one pound applied to the wheel1 will then raise ten pounds on the axle4 ,what is a windlass8 ,a windlass is another form of the wheel and axle1 as is shown in ,fig4 #ed4 ,illustration3 ,fig4 #ed4 ,what is used in a windlass in place of the wheel8 ,a crank or handle is used in place of the wheel4 ,does the crank take the place of the wheel8 ,yes2 when the crank is turned1 it forms a circle the same as the outside of the wheel4 ,to what use is the windlass often applied8 ,the windlass is often used to draw water from wells4 ,pulley4 ,what is a pulley8 ,a pulley is a wheel with a groove or hollow cut in its edge4 ,what is the groove for8 ,the groove is cut so that a rope may move over the wheel without slipping off4 ,illustration3 ,fig4 #ee4 ,in ,fig4 #ee1 where is the power applied8 ,the power is applied to one end of the rope by the hand4 ,where is the weight8 ,the weight is attached to the other end of the rope4 ,when the power and the weight are equal1 what do they do8 ,they balance each other1 and neither of them will move4 ,when the power is greater than the weight1 what takes place8 ,the weight is then lifted up4 ,of what use is the single pulley8 ,the single pulley is used for hoisting flags to the top of high poles1 for raising sails to the topmasts of vessels1 and for raising weights to the upper stories of mills and factories4 ,how many pulleys are needed1 when a horse is to raise the weight8 ,when a horse is to raise the weight1 two pulleys are needed1 as may be seen in ,fig4 #ef4 ,illustration3 ,fig4 #ef4 ,to what use do farmers apply the pulley8 ,they arrange the pulleys so as to lift the hay into their barns1 by means of a horse2 thus saving themselves much hard labor4 ,inclined ,plane4 ,when one end of a plank is raised up1 while the other end remains on the floor1 is its surface level8 ,no2 its surface is not level4 ,what may the surface of the plank be called8 ,it may be called an inclined surface1 or an inclined plane4 ,what is an inclined plane8 ,an inclined plane is a surface that inclines upwards or downwards4 ,of what use is the inclined plane8 ,it aids very much in raising weights4 ,are all planes inclined alike8 ,no2 some planes are much steeper than others4 ,illustration3 ,fig4 #eg4 ,in ,fig4 #eg1 where is the power8 ,the power is at ,p4 ,where is the weight8 ,the weight is at ,w4 ,upon what does the power and the weight depend8 ,they depend upon the height and the length of the inclined plane4 ,when an inclined plane is ten feet long and only one foot high1 how much will one pound at ,p balance8 ,one pound at ,p will balance ten pounds at ,w4 ,when an inclined plane ten feet long is two feet high1 how much will one pound at ,p balance8 ,one pound at ,p will then balance only five pounds at ,w2 because the plane is five times as long as it is high4 ,where else may the power be exerted8 ,the power may be exerted behind the weight1 as in ,fig4 #eh4 ,illustration3 ,fig4 #eh4 ,will any more power be needed behind the weight than before it8 ,no2 the power required is the same in both cases4 ,would it require as much power to roll barrels into a wagon as to lift them in8 ,no2 they can be rolled into a wagon much more easily than lifted in4 ,can they be taken out of the wagon any more easily on an inclined plane than without one8 ,yes2 they can be taken out more easily on an inclined plane4 ,why are drays1 used in cities1 made in the form of the inclined plane8 ,so that barrels and hogsheads may the more easily be rolled on them4 ,are our stairs in the form of the inclined plane8 ,yes2 they are inclined planes with steps cut in them to make the ascent easy4 ,why are house-roofs made in the form of the inclined plane8 ,so that the water falling on them may run off readily4 ,what familiar example of the inclined plane may be mentioned8 ,the hills1 all over the country1 are so many inclined planes4 ,of what use are the hills8 ,the hills carry off the waste water from the earth1 so that it is kept dry enough for plants to grow4 ,what other example of the inclined plane may be mentioned8 ,the beds of the creeks and rivers are so many inclined planes down which their waters flow4 ,wedge4 ,what is a wedge8 ,a wedge is a double inclined plane1 as is represented in ,fig4 #ei4 ,illustration3 ,fig4 #ei4 ,of what use is the wedge8 ,the wedge is used in splitting logs of wood and blocks of stone4 ,for what other purposes is the wedge used8 ,the wedge is used to fasten handles in hammers1 hatchets1 axes1 and hoes4 ,how is power applied to the wedge8 ,power is applied to the wedge by means of sudden blows from a hammer4 ,what prevents the wedge from flying back after the blow8 ,the friction between the wedge and the other body1 keeps it from flying back4 ,what instruments are made in the form of a wedge8 ,knife-blades1 hatchets1 axes1 razors1 and cutting instruments of nearly all kinds1 are in the form of the wedge4 ,screw4 ,what is a screw8 ,a screw is another form of the inclined plane4 ,where is the inclined plane on a screw8 ,it begins at the bottom of the screw1 and winds around and around the screw until it reaches the top1 as is shown in ,fig4 #fj4 ,illustration3 ,fig4 #fj4 ,what is this inclined plane called8 ,it is called the thread of the screw4 ,how do the threads affect the screw8 ,when the threads are far apart1 the inclined plane is steep2 but it becomes less steep the nearer the threads are together4 ,when will the screw exert the most power8 ,the screw will exert the most power1 when its threads are nearest together4 ,of what use are screws1 such as is shown in ,fig4 #fj8 ,screws are used to fasten hinges and bolts on doors and shutters1 and to fasten pieces of wood together in the construction of houses1 boats1 wagons1 and other things4 ,for what other purposes is the screw used8 ,the screw is used where much power is needed1 as in the vise2 where pressure is desired1 as in copying letters1 and in coining money2 and1 also1 for squeezing the juice from apples1 grapes1 and sugar-cane4 ,illustration3 ,fig4 #fa4 ,in what does a screw like that in ,fig4 #fa work8 ,it works in a nut which has threads cut on the inside1 so that the threads of the screw move in them4 ,where is the power applied8 ,the power is applied to the lever4 ,can heavy bodies be raised by means of this screw8 ,yes2 loaded cars1 and even heavy buildings1 may be raised by means of a screw of this kind4 ,illustration3 ,sewing machine4 ,illustration3 ,decoration4 ,,chapter ,,xi4 ,electricity4 ,illustration3 ,illustrated ,capital ,w ,when a cat's back is rubbed in the dark1 what does it give off8 ,it gives off small sparks4 ,what are these small sparks called8 ,they are called electric sparks1 or electricity4 ,if a horse be rubbed in the winter when it is dark1 what will be given off from him8 ,electricity will be given off from the horse4 ,when sealing-wax is rubbed with a silk handkerchief1 or a piece of flannel1 what is produced8 ,electricity is produced in the sealing-wax4 ,what will this electricity in the sealing-wax do8 ,it will attract bits of paper1 straw1 feathers1 and hairs1 when it is held near them4 ,what other substance will act the same as the sealing-wax8 ,a dry glass tube will act in the same manner when rubbed4 ,where is electricity found8 ,electricity is found in every body1 and in every thing4 ,how is electricity developed8 ,electricity is developed by motion1 by friction1 and by almost every change that takes place4 ,is electricity found in the air8 ,yes2 the air is almost constantly electrified4 ,with what is electricity often accompanied8 ,electricity is often accompanied by heat and light4 ,how many kinds of electricity are there8 ,there are two kinds of electricity4 ,what are they called8 ,they are called positive and negative electricity4 ,what do these two kinds of electricity always do8 ,they always attract each other4 ,when one body contains positive and the other body negative electricity1 what will the two bodies do8 ,they will rush together4 ,when both bodies are positive or both are negative1 what will they do8 ,they will repel each other4 ,when a body permits electricity to pass freely through it1 what is it called8 ,it is called a good conductor of electricity4 ,what substances are good conductors of electricity8 ,metals1 charcoal1 water1 animals1 vegetables1 flame1 and smoke4 ,when a body does not permit the electricity to pass through it1 what is it called8 ,it is called a non-conductor of electricity4 ,what substances are non-conductors of electricity8 ,gutta-percha1 sulphur1 glass1 silk1 wool1 hair1 feathers1 cotton1 and paper4 ,what is lightning8 ,lightning is electricity passing from one place to another4 ,when does lightning pass from one cloud to another cloud8 ,whenever one cloud becomes filled with more electricity than another1 the cloud having the most electricity gives off a portion to the cloud having the least electricity4 ,when does lightning pass from the earth to a cloud8 ,whenever the earth contains more electricity than the cloud does4 ,when does lightning pass from a cloud to the earth8 ,whenever the cloud contains more electricity than the earth does4 ,how near are the clouds when the lightning comes to the earth8 ,the clouds are seldom half a mile away when the lightning comes from them to the earth4 ,what noise is made by the lightning8 ,the lightning passes so quickly through the air1 that it makes a noise called thunder4 ,do we always hear the thunder when there is lightning8 ,no2 the lightning is sometimes so far away that the thunder cannot be heard4 ,what bodies attract the lightning to the earth8 ,tall trees1 steeples1 high houses1 and mountains4 ,does the lightning do any harm8 ,yes2 it does much harm by destroying trees1 houses1 animals1 and1 indeed1 almost everything in its course4 ,what does lightning sometimes do with buildings8 ,it sets the buildings on fire so that they are burned4 ,how are buildings protected from injury by lightning8 ,they are protected by means of the lightning-rod1 which was invented by ,dr4 ,franklin4 ,of what is the lightning-rod made8 ,the lightning-rod is made of some metal1 usually of iron or copper1 which is a good conductor of electricity4 ,what does the lightning-rod do when the building is struck8 ,the lightning-rod conducts the electricity to the earth1 so that it does not injure the building4 ,must the lightning-rod be higher than the building8 ,yes2 because the lightning is apt to strike the highest object4 ,of what should the point of the rod be made8 ,the point should be made of silver or platinum1 so that it will always remain bright4 ,should the rod extend deep into the ground8 ,the rod should extend four or five feet beneath the surface of the earth4 ,why should ashes or charcoal be put around the bottom of the rod8 ,because they are good conductors and will help to conduct the lightning into the earth4 ,how large should the lightning-rod be8 ,if made of iron1 the lightning-rod should be about three-fourths of an inch in diameter4 ,why is glass put around the rod where it is joined to the building8 ,the glass is a non-conductor1 and prevents the lightning from leaving the rod4 ,why is it not safe to stand near a fire during a thunder-storm8 ,because the fire is a good conductor1 and sometimes draws the electricity into the room4 ,what part of the room is the safest place8 ,the middle of a room is thought to be the safest place4 ,is a feather-bed a safe place8 ,yes2 because the feathers are a non-conductor1 and will not attract the lightning4 ,is dry air a non-conductor of electricity8 ,yes2 dry air is a non-conductor of electricity4 ,when are thunder-storms most frequent8 ,thunder-storms are more frequent in summer than in winter1 and more so in the afternoon than in the morning4 ,by what are thunder-storms usually attended8 ,they are usually attended by some change in the direction of the wind4 ,where do thunder-storms generally prevail8 ,they generally prevail in the lower regions of the air1 near the earth4 ,what is the rapidity of lightning8 ,the rapidity of lightning is probably not less than #bej1jjj miles in a second1 and the flash does not exceed the millionth part of a second in duration4 ,magnetism4 ,of what does magnetism treat8 ,magnetism treats of the property of magnets4 ,what is a magnet8 ,a magnet is a piece of iron ore having the power of attracting iron and steel4 ,how many kinds of magnets are there8 ,there are two kinds of magnets3 natural magnets1 and artificial magnets4 ,what other name is given to a natural magnet8 ,it is called a loadstone4 ,where are natural magnets or loadstones found8 ,they are dug out of the earth1 and are found most abundantly in ,norway and ,sweden4 ,what is an artificial magnet8 ,an artificial magnet is one made by magnetizing a bar of steel4 ,how may a bar of steel be magnetized8 ,a bar of steel1 when rubbed on a natural magnet1 becomes magnetized4 ,when the bar of steel is bent in the shape of a horse-shoe1 what is it called8 ,it is then called a horse-shoe magnet1 from its shape4 ,where does a magnetic bar always point1 when it is made to move easily on a pivot8 ,one end of it always points to the north1 and the other end to the south4 ,what are the ends of the magnet called8 ,the north end is called the positive1 and the south end is called the negative4 ,what is there curious about the magnet8 ,the positive end of one magnet always attracts the negative end of every other magnet2 but if the two positive or the two negative ends are brought together1 they will repel each other4 ,why are artificial magnets made of steel8 ,because steel will remain magnetized1 but iron soon loses the magnetic properties4 ,what is a compass8 ,a compass is an instrument containing a magnetic needle1 so balanced as to move easily on a pivot4 ,in what direction does this needle always point8 ,this needle always points toward the north4 ,by whom is the compass used8 ,it is used by travellers to guide them on their journey2 by surveyors to mark out the boundary lines between different properties2 and by seamen to point out their way across the sea from one place to another4 ,before the ,mariner's ,compass was invented1 seamen were afraid to venture out of the sight of land1 for fear of being lost on the ocean2 for they then had no means of telling where they were1 or in what direction to guide their vessels1 so as to reach the land again4 ,electro-,magnetism4 ,are magnetism and electricity much alike8 ,yes2 they are so nearly alike that many persons think they are identical4 ,what is an electro-magnet8 ,an electro-magnet is a magnet obtained by means of electricity4 ,of what is the magnet made8 ,the magnet is made of soft iron1 around which are wound a great many coils of wire1 and these are covered with silk4 ,how is the soft iron made into a magnet8 ,the iron is magnetized by the passage of electricity through the wire4 ,of what use is this magnet8 ,it is used in the electro-magnetic telegraph4 ,when and where was the first line of telegraph built8 ,the first line of telegraph was built in #ahdd1 from ,washington to ,baltimore1 by ,professor ,morse4 ,what is the principle of the telegraph8 ,at one end of the telegraph wire is an electrical battery1 and at the other end is an electro-magnet4 ,when a message is to be sent1 the electricity is transmitted through the wire to the soft iron of the electro-magnet1 which causes the iron to move1 and this motion is conveyed to the machinery1 which is needed to print the message in letters or signals1 so as to be understood4 ,does electricity move rapidly8 ,yes2 its velocity is such as to move around the earth in a quarter of a second4 ,what is the electrical battery called8 ,the electrical battery is called a key4 ,what is the electro-magnet called8 ,the electro-magnet is called a receiver4 ,for what are the key and receiver used8 ,the key is used for sending messages1 and the receiver for receiving them4 ,what must each station have8 ,each station must have both a key and a receiver1 so as to send as well as receive messages4 ,what is the ,atlantic cable8 ,the ,atlantic cable is a telegraphic wire reaching across the ,atlantic ,ocean1 from ,america to ,europe4 ,when was the first ,atlantic cable laid8 ,the first ,atlantic cable was successfully laid in #ahff1 between ,newfoundland and ,ireland4 ,it is eighteen hundred and sixty-four miles long1 and its success is chiefly due to ,cyrus ,w4 ,field4 ,of what use is the ,atlantic cable8 ,the ,atlantic cable forms a telegraphic connection between ,europe and ,america1 so that news may be sent from one country to the other in a few moments of time2 thus the people of the two continents1 although so far apart1 can communicate with each other many times in a single day4 ,illustration3 ,fruit bowl4 ,,the ,elements of ,natural ,philosophy ,by ,e4 ,j4 ,,houston1 ,a4,m41 ,professor of ,physics and ,physical ,geography in the ,central ,high ,school1 ,philadelphia1 ,pa4 ,this book is intended for ,graded ,schools1 ,academies1 ,seminaries1 ,normal ,schools1 etc4 ,it gives the elements of the science in a concise form and in logical sequence1 so that the book forms a system of ,natural ,philosophy1 and not a mere collection of disconnected facts4 ,it is fully 8up to the times0 in every respect1 and gives full descriptions of the more important discoveries lately made in ,physical ,science2 the ,electric ,light1 the ,telephone1 the ,microphone1 the ,phonograph1 etc41 are all described and illustrated4 ,an examination of the work will show that no expense has been spared to bring it up to the highest standard as regards illustration and typography4 ,we invite the attention of ,teachers to our ,publications1 a ,catalogue of which will be sent on application4 ,on our ,list will be found some of the most popular of modern ,text-,books4 ,please address ,eldredge ,bro41 #ag ,north ,seventh ,street1 ,,philadelphia4 ,illustration3 ,,morgan ,,hanford4 ,books1 ,stationery ,music4 #f ,north ,st4 ,,middletown4 ,n4,y4 ,illustration3 ,,eldredge ,,brother ,,educational ,,publishers4 ,no4 #ag ,n,,th4 ,,seventh ,,st4 --,philadelphia-- ,transcriber's ,notes --,retained publication information from the printed edition3 this e,book is public-domain in the country of publication4 --,corrected a few palpable typographical errors4 --,in the text versions only1 text in italics is delimited by underscores4