,a ,,guide ,,to ,,the ,,scientific ,,knowledge ,,of ,,things ,,familiar2 ,,by ,,the ,,rev4 ,,dr4 ,,brewer1 ,,trinity ,,hall1 ,,cambridge1 ,,head ,,master ,,of ,,king',s ,,college ,,school1 ,,norwich1 ,,in ,,union ,,with ,,king',s ,,college1 ,,london4 ,,london3 ,,jarrold ,,and ,,sons1 #dg1 ,,st4 ,,paul',s ,,churchyard1 ,,also ,,hamilton ,,and ,,co41 ,,simpkin ,,and ,,co41 ,,and ,,whittaker ,,and ,,co4 ,,preface4 ,of all science1 none is more generally interesting than that which explains the common phenomena of life4 ,we see that salt and snow are both white1 a rose red1 leaves green1 and the violet a deep purple2 but how few persons ever ask the reason why6 ,we know that a flute produces a musical sound1 and a cracked bell a discordant one--that fire is hot1 ice cold1 and a candle luminous--that water boils when subjected to heat1 and freezes from cold2 but when a child looks up into our face and asks us why1--how many times is it silenced with a frown1 or called very foolish for asking such silly questions6 ,the object of the present book is to explain about #bjjj of these silly questions 7which are often more easily asked than answered7 in language so simple that a child may understand it1 yet not so childish as to offend the scientific2 and in order that the answers may be strictly correct1 not only the most approved modern authors have been consulted1 but the manuscript has been submitted sheet by sheet to the revision of two gentlemen of acknowledged reputation for scientific attainments4 ,to the ,,rev4 ,a4 ,,bath ,,power1 ,m4 ,a4 especially1 great obligation is due1 for a careful revision of the whole manuscript1 for many excellent hints1 and useful additions4 ,in conclusion1 so much diligence has been bestowed upon this little work for nearly ten years1 so much useful information has been supplied by scientific friends1 and so minute a revision has been made of every answer1 that it is no presumption to express a hope that this ,guide to the ,scientific ,knowledge of ,things ,familiar will become generally useful and acceptable1 not only to the young1 but to those advanced to maturer life4 ,in this work some questions occur more than once1 because they serve to illustrate different principles2 and whenever cognate questions occur1 the answers have been rendered as similar as possible1 in order to assist the memory of the learner4 ,,subjects ,,of ,,the ,,chapters4 ,,part ,i4--,,heat4 ,i4--,the ,,sun a source of heat ,,ii4--,,electricity a source of heat ,thunder and lightning ,,iii4--,,chemical ,,action a source of heat ,,iii4--,combustion ,,iv4--,smoke and smoky chimneys ,v4--,lamps and candles ,,vi4--,animal heat ,,vii4--,,mechanical ,,action a source of heat ,,vii4--,percussion ,,viii4--,friction ,,viii4--,compression ,,ix4--,,effects ,,of ,,heat ,x4--,expansion ,,xi4--,liquefaction ,,xi4--,vaporization 7clouds7 ,,xii4--,evaporation ,,xiii4--,,communication ,,of ,,heat ,,xiii4--,conduction ,,xiv4--,absorption ,,xv4--,reflection ,,xvi4--,radiation 7dew7 ,,xvii4--,convection 7boiling7 ,,part ,,ii4--,,air4 ,,xviii4--,,air ,rust ,tarnish ,,xix4--,,carbonic ,,acid ,,gas ,froth ,effervescence ,fermentation1 c4 ,,xx4--,,carburetted ,,hydrogen ,,gas ,fire damp ,safety lamp ,,xxi4--,,phosphuretted ,,hydrogen ,,gas ,ignis fatuus ,ghosts ,,xxii4--,,wind ,,xxiii4--,,barometer ,ten special ,rules ,,xxiv4--,,snow4 ,,hail4 ,,rain ,,xxv4--,,water ,,xxvi4--,,ice ,frost ,freezing mixtures ,,xxvii4--,,light ,reflection ,telescopes ,refraction ,spectacles ,rainbows ,colour ,,xxviii4--,,sound ,ear trumpets ,echoes ,,xxix4--,,miscellaneous ,attraction ,anti-putrescents ,sleep ,dreams ,glossary ,index ,,part ,i4 ,,heat4 ,,introduction4 ,q4 ,what is heat8 ,a4 ,the sensation of warmth4 ,q4 ,how is this sensation produced8 ,a4 ,when we touch a substance of higher temperature than ourselves1 the warmer substance keeps parting with its heat1 till both are of equal temperature4 ,q4 ,what is that stream of heat called1 which flows thus1 from one body1 to another8 ,a4 ,,calo',,ric4 ,caloric1 therefore1 is the matter of heat1 which passes from body to body2 but ,,heat is the sensation1 of warmth1 produced by the influx of ,calo'ric4 ,q4 ,what are the four principal ,,sources of heat8 ,a4 #a4--,the ,sun4 #b4--;,electricity4 #c4--;,chemical ,action3 and #d4--,mechanical ,action4 ,q4 ,what are the principal ,,effects of heat8 ,a4 ,expansion1 ,liquefaction1 ,vaporization1 and ,ignition4 ,,chapter ,i4 ,q4 ,what is the ,,principal source of ,heat8 ,a4 ,the ,,sun4 ,q4 ,why do ,,burning ,,glasses set fire to substances submitted to their power8 ,a4 ,the rays of the sun1 collected by the ,burning ,glass1 are all bent to one point1 called the focus2 thus the heat and light1 7which should be diffused over the whole glass17 being gathered together into one point1 are very greatly increased4 ,q4 ,why is there a ,,dark ,,rim round this focus8 ,a4 ,because the rays of light1 which should have fallen there1 are bent into the focus1 and the space around1 7being deprived of these rays7 is accordingly darkened4 ,q4 ,are ,,all the rays bent into one point8 ,a4 ,no1 not quite all3 and1 therefore1 the rim round the focus is only slightly shadowed4 ,,chapter ,,ii4 ,q4 ,what is the second chief source of heat8 ,a4 ,,electricity4 ,q4 ,what is ,,lightning8 ,a4 ,lightning is only an ,electric ,spark1 taken from the clouds4 ,q4 ,what causes the discharge of an electric cloud8 ,a4 ,when a cloud1 overcharged with electric fluid1 approaches another which is under-charged1 the fluid rushes from the former into the latter1 till both have the same quantity4 ,q4 ,is there any ,,other cause of lightning1 besides the one just mentioned8 ,a4 ,yes2 sometimes mountains1 trees1 and steeples1 will discharge a lightning cloud floating near2 and sometimes electric fluid rushes out of the earth1 into the clouds4 ,q4 ,what produces ,,electricity in the ,,clouds8 ,a4 #ast--,the evaporation from the earth's surface4 #bndly--,the chemical changes perpetually going on3 and #crdly--,currents of air of unequal temperature1 excite electricity by friction1 as they pass by each other4 ,q4 ,how ,,high are the ,,lightning-,,clouds from the earth8 ,a4 ,electrical clouds are the lowest of all clouds2 they are rarely more than #gjj yards above the ground2 and sometimes1 they actually touch the earth with one of their edges4 ,q4 ,how high are the clouds generally8 ,a4 ,in a fine day1 the clouds are often #d or #e miles above our head2 but the average height of the clouds is from #a-a_/b to #b miles4 ,q4 ,why is lightning sometimes ,,forked8 ,a4 ,when the lightning-cloud is a long way off1 the resistance of the air is so great1 that the electrical current is diverted into a zig-zag course4 ,q4 ,why does the resistance of the air make the lightning zig-zag8 ,a4 ,as the lightning condenses the air1 in the immediate advance of its path2 it keeps flying from side to side1 in order to pass where there is the least resistance4 ,q4 ,how does lightning ,,condense the air in the immediate advance of its path8 ,a4 ,the air is condensed by the rapidity of the lightning-flash4 ,q4 ,why is ,,forked ,,lightning more ,,dangerous than a straight flash8 ,a4 ,whatever resists the flash1 diverts its course2 and when terrestrial objects offer resistance to the current1 they are in great danger of being destroyed4 ,q4 ,why are there sometimes ,,two flashes of forked lightning at the same moment8 ,a4 ,sometimes 7in very severe storms7 a flash of lightning will divide into two or more parts2 and then each branch assumes the zig-zag form4 ,q4 ,why is the ,,flash sometimes quite ,,straight8 ,a4 ,when the lightning-cloud hovers near the earth1 as the flash meets with very little resistance1 it is not diverted2 or 7in other words7 the flash is straight4 ,q4 ,what is the cause of ,,sheet ,,lightning8 ,a4 ,it is only the reflection of distant flashes1 not distinctly visible3 and sometimes several flashes 7from different clouds7 intermingle1 and form one vast blaze or sheet of lightning4 ,q4 ,which ,,form of lightning is the most ,,dangerous8 ,a4 ,the ball of fire is by far the most dangerous2 and the zig-zag lightning is next in danger4 ,sheet lightning is not often attended with danger4 ,q4 ,why are ,,balls ,,of ,,fire so very dangerous8 ,a4 ,because 7whenever they fall7 much mischief is occasioned by their bursting1 which they always do1 with an explosion like that of a cannon4 ,q4 ,do these ,,balls ,,of ,,lightning ever run along the ground8 ,a4 ,yes2 they often run a considerable way along the ground1 then stop for a little time1 and burst in numberless pieces3 sometimes each of these pieces will explode2 and at other times1 the whole ball will burst at once1 producing most mischievous consequences4 ,q4 ,what mischief will these balls of fire produce8 ,a4 ,they will set houses and barns on fire2 and kill all cattle and human beings1 which happen to be in their course4 ,q4 ,why does ,,lightning sometimes ,,kill men and beasts8 ,a4 ,when the electric current passes through a man or beast1 it produces so violent an action upon the nerves1 that it destroys life4 ,q4 ,when is a person struck dead by lightning8 ,a4 ,only when his body forms a part of the lightning's path3 i4 e4 when the electric fluid 7in its way to the earth7 actually passes through his body4 ,q4 ,why are ,,men sometimes ,,maimed by lightning8 ,a4 ,because lightning strikes with amazing force1 whatever opposes it3 and if a man stand in the way1 it strikes him such a blow1 as to maim him4 ,q4 ,what is ,,thunder8 ,a4 ,lightning parts the air through which it passes2 and when the parted air closes again1 the noise made by the concussion1 is called ,thunder4 ,q4 ,why does lightning ,,part the air through which it passes8 ,it does not part a rod of iron4 ,a4 ,iron is a conductor1 and therefore allows the fluid to go freely through it3 but air being a non-conductor1 resists the lightning2 which1 therefore1 rips it open1 in order to pass through it4 ,q4 ,why is ,,thunder sometimes ,,one ,,vast ,,crash8 ,a4 ,when the lightning-cloud is near the earth1 as the flash is straight1--the whole volume of air 7through which it passes7 collapses at once2 and produces one unbroken sudden crash4 ,q4 ,what is meant by the air collapsing8 ,a4 ,when the rent air closes again1 it is said to collapse4 ,q4 ,why is the ,,peal sometimes an ,,irregular mangling broken ,,roar8 ,a4 ,when the lightning-cloud is a long way off1 as the flash is zigzag1 the air does not collapse all at once2 and as we hear the concussion of one part after another1 the peal is broken1 protracted1 and irregular4 ,q4 ,which part of the collapsing air do we hear first8 ,a4 ,that part nearest the earth2 then the strata above2 and last of all1 that in the immediate vicinity of the cloud4 ,q4 ,what is meant by ,,strata of air8 ,a4 ,if a board were laid upon the earth1 and several other boards were piled upon it1 this pile would represent strata of wood4 ,q4 ,how does this illustration apply to the air8 ,a4 ,a layer of air covers the earth2 another layer rests upon it2 and thus layer is piled upon layer1 for #ej miles in height4 ,each layer is a stratum of air2 and the plural of stratum is strata4 ,q4 ,why do we hear the collapsing of the air ,,nearest the earth ,,first8 ,a4 ,because sound takes a whole second of time to travel #chj yards2 but the air is ripped from top to bottom instantaneously3 if1 therefore1 the cloud were #ajjj yards off1 we should hear the collapsing of the lowest strata nearly three seconds1 before we heard that in the immediate vicinity of the cloud4 ,q4 ,why is the ,,thunder sometimes like a deep ,,growl8 ,a4 ,when the storm is far distant1 the thunder sounds like a deep growl4 ,q4 ,does not ,,scenery affect the sound of thunder8 ,a4 ,yes2 the flatter the country1 the more unbroken the peal3 ,mountain scenery breaks the peal1 and makes it harsh and irregular4 ,q4 ,what is the cause of ,,rolling ,,thunder8 ,a4 ,the rolling is produced by the reverberation of the thunder along the massive clouds4 ,q4 ,what is meant by the reverberation8 ,a4 ,the echo4 ,q4 ,why is a flash of lightning generally followed by a ,,pouring ,,rain8 ,a4 ,the cloud collapses1 as soon as the electric fluid has left it2 and the water it contained is squeezed out4 ,q4 ,why is a flash of lightning generally followed by a ,,gust of ,,wind8 ,a4 ,the flash rent the air asunder through which it darted2 and when the two parts collapse1 a rapid motion is produced1 which we call wind3 the vibration of the thunder contributes also to agitate the air4 ,q4 ,what is meant by the ,,vibration of the thunder8 ,a4 ,the quivering motion it gives to the air1 by its loud sound4 ,q4 ,why is there ,,no ,,thunder to what is called ,,summer ,,lightning8 ,a4 ,because the lightning-clouds are so far off1 that the sound of the thunder is lost1 before it reaches the earth4 ,q4 ,do ,,thunder-,,bolts ever drop from the clouds8 ,a4 ,no2 the notion of thunder-bolts falling from the clouds1 arises from the globular form1 that is sometimes assumed by a flash of lightning4 ,q4 ,why is the ,,thunder often several moments ,,after the ,,flash8#a ,a4 ,the flash travels nearly a million times faster than the thunder2 if1 therefore1 the thunder has far to come1 it will not reach the earth till a considerable time after the flash4 #a ,the speed of lightning is so great1 that it would go #dhj times round the earth in one minute3 whereas1 thunder would go scarcely #ac miles in the same space of time4 ,q4 ,can we not tell the ,,distance of a thunder-cloud1 by observing the interval which elapses between the flash and the peal8 ,a4 ,yes2 the flash is instantaneous1 but the thunder will take a whole second of time to travel #chj yards3 hence1 if the flash is #e seconds before the thunder1 the cloud is #aijj yards off4 7i4 e4 #chj #e #aijj yards47 ,q4 ,what ,,places are most ,,dangerous to be in1 during a ,,storm8 ,a4 ,it is very dangerous to be near a tree1 or lofty building2 it is dangerous also1 to be near a river1 or any running water4 ,q4 ,why is it ,,dangerous to be ,,near a ,,tree1 or lofty building1 during a thunder-storm8 ,a4 ,because a tall pointed object1 7like a tree or spire17 will frequently discharge a lightning-cloud2 and then the electric fluid will pass down it1 in its way to the earth4 ,q4 ,how can a ,,tree or ,,spire ,,discharge a lightning-cloud8 ,a4 ,a lightning-cloud 7floating over a plain7 may be too far off to be discharged by it2 but as a tree1 or spire1 would shorten the distance between the cloud and its conductor1 it might no longer be too far off a conductor to be discharged4 ,q4 ,is not air a ,,conductor of lightning8 ,a4 ,no2 dry air is not a conductor of lightning2 and therefore1 the flash rends it in twain1 to get to some conductor4 ,q4 ,why would it be dangerous to stand near a tree or spire1 while lightning is passing down it8 ,a4 ,because the electric fluid 7called lightning7 always rushes down the outside of the tree or spire2 and if any one were standing near1 might pass through him1 and kill or maim him4 ,q4 ,does lightning go through the inside or outside of a tree8 ,a4 ,it rolls down the outside of a tree2 but passes through the inside of a man4 ,q4 ,why does lightning pass down the ,,outside of a tree8 ,a4 ,lightning always makes choice of the best conductors2 and the outside of a tree is a better conductor than the inside4 ,q4 ,why does lightning pass through the ,,inside of a man8 ,a4 ,as the fluids of the human body make a better conductor than the skin1 therefore lightning passes through a man1 and not down the skin4 ,q4 ,why is it ,,dangerous to be near a deep ,,river1 or any other running water1 during a thunder-storm8 ,a4 ,because running water is a good conductor2 and lightning always takes in its course the best conductors4 ,q4 ,why is it dangerous for a man to be near water1 in a thunder-storm8 ,a4 ,because the height of a man may be sufficient to discharge a cloud3 and 7if there were no taller object nigh7 the lightning might make the man its conductor to the water4 ,q4 ,why is it ,,dangerous to ,,ring ,,church-,,bells during a thunder-storm8 ,a4 ,for two reasons3 #ast--,because the steeple may discharge the lightning-cloud1 in consequence of its mere height4 #bndly--,the swinging of the bells causes a current of air1 which collects electric fluid4 ,q4 ,why is it unsafe to ,,run or ,,drive ,,fast during a thunder-storm8 ,a4 ,the rapid motion of running causes a current of air1 which collects electric fluid1 and is often fatal4 ,q4 ,what ,,parts of a ,,dwelling are most ,,dangerous during a thunder-storm8 ,a4 ,the fire-place1 7especially if the fire be lighted72 the attics and cellar4 ,it is also dangerous to sit close by the walls2 to ring the bell2 or to bar the shutters1 during a thunder-storm4 ,q4 ,why is it ,,dangerous to sit ,,before a ,,fire1 during a thunder-storm8 ,a4 ,because the heated air and soot are conductors of lightning2 especially when connected with such excellent conductors as the stove1 fender1 and fire-irons4 ,q4 ,why are the ,,attics and ,,cellar ,,dangerous1 during a thunder-storm8 ,a4 ,lightning sometimes passes from the clouds to the earth1 and sometimes from the earth to the clouds2 and therefore1 the middle story of a house is always the safest to be in1 during a thunder-storm4 ,q4 ,when does lightning pass ,,from ,,the ,,earth to the ,,clouds8 ,a4 ,when the clouds are in a negative state of electricity4 ,q4 ,when does lightning pass ,,from ,,the ,,clouds to the ,,earth8 ,a4 ,when the clouds are in a positive state of electricity4 ,q4 ,what is meant by the clouds being in a positive state of electricity8 ,a4 ,when the clouds contain more electric fluid than they generally do1 they are said to be in a positive state of electricity4 ,q4 ,what is meant by the clouds being in a negative state of electricity8 ,a4 ,when the clouds contain less electric fluid than they ought to do1 they are said to be in a negative state of electricity4 ,q4 ,does the flash proceed from a negative or positive body8 ,a4 ,always from a positive body1 or one over-burdened with electric fluid4 ,q4 ,when lightning flashes from the earth to the clouds1 what is the flash called8 ,a4 ,it is called the returning stroke2 because the earth 7being over-burdened with electric fluid7 returns the surplus quantity to the clouds4 ,q4 ,why is it ,,dangerous to lean ,,back ,,against ,a ,,wall during a thunder-storm8 ,a4 ,because the electric fluid sometimes runs down the wall of a house or room2 and 7as a man is a better conductor than a brick wall71 would make him its path1 and injure him4 ,q4 ,why is it dangerous to ,,ring a ,,bell during a thunder-storm8 ,a4 ,bell-wire is an excellent conductor2 and 7if a person were to touch the bell-handle71 the electric fluid1 passing down the wire1 might run through his hand and injure it4 ,q4 ,why would the lightning run through a man touching a bell-handle8 ,a4 ,because the human body is a better conductor than the wall 7between the bell-handle and the floor72 and as lightning always chooses the best conductors for its path1 it would 7in this case7 pass through the man1 and injure him4 ,q4 ,why is it ,,dangerous to ,,bar a ,,shutter during a thunder-storm8 ,a4 ,the iron shutter-bar is an excellent conductor2 and 7if a person were touching the bar71 the electric fluid passing down it1 might run from the bar through the person touching it1 and injure him4 ,q4 ,why is it dangerous to be in a ,,crowd during a thunder-storm8 ,a4 ,for two reasons4 #ast--,because a mass of people form a better conductor than an individual3 and #bndly--,the vapour from a crowd increases the danger of such a place4 ,q4 ,why is a ,,mass of bodies a better conductor than a single body8 ,a4 ,each living body is a conductor of electricity2 and a connected mass of such conductors is more likely to be struck1 than a single individual4 ,q4 ,why is the danger increased by the ,,vapour which rises from a crowd8 ,a4 ,vapour is a conductor1 and therefore1 may determine the shock2 especially when connected with so many living bodies4 ,q4 ,why is a ,,theatre dangerous1 during a thunder-storm8 ,a4 ,because the crowd assembled there1 and the great vapour arising from so many living bodies1 render a theatre an excellent conductor of lightning4 ,q4 ,why is a ,,flock of sheep in greater danger than a smaller number8 ,a4 ,because each sheep is a conductor of lightning1 and the greater the number1 the better its conducting power2 besides1 the vapour arising from a flock of sheep increases its conducting power1 and its danger4 ,q4 ,why is a ,,herd of cattle in danger during a storm8 ,a4 #ast--,the number of living bodies increases the conducting power of the animal fluids3 and #bndly--,the vapour arising from a herd is also a good conductor4 ,q4 ,if a person be ,,abroad in a thunder-storm1 what place is the ,,safest8 ,a4 ,any spot about #bj or #cj feet from some tall tree or building2 unless that spot be near to running water4 ,q4 ,why would it be safe to stand #bj or #cj feet from some tall tree1 in a thunder-storm8 ,a4 ,because the lightning would always choose the tall tree as a conductor1 rather than the shorter man2 and he would not be sufficiently near the tree1 to be injured by the electric current passing down it4 ,q4 ,if a person be in ,a ,,carriage in a thunder-storm1 in what way can he travel most ,,safely8 ,a4 ,he should not lean against the carriage2 but sit upright1 without touching any of the four sides4 ,q4 ,why should not a person lean ,,against the carriage in a storm8 ,a4 ,because the electric fluid might run down the sides of the carriage2 and 7if a person were leaning against the sides71 would make choice of him for a conductor1 and perhaps destroy life4 ,q4 ,if a person be in ,a ,,house during a thunder storm1 what place is ,,safest8 ,a4 ,any room in the middle story4 ,the middle of the room is best2 especially if you place yourself on a mattrass1 bed1 or hearth-rug4 ,q4 ,why is the ,,middle ,,story of a house ,,safest in a thunder-storm8 ,a4 ,because 7even if the fluid struck the house71 its strength would be exhausted before it reached the middle story4 ,q4 ,why is the ,,middle of the ,,room more ,,safe1 than any other part of it1 in a thunder-storm8 ,a4 ,because1 if the lightning came into the room at all1 it would come down the chimney or walls of the room2 and therefore1 the further distant from these1 the better4 ,q4 ,why is a ,,mattrass ,,bed1 or ,,hearth-,,rug a good security against injury from lightning8 ,a4 ,because they are all non-conductors2 and1 as lightning always takes in its course the best conductors1 it would not select such things as these4 ,q4 ,is it better to be ,,wet or dry during a storm8 ,a4 ,to be wet3 if a person be in the open field1 the best thing he can do1 is to stand about #bj feet from some tree1 and get completely drenched to the skin4 ,q4 ,why is it better to be ,,wet than dry8 ,a4 ,because the wet clothes would form a far better conductor than the fluids of our body2 and1 lightning would roll down the wet clothes1 without touching our body at all4 ,q4 ,what is the ,,safest thing a person can do to avoid injury from lightning8 ,a4 ,he should draw his bedstead into the middle of his room1 commit himself to the care of ,god1 and go to bed2 remembering that our ,lord has said1 ,the very hairs of your head are all numbered4 ,q4 ,what is a ,,lightning-,,conductor8 ,a4 ,a metal rod fixed in the earth1 running up the whole height of a building1 and rising in a point above it4 ,q4 ,what metal is the best for this purpose8 ,a4 ,stout copper wire4 ,q4 ,why is ,,copper wire better than iron8 ,a4 #ast--,because copper is a better conductor than iron3 #bndly--,it is not so easily fused or melted3 and #crdly--,it is not so much injured by weather4 ,q4 ,what is the ,,good of a lightning-conductor8 ,a4 ,metal wire is a most excellent conductor2 and as the lightning makes choice of the best conductors1 it would run down the metal wire1 rather than the bricks of the building4 ,q4 ,how far will the beneficial influence of a lightning-conductor extend8 ,a4 ,it will protect a circumference all round1 the diameter of which is 7at least7 #d times as long as that part of the rod1 which rises above the building4 ,q4 ,give me an example4 ,a4 ,if the rod rise #b feet above the house1 it will protect the building for 7at least7 #h feet all round4 ,q4 ,why are not lightning-conductors more generally used8 ,a4 ,because they are often productive of more harm than good4 ,q4 ,how can lightning-conductors be productive of ,,harm8 ,a4 ,if the rod be broken by weather or accident1 the electric fluid 7being obstructed in its path7 will rend the building into fragments4 ,q4 ,is there any ,,other evil to be apprehended from a lightning rod8 ,a4 ,yes2 if the rod be not big enough to conduct the whole current to the earth1 the lightning will fuse the metal1 and greatly injure the building4 ,q4 ,how stout is it needful for the copper wire to be1 that it may conduct the fluid safely to the earth8 ,a4 ,it should be 7at least7 one inch in diameter4 ,q4 ,why does ,,lightning sometimes ,,knock ,,down ,,houses and churches8 ,a4 ,the steeple1 or chimney is first struck2 the lightning then darts to the iron bars and cramps employed in the building2 and 7as it darts from bar to bar7 shatters to atoms the bricks and stones1 which oppose its progress4 ,q4 ,can you tell me how ,st4 ,bride's ,church 7,london7 was nearly destroyed by lightning1 about #ajj years ago8 ,a4 ,the lightning first struck the metal vane1 and ran down the rod2 it then darted to the iron cramps1 employed to support the building2 and 7as it flew from bar to bar7 smashed the stones of the church1 which lay between4 ,q4 ,why did the lightning fly about from place to place1 and not pass down in a straight course8 ,a4 ,because it always takes in its course the best conductors2 and will fly both right and left1 in order to reach them4 ,q4 ,why does ,,lightning turn ,,milk ,,sour8 ,a4 ,lightning causes the gases of the air 7through which it passes7 to combine1 and thus produces a poison1 called nitric acid2 some small portion of which1 mixing with the milk1 turns it sour4#b 7,n4 ,b4 ,sometimes1 the mere heat of the air1 during the storm1 turns milk sour47 #b ,the air is composed of two gases1 called oxygen and hydrogen1 mixed together1 but not combined4 ,if oxygen is combined with nitrogen1 it produces five deadly poisons1 viz4--nitrous oxide1 nitric oxide1 hyponitrous acid1 nitrous acid1 and nitric acid1 according to the proportion of each gas in the combination4 ,q4 ,what is the difference between ,,combining and ,,mixing8 ,a4 ,when different ingredients mingle without undergoing any chemical change1 they are said to be mixed2 but when the natural properties of each are altered by the union1 then those ingredients are said to be combined4 ,q4 ,give me an example4 ,a4 ,if different coloured sands be shaken together in a bottle1 the various grains will mix together1 but not combine3 but if water be poured on quick lime1 the water will combine with the lime1 and not mix with it4 ,q4 ,why are the different grains of sand said to be ,,mixed1 when they are shaken together8 ,a4 ,because they are mingled together1 but the property of each grain remains the same as it was before4 ,q4 ,why is water poured on lime1 said to ,,combine with it8 ,a4 ,because the properties1 both of the water and the lime1 are altered by the mixture3 the lime alters the character of the water1 and the water alters the character of the lime4 ,q4 ,do oxygen and nitrogen ,,combine1 or only ,,mix together1 in common atmospheric air8 ,a4 ,they only mix together1 as grains of sand would do1 when shaken in a bottle4 ,when oxygen and nitrogen combine1 they do not constitute air1 but acid poisons4 ,q4 ,why does ,,lightning turn ,,beer ,,sour1 although contained in a close cask8 ,a4 ,if the beer be new1 and the process of fermentation not complete1 lightning will so accelerate the process1 as to turn the liquor sour4 ,q4 ,why is ,,not old beer and strong ,,porter made ,,sour by lightning8 ,a4 ,because the fermentation is complete already2 and1 therefore1 is not affected by electrical influence4 ,q4 ,why is ,,metal sometimes ,,fused by lightning8 ,a4 ,because the dimension of the metal is too small1 to afford a path for the electric current4 ,q4 ,why does ,,lightning ,,purify the ,,air8 ,a4 ,for two reasons3 #ast--,because the oxygen and nitrogen of the air combine1#c and produce nitric acid3 #bndly--,because the agitation of the storm stirs up the air4 #c ,the oxygen and hydrogen are not combined1 but simply mixed in the ordinary air2 but the lightning causes the mixed elements to combine4 ,q4 ,how does the production of nitric acid purify the air8 ,a4 ,nitric acid acts very powerfully in destroying exhalations1 arising from putrid vegetable and animal matters4 ,q4 ,why is ,,lightning more common in ,,summer and ,,autumn1 than in spring and winter8 ,a4 ,the heat of summer and autumn produces great evaporation2 and the conversion of water to vapour1 always develops electricity4 ,q4 ,why does a ,,thunder-,,storm generally follow very ,,dry weather1 and rarely succeeds continued ,,wet8 ,a4 ,the clouds are always charged with electricity2 but dry air 7being a non-conductor71 will not conduct the surplus fluid from the clouds to the earth3 so it violently rends the dry air with a flash1 in order to relieve the cloud1 and reach the earth4 ,q4 ,what is the general ,,direction of a ,,thunder-,,storm8 ,a4 ,either from east to west2 or else from north to south4 ,q4 ,why is ,,electricity excited by ,,friction8 ,a4 ,electricity1 like heat1 exists in all matter2 but is often in a latent state3 friction disturbs it1 and brings it into active operation4 7see p4 #ca47 ,q4 ,why is a ,,tree sometimes ,,scorched by lightning1 as if it had been set on fire8 ,a4 ,lightning scorches it by its own positive heat1 just the same as fire would4 ,q4 ,why is the ,,bark of a ,,tree often ripped quite off by a flash of lightning8 ,a4 ,as the lightning runs down the tree1 it develops the latent heat so rapidly1 that it carries the bark of the tree along with it1 while it seeks to escape4 ,q4 ,why are ,,boughs of ,,trees broken off by lightning8 ,a4 ,the mechanical force of lightning is very great2 and when the flash strikes a tree1 it will often break off the boughs by the force with which it strikes against it4 ,q4 ,why is an electric shock felt ,,most at the ,,elbow ,,joint8 ,a4 ,because the path of the fluid is obstructed by the joint3 and the shock felt at the elbow is caused by the fluid leaping from one bone to another4 ,,chapter ,,iii4 ,q4 ,what is the third chief source of heat8 ,a4 ,,chemical ,,action4 ,q4 ,what is meant by chemical action being the source of heat8 ,a4 ,many things1 when their chemical constitution is changed1 7either by the abstraction of some of their gases1 or by the combination of others not before united17 evolve heat1 while the change is going on4 ,q4 ,explain by illustration what you mean4 ,a4 ,water is cold1 and sulphuric acid is cold2 but if these two cold liquids be mixed together1 they will produce boiling heat4 ,q4 ,why will ,,cold ,,water1 mixed with ,,sulphuric ,,acid1 produce heat8 ,a4 ,because water 7being lighter than sulphuric acid71 is condensed by the heavier liquid2 and its heat is squeezed out1 as water from a sponge4 ,q4 ,why does ,,cold ,,water1 poured on ,,lime1 make it intensely ,,hot8 ,a4 ,the heat is evolved by the chemical action1 produced by the cold water combining with the lime4 ,q4 ,where does the heat come from8 ,a4 ,it was in the water and lime before2 but was in a latent state4 ,q4 ,was there heat in the cold water and lime1 before they were mixed together8 ,a4 ,yes4 ,all bodies contain heat2 the coldest ice1 as well as the hottest fire4 ,q4 ,is there ,,heat even in ,,ice8 ,a4 ,yes4 ,but it is latent1 7i4 e4 not perceptible to our senses74#d #d ,latent1 from the ,latin word1 ,lateo1 7to lie hid47 ,q4 ,how do you know there is heat1 if you cannot perceive it8 ,a4 ,thus3--,ice is #cb by the thermometer2 but if ice be melted over a fire1 7though #adj of heat are thus absorbed17 it will feel no hotter than it was before4 7i4 e4 it will be only #cb1 and not #agb7e4 #e #cb1 i4 e4 #cb degrees2 #adj1 i4 e4 #adj degrees1 c4 ,q4 ,what becomes of the #adj1 which went into the ice to melt it8 ,a4 ,it is hidden in the water2 or 7to speak more scientifically7 it is stored up in a latent state4 ,q4 ,how much heat may be thus secreted or made latent8 ,a4 ,all things contain a vast quantity of latent heat2 but1 as much as #aadj of heat may remain latent in water4 ,q4 ,how can #aadj of heat be added to water1 without being perceptible to our feelings8 ,a4 #ast--#adj of heat are hidden in the water1 when ice is melted by the sun or fire4 #bndly--#ajjj more of heat are secreted1 when water is converted into steam4 ,thus1 before ice is converted into steam1 #aadj of heat become latent4#f #f ,thus1 one pint of boiling water1 7#bab according to the thermometer17 will make #ahjj pints of steam2 but the steam is no hotter to the touch than boiling water1 both are #bab3 therefore1 when water is converted into steam1 #ajjj of heat become latent4 ,hence1 before ice is converted to steam1 it must contain #aadj of latent heat4 ,q4 ,can we be made to ,,feel the heat of ,,ice or snow8 ,a4 ,yes4 ,into a pint of snow put half as much salt2 then plunge your hand into the liquid2 and it will feel so intensely cold1 that the snow itself will seem quite warm in comparison to it4 ,q4 ,is ,,salt and ,,snow really ,,colder than snow8 ,a4 ,yes1 many degrees2 and by dipping your hand into the mixture first1 and into snow afterwards1 the mere snow will seem to be comparatively warm4 ,q4 ,what is ,,fire8 ,a4 ,combustion is another instance of heat1 arising from chemical action4 ,q4 ,what two things are essential to produce combustion8 ,a4 ,fuel and air4 ,q4 ,what are the elements of fuel8 ,a4 ,as bread is a compound of flour1 yeast1 and salt2 so fuel is a compound of hydrogen and carbon4 ,q4 ,what are the ,,elements of atmospheric ,,air8 ,a4 ,the air is a compound of oxygen and nitrogen mixed together2 in the proportion of five gallons of nitrogen1 to one of oxygen4 ,q4 ,what is ,,carbon8 ,a4 ,the solid part of fuel4 ,it abounds also in all animal bodies1 earths1 and minerals4 ,q4 ,mention some different ,,species of ,,carbon4 ,a4 ,common charcoal1 lamp-black1 coke1 black lead1 and the diamond1 are all varieties of carbon4 ,q4 ,what is ,,hydrogen8 ,a4 ,an inflammable gas4 ,the gas used in our streets1 is only the hydrogen gas driven out of coals by heat4 ,q4 ,what are the peculiar characteristics of hydrogen gas8 ,a4 ,though this gas itself will burn1 yet a candle will not burn when immersed in it2 nor can an animal live in it4 ,hydrogen gas is the lightest of all known substances4#g #g ,hydrogen gas may be made thus3--,put some pieces of zinc or iron filings into a glass3 pour over them a little sulphuric acid 7vitriol71 diluted with twice the quantity of water2 then cover the glass over for a few minutes1 and hydrogen gas will be given off4 ,,exp4 ,if a flame be put into the glass1 an ,,explosion will be made4 ,if the experiment be tried in a phial1 which has a piece of tobacco-pipe run through the cork2 and a light held a few moments to the top of the pipe1 a ,,flame will be made4 ,if a balloon be held over the phial1 7so that the gas can inflate it17 the balloon will ascend in a very few minutes4 ,q4 ,what is ,,oxygen8 ,a4 ,a gas1 much heavier than hydrogen2 which gives brilliancy to flame1 and is essential to animal life4#h #h ,oxygen gas is much more troublesome to make than hydrogen4 ,the cheapest plan is to put a few ounces of manganese 7called the black oxide of manganese7 into an iron bottle1 furnished with a bent tube2 set the bottle on a fire till it becomes red hot1 and put the end of the tube into a pan of water4 ,in a few minutes1 bubbles will rise through the water2 these bubbles are oxygen gas4 ,these bubbles may be collected thus3--,fill a common bottle with water2 hold it topsy-turvy over the bubbles which rise through the pan1 but be sure the mouth of the bottle be held in the water4 ,as the bubbles rise into the bottle1 the water will run out2 and when all the water has run out1 the bottle is full of gas4 ,cork the bottle while the mouth remains under water2 set the bottle on its base2 cover the cork with lard or wax1 and the gas will keep till it be wanted4 ,n4 ,b4 ,the quickest way of making oxygen gas1 is to rub together in a mortar half an ounce of oxide of copper1 and half an ounce of chlorate of potassa4 ,put the mixture into a common oil flask1 furnished with a cork which has a bent tube thrust through it4 ,heat the bottom of the flask over a candle or lamp2 and when the mixture is red hot1 oxygen gas will be given off4 ,note--the tube must be immersed in a pan of water1 and the gas collected as before4 7,chlorate of potassa may be bought at any chemist's2 and oxide of copper may be procured by heating a sheet of copper red hot1 and when cool1 striking it with a hammer3 the scales that peel off1 are oxide of copper47 ,,exp4 ,put a piece of red hot charcoal1 7fixed to a bit of wire17 into your bottle of oxygen gas2 and it will throw out most dazzling sparks of light4 ,blow a candle out2 and while the wick is still red1 hold the candle 7by a piece of wire17 in the bottle of oxygen gas2 the wick will instantly ignite1 and burn brilliantly4 7,burning sulphur emits a blue flame1 when immersed in oxygen gas47 ,q4 ,what is ,,nitrogen8 ,a4 ,nitrogen is another invisible gas4 ,it will not burn1 like hydrogen2 and an animal cannot live in it3 it abounds in animal and vegetable substances1 and is the chief ingredient of the common air4#i #i ,nitrogen gas may easily be obtained thus3--,put a piece of burning phosphorus on a little stand1 in a plate of water2 and cover a bell glass over4 7,be sure the edge of the glass stands in the water47 ,in a few minutes the air will be decomposed1 and nitrogen alone remain in the bell glass4 7,n4,b4 ,the white fume which will arise and be absorbed by the water in this experiment1 is phosphoric acid2 i4 e4 phosphorus combined with oxygen of the air47 ,q4 ,why is there so much nitrogen in the air8 ,a4 ,in order to dilute the oxygen4 ,if the oxygen were not thus diluted1 fires would burn out1 and life would be exhausted too quickly4 ,q4 ,what three elements are necessary to produce ,,combustion8 ,a4 ,hydrogen gas1 carbon1 and oxygen gas2 the two former in the fuel1 and the last in the air which surrounds the fuel4 ,q4 ,what causes the combustion of the fuel8 ,a4 ,the hydrogen gas of the fuel being set free1 and excited by a piece of lighted paper1 instantly unites with the oxygen of the air1 and makes a yellow flame3 this flame heats the carbon of the fuel1 which also unites with the oxygen of the air1 and produces carbonic acid gas4 ,q4 ,what is carbonic acid gas8 ,a4 ,only carbon 7or charcoal7 combined with oxygen gas4 ,q4 ,why does ,,fire produce ,,heat8 ,a4 #ast--,by liberating latent heat from the air and fuel3 and #bndly--,by throwing into rapid motion the atoms of matter4 ,q4 ,how is latent ,,heat liberated by ,,combustion8 ,a4 ,when the oxygen of the air combines with the hydrogen of the fuel1 the two gases condense into water2 and latent heat is squeezed out1 as water from a sponge4 ,q4 ,how are the ,,atoms ,,of ,,matter ,,disturbed by ,,combustion8 ,a4 #ast--,when hydrogen of fuel and oxygen of air condense into water1 a vacuum is made2 and the air is disturbed1 as a pond would be1 if a pail of water were taken out of it3 and #bndly--,when the carbon of fuel and oxygen of air expand into carbonic acid gas1 the air is again disturbed1 as it would be by the explosion of gunpowder4 ,q4 ,how does fire condense ,,hydrogen and ,,oxygen into ,,water8 ,a4 ,the hydrogen of fuel and oxygen of air 7liberated by combustion7 combining together1 condense into water4 ,q4 ,how does fire expand ,,carbon into ,,carbonic ,,acid ,,gas8 ,a4 ,the carbon of fuel and oxygen of air 7combining together in combustion7 expand into a gas1 called carbonic acid4 ,q4 ,why is a ,,fire 7after it has been long burning7 ,,red ,,hot8 ,a4 ,when coals are heated throughout1 the carbon is so completely mixed with the oxygen of the air1 that the whole surface is in a state of combustion1 and therefore red hot4 ,q4 ,in a ,,blazing fire1 why is the ,,upper surface of the ,,coals ,,black1 and the ,,lower surface ,,red8 ,a4 ,carbon 7being very solid7 requires a great degree of heat to make it unite with the oxygen of the air4 ,when fresh coals are put on1 their under surface is heated before the upper surface2 and one is red 7or in a state of combustion71 while the other is black4 ,q4 ,which burns the quicker1 a ,,blazing fire1 or a ,,red ,,hot one8 ,a4 ,a blazing fire burns out the fuel quickest4 ,q4 ,why do ,,blazing ,,coals ,,burn ,,quicker than red hot ones8 ,a4 ,in red hot coals1 only the mere surface is in a state of combustion1 because the carbon is solid2 but in a blazing fire1 7where the gases are escaping71 the whole volume of the coal throughout is in a state of decomposition4 ,q4 ,what is ,,smoke8 ,a4 ,unconsumed parts of fuel 7principally carbon71 separated from the solid mass1 and carried up the chimney by the current of hot air4 ,q4 ,why is there ,,more ,,smoke when ,,coals are ,,fresh added1 than when they are red hot8 ,a4 ,carbon 7being solid71 requires a great degree of heat to make it unite with oxygen1 7or1 in other words1 to bring it into a state of perfect combustion73 when coals are fresh laid on1 more carbon is separated than can be reduced to combustion2 and so it flies off in smoke4 ,q4 ,why is there so ,,little ,,smoke with a ,,red ,,hot ,,fire8 ,a4 ,when a fire is red hot1 the entire surface of the coals is in a state of combustion2 so a very little flies off unconsumed1 as smoke4 ,q4 ,why are there ,,dark and ,,bright ,,spots in a ,,clear cinder ,,fire8 ,a4 ,because the intensity of the combustion is greater in some parts of the fire1 than it is in others4 ,q4 ,why is the intensity of the combustion so unequal8 ,a4 ,because the air flies to the fire in various and unequal currents4 ,q4 ,why do we see all sorts of ,,grotesque ,,figures in hot ,,coals8 ,a4 ,because the intensity of combustion is so unequal1 7owing to the gusty manner in which the air flies to the fuel2 and the various shades of red1 yellow1 and white heat mingling with the black of the unburnt coal71 produce strange and fanciful resemblances4 ,q4 ,why does ,,paper ,,burn more readily than wood8 ,a4 ,merely because it is of a more fragile texture2 and1 therefore1 its component parts are more easily heated4 ,q4 ,why does ,,wood ,,burn more readily than coal8 ,a4 ,because it is not so solid2 and1 therefore1 its elemental parts are more easily separated1 and made hot4 ,q4 ,when a ,,fire is ,,lighted1 why is ,,paper laid at the ,,bottom1 against the grate8 ,a4 ,because paper 7in consequence of its fragile texture71 so very readily catches fire4 ,q4 ,why is ,,wood laid on the top of the paper8 ,a4 ,because wood1 7being more substantial71 burns longer than paper2 and1 therefore1 affords a longer contact of flame to heat the coals4 ,q4 ,why would not paper do without wood8 ,a4 ,because paper burns out so rapidly1 that it would not afford sufficient contact of flame to heat the coals to combustion4 ,q4 ,why would not ,,wood do ,,without shavings1 straw1 or paper8 ,a4 ,because wood is too substantial to be heated into combustion1 by the flame issuing from a mere match4 ,q4 ,why would not the paper do as well1 if placed on the ,,top of the coals8 ,a4 ,as every blaze tends upwards1 if the paper were placed on the top of the fire1 its blaze would afford no contact of flame to fuel lying below4 ,q4 ,why should ,,coal be placed ,,above the wood8 ,a4 ,as every flame tends upwards1 if the wood were above the coal1 the flame would not rise through the coal to heat it4 ,q4 ,why is a ,,fire ,,kindled at the ,,lowest ,,bar of a grate8 ,a4 ,as every flame tends upwards2 when a flame is made at the bottom of a fire1 it ascends through the fuel and heats it3 whereas1 if the fire were lighted from the top1 the flame would not come into contact with the fuel piled below4 ,q4 ,why does ,,coal make such ,,excellent ,,fuel8 ,a4 ,because it is so very hard and compact1 that it burns away very slowly4 ,q4 ,why will ,,cinders become ,,red ,,hot1 quicker than ,,coals8 ,a4 ,because they are more porous and less solid2 and are1 therefore1 sooner reduced to a state of combustion4 ,q4 ,why will not ,,iron ,,cinders burn8 ,a4 ,iron cinders are cinders saturated with oxygen2 they are unfit for fuel1 because they can imbibe no more oxygen1 being saturated already4 ,q4 ,why are ,,cinders lighter than ,,coals8 ,a4 ,because their vapour1 gases1 and volatile parts1 have been driven off by previous combustion4 ,q4 ,why will not ,,stones do for fuel1 as well as ,,coals8 ,a4 ,because they contain no hydrogen 7or inflammable gas7 like coals4 ,q4 ,why will not ,,wet ,,kindling light a fire8 ,a4 #ast--,because the moisture of the wet kindling prevents the oxygen of the air from getting to the fuel to form it into carbonic acid gas3 and #bndly--,the heat of the fire is perpetually drawn off1 by the conversion of water into steam4 ,q4 ,why does ,,dry wood burn ,,better than ,,green8 ,a4 #ast--,because no heat is carried away1 by the conversion of water into steam3 and #bndly--,the pores of dry wood are filled with air1 which supply the fire with oxygen4 ,q4 ,why do ,,two pieces of ,,wood burn ,,better than ,,one8 ,a4 #ast--,because they help to entangle the heat of the passing smoke1 and throw it on the fuel3 and #bndly--,they help to entangle the air that passes over the fire1 and create a kind of eddy or draught4 ,q4 ,why does ,,salt ,,crackle when thrown into a ,,fire8 ,a4 ,salt contains water2 and the cracking of the salt is owing to the sudden conversion of the water into steam4 ,q4 ,why will not wood or paper burn1 if they are steeped in a solution of ,,potash1 phosphate of ,,lime1 or ,,ammonia 7hartshorn78 ,a4 ,because any al'kali 7such as potash7 will arrest the hydrogen 7as it escapes from the fuel71 and prevent its combination with the oxygen of air4 ,q4 ,what is an al'kali8 ,a4 ,the con'verse of an acid2 as bitter is the con'verse of sweet1 or insipid the con'verse of pungent4 ,q4 ,why does a ,,jet of ,,flame sometimes burst into the room ,,through ,,the ,,bars ,,of ,a ,,stove8 ,a4 ,the iron bars conduct heat to the interior of some lump of coal3 and its volatile gas 7bursting through the weakest part7 is kindled by the glowing coals over which it passes4 ,q4 ,why is this ,,jet sometimes of a ,,greenish ,,yellow colour8 ,a4 ,when a lump of coals lies over the hot bars1 or the coals below it are not red hot1 the gas which bursts from the lump escapes unburnt1 and is of a greenish colour4 ,q4 ,why does the gas escape ,,unburnt8 ,a4 ,because neither the bars nor coals 7over which it passes7 are red-hot4 ,q4 ,why does a ,,bluish ,,flame sometimes flicker on the surface of hot cinders8 ,a4 ,gas from the hot coals at the bottom of the grate mixing with the carbon of the coals above1 produces an inflammable gas 7called carbonic oxide71 which burns with a blue flame4 ,q4 ,why is the ,,flame of a good fire ,,yellow8 ,a4 ,because both the hydrogen and carbon of the fuel are in a state of perfect combustion4 ,it is the white heat of the carbon1 which gives the pale yellow tinge to the flaming hydrogen4 ,q4 ,what is ,,light8 ,a4 ,rapid undulations of a fluid called ether1 striking on the eye4 ,q4 ,how does ,,combustion make these undulations of ,,light8 ,a4 ,the atoms of matter 7set in motion by heat7 striking against this ether1 produce undulations in it2 as a stone thrown into a stream1 would produce undulations in the water4 ,q4 ,how can ,,undulations of ether produce ,,light8 ,a4 ,as sound is produced by undulations of air striking on the ear2 so light is produced by undulations of ether striking on the eye4 ,q4 ,what is ,,ether8 ,a4 ,a very subtile fluid1 which pervades and surrounds every thing we see4 ,q4 ,mention a simple experiment to prove that ,,light is produced by rapid ,,motion4 ,a4 ,when a fiddle-string is jerked suddenly1 its rapid vibration produces a grey light2 and when a carriage wheel revolves very quickly1 it sends forth a similar light4 ,q4 ,does ,,heat ,,always produce ,,light8 ,a4 ,no3 the heat of a stack of hay1 or reeking dunghill1 though very great1 is not sufficient to produce light4 ,q4 ,why is a ,,yellow ,,flame brighter than a ,,red ,,hot ,,coal8 ,a4 ,because yellow rays always produce the greatest amount of light2 though red rays produce the greatest amount of heat4 ,q4 ,why is the ,,light of a fire ,,more ,,intense sometimes than at others8 ,a4 ,the intensity of fire-light depends upon the whiteness to which the carbon is reduced1 by combustion4 ,if the carbon be white hot1 its combustion is perfect1 and the light intense2 if not1 the light is obscured by smoke4 ,q4 ,why will not ,,cinders ,,blaze1 as well as ,,fresh coals8 ,a4 ,the flame of coals is made chiefly by hydrogen gas4 ,as soon as this gas is consumed1 the hot cinders produce only an invisible gas1 called carbonic acid4 ,q4 ,where does the hydrogen gas of a fire come from8 ,a4 ,the fuel is decomposed 7by combustion7 into its simple elements1 carbon and hydrogen gas4 7see p4 #cc7 ,q4 ,why does not a ,,fire ,,blaze on a ,,frosty ,,night1 so long as it does upon another night8 ,a4 ,the air 7being very cold7 rushes to the fire so rapidly1 that the coals burn out faster1 and the inflammable gas is sooner consumed4 ,q4 ,why does a ,,fire burn ,,clearest on a ,,frosty night8 ,a4 ,because the volatile gases are quickly consumed2 and the solid carbon plentifully supplied with air1 to make it burn bright and intensely4 ,q4 ,why does a ,,fire burn more intensely in ,,winter than in ,,summer time8 ,a4 ,because the air is colder in winter1 than in summer-time4 ,q4 ,how does the ,,coldness of the air increase the ,,heat of a fire8 ,a4 ,for two reasons3 #ast--,because cold air being more condensed than hot air1 contains a greater body3 and #bndly--,cold air rushes more quickly to the fire1 and supplies more oxygen4 ,q4 ,why does the ,,sun1 shining on a ,,fire1 make it ,,dull1 and often put it out8 ,a4 #ast--,when the sun shines1 the air is rarefied2 and1 therefore1 flows more slowly to the fire4 #bndly--,as the air is rarefied1 even that which reaches the fire1 affords less nourishment4 ,q4 ,why does the air flow to the fire more ,,tardily for being ,,rarefied8 ,a4 ,the greater the contrast 7between the external air1 and that which has been heated by the fire7 the more rapid will be the current of air towards that fire4 ,q4 ,why does rarefied air afford ,,less ,,nourishment to fire1 than cold air8 ,a4 ,because it is spread out1 7like a piece of gold beaten into leaf72 and as a square inch of gold leaf will not contain so much gold as a square inch of bullion--so1 a square inch of rarefied air has less body1 than a square inch of cold air4 ,q4 ,why does a ,,fire burn more fiercely in the ,,open ,,air8 ,a4 #ast--,because the air out-of-doors is more dense1 than the air in-doors3 and #bndly--,because air is more freely supplied to a fire out-of-doors4 ,q4 ,why is the air out-of-doors more ,,dense than that in-doors8 ,a4 ,because the circulation is more free2 and as soon as any portion has been rarefied1 it instantly escapes1 and is supplied by colder currents4 ,q4 ,why does not a ,,fire burn so freely in a ,,thaw1 as in a ,,frost8 ,a4 ,during a thaw1 the air is filled with vapour2 and1 both moves too slowly1 and is too much diluted to nourish the fire4 ,q4 ,why does a ,,fire burn so fiercely in ,,windy weather8 ,a4 ,in windy weather the air is rapidly changed1 and affords plentiful nourishment to the fire4 ,q4 ,why do a pair of ,,bellows get a fire up8 ,a4 ,a pair of bellows1 7like the wind71 drives the air more rapidly to the fire2 and the plentiful supply of oxygen soon makes the fire burn intensely4 ,q4 ,why is a ,,candle ,,blown ,,out by the breath1 and not made more intense1 like a fire8 ,a4 ,as the flame of a candle is confined to a very small wick1 it is severed from it by the breath2 and 7being unsupported7 must go out4 ,q4 ,why is a ,,smouldering ,,wick sometimes ,,rekindled by blowing it8 ,a4 ,the breath carries the air to it with great rapidity2 and the oxygen of the air kindles the red hot wick1 as it kindles charred wood4 ,q4 ,why is not the red hot wick kindled by the air ,,around it1 without ,,blowing it8 ,a4 ,because oxygen is not supplied with sufficient freedom1 unless it be blown to the wick4 ,q4 ,when is this experiment most likely to succeed8 ,a4 ,in frosty weather2 because the air contains more oxygen then1 being condensed by the cold4 ,q4 ,why does a ,,poker1 ,,laid ,,across a dull ,,fire1 revive it8 ,a4 ,for two reasons4 #ast--,because the poker concentrates the heat1 and therefore increases it3 and #bndly--,because the poker arrests the air which passes over the fire1 and produces a draught4 ,q4 ,why do ,,several ,,pieces of ,,wood or coal burn ,,better than ,,one8 ,a4 ,when there are two or three pieces of wood on a fire1 the air 7circulating round them7 produces an eddy or draught1 which draws up the fire4 ,q4 ,why are ,,stoves fixed on the ,,floor of a room8 ,a4 ,in order that the air1 on the lower part of the room1 may be heated by the fire4 ,q4 ,would not the air of the lower part of a room be heated equally well1 if the stoves were fixed higher up8 ,a4 ,no2 the heat of a fire has a very little effect upon the air below the level of the grate2 and1 therefore1 every grate should be as near to the floor as possible4 ,q4 ,why are our ,,feet so ,,cold when we sit close by a good fire8 ,a4 ,as the fire consumes the air which passes over it1 cold air rushes through the crevices of the doors and windows along the bottom of the room to supply the deficiency2 and these currents of cold air1 rushing constantly over our feet1 deprive them of their warmth4 ,q4 ,if a piece of ,,paper be laid ,,flat on a clear fire1 it will ,,not ,,blaze1 but ,,char4 ,why so8 ,a4 ,the carbon of a clear fire1 being sufficiently hot to unite with the oxygen of the air1 produces carbonic acid gas1 which soon envelops the paper laid flat upon the cinders3 but carbonic acid gas will not blaze4 ,q4 ,if you ,,blow the paper1 it will ,,blaze immediately4 ,why so8 ,a4 ,by blowing1 or opening the door suddenly1 the carbonic acid is dissipated1 and the paper is instantly fanned into flame4 ,q4 ,why does ,,water ,,extinguish a ,,fire8 #ast--,because the water forms a coating over the fuel1 and keeps it from the air3 #bndly--,the conversion of water into steam1 draws off the heat of the burning fuel4 ,q4 ,why does a ,,little ,,water make a fire ,,fiercer1 while a ,,larger quantity of water puts it ,,out8 ,a4 ,water is composed of oxygen and hydrogen2 when1 therefore1 the fire can decompose the water into its simple elements1 it serves for fuel to the flame4 ,q4 ,how can ,,water serve for ,,fuel to fire8 ,a4 ,the hydrogen of the water will burn with a flame2 and the oxygen of the water will increase the intensity of that flame4 ,q4 ,if a house be on fire1 is too ,,little water worse than ,,no water at all8 ,a4 ,certainly4 ,unless the water be supplied so plentifully as to quench the fire1 it will increase the intensity1 like fuel4 ,q4 ,when will water ,,extinguish ,,fire8 ,a4 ,when the supply is so rapid and abundant1 that the fire cannot convert it into steam4 ,q4 ,does not a very ,,little water ,,slacken the heat of fire8 ,a4 ,yes1 till it is converted into steam2 but then it increases the intensity of fire1 and acts like fuel4 ,q4 ,why does the ,,wick of a candle 7when the flame has been blown out7 ,,catch ,,fire so readily8 ,a4 ,as the wick is already very hot1 a little extra heat will throw it into flame4 ,q4 ,why does the ,,extra heat revive the flame8 ,a4 ,because it again liberates the hydrogen of the tallow1 and ignites it4 ,q4 ,cannot ,,wood be made to ,,blaze without actual contact with fire8 ,a4 ,yes2 if a piece of wood be held near the fire for a little time it will blaze1 even though it does not touch the fire4 ,q4 ,why will ,,wood ,,blaze1 even if it does not touch the fire8 ,a4 ,the heat of the fire drives out the hydrogen gas of the wood2 which is inflamed by contact with the red-hot coals4 ,q4 ,why will a ,,neighbour',s ,,house sometimes ,,catch ,,fire1 though no flame of the burning house ever touches it8 ,a4 ,the heat of the burning house sets at liberty the hydrogen gas of the neighbouring wood-work1 which is ignited by the flames or red-hot bricks of the house on fire4 ,q4 ,what is ,,coke8 ,a4 ,coal freed from its volatile gases1 by the action of artificial heat4 ,q4 ,why do ,,arnott',s ,,stoves sometimes ,,smell so strong of ,,sulphur8 ,a4 ,the fire is made of coke1 which contains sulphur2 and1 whenever the draught is not rapid enough to drive the sulphur up the flue1 it is emitted into the room4 ,q4 ,what is meant by ,,spontaneous ,,combustion8 ,a4 ,ignition produced by the action of one uninflamed body on another4 ,q4 ,give an example of spontaneous combustion4 ,a4 ,goods packed in a warehouse will often catch fire of themselves2 especially such goods as cotton1 flax1 hemp1 rags1 c4 ,q4 ,why do such ,,goods sometimes ,,catch ,,fire of themselves8 ,a4 ,because they are piled together in very great masses in a damp state or place4 ,q4 ,why does this produce spontaneous combustion8 ,a4 ,the damp produces decay or the decomposition of the goods1 and the great heat of the piled-up mass makes the decaying goods ferment4 ,q4 ,how does this ,,fermentation produce ,,combustion8 ,a4 ,during fermentation1 carbonic acid gas is given off by the goods1--a slow combustion ensues1--till at length the whole pile bursts into flame4 ,q4 ,why is the ,,heat of a ,,large ,,mass of goods ,,greater than that of a smaller quantity8 ,a4 ,because compression squeezes out heat1 as water is squeezed from a sponge2 and as the goods of a large pile are greatly compressed1 much of their latent heat is squeezed out4 ,q4 ,why do ,,hay-,,stacks sometimes ,,catch ,,fire of themselves8 ,a4 ,either because the hay was got up damp1 or because rain has penetrated the stack4 ,q4 ,why will a ,,hay-,,stack ,,catch ,,fire if the hay be damp8 ,a4 ,damp hay soon decays1 and undergoes a state of fermentation2 during which1 carbonic acid gas is given off1 and the stack catches fire4 ,q4 ,why does roasted ,,coffee sometimes ,,catch ,,fire spontaneously8 ,a4 ,the heat of coffee is greatly increased by being roasted2 and the carbon of the coffee uniting with the oxygen of the air1 produces carbonic acid gas1 and bursts into flame4 ,q4 ,why do old ,,rags1 used for ,,cleaning ,,lamps and ,,candles1 sometimes set a ,,house on ,,fire8 ,a4 ,because they very readily ferment1 and 7during fermentation7 throw off exceedingly inflammable gases4 7,n4,b4 ,lamp-black mixed with linseed oil is more liable to spontaneous combustion1 than anything that servants handle47 ,,chapter ,,iv4 ,,smoke4 ,q4 ,why does ,,smoke ,,ascend the chimney8 ,a4 ,as the air of the room passes over the fire1 it becomes heated2 and 7being thus made lighter17 ascends the chimney1 carrying the smoke with it4 ,q4 ,what is ,,smoke8 ,a4 ,small particles of carbon1 separated by combustion from the fuel1 but not consumed4 ,q4 ,why do ,,smoke and steam ,,curl1 as they ascend8 ,a4 ,because they are moved in a right line1 and then pushed on all sides2 and this forces them into a circular motion4 ,q4 ,what are ,,blacks8 ,a4 ,when the hot air of the chimney has been cooled by the external air1 it can no longer buoy up the solid smoke2 so it falls to the earth in condensed flakes1 called blacks4 ,q4 ,why are there ,,no ,,blacks in the smoke of a ,,railway engine8 ,a4 ,the smoke of a railway engine consists chiefly of watery vapour1 which dissolves in air1 as sugar does in water2 but the smoke of a common chimney consists of small fragments of unburnt fuel4 ,q4 ,why does a ,,copper ,,hole ,,draw up more fiercely than an ,,open stove8 ,a4 ,as the air1 which supplies the copper hole1 must pass through the furnace1 it becomes exceedingly heated1 and rushes up the chimney with great violence4 ,q4 ,what produces the ,,roaring noise made by a ,,copper-,,hole fire8 ,a4 ,air rushing rapidly through the crevices of the iron door1 and up the chimney flue4 ,q4 ,why is the ,,roar ,,less1 if the copper-hole ,,door be thrown ,,open8 ,a4 ,because fresh air gets access to the fire more easily2 and as the air is not so intensely heated1 its motion is not so violent4 ,q4 ,why do some ,,chimneys ,,smoke8 ,a4 ,if fresh air is not admitted into a room1 as fast as it is consumed by the fire1 a current of air will rush down the chimney to supply the deficiency1 and bring the smoke along with it4 ,q4 ,what prevents air being supplied1 as fast as it is consumed by the fire8 ,a4 ,leather and curtains round the doors2 sand-bags at the threshhold and on the window-frames2 and other contrivances to keep out the draught4 ,q4 ,why is it needful for cold fresh air to be so constantly supplied8 ,a4 ,if water be taken with a pail out of a river1 other water will rush towards the hole1 as soon as the pail is lifted out2 and if air be taken from a room1 7as it is1 when some of it goes up the chimney7 other air will rush towards the void to fill it up4 ,q4 ,why will it come down the chimney8 ,a4 ,because if doors and windows are all made air-tight1 it can get to the room in no other way4 ,q4 ,what is the best ,,remedy in such a case8 ,a4 ,the speediest remedy is to open the door or window3 but by far the best remedy is to carry a small tube from the hearth into the external air4 ,q4 ,why is that the ,,best remedy8 ,a4 ,because the fire will be plentifully supplied with air by the tube2 the doors and windows may all remain air-tight2 and we may enjoy a warm fireside1 without the inconvenience of draughts and cold feet4 ,q4 ,why is a ,,chimney raised so high above the ,,roof8 ,a4 ,if it were not so1 it would smoke2 as all funnels do which are too short4 ,q4 ,what is meant by the funnel1 or flue of a chimney8 ,a4 ,that part of a chimney through which the smoke passes1 is called the funnel1 or flue4 ,q4 ,why does a ,,chimney ,,smoke1 if the funnel be very short8 ,a4 ,because the draught of a short flue is too slack to carry the smoke up the chimney4 ,q4 ,why is the ,,draught of a ,,short ,,flue more ,,slack that that of a long one8 ,a4 ,for many reasons4 #ast--,the fire is always dull and sluggish if the chimney be too short4 #bndly--,the smoke rolls out of the chimney1 before it has acquired its full velocity4 #crdly--,the wind1 rain1 and air1 have more influence over a short funnel1 than over a long one4 ,q4 ,why is the ,,fire always ,,dull and sluggish if the ,,chimney-,,flue be very ,,short8 ,a4 ,because the draught is so bad3 and as the rarefied air passes up the chimney very tardily1 fresh air flows as tardily towards the fire1 to supply it with oxygen4 ,q4 ,on what does the ,,intensity of fire depend8 ,a4 ,the intensity of fire is always in proportion to the quantity of oxygen with which it is supplied4 ,q4 ,why does not ,,smoke acquire its full ,,velocity in a ,,short funnel8 ,a4 ,because the higher smoke ascends in a flue1 7provided it be clear and hot7 the faster it goes2 7as a stone falls faster and faster the lower it descends73 if1 therefore1 a funnel be very short1 the smoke never acquires its full velocity4 ,q4 ,does the ,,draught of a chimney depend on the ,,speed of the ,,smoke through the flue8 ,a4 ,yes4 ,the more quickly hot air flies up the chimney1 the more quickly cold air will rush towards the fire to supply the place2 and1 therefore1 the longer the flue1 the greater the draught4 ,q4 ,why is the ,,draught of a ,,long ,,flue greater than that of a short one8 ,a4 ,because the higher smoke ascends1 the faster it goes2 7as a stone falls faster and faster1 the nearer it approaches to the earth73 if1 therefore1 a funnel be long1 the smoke acquires great velocity1 and the draught is great4 ,q4 ,if a ,,chimney be ,,too ,,short1 and cannot be lengthened1 what is the best ,,remedy to prevent smoking8 ,a4 ,to contract the opening of the chimney contiguous to the stove4 ,q4 ,why will a ,,smaller ,,opening against the stove ,,prevent the ,,smoking8 ,a4 ,as all the air 7which enters the chimney7 must pass near the fire1 it will become greatly heated1 and rise rapidly through the funnel2 and this increase of heat will compensate for the shortness of the flue4 ,q4 ,why will a ,,room ,,smoke1 if there be ,,two ,,fires in it8 ,a4 ,because the fiercer fire will exhaust the most air2 and draw from the smaller one1 to supply its demand4 ,q4 ,why will a chimney ,,smoke if there be a ,,fire in ,,two ,,rooms communicating with each other8 ,a4 ,whenever the door between the two rooms is opened1 air will rush from the chimney of the inferior fire1 to supply the other2 and both rooms will be filled with smoke4 ,q4 ,what is the ,,remedy in this case8 ,a4 ,let a tube be carried from the hearth of each stove1 into the external air2 and then each fire will be so well supplied1 that neither will need to borrow from the other4 ,q4 ,why do ,,vestry ,,chimneys so often ,,smoke8 ,a4 ,because the wind 7striking against the steeple7 is reflected back2 and tumbles down the vestry chimney1 forcing the smoke into the room4 ,q4 ,,what ,,winds make vestry chimneys smoke8 ,a4 ,those from the north-east or south-east2 according to the position of the vestry4 ,q4 ,why will the ,,eastern winds make ,,vestries ,,smoke1 more than those from the west8 ,a4 ,because they strike against the steeple1 and bound back to the vestry chimney3 but western winds cannot rebound over the roof of a church4 7,n4 ,b4 ,the steeple of a church is always due west1 and the other end of the church due east2 if1 therefore1 a western wind rebound1 it would rebound to the west1 or away from the church1 and not towards it47 ,q4 ,why does a ,,house in a ,,valley very often ,,smoke8 ,a4 ,because the wind 7striking against the surrounding hills7 rebounds back again upon the chimney1 and destroys its draught4 ,q4 ,what is the common ,,remedy in both these cases8 ,a4 ,to fix a cowl on the chimney top1 to turn like a weather-cock1 and present its back to the wind4 ,q4 ,why will not a ,,cowl always ,,prevent a chimney ,,smoking8 ,a4 ,if the wind be strong1 it will keep the opening of the cowl towards the steeple or hill2 and then the reflected wind will blow into the cowl1 and down the chimney4 ,q4 ,as a cowl is such a poor remedy1 can any ,,other be devised8 ,a4 ,if the chimney flue can be carried higher than the steeple or hills1 no wind can enter the flue4 ,q4 ,why cannot the wind enter a chimney flue1 if it be carried up ,,higher than the steeple or hills8 ,a4 ,because the reflected wind would strike against the sides of the chimney-flue1 and not pass over the opening at all4 ,q4 ,in what ,,other cases will a ,,chimney ,,smoke8 ,a4 ,if both door and chimney be placed on the same side of a room1 the chimney will often smoke4 ,q4 ,why will a ,,chimney ,,smoke1 if the ,,door and ,,stove are both on the ,,same ,,side8 ,a4 ,because when the door is opened1 a current of air will blow into the chimney-place1 and drive the smoke into the room4 ,q4 ,what ,,remedy can be applied to this evil8 ,a4 ,the door must be set opposite to the chimney1 or nearly so2 and then the draught from the door will blow the smoke up the chimney1 and not into the room4 ,q4 ,why will a ,,chimney ,,smoke if it ,,needs ,,sweeping8 ,a4 ,because the obstruction in the chimney 7presented by the loose soot1 to the free passage of the smoke7 delays its current1 and prevents the draught4 ,q4 ,why will a ,,chimney ,,smoke1 if ,,out ,,of ,,repair8 ,a4 #ast--,because the loose mortar and bricks obstruct the smoke3 and #bndly--,the cold air 7oozing through the chinks7 chills the air in the chimney1 and prevents its ascent4 ,q4 ,why will an ,,arnott',s ,,stove ,,smoke1 if the joints of the flue do not fit air-tight8 ,a4 ,because the cold air 7which gets through the joints7 chills the air in the flue1 and prevents its ascent4 ,q4 ,why does an old fashioned ,,farm ,,chimney-,,place so often smoke8 ,a4 ,because the opening is so very large1 that much of the air which goes up the chimney1 has never passed near the fire2 and this cold air mixing with the other1 so reduces its temperature1 that it ascends very slowly1 and the draught is destroyed4 ,q4 ,why does a chimney smoke1 if the ,,draught be ,,slack8 ,a4 ,because1 unless the current of air up the chimney be very powerful1 it cannot buoy the smoke up through the flue4 ,q4 ,if the opening of a chimney be ,,too ,,large1 what ,,remedy can be applied8 ,a4 ,the chimney-place must be contracted4 ,q4 ,why will ,,contracting the chimney-place ,,prevent its ,,smoking8 ,a4 ,as the air will then pass nearer the fire1 it will be more heated1 and fly up the chimney much faster4 ,q4 ,why do almost all ,,chimneys ,,smoke in ,,gusty weather8 ,a4 ,the gust 7blowing the air away from the top of the chimney7 removes 7for a time7 all resistance to the smoke3 but when the wind lulls again1 the resistance of the air suddenly returns--the draught is checked--and a puff of smoke rushes into the room4 ,q4 ,what is the use of a ,,chimney-,,pot8 ,a4 ,when the opening of a chimney is large1 the top must be contracted by a chimney-pot1 in order to increase the draught4 ,q4 ,how does a ,,chimney-,,pot ,,increase the ,,draught of a chimney8 ,a4 ,as the same quantity of hot air has to escape through a much smaller opening1 it must pass through more quickly4 ,q4 ,why do tin ,,blowers help to get a fire up8 ,a4 ,because they compel the air to go through the fire1 and not over it2 therefore the fire is well supplied with oxygen1 and the draught greatly increased4 ,q4 ,why does a tin ,,blower ,,increase the ,,draught8 ,a4 ,as all the air which enters the chimney has to pass through the fire1 it is much hotter1 and ascends the chimney very fast2 and the faster the air flies up the chimney1 the faster it rushes towards the fire also4 ,q4 ,why does a parlour often ,,smell disagreeably of ,,soot in ,,summer-,,time8 ,a4 ,the air in the chimney 7being colder than the air in the parlour7 descends into the room1 and leaves a disagreeable smell of soot behind4 ,q4 ,why are the ,,ceilings of ,,public ,,offices so ,,black and filthy8 ,a4 ,the heated air ascending1 carries the dust and fine soot to the ceiling2 where the hot air escapes through the plaster1 and leaves the soot and dust behind4 ,q4 ,why are ,,some parts of the ceiling ,,blacker and more filthy than others8 ,a4 ,as the air cannot penetrate the thick joists of the ceiling1 it passes by those parts1 and deposits its soot and dust on those which are more penetrable4 ,q4 ,what is ,,charcoal8 ,a4 ,wood which has been exposed to a red heat1 till it has been deprived of all its gases and volatile parts4 ,q4 ,why is a ,,charcoal ,,fire hotter than a wood fire8 ,a4 ,because so large a quantity of water has been abstracted from the fuel1 by the red heat to which it has been already exposed4 ,q4 ,why does charcoal ,,remove the ,,taint of meat8 ,a4 ,because it absorbs all odoriferous effluvia1 whether they arise from putrefying animal or vegetable matter4 ,q4 ,why is ,,water ,,purified by being filtered through charcoal8 ,a4 ,charcoal absorbs the impurities of the water1 and removes all disagreeable tastes and smells1 whether they arise from animal or vegetable matter4 ,q4 ,why are water and wine ,,casks ,,charred inside8 ,a4 ,charring the inside of the cask reduces it to a kind of charcoal2 and charcoal 7by absorbing animal and vegetable impurities7 keeps the liquor sweet and good4 ,q4 ,why does a piece of ,,burnt ,,bread1 steeped in impure ,,water1 make it fit to drink8 ,a4 ,the surface of the bread is reduced to charcoal by being burnt2 and the charcoal surface of the bread abstracts all the impurities of the water1 and makes it palatable4 ,q4 ,why should the ,,toast and ,,water1 placed by the side of the sick1 be made of ,,burnt ,,bread8 ,a4 ,the surface of the bread being reduced to charcoal by being burnt1 prevents the water from being affected by the impurities of the sick room4 ,q4 ,why are ,,timbers1 which are to be exposed to damp1 ,,charred8 ,a4 ,charcoal undergoes no change by exposure to air and water2 therefore timber will resist weather much longer1 after it has been charred4 ,,chapter ,v4 ,,lamps ,,and ,,candles4 ,q4 ,of what are ,,oil1 ,,tallow1 and ,,wax composed8 ,a4 ,principally of carbon and hydrogen gas4 ,the solid part is carbon1 the volatile part is gas4 ,q4 ,what is ,,carbon8 ,a4 ,a solid substance1 generally of a black colour2 well known under the forms of charcoal1 lamp-black1 coke1 black-lead1 c4 ,q4 ,what is ,,hydrogen ,,gas8 ,a4 ,the principal ingredient of water4 ,it is well known in the form of common coal gas3 it burns so readily that it used to be called inflammable air4#aj #aj ,to make hydrogen gas1 see p4 #cd4 ,q4 ,why does a ,,candle ,,burn when lighted8 ,a4 ,the heat of the lighted wick decomposes the tallow into its elementary parts of carbon and hydrogen2 and the hydrogen of the tallow1 combining with the oxygen of the air1 produces flame4 ,q4 ,why is the ,,flame of a candle ,,hot8 ,a4 #ast--,because the flame liberates latent heat from the air and tallow3 and #bndly--,it throws into rapid motion the atoms of matter4 ,q4 ,how is ,,latent ,,heat liberated by the flame of a ,,candle8 ,a4 ,when the hydrogen of the tallow and oxygen of the air combine1 they condense into water2 and much of their latent heat is squeezed out4 ,q4 ,how are the ,,atoms of ,,matter disturbed by the flame of a candle8 ,a4 #ast--,when the hydrogen of the tallow and oxygen of the air condense into water1 a vacuum is made2 and the air is disturbed1 as a pond would be1 if a pail of water were taken out4 #bndly--,when the carbon of tallow and oxygen of the air expand into carbonic acid gas1 the air is again disturbed2 in a similar way as by the explosion of gunpowder4 ,q4 ,why does the flame of a ,,candle produce ,,light8 ,a4 ,the chemical changes made by combustion1 excite undulations of ether1 which 7striking the eye7 produce light4 7see p4 #df47 ,q4 ,why is the ,,flame of a ,,candle ,,yellow8 ,a4 ,only the outer coat of the flame is yellow2 the lower part of the flame is violet2 and the inside of the flame is hollow4 ,q4 ,why is the outside of the flame ,,yellow8 ,a4 ,because the carbon of the tallow 7being in a state of perfect combustion7 is made white-hot4 ,q4 ,why is the ,,bottom part ,,purple of the flame of a candle8 ,a4 ,the bottom part of the flame is overladen with hydrogen1 raised from the tallow by the burning wick2 and this half-burnt gas gives a purple tinge to the flame4 ,q4 ,why is the ,,inside of the flame of a candle ,,hollow8 ,a4 ,because it is filled with vapour1 raised from the candle by the heat of the wick4 ,q4 ,describe the different parts of the ,,flame of a common ,,candle4 ,a4 ,the flame consists of three cones4 ,the innermost cone is hollow2 the intermediate cone of a dingy purple hue2 and the outside cone is yellow4 ,q4 ,why is the intermediate cone of a flame ,,purple1 as well as the ,,bottom of the flame4 ,a4 ,because the gases are not in a state of perfect combustion2 but contain an excess of hydrogen1 which gives this cone a purple tinge4 ,q4 ,why is not the ,,middle cone in a state of perfect combustion1 as well as the ,,outer cone8 ,a4 ,because the outer cone prevents the oxygen of the air from getting freely to the middle of the cone2 and without the free access of oxygen gas1 there is no such thing as complete combustion4 ,q4 ,why does the ,,flame of a candle point ,,upwards8 ,a4 ,the flame heats the surrounding air1 which 7being hot7 rapidly ascends1 and drives the flame upwards at the same time4 ,q4 ,why is the ,,flame of a candle ,,pointed at the top1 like a cone8 ,a4 ,the upper part of a flame is more volatile than the lower parts2 and as it affords less resistance to the air1 is reduced to a mere point4 ,q4 ,why is the ,,upper part of a flame more ,,volatile than the lower parts8 ,a4 ,the lower parts of the flame are laden with unconsumed gas and watery vapour2 which present considerable resistance to the air4 ,q4 ,why is the ,,flame of a candle ,,blown ,,out by a puff of breath8 ,a4 ,as the flame of a candle is attached to a very small wick1 a puff of breath severs the flame from the wick2 and it goes out for want of support4 ,q4 ,why does the ,,flame of a candle make a ,,glass ,,damp1 which is held over it8 ,a4 ,the hydrogen of the tallow combining with the oxygen of the air1 produce a watery vapour1 which is condensed by the cold glass held above the flame4 ,q4 ,why does our hand1 held ,,above a candle1 suffer from the heat of the flame so much more1 than when it is placed ,,below the flame1 or on ,,one ,,side of it8 ,a4 ,because the hot gases and air 7in their ascent7 come in contact with the hand placed above the flame3 but when the hand is placed below the flame1 or on one side1 it only feels heat from radiation4 ,q4 ,why is a ,,rush ,,light extinguished so much more quickly than a cotton-wicked candle8 ,a4 ,as the rush wick is smooth and hard1 the mere motion of the air 7produced by carrying the candle from one place to another17 is sufficient to sever the flame from the rush4 ,q4 ,why is it more difficult to blow out a ,,cotton wick8 ,a4 ,the cotton wick is quite full of small threads or filaments1 which help to hold the flame on the wick1 like the roots of a tree4 ,q4 ,why does an ,,extinguisher put a candle out8 ,a4 ,because the air in the extinguisher is soon exhausted of its oxygen by the flame3 and when there is no oxygen to support it1 the flame goes out4 ,q4 ,why does not a candle set fire to a ,,piece ,,of ,,paper twisted into an extinguisher1 and used as such8 ,a4 #ast--,because the flame very soon exhausts the little oxygen contained in the paper extinguisher3 and #bndly--,the flame invests the inside of the paper extinguisher with carbonic acid gas1 which prevents it from blazing4 ,q4 ,why is a ,,long ,,wick never upright8 ,a4 ,because it is bent by its own weight4 ,q4 ,why is a ,,long ,,wick covered with an ,,efflorescence at the top8 ,a4 ,the knotty or flowery appearance of the top of a wick arises from an accumulation of particles partly separated1 but still loosely hanging to the wick4 ,q4 ,why is not the ,,end of a long wick ,,burnt ,,off1 as it hangs over the flames8 ,a4 ,because the length of the wick so diminishes the heat of the flame1 that it is not hot enough to burn it off4 ,q4 ,why do ,,palmer',s ,,metallic ,,wicks never need ,,snuffing8 ,a4 ,the wick is divided into two parts1 each of which bends outward to the outside of the flame2 where the end is intensely heated1 and separated from the wick by the current of air up the candle4 ,q4 ,why do common ,,candles require to be ,,snuffed8 ,a4 ,because the heat of the flame is not sufficient to consume the wick2 and the longer the wick grows1 the less heat the flame produces4 ,q4 ,why do ,,wax ,,candles ,,never need ,,snuffing8 ,a4 ,the wick of wax candles is made of very fine thread1 which the heat of the flame is sufficient to consume3 but the wick of tallow candles is made of coarse cotton1 which is too substantial to be consumed by the heat of the flame1 and must be cut off by snuffers4 ,q4 ,why does a ,,pin1 stuck in a ,,rush-,,light1 ,,extinguish it8 ,a4 ,because a pin 7being a good conductor71 carries away the heat of the flame from the wick1 and prevents the combustion of the tallow4 ,q4 ,what is the ,,smoke of a ,,candle8 ,a4 ,solid particles of carbon separated from the wick and tallow1 but not consumed4 ,q4 ,why are ,,some particles consumed and not ,,others8 ,a4 ,the combustion of the carbon depends upon its combining with the oxygen of the air3 but as the outer surface of the flame prevents the access of air to the interior parts1 therefore much of the carbon of those parts passes off in smoke4 ,q4 ,why do ,,lamps ,,smoke8 ,a4 ,either because the wick is cut unevenly1 or else because it is turned up too high4 ,q4 ,why does a ,,lamp ,,smoke when the ,,wick is cut ,,unevenly8 ,a4 #ast--,because the points of the jagged edge 7being very easily separated from the wick17 load the flame with more carbon than it can consume3 and #bndly--,as the heat of the flame is greatly diminished by these bits of wick1 it is unable to consume even the usual quantity of smoke4 ,q4 ,why does a ,,lamp ,,smoke when the ,,wick is turned up too ,,high8 ,a4 ,because more carbon is separated from the wick than can be consumed by the flame4 ,q4 ,why do not ,argand burners smoke8 ,a4 ,because a current of air passes through the middle of the flame2 and therefore the carbon of the interior is consumed1 as well as that in the outer coating of the flame4 ,q4 ,why does a ,,lamp-,,glass ,,diminish the ,,smoke of a lamp8 ,a4 ,because it both concentrates and reflects the heat of the flame2 in consequence of which1 the heat is so greatly increased1 that very little carbon escapes unconsumed4 ,,chapter ,,vi4 ,,animal ,,heat4 ,q4 ,what is the cause of ,,animal ,,heat8 ,a4 ,animal heat is produced by the combustion of hydrogen and carbon in the capillary veins4 ,q4 ,what are ,,capillary ,,veins8 ,a4 ,veins as small as hairs running all over the body2 so called from the ,latin word capilla'ris 7like a hair74 ,q4 ,do these ,,capillary ,,veins run all over the human body8 ,a4 ,yes4 ,whenever blood flows from a wound1 some vein must be divided2 and as you cannot insert a needle into any part of the body without bringing blood1 therefore these little veins must run through every part of the human frame4 ,q4 ,how do ,,hydrogen gas and ,,carbon get into these very little veins8 ,a4 ,the food we eat is converted into blood1 and blood contains both hydrogen and carbon4 ,q4 ,how does ,,combustion take place in the veins8 ,a4 ,the carbon of the blood combines with the oxygen of the air we breathe1 and forms into carbonic acid gas4 ,q4 ,what ,,becomes of this ,,carbonic ,,acid ,,gas formed in the human blood8 ,a4 ,some of it is thrown off by the breath2 and the rest of it is absorbed by the blood1 to keep up the animal heat4 ,q4 ,what is the cause of the ,,combustion of ,,fire8 ,a4 ,the carbon of fuel unites with the oxygen of the air1 and forms carbonic acid gas4 ,q4 ,what is the cause of the ,,combustion of a ,,candle or ,,lamp8 ,a4 ,the carbon of the oil or tallow unites with the oxygen of the air1 and forms carbonic acid gas4 ,q4 ,what is the cause of ,,spontaneous ,,combustion8 ,a4 ,the piled-up goods ferment from heat and damp2 and 7during fermentation7 carbonic acid gas is formed1 as in the two former cases4 ,q4 ,does the ,,heat of the ,,human ,,body arise from the ,,same ,,cause as the heat of ,,fire8 ,a4 ,yes1 precisely4 ,the carbon of the blood1 combining with the oxygen of air inhaled1 produces carbonic acid gas1 which is attended with combustion4 ,q4 ,if animal heat is produced by ,,combustion1 why does not the human body ,,burn ,,up like a coal or candle8 ,a4 ,it actually does so4 ,every muscle1 nerve1 and organ of the body1 actually wastes away like a burning candle2 and 7being reduced to air and ashes7 is rejected from the system as useless4 ,q4 ,if every bone1 muscle1 nerve1 and organ1 is thus consumed by combustion1 why is not the ,,body entirely ,,consumed8 ,a4 ,it would be so1 unless the parts destroyed were perpetually renewed3 but as a lamp will not go out1 so long as it is supplied with fresh oil2 neither will the body be consumed1 so long as it is supplied with sufficient food4 ,q4 ,when a man is ,,starved1 what parts of the body go first8 ,a4 ,first the fat1 because it is the most combustible2 then the muscles2 last of all the brain2 and then the man dies1 like a candle which is burnt out4 ,q4 ,why does ,,want of sufficient ,,nourishment often produce ,,madness8 ,a4 ,after the fat and muscles of the body have been consumed by animal combustion1 the brain is next attacked2 and 7unless the patient dies7 madness must ensue from starvation4 ,q4 ,why does a man ,,shrink when ,,starved8 ,a4 ,a starved man shrinks just as a fire does1 unless it be supplied with sufficient fuel4 ,q4 ,what is the ,,fuel of the ,,body8 ,a4 ,food is the fuel of the body2 and the carbon of the food mixing with the oxygen of the air1 evolves heat in the same way that a fire or candle does4 ,q4 ,why is ,,every part of the ,,body ,,warm8 ,a4 ,as the capillary veins run through every part of the human body1 and the combustion of blood takes place in the capillary veins1 therefore every part of the body is warm4 ,q4 ,why does ,,running make us ,,warm8 ,a4 ,when we run1 we inhale air more rapidly2 and the rapidity with which we inhale air fans the combustion of our body1 as a pair of bellows quickens the flame of a common fire4 ,q4 ,how does ,,inhaling ,,air ,,rapidly make the body feel ,,warm8 ,a4 ,as the combustion of the blood is more rapid1 7in consequence of the introduction of more oxygen from the air71 therefore the blood is more heated1 and every part of the body is warmer also4 ,q4 ,why does ,,hard ,,work produce ,,hunger8 ,a4 ,because it produces quicker respiration2 by which means a larger amount of oxygen is introduced into the lungs1 and the capillary combustion increased4 ,hunger is the notice 7given by our body7 to remind us1 that our food-fuel must be replenished4 ,q4 ,why does ,,singing make us ,,hungry8 ,a4 ,singing increases respiration2 and as more oxygen is introduced into the lungs1 our food-fuel is more rapidly consumed4 ,q4 ,why does ,,reading ,,aloud make us feel ,,hungry8 ,a4 ,reading aloud increases respiration2 and as more oxygen is introduced into the lungs1 our food-fuel is more rapidly consumed4 ,q4 ,why do we feel ,,more ,,hungry in the ,,day-,,time than in the ,,night-,,time8 ,a4 ,as we breathe more slowly during sleep1 therefore1 less oxygen is introduced into the lungs to consume our food-fuel4 ,q4 ,why do we need ,,warmer ,,clothing by ,,night than by ,,day8 ,a4 #ast--,because the night is generally colder than the day4 #bndly--,as our respiration is slower1 our animal combustion is slower also2 in consequence of which1 our bodies are more cold4 ,q4 ,why do we ,,perspire when very ,,hot8 ,a4 ,the pores of the body are like the safety valves of a steam-engine2 when the heat of the body is too great1 the combustible gas and grease flow out in perspiration1 instead of burning in the blood4 ,q4 ,why do persons feel ,,lazy and averse to exercise1 when they are ,,half-,,starved or ,,ill-,,fed8 ,a4 ,animal food contains great nourishment1 and produces a desire for active occupations2 but when the body is not supplied with strong food1 this desire for muscular action ceases1 and the person grows slothful4 ,q4 ,why have persons1 who follow ,,hard ,,out-,,of-,,doors ,,occupations1 more ,,appetite than those who are engaged in ,,sedentary pursuits8 ,a4 ,hard bodily labour in the open air causes much oxygen to be conveyed into the lungs by inspiration2 the combustion of the food is carried on quickly2 animal heat increased2 and need for nutritious food more quickly indicated by craving hunger4 ,q4 ,why have persons who follow ,,sedentary ,,pursuits less ,,appetite than ploughmen and masons8 ,a4 #ast--,the air they inhale is not so pure1 because its oxygen is partly exhausted3 and #bndly--,their respiration is neither so quick nor strong1 and therefore the combustion of their food is carried on more slowly4 ,q4 ,why do we like strong ,,meat and ,,greasy food when the ,,weather is very ,,cold8 ,a4 ,strong meat and grease contain large portions of hydrogen1 which 7when burned in the blood7 produce a larger amount of heat than any other kind of food4 ,q4 ,why do persons ,,eat ,,more food in ,,cold weather1 than in hot8 ,a4 ,in cold weather the body requires more fuel to keep up the same amount of animal heat2 and as we put more coals on a fire on a cold day to keep our room warm1 so we eat more food on a cold day to keep our body warm4 ,q4 ,why does ,,cold produce ,,hunger8 ,a4 #ast--,the air contains more oxygen in cold weather2 and as fires burn fiercer1 so animal combustion is more rapid3 and #bndly--,we are more active in cold weather2 and increased respiration acts like a pair of bellows on the capillary combustion4 ,q4 ,why does rapid ,,digestion produce a craving ,,appetite8 ,a4 ,this is a wise providence to keep our bodies in health2 in order that the body itself may not be consumed1 it gives notice 7by hunger7 that the capillary fires need replenishing4 ,q4 ,why do we feel a desire for ,,activity in cold weather8 ,a4 #ast--,because activity increases the warmth of the body1 by fanning the combustion of the blood3 and #bndly--,the strong food we eat creates a desire for muscular exertion4 ,q4 ,why are the ,esquimeaux so passionately fond of ,,train ,,oil and ,,whale ,,blubber8 ,a4 ,oil and blubber contain a very large amount of hydrogen1 which is exceedingly combustible2 and as these people live in climates of intense cold1 the heat of their bodies is increased by the greasy nature of their food4 ,q4 ,why do we feel a dislike to strong meat and greasy foods in very hot weather8 ,a4 ,strong meat and grease contain so much hydrogen1 that they would make us intensely hot2 and therefore we refuse them in hot weather4 ,q4 ,why do we like fruits and vegetables so very much in hot weather8 ,a4 ,fruits and vegetables contain less carbon than meat1 and therefore produce less blood3 instead of blood1 they combine into water as they are digested1 and keep the body cool4 ,q4 ,why do people say that ,,fruits and ,,vegetables ,,cool the ,,blood8 ,a4 #ast--,because they deprive the blood of carbon1 which is the chief cause of animal heat3 and #bndly--,these gases coalesce into water1 which greatly tempers the animal heat4 ,q4 ,why do we feel ,,lazy and averse to activity in very ,,hot ,,weather8 ,a4 #ast--,because muscular activity would increase the heat of the body1 by quickening the respiration3 and #bndly--,the food we eat in hot weather1 not being greasy1 naturally abates our desire for bodily activity4 ,q4 ,why do the inhabitants of tropical countries live chiefly upon rice and fruit8 ,a4 ,rice and fruit by digestion are mainly converted into water1 and 7by cooling the blood7 prevent the tropical heat from feeling so oppressive4 ,q4 ,why are ,,poor ,,people generally ,,averse to ,,cleanliness8 ,a4 #ast--,cleanliness increases hunger2 and as poor people are generally ill-fed1 they are averse to cleanliness4 #bndly--,dirt is warm1 7thus pigs who love warmth1 are fond of dirt72 and as poor people are generally ill-clad1 they like the warmth of dirt4 ,q4 ,why are ,,poor ,,people generally ,,averse to ,,ventilation8 ,a4 #ast--,because ventilation increases the oxygen of the air1--the combustion of food1--and the cravings of appetite3 and #bndly--,ventilation cools the air of our rooms3 poor people1 therefore1 7who are generally ill-clad7 love the warmth of an ill-ventilated apartment4 ,q4 ,why does ,,flannel1 c4 make us ,,warm8 ,a4 ,flannel and warm clothing do not make us warm1 but merely prevent the body from becoming cold4 ,q4 ,how does flannel1 c4 prevent the body from becoming cold8 ,a4 ,flannel 7being a bad conductor7 will neither carry off the heat of the body into the cold air1 nor suffer the cold of the air to come into contact with our warm bodies2 and thus it is that flannel clothing keeps us warm4 ,q4 ,why are ,,frogs and ,,fishes ,,cold-,,blooded animals8 ,a4 ,because they consume so little air2 and without a plentiful supply of air1 combustion is so slow1 that very little animal heat is evolved4 ,q4 ,why is a ,,dead ,,body ,,cold8 ,a4 ,air is no longer conveyed to the lungs after respiration has ceased2 and1 therefore1 animal heat is no longer evolved by combustion4 ,,chapter ,,vii4 ,,mechanical ,,action4 #a4--,,percussion4 ,q4 ,how is heat produced by ,,mechanical ,,action8 ,a4 #a4--;,by ,percussion4 #b4--;,by ,friction4 #c4--;,by ,condensation4 ,q4 ,what is meant by ,,percussion8 ,a4 ,the act of striking2 as when a blacksmith strikes a piece of iron on his anvil with his hammer4 ,q4 ,why does ,,beating ,,iron make it ,,red-,,hot8 ,a4 ,beating the iron condenses the particles of the metal2 and squeezes out its latent heat1 as water from a sponge4 ,q4 ,does ,,cold iron contain ,,heat8 ,a4 ,yes2 every thing contains heat2 but when a thing feels cold1 its heat is ,,latent4 ,q4 ,what is meant by ,,latent ,,heat8 ,a4 ,heat not perceptible to our feeling4 ,when anything contains heat without feeling the hotter for it1 that heat is called latent4 7,see p4 #ca47 ,q4 ,does ,,cold iron contain latent ,,heat8 ,a4 ,yes2 and when a blacksmith compresses the particles of the iron by his hammer1 he squeezes out this latent heat1 and makes the iron red-hot4 ,q4 ,how did blacksmiths use to ,,light ,,their ,,matches before the general use of lucifers8 ,a4 ,they used to place a soft iron nail upon their anvil2 strike it two or three times with a hammer2 and the point became sufficiently hot to light a brimstone match4 ,q4 ,how can a ,,nail 7beaten by a hammer7 ,,ignite a brimstone ,,match8 ,a4 ,as the particles of the nail are compressed by the hammer1 it cannot contain so much heat as it did before2 so some of it flies out 7as water flows from a sponge when it is squeezed74 ,q4 ,why does ,,striking a ,,flint against a piece of ,,steel produce a ,,spark8 ,a4 ,the blow condenses those parts of the flint and steel which strike together1 and squeezes out their latent heat4 ,q4 ,how does this development of ,,heat produce a ,,spark8 ,a4 ,a very small fragment 7either of the steel or flint7 is knocked off red-hot1 and sets fire to the tinder on which it falls4 ,q4 ,why is it needful to keep ,,blowing the ,,tinder with the breath8 ,a4 ,because blowing the tinder1 drives the oxygen of the air towards it4 ,q4 ,where does the ,,oxygen of the air ,,come ,,from1 which is blown to the lighted tinder8 ,a4 ,the air itself is composed of two gases 7nitrogen and oxygen7 mixed together4 7,every #e lbs4 of common air contain #d lbs4 of nitrogen1 and #a lb4 of oxygen47 ,q4 ,what is the good of ,,blowing ,,oxygen ,,gas to lighted tinder8 ,a4 ,oxygen gas supports combustion2 and lighted tinder is quickened by the breath1 in the same way as a dull fire is revived by a pair of bellows4 ,q4 ,why do ,,horses sometimes ,,strike ,,fire with their ,,feet8 ,a4 ,when iron horse-shoes strike against the flint-stones of the road1 very small fragments 7either of the shoe or stones7 are knocked off red-hot1 and look like sparks4 ,q4 ,what makes these fragments ,,red-,,hot8 ,a4 ,the percussion condenses the part struck1 and squeezes out its latent heat4 ,,chapter ,,viii4 #b4--;,,friction4 #c4--;,,condensation4 ,q4 ,what is meant by ,,friction8 ,a4 ,the act of rubbing two things together2 as the ,indians rub two pieces of wood together to produce fire4 ,q4 ,how do the ,indians produce ,,fire1 by merely ,,rubbing ,,two ,,pieces of dry ,,wood ,,together8 ,a4 ,they take a piece of dry wood 7sharpened to a point71 which they rub quickly up and down a flat piece1 till a groove is made2 and the saw-dust 7collected in this groove7 soon catches fire4 ,q4 ,why does the saw-dust of the ,,wood ,,catch ,,fire by ,,rubbing8 ,a4 ,the latent heat of the wood is developed by friction2 because the particles of the wood are squeezed closer together1 and the heat pours out1 as water from a sponge4 7,the best woods for this purpose are box-wood against mulberry1 or laurel against poplar or ivy47 ,q4 ,do not ,,carriage ,,wheels sometimes ,,catch ,,fire8 ,a4 ,yes2 if the wheels be dry1--or fit too tightly1--or revolve very rapidly1--they often catch fire4 ,q4 ,why do wheels catch fire in such cases8 ,a4 ,the friction of the wheels against the axle-tree is so great1 that their latent heat is disturbed1 and produces ignition4 ,q4 ,what is the use of ,,greasing ,,cart ,,wheels8 ,a4 ,the grease lessens the friction2 and 7by diminishing the friction7 the latent heat is less disturbed4 ,q4 ,why is the ,,top of a ,,mountain ,,colder than the ,,valley beneath1 although it be two or three miles nearer to the sun8 ,a4 #ast--,because the air on a mountain is less compressed1 than the air in a valley4 #bndly--,it is more rarefied3 and #crdly--,it is less heated by reflection4 ,q4 ,why is air ,,colder on a mountain because it is ,,less ,,compressed8 ,a4 ,as the air in a valley is more compressed 7by the mass of air above7 than that on the top of a mountain1 therefore more heat runs out2 just as more water runs from a sponge1 the closer it is squeezed together4 ,q4 ,why is a mountain-top ,,colder than a valley1 because the ,,air there is ,,more ,,rarefied8 ,a4 ,as the air is more rarefied1 its heat is diffused over a larger space and is less intense2 just as a candle would show less light in a large room1 than in a small one4 ,q4 ,why is a mountain-top ,,colder than a valley1 because the ,,air there is ,,less ,,heated by ,,reflection8 ,a4 ,air is not heated by the sun1 but by reflection from the surface of the earth2 and as there is no earth round a mountain-top to reflect heat1 therefore the air there is intensely cold4 ,q4 ,why does ,,rubbing our ,,hands and ,,faces make them feel ,,warm8 ,a4 ,chiefly because the friction excites the latent heat of our hands and faces1 and makes it sensible to our feeling4 ,q4 ,when a man has been almost ,,drowned1 why is suspended animation ,,restored by ,,rubbing8 ,a4 ,the vital heat of the body 7which had become latent by the action of the water7 is again developed by friction3 and1 as soon as this animal heat can be excited1 the vital powers of the body are restored4 ,q4 ,why do two pieces of ,,ice 7rubbed together7 ,,melt8 ,a4 ,ice contains #adj degrees of latent heat1 and 7when two pieces are rubbed together7 their particles are compressed1 and this latent heat rolls out and melts the ice4 ,q4 ,are not ,,forests sometimes ,,set on ,,fire by friction8 ,a4 ,yes2 when two branches or trunks of trees 7blown about by the wind7 rub violently against each other1 their latent heat is developed1 and sets fire to the forest4 ,q4 ,what is meant by ,,compression8 ,a4 ,the act of bringing parts nearer together2 as a sponge is compressed by being squeezed in the hand4 ,q4 ,cannot ,,heat be evolved from common air merely by ,,compression8 ,a4 ,yes2 if a piece of ,german tinder be placed at the bottom of a glass tube1 and the air in the tube compressed by a piston1#aa the tinder will catch fire4 #aa ,in a common syringe or squirt1 the handle part which contains the sucker 7and is forced up and down71 is called ,the ,piston4 ,q4 ,why will the tinder catch fire8 ,a4 ,because the air is compressed2 and its latent heat being squeezed out1 sets fire to the tinder at the bottom of the tube4 ,,chapter ,,ix4 ,,effects ,,of ,,heat4 #a4--;,,expansion4 ,q4 ,what are the principal ,,effects of ,,heat8 ,a4 #a4--;,expansion4 #b4--,liquefaction4 #c4--,vaporization4 #d4--;,evaporation2 and #e4--;,ignition4 ,q4 ,does ,,heat ,,expand the ,,air8 ,a4 ,yes2 if a bladder 7partially filled with air7 be tied up at the neck1 and laid before the fire1 the air will swell till the bladder bursts4 ,q4 ,why will the ,,air ,,swell1 if the bladder be laid before the fire8 ,a4 ,because the heat of the fire gets between the particles of air1 and drives them further apart from each other2 which causes the bladder to expand4 ,q4 ,why do unslit ,,chestnuts ,,crack with a loud noise1 when ,,roasted8 ,a4 ,chestnuts contain a great deal of air1 which is expanded by the heat of the fire2 and1 as the thick rind prevents the air from escaping1 it violently bursts through1 slitting the rind1 and making a great noise4 ,q4 ,what occasions the loud ,,crack or report which we hear8 ,a4 #ast--,the sudden bursting of the rind makes a report1 in the same way as a piece of wood or glass would do1 if snapped in two3 and #bndly--,the escape of hot air from the chestnut makes a report also1 in the same way as gunpowder1 when it escapes from a gun4 ,q4 ,why does the sudden ,,bursting of the rind1 or ,,snapping of a piece of wood1 make a ,,report8 ,a4 ,as the attraction of the parts is suddenly overcome1 a violent jerk is given to the air2 this jerk produces rapid undulations in the air1 which 7striking upon the ear7 give the brain the sensation of sound4 ,q4 ,why does the ,,escape ,,of ,,air from the chestnut1 or the ,,explosion of ,,gunpowder1 produce a ,,report8 ,a4 ,because a quantity of air 7suddenly let loose7 pushes against the air around1 in order to make room for itself2 and as the air of the chestnut slaps against the air of the room1 a report is made1 7as when ,i slap a book or table74 ,q4 ,if a ,,chestnut be ,,slit1 it will ,,not ,,crack2 why is this8 ,a4 ,because the heated air of the chestnut can freely escape through the slit in the rind4 ,q4 ,why does an ,,apple spit and ,,spurt about1 when roasted8 ,a4 ,an apple contains a vast quantity of air1 which 7being expanded by the heat of the fire7 bursts through the peel1 carrying the juice of the apple along with it4 ,q4 ,does an ,,apple contain ,,more ,,air1 in proportion1 than a ,,chestnut8 ,a4 ,yes1 much more4 ,there is as much condensed air in a common apple1 as would fill a space #dh times as big as the apple itself4 ,q4 ,where is all this quantity of ,,air stowed in the ,,apple8 ,a4 ,the inside of an apple is made up of little cells 7like a honey-comb71 each of which contains a portion of the air4 ,q4 ,when an ,,apple is ,,roasted1 why is one part made ,,soft1 while all the rest remains hard8 ,a4 ,when an apple is roasted1 the air in the cells next to the fire is expanded and flies out2 the cells are broken1 and their juices mixed together2 so the apple collapses 7from loss of air and juice71 and feels soft in those parts4 ,q4 ,what is meant by the apple ,,collapsing8 ,a4 ,the plumpness gives way1 and the apple becomes flabby and shrivelled4 ,q4 ,why do ,,sparks of fire start 7with a crackling noise7 from pieces of ,,wood laid upon a ,,fire8 ,a4 ,the air in the wood 7expanded by the heat71 forces its way through the pores of the log2 and carries along with it the covering of the pore1 which resisted its passage4 ,q4 ,what is meant by the ,,pores of the ,,wood8 ,a4 ,very small holes in the wood1 through which the sap circulates4 ,q4 ,what are the ,,sparks ,,of ,,fire1 which burst from the ,,wood8 ,a4 ,very small pieces of wood red hot1 separated from the log by the force of the air1 as it bursts from its confinement4 ,q4 ,why does ,,deal make more snapping than any ,,other ,,wood8 ,a4 ,the pores of deal are very large1 and contain much more air than wood of a closer grain4 ,q4 ,why does ,,dry ,,wood make more ,,snapping than ,,green ,,wood8 ,a4 ,in green wood the pores are filled with sap1 and therefore contain very little air2 but in dry wood the sap is dried up1 and the pores are filled with air instead4 ,q4 ,why does ,,dry wood ,,burn more easily than ,,green or wet wood8 ,a4 ,because the pores of dry wood are filled with air1 which supports combustion2 but the pores of green or wet wood are filled with vapour1 which extinguishes flame4 ,q4 ,why does ,,vapour ,,extinguish ,,flame8 #ast--,because the coat of water 7which wraps the fuel round7 prevents the oxygen of the air from getting to the fuel1 to form into carbonic acid gas3 and #bndly--,heat is perpetually carried off1 by the formation of the sap or water into steam4 7,carbonic acid gas is a compound of carbon and oxygen4 ,the solid part of the fuel is carbon1 and one of the gases of the air is oxygen47 ,q4 ,what has ,,carbonic ,,acid ,,gas to do with ,,combustion8 ,a4 ,combustion is produced by the chemical action which takes place1 while the carbon of fuel unites with the oxygen of air1 and forms carbonic acid gas4 7,see p4 #cf47 ,q4 ,why do ,,stones ,,snap and fly about1 when heated in the ,,fire8 ,a4 ,the air in the stones 7expanded by the heat of the fire71 meets with great resistance from the close texture of the stone2 and1 therefore1 bursts forth with great violence1 tearing the stone to atoms1 and forcing the fragments into the room4 ,q4 ,must not ,,air be very ,,strong1 to shatter into atoms a hard stone8 ,a4 ,yes4 ,all the dreadful effects of gunpowder are merely the results of the sudden expansion of air4 ,q4 ,when bottled ,,ale and ,,porter is set before a ,,fire1 why is the ,,cork ,,forced ,,out sometimes8 ,a4 ,if the bottle be not quite full1 there will be air between the liquor and the cork2 this air 7expanded by the heat of the fire7 forces out the cork4 ,q4 ,why does ,,ale or ,,porter ,,froth more1 after it has been set before the fire8 ,a4 ,the froth of ale or porter depends upon the pressure to which it is subjected2 and as the air 7between the liquor and the cork7 is expanded by the heat1 it presses against the liquor1 and increases the quantity of froth4 ,q4 ,why is the ,,froth of ale and porter ,,increased by ,,pressure8 ,a4 ,because the liquor absorbs carbonic acid so long as it is under pressure2 and the moment that the pressure is removed1 the carbonic acid escapes in foam or froth4 ,q4 ,when a boy makes a ,,balloon1 and sets fire to the cotton or sponge 7which has been steeped in spirits of wine71 why is the balloon ,,inflated1 or blown out8 ,a4 ,the air inside the balloon is expanded by the flame1 till the whole balloon is blown out without a crumple4 ,q4 ,why does the ,,balloon ,,rise1 after it has been inflated by the expanded air8 ,a4 ,the same quantity of air is expanded to three or four times its original volume2 and is made so much lighter than common air1 that even when all the paper1 wire1 and cotton are added1 it is still lighter bulk for bulk4 ,q4 ,what is meant by being lighter bulk for bulk8 ,a4 ,if the balloon be #c square feet in size1 it is lighter 7when inflated7 than #c square feet of common air1 and therefore floats through it2 as a cork 7at the bottom of a tub of water7 would rise to the surface4 ,q4 ,why does ,,smoke ,,rush ,,up a ,,chimney8 ,a4 ,the heat of the fire expands the air in the chimney2 and 7being thus made lighter than the air around71 it rises up the chimney1 and carries the smoke in its current4 ,q4 ,why has a ,,long ,,chimney a greater ,,draught than a short one8 ,a4 ,because air rises faster and faster the higher it ascends in a chimney flue2 the same as a stone falls faster and faster the nearer it approaches to the ground4 ,q4 ,why will a ,,long chimney ,,smoke1 unless the ,,fire be pretty ,,fierce8 ,a4 ,if the fire be not pretty fierce1 its heat will not be sufficient to rarefy all the air in the chimney2 and then the chimney will smoke4 ,q4 ,why will the chimney smoke1 if the fire be not ,,big enough to heat ,,all the air in the ,,chimney ,,flue8 ,a4 ,because the cold air 7condensed in the upper part of the flue71 will sink from its own weight1 and sweep the ascending smoke back with it into the room4 ,q4 ,what is the use of a ,,cowl upon a chimney-pot8 ,a4 ,the cowl acts as a screen against the wind1 to prevent it from blowing into the chimney4 ,q4 ,what ,,harm would the ,,wind do1 if it were to ,,blow into a ,,chimney8 ,a4 #ast--,it would prevent the smoke from getting out3 and #bndly--,the cold air 7introduced into the chimney by the wind7 would fall down the flue1 and drive the smoke with it back into the room4 ,q4 ,why does a ,,smoke-,,jack turn round in a chimney8 ,a4 ,the current of hot air up the chimney1 striking against the oblique vanes of the smoke-jack1 drives them round and round2 in the same way as the sails of a wind-mill are driven round by the wind4 ,q4 ,why are some things ,,solid1 others ,,liquid1 and others ,,gaseous8 ,a4 ,as heat enters any substance1 it drives its particles further asunder2 and a solid 7like ice7 becomes a liquid2 and a liquid 7like water7 becomes a gas4 ,q4 ,why does ,,water ,,simmer before it boils8 ,a4 ,the particles of water near the bottom of the kettle 7being formed into steam sooner than the rest7 shoot upwards2 but are condensed again 7as they rise7 by the colder water1 and produce what is called simmering4 ,q4 ,what is meant by ,,simmering8 ,a4 ,a gentle tremor or undulation on the surface of the water4 ,when water simmers1 the bubbles collapse beneath the surface1 and the steam is condensed to water again3 but when water boils1 the bubbles rise to the surface1 and steam is thrown off4 ,q4 ,why does a ,,kettle ,,sing when the water simmers8 ,a4 ,because the air 7entangled in the water7 escapes by fits and starts through the spout of the kettle2 which makes a noise like a wind instrument1 when it is blown into4 ,q4 ,why does ,,not a kettle ,,sing1 when the water ,,boils8 ,a4 ,as all the water is boiling hot1 the steam meets with no impediment1 but freely escapes in a continuous stream4 ,q4 ,when does a kettle sing most8 ,a4 ,when it is set on a hob to boil4 ,q4 ,why does a kettle ,,sing ,,more when it is set on the ,,side of a fire1 than when it is set in the ,,midst of the fire8 ,a4 ,when the kettle is set on the hob to boil1 the heat is applied very partially3 one side is hotter than the other1 and therefore the steam is more entangled4 ,q4 ,why does a ,,kettle sing1 when the boiling water begins to ,,cool again8 ,a4 ,because the upper surface cools first2 and the steam 7still rising from the lower parts of the kettle7 is again entangled1 and escapes fitfully4 ,q4 ,why does ,,boiling ,,water ,,swell8 ,a4 ,water 7like air7 expands by heat4 ,the heat of the fire drives the particles of water further apart from each other2 and 7as they are not packed so closely together7 they take up more room2 or 7in other words7 the water swells4 ,q4 ,what is meant when it is said1 that ,,heat drives the ,,particles of water further ,,apart from each other4 ,a4 ,water is composed of little globules1 like very small grains of sand2 the heat drives these particles away from each other2 and 7as they then require more room7 the water swells4 ,q4 ,why does ,,boiling ,,water ,,bubble8 ,a4 ,water contains air2 and 7as the water is heated7 the air is driven out1 and raises a bubble in that part of the water which resists its escape4 ,q4 ,why does a ,,kettle sometimes ,,boil ,,over8 ,a4 ,liquids expand very much by heat2 if1 therefore1 a kettle be filled with cold water1 some of it must run over as soon as it is expanded by heat4 ,q4 ,but ,i have seen a ,,kettle ,,boil ,,over1 although it has not been filled ,,full of ,,water2 how do you account for ,,that8 ,a4 ,if a fire be very fierce1 the air is expelled so rapidly1 that the bubbles are very numerous2 and 7towering one above the other7 reach the top of the kettle1 and fall over4 ,q4 ,why is a pot1 which is full to ,,overflowing 7while the water is boiling ,,hot71 ,,nothing ,,like ,,full1 when it has been taken off the fire for a short time8 ,a4 ,when the water was swelled by boiling heat1 it filled the pot even to overflowing2 but as soon as the water is condensed by cold1 it contracts again1 and occupies a much less space4 ,q4 ,why does the water of a ,,kettle run out of the ,,spout when it ,,boils8 ,a4 ,because the steam cannot escape so fast as it is formed1 and 7being confined in the kettle7 presses on the water with great power1 and forces it out of the spout4 ,q4 ,how can the ,,pressure of ,,steam on the ,,surface of the water1 ,,force the water through the ,,kettle-,,spout8 ,a4 ,in the same manner as the pressure of air on the mercury of a barometer1 forces the quicksilver up the glass tube4 ,q4 ,what causes the ,,rattling ,,noise so often made by the ,,lid of a saucepan or boiler8 ,a4 ,the steam 7seeking to escape7 forces up the lid of the boiler1 and the weight of the lid causes it to fall back again3 this being done frequently1 produces a rattling noise4 ,q4 ,if the steam ,,could ,,not ,,lift ,,up ,,the ,,lid of the boiler1 how would it escape8 ,a4 ,if the lid fitted so tightly1 that the steam could not raise it up1 the boiler would burst into fragments1 and the consequences might be fatal4 ,q4 ,when steam pours out from the spout of a kettle1 the ,,stream begins apparently ,,half ,,an ,,inch off the ,,spout2 why does it not begin ,,close to the spout8 ,a4 ,steam is really invisible2 and the half-inch 7between the spout and the stream of mist7 is the real steam1 before it has been condensed by air4 ,q4 ,why is not ,,all the stream ,,invisible1 as well as that half-inch8 ,a4 ,as the steam comes in contact with the colder air1 the invisible particles 7being condensed71 roll one into another1 and look like a thick mist4 ,q4 ,what ,,becomes ,,of the ,,steam8 for it soon vanishes4 ,a4 ,after it is condensed into mist1 it is dissolved by the air1 and dispersed abroad as invisible vapour4 ,q4 ,and what ,,becomes of the ,,invisible ,,vapour8 ,a4 ,being lighter than air1 it ascends to the upper regions1 where 7being again condensed7 it contributes to form clouds4 ,q4 ,why does a ,,metal ,,spoon1 left in a saucepan1 ,,retard the process of ,,boiling8 ,a4 ,the metal spoon 7being an excellent conductor7 carries off the heat from the water2 and 7as heat is carried off by the spoon7 the water takes a longer time to boil4 ,q4 ,why will a ,,pot 7filled with water7 ,,never ,,boil1 when immersed in ,,another vessel full of water also8 ,a4 ,because water can never be heated above the boiling point3 all the heat absorbed by the water after it boils1 is employed in converting the water into steam4 ,q4 ,how does the conversion of water into steam prevent the ,,inner ,,pot from ,,boiling8 ,a4 ,the moment the water in the larger pot is boiling hot 7or #bab71 steam is formed1 and carries off some of its heat2 therefore1 #bab degs4 of heat can never pass through it1 to raise the inner vessel to the same heat4 ,q4 ,why do ,,sugar1 ,,salt1 c4 ,,retard the process of ,,boiling8 ,a4 ,because they have a tendency to fix water by chemical attraction2 and therefore retard its conversion into steam4 ,q4 ,if you want water to boil1 without ,,coming ,,in ,,contact with the ,,saucepan1 what plan must you adopt8 ,a4 ,immerse the pot 7containing the water you want to boil7 in a saucepan containing strong brine1 or sugar4 ,q4 ,why would the ,,inner vessel boil1 if the ,,outer vessel contained strong ,,brine8 ,a4 ,though water boils at #bab degs4 of heat1 yet brine will not boil till raised to #bah or #bbj degs4 ,therefore1 #bab degs4 of heat may easily pass through brine to raise the vessel immersed in it to boiling heat1 before any of it is carried off by steam4 ,q4 ,why will brine impart to another vessel ,,more than #bab1 and water ,,not ,,so ,,much8 ,a4 ,because both liquids will impart heat till they boil1 and then they can impart heat no longer4 ,q4 ,why can they impart no extra heat after they boil8 ,a4 ,because all extra heat is spent in making steam4 ,hence water will not boil a vessel of water immersed in it1 because it cannot impart to it #bab degs4 of heat3 but brine will1 because it can impart more than #bab degs4 of heat1 without being converted itself into steam4 ,ether boils at #ajd degs4 ,alcohol - - #agc-a_/b ,water - - #bab ,water with one-fifth salt #bai ,syrup boils at #bba ,oil of turpentine1 #cjd ,sulphuric acid #dgb ,linseed oil - #fdj c4 c4 ,any liquid which boils at a lower degree can be made to boil if immersed in a liquid which boils at a higher degree4 ,thus a cup of ether can be made to boil in a saucepan of water4 ,a cup of water in a saucepan of brine or syrup4 ,but a cup of water will not boil if immersed in ether2 nor a cup of syrup in water4 ,q4 ,why are ,,clouds ,,higher on a ,,fine ,,day8 ,a4 #ast--,because the air 7expanded by heat7 drives them higher up3 and #bndly--,the clouds themselves are lighter1 and therefore more buoyant4 ,q4 ,why are the ,,clouds ,,lighter on a ,,fine ,,day8 ,a4 ,because their mists are either absorbed by the dry air1 or vapourized by the hot sun4 ,q4 ,why is a ,,cup ,,put topsy-turvy into a ,,fruit-,,pie8 ,a4 ,its principal use is to hold the crust up1 and prevent it from sinking1 when the cooked fruit gives away under it4 ,q4 ,does not the cup ,,prevent the ,,fruit of the pie from ,,boiling ,,over8 ,a4 ,no1 by no means2 it would rather tend to make it boil over1 than otherwise4 ,q4 ,why would the cup tend rather to ,,make the ,,fruit ,,boil ,,over8 ,a4 ,as soon as the pie is put into the oven1 the air in the cup will begin to expand1 and drive every particle of juice from under it2 the pie dish1 therefore1 will have a cup-full less room to hold its fruit1 than if the cup were taken out4 ,q4 ,if the juice is driven ,,out of the cup1 why is the ,,cup always ,,full of ,,juice1 when the pie is cut up8 ,a4 ,immediately the pie is drawn1 the air in the cup begins to condense again1 and occupy a smaller space2 in consequence of which1 there is no longer enough air to fill the cup1 and so juice rushes in to fill up the deficiency4 ,q4 ,why does ,,juice rush into the cup1 because the cup is ,,not ,,full of ,,air8 ,a4 ,as the external air presses upon the surface of the juice1 it rushes into the cup unobstructed2 as mercury rises through the tube of a barometer through similar pressure4 ,,chapter ,x4 ,,expansion ,,from ,,heat4 7,continued47 ,q4 ,does heat expand every thing ,,else ,,besides air and water8 ,a4 ,yes2 every thing 7that man is acquainted with7 is expanded by heat4 ,q4 ,why does a ,,cooper make his ,,hoops ,,red-,,hot1 when he puts them on a tub8 ,a4 #ast--,as iron expands by heat1 the hoops will be larger when they are red-hot2 and will1 therefore1 fit more easily on the tub3 and #bndly--,as iron contracts by cold1 the hoops will shrink as they cool down1 and girt the tub with a tighter grasp4 ,q4 ,why does a ,,wheelwright make his hoops ,,red-,,hot1 which he fixes on the ,,nave of a ,,wheel8 ,a4 #ast--,that they may fit on more easily3 and #bndly--,that they may girt the nave more tightly4 ,q4 ,why will the wheelwright's ,,hoop ,,fit the nave ,,more ,,easily1 because they are made ,,red-,,hot8 ,a4 ,as iron expands by heat1 the hoops will be larger when they are hot2 and 7being larger7 will go on the nave more easily4 ,q4 ,why will the ,,hoops1 which have been ,,put ,,on ,,hot1 girt the nave more ,,firmly8 ,a4 ,as iron contracts by cold1 the hoops will shrink as they cool down2 and1 therefore1 girt the nave with a tighter grasp4 ,q4 ,why does a farrier put the ,,horse-,,shoe on ,,hot8 ,a4 ,that it may stick the closer1 when it has contracted by cold4 ,q4 ,why does a ,,stove make a ,,cracking ,,noise1 when a fire is very hot8 ,a4 ,the iron stove expands by heat1 and 7as it swells7 the parts rub both against each other1 and against the bricks around1 driving them further off2 and this produces a cracking noise4 ,q4 ,why does a ,,stove make a similar ,,cracking ,,noise1 when a large ,,fire is ,,taken ,,down8 ,a4 ,the iron stove contracts again1 as soon as the fire is removed2 and 7as it shrinks into a smaller space7 the parts rub against each other again1 and the bricks are again disturbed2 and this produces a cracking noise4 ,q4 ,why does the ,,plaster round a ,,stove ,,crack and fall away8 ,a4 ,when the fire is lighted1 the iron-work 7which expands more than the brick-work and plaster7 pushes away the bricks and plaster3 but when the fire is put out1 the metal shrinks again1 and leaves the setting behind4 ,q4 ,why does the ,,plaster ,,fall ,,away8 ,a4 ,as a chink is left 7between the setting and the stove71 the plaster will frequently fall away from its own weight4 ,q4 ,what ,,other cause contributes to ,,bring the ,,plaster ,,down8 ,a4 ,as the heat of the fire varies1 the size of the iron stove varies also2 and this swelling and perpetually contracting1 keeps up such a constant disturbance about the plaster1 that it cracks and falls off1 leaving the fire-place very unsightly4 ,q4 ,why does the ,,mercury of a ,,thermometer ,,rise in hot weather8 ,a4 ,heat expands the metal2 and as the metal is increased in bulk1 it occupies a larger space1 7or1 in other words1 rises higher in the tube47 ,q4 ,why is a ,,glass ,,broken1 when ,,hot ,,water is poured into it8 ,a4 ,because the inside of the glass is expanded by the hot water1 and not the outside2 so the glass snaps for want of flexibility4 ,q4 ,why is not the ,,outside of the ,,glass expanded by the hot water1 as well as the ,,inside8 ,a4 ,glass is a non-conductor of heat2 and1 therefore1 breaks before the heat of the inner surface is conducted to the outside4 ,q4 ,why does a ,,glass snap1 because the ,,inner surface is ,,hotter than the ,,outer8 ,a4 ,glass is expanded by heat2 and as the inner surface expands1 it stretches the outer surface till it snaps4 ,q4 ,why is a ,,china ,,cup broken1 if ,,hot ,,water be poured over it1 or into it8 ,a4 ,china is a non-conductor2 and1 as the inner surface expands by the heat1 before the outer one1 it forms an arch1 and pulls the parts of the cup asunder4 ,q4 ,why does the ,,bottom ,,come ,,off1 if a ,,glass ,,beaker be set on a warm ,,hob8 ,a4 ,glass is a non-conductor2 and1 as the bottom of the glass 7from the warmth of the hot stove7 expands1 before the sides are heated1 the two parts separate the one from the other4 ,,chapter ,,xi4 #b4--,,liquefaction4 #c4--,,vaporization4 ,q4 ,what is meant by ,,liquefaction8 ,a4 ,the state of being melted2 as ice is melted by the heat of the sun4 ,q4 ,why is ,,ice ,,melted by the ,,heat of the ,,sun8 ,a4 ,the heat of the sun 7entering the solid ice7 forces its particles asunder1 till their attraction of cohesion is sufficiently overcome1 to convert the solid ice into liquid4 7,see p4 #aab47 ,q4 ,why are ,,metals ,,melted by the heat of ,,fire8 ,a4 ,the heat of the fire 7entering the solid metal7 forces its particles asunder1 till their attraction of cohesion is sufficiently overcome1 to convert the solid metal to a liquid4 ,q4 ,why is ,,water converted to ,,steam by the heat of ,,fire8 ,a4 ,the heat of the fire 7entering the water7 divides its globules into very minute bubbles1 which 7being made lighter than air7 fly off from the surface in the form of steam4 ,q4 ,why does not ,,wood ,,melt1 like metal8 ,a4 ,because the heat of the fire decomposes the wood into gas1 smoke1 and ashes2 and the different parts separate from each other4 ,q4 ,what is meant by ,,vaporization8 ,a4 ,the conversion of liquid into vapour2 as water is converted into vapour by the heat of the sun4 ,q4 ,what are ,,clouds8 ,a4 ,moisture evaporated from the earth1 and collected in the upper regions of the air4 ,q4 ,what is the difference between a ,,fog and a ,,cloud8 ,a4 ,clouds and fogs differ only in one respect4 ,clouds are elevated above our heads3 but fogs come in contact with the surface of the earth4 ,q4 ,if ,,clouds are ,,water1 why do they ,,float on the air8 ,a4 #ast--,the vapour of clouds is composed of very minute bubbles 7called ves'cicles71 which float like soap bubbles3 and #bndly--,warm air 7between the bubbles7 keeps them apart1 and makes the mass lighter2 and the currents of air 7which constantly ascend from the warm earth7 buoy them up4 ,q4 ,why does ,,vapour sometimes form into ,,clouds1 and sometimes rest upon the earth as ,,mist or ,,fog8 ,a4 ,when the surface of the earth is warmer than the air1 the vapour of the earth 7being condensed by the chill air7 becomes mist or fog4 ,but when the air is warmer than the earth1 the vapour rises through the air1 and becomes cloud4 ,q4 ,are ,,all clouds ,,alike8 ,a4 ,no4 ,they vary greatly in density1 height1 and colour4 ,q4 ,what is the chief ,,cause of fog and ,,clouds8 ,a4 ,the changes of the wind4 ,q4 ,how can the ,,changes of the ,,wind affect the ,,clouds8 ,a4 ,if a cold current of wind blows suddenly over any region1 it condenses the invisible vapour of the air into cloud or rain3 but if a warm current of wind1 blows over any region1 it disperses the clouds1 by absorbing their vapour4 ,q4 ,what ,,countries are the ,,most ,,cloudy8 ,a4 ,those where the winds are most variable1 as ,britain4 ,q4 ,what ,,countries are the ,,least cloudy8 ,a4 ,those where the winds are not variable1 as ,egypt4 ,q4 ,what ,,distance are the ,,clouds from the ,,earth8 ,a4 ,some thin light clouds are elevated above the highest mountain-top2 some heavy ones touch the steeples1 trees1 and even the earth3 but the average height is between one and two miles4 7,streaky curling clouds1 like hair1 are often five or six miles high47 ,q4 ,what ,,clouds are the ,,lowest8 ,a4 ,those that are most highly electrified3 lightning clouds are rarely more than about #gjj yards above the ground2 and very often actually touch the earth with one of their edges4 ,q4 ,what is the ,,thickness of the ,,clouds8 ,a4 ,some clouds are #bj square miles in surface1 and above a mile in thickness2 while others are only a few yards or inches4 ,q4 ,how can persons ascertain the thickness of a cloud8 ,a4 ,as the tops of high mountains are generally above the clouds2 therefore1 travellers 7who climb the mountains7 may pass quite through the clouds1 into a clear blue firmament1 when they may see the clouds beneath their feet4 ,q4 ,why are the ,,clouds so ,,variable in ,,shape8 ,a4 ,the shape of clouds depends upon two things3--,their state of electricity1 and the wind4 ,q4 ,how can ,,electricity affect the ,,shape of ,,clouds8 ,a4 ,if one cloud be full of electricity1 and another not1 they will be attracted to each other1 and either coalesce1--diminish in size1--or vanish altogether4 ,q4 ,which clouds assume the most ,,fantastic shapes8 ,a4 ,those that are the most highly electrified4 ,q4 ,what effect have ,,winds on the ,,shape of ,,clouds8 ,a4 ,they sometimes absorb them entirely3 sometimes increase their volume and density2 and sometimes change the position of their parts4 ,q4 ,how can ,,winds ,,absorb ,,clouds altogether8 ,a4 ,a warm dry wind will convert the substance of the clouds into invisible vapour1 and carry it in its own current4 ,q4 ,how can ,,winds ,,increase the bulk and density of ,,clouds8 ,a4 ,a cold current of wind will condense the invisible vapour of the air1 and add it to the clouds as it passes by4 ,q4 ,how can ,,winds ,,change the ,,shape of ,,clouds by altering the position of their parts8 ,a4 ,because clouds are so voluble and light1 that every breath of wind changes the position of those ves'cicles or bubbles4 ,q4 ,what are the general ,,colours of the ,,clouds8 ,a4 ,white and grey1 when the sun is above the horizon3 but red1 orange1 and yellow1 at sun-rise and sun-set4 ,the blue sky cannot be considered as clouds at all4 ,q4 ,why are the ,,last ,,clouds of ,,evening generally of a ,,red tinge8 ,a4 ,because red rays are the least refrangible of all2 and1 therefore1 are the last to disappear4 ,q4 ,what is meant by being ,,less ,,refrangible8 ,a4 ,being less able to be bent4 ,blue and green rays being very easily bent 7by the resistance of the air7 are thrown off from the horizon2 but red rays not being bent back in the same way1 give a tinge to the evening clouds4 ,q4 ,why are ,,morning ,,clouds generally of a ,,red tinge8 ,a4 ,because red rays are the least refrangible of all1 and not being bent back by the air 7like blue and green71 strike upon the horizon1 and give a tinge to the morning clouds4 ,q4 ,why is not the reflection of clouds always ,,alike8 ,a4 ,because their size1 density1 and situation in regard to the sun1 vary perpetually2 so that sometimes one colour is reflected1 and sometimes another4 ,q4 ,what regulates the ,,motion of the ,,clouds8 ,a4 ,the motion of the clouds is generally directed by the winds2 but sometimes electricity will influence their motion also4 ,q4 ,how do you know that ,,clouds move by ,,other influences besides ,,wind8 ,a4 ,because we often see in calm weather small clouds meeting each other from opposite directions4 ,q4 ,how do you know that ,,electricity affects the motion of the clouds8 ,a4 ,because clouds often meet from opposite directions2 and 7after they have discharged their opposite electricities into each other7 vanish altogether4 ,q4 ,into how many ,,classes are the different sorts of ,,clouds generally divided8 ,a4 ,into three classes3--viz4 ,simple1 ,intermediate1 and ,compound4 ,q4 ,how are ,,simple ,,clouds sub-divided8 ,a4 #a4--;,cirrus4 #b4--;,cum'ulus2 and #c4--,stra'tus4 ,q4 ,what are ,,cirrus ,,clouds8 ,a4 ,clouds like fibres1 loose hair1 or thin streaks1 are called cirrus clouds4 ,q4 ,why are these clouds called ,,cirrus8 ,a4 ,from the ,latin word1 cirrus 7a lock of hair1 or curl73 they are the most elevated of all clouds4 ,q4 ,what do ,,cirrus clouds ,,portend8 ,a4 ,when the streamers point upwards1 the clouds are falling1 and rain is at hand3 but when the streamers point downwards1 expect easterly wind or drought4 ,q4 ,what are ,,cum',,ulus ,,clouds8 ,a4 ,cum'ulus clouds are lumps like great sugar-loaves1--volumes of smoke1--or mountain towering over mountain4 ,q4 ,why are these monster masses called ,,cum',,ulus ,,clouds8 ,a4 ,from the ,latin word1 cum'ulus 7a mass or pile74 ,q4 ,what do ,,cum',,ulus clouds ,,foreshow8 ,a4 ,when these piles of cloud are fleecy1 and sail against the wind1 they indicate rain2 but when their outline is very hard1 and they come up with the wind1 they foretell fine weather4 ,cumulus clouds should be smaller towards evening than they are at noon4 ,if they increase in size at sun-set1 a thunder-storm may be expected in the night4 ,q4 ,what are ,,stra',,tus ,,clouds8 ,a4 ,creeping mists1 especially prevalent in a summer's evening3 these clouds rise at sun-set in low damp places1 and are always nearer the earth1 than any other sort of cloud4 ,q4 ,why are these mists called ,,stra',,tus clouds8 ,a4 ,from the ,latin word1 stra'tus 7laid low1 or that which lies low74 ,q4 ,how are the ,,intermediate ,,clouds sub-divided8 ,a4 ,into two sorts4 #a4--,the ,cirro-,cum'ulus2 and #b4--,the ,cirro-,stra'tus4 ,q4 ,what are ,,cirro-,,cum',,ulus ,,clouds8 ,a4 ,when cirrus clouds spring from a massy centre2 or when heavy masses of cloud terminate at their edges in long streaks1 or what are called mares' tails4 ,a system of small round clouds may be called cirro-cum'ulus4 ,q4 ,what do ,,cirro-,,cum',,ulus clouds generally ,,forebode8 ,a4 ,continued drought1 or hot dry weather4 ,q4 ,what are ,,cirro-,,stra',,tus ,,clouds8 ,a4 ,they compose what is generally called a mackarel sky4 ,this class of clouds always indicate rain and wind2 hence the proverb-- ,mackarels' scales and mares' tails ,make lofty ships to carry low sails4 ,q4 ,how are ,,compound ,,clouds sub-divided8 ,a4 ,compound clouds are also sub-divided into two sorts4 #a4--,the ,cum'ulo-stra'tus2 and #b4--,the ,nimbus4 ,q4 ,what is meant by ,,cum',,ulo-,,stra',,tus clouds8 ,a4 ,those clouds which assume all sorts of gigantic fancy forms2 such as vast towers and rocks1--huge whales and dragons1--scenes of battle1--and cloudy giants4 ,this class of clouds is the most romantic and strange of all4 ,q4 ,what do the cumulo-stratus clouds foretell8 ,a4 ,a change of weather2 either from fine to rain1 or from rain to fine weather4 ,q4 ,what are ,,nimbus ,,clouds8 ,a4 ,nimbus is the ,latin word for clouds which bring a storm2 and all clouds from which rain falls are so named4 ,q4 ,what ,,appearance takes place in the ,,clouds at the approach of ,,rain8 ,a4 ,the cum'ulus cloud becomes stationary1 and cirrus streaks settle upon it1 forming cumulo-stratus clouds2 which are black at first1 but afterwards of a grey colour4 ,q4 ,why do ,,clouds gather ,,round ,,mountain-,,tops8 ,a4 ,because 7as they float along7 they dash against the mountains2 and 7being arrested in their motion7 collect round the top4 ,q4 ,what is the ,,use of ,,clouds8 ,a4 #ast--,they act as screens to arrest the radiation of heat from the earth3 #bndly--,they temper the heat of the sun's rays3 and #crdly--,they are the great store-houses of rain4 ,q4 ,why is ,,wind said to ,,blow ,,up the ,,clouds8 ,a4 ,when a dry wind travels over sea1 and accumulates more vapour than the air can sustain1 it relinquishes a part 7as it flies along7 in the form of clouds4 ,q4 ,why does ,,wind sometimes ,,drive ,,away the ,,clouds8 ,a4 ,when wind travels over dry climes or thirsty deserts1 it becomes so dry itself1 that it absorbs vapour from the clouds1 and disperses them4 ,q4 ,what is the ,,cause of a ,,red ,,sun-,,set8 ,a4 ,because the vapour of the air is not actually condensed into clouds1 but only on the point of being condensed2 in which state it bends the red rays of the sun towards the horizon1 where they are reflected at sun-set4 ,q4 ,why is a ,,red ,,sun-,,set an indication of a ,,fine ,,day to-morrow8 ,a4 ,because 7notwithstanding the cold of sun-set7 the vapours of the earth are not condensed into clouds4 ,our ,lord referred to this prognostic in the following words3 ,when it is evening ye say1 it will be fair weather1 for the sky is red4 7,matt4 xvi4 #b47 ,q4 ,what is the cause of a coppery ,,yellow ,,sun-,,set8 ,a4 ,because the vapour of the air is actually condensed into clouds2 in which case it refracts 7or bends7 the yellow rays of the sun towards the horizon1 where they are reflected at sun-set4 ,q4 ,why is a ,,yellow ,,sunset an indication of ,,wet8 ,a4 ,because the vapours of the air are already condensed into clouds2 rain1 therefore1 may be shortly expected4 ,q4 ,what is the cause of a ,,red ,,sun-,,rise8 ,a4 ,vapour in the upper region of the air just on the point of being condensed4 ,q4 ,why is a ,,red and ,,lowering sky at ,,sunrise an indication of a ,,wet ,,day8 ,a4 ,because the higher regions of the air are laden with vapour1 on the very point of condensation1 which the rising sun cannot disperse4 ,hence our ,lord's observation1 ,in the morning 7ye say7 it will be foul weather to-day1 for the sky is red and lowering4 7,matt4 xvi4 #c47 ,q4 ,why is a ,,grey ,,morning an indication of a ,,fine ,,day8 ,a4 ,because that air alone contiguous to the earth is damp and full of vapour4 ,there are no vapours in the higher regions of the air to reflect red rays2 and hence the morning-light looks grey4 ,q4 ,what difference 7in the state of the air7 is required1 to make a ,,grey and ,,red ,,sunrise8 ,a4 ,in a grey sunrise1 only that portion of air contiguous to the earth is filled with vapour2 all the rest is clear and dry4 ,but in a red sunrise the air in the upper regions is so full of vapour that the rising sun cannot disperse it4 ,q4 ,why is a ,,grey ,,sunset an indication of ,,wet8 ,a4 ,if the air on the surface of the earth be very damp at sunset1 it is a proof that the air is saturated with vapour1 and wet may be expected3 hence the proverb-- ,evening red and morning grey ,will set the traveller on his way2 ,but evening grey and morning red ,will bring down rain upon his head4 ,q4 ,the proverb says1 ,a ,,rainbow in the ,,morning is the shepherd's ,,warning3 why is it so8 ,a4 ,a rainbow can only be formed when the clouds 7containing or dropping rain7 are opposite the sun3 a morning rainbow1 therefore1 is always in the west1 and indicates that bad weather is on the road to us4 ,q4 ,why does a ,,rainbow in the ,,west indicate that ,,bad ,,weather is on the road to us8 ,a4 ,because our heavy rains are usually brought by west or south-west winds2 and1 therefore1 clouds which reflect the colour of the rainbow in the west1 are coming up with the wind1 bringing rain with them4 ,q4 ,the proverb says1 ,a ,,rainbow at ,,night1 is the shepherd's ,,delight2 why is it so8 ,a4 ,as a rainbow is always opposite to the sun1 therefore a rainbow at night is in the east1 and indicates that bad weather is leaving us4 ,q4 ,why does a ,,rainbow in the ,,east indicate that bad weather is ,,leaving us8 ,a4 ,as west and south-west winds bring rain1 if the clouds have been driven from the west to the east1 they have passed over us1 and are going away from us4 ,q4 ,what is meant by an ,,aurora ,,borea',,lis1 or northern light8 ,a4 ,a luminous white cloud in the north of the sky at night-time4 ,sometimes streaks of blue1 purple1 and red1--and sometimes flashes of light1 are seen also4 ,in our island this phenomenon generally rises from a dark cloud 7running from the north to the east and west7 elevated about #aj or #bj degrees above the horizon3 above this dark bed of clouds the luminous white light appears4 ,q4 ,what is the ,,cause of the ,,aurora ,,borealis1 or northern light8 ,a4 ,electricity in the clouds4 ,q4 ,why is the ,,aurora ,,borealis generally a ,,white light8 ,a4 ,because the electric fluid passes through air extremely rarefied3 and whenever electric fluid passes through air much rarefied1 it always produces a white light4 ,q4 ,why are there sometimes ,,different ,,colours in the aurora borealis1 such as yellow1 red1 and purple8 ,a4 ,because the electric fluid passes through air of different densities4 ,the most rarefied air produces a white light2 the most dry air1 red2 and the most damp produces yellow streaks4 ,q4 ,does the ,,aurora ,,borealis forbode fine weather or ,,wet8 ,a4 ,when its corruscations are very bright1 it is generally followed by stormy moist unsettled weather4 ,q4 ,why does a ,,haze round the ,,sun indicate ,,rain8 ,a4 ,because the haze is caused by very fine rain falling in the upper regions of the air2 when this is the case1 a rain of #e or #f hours continuance1 may be expected4 ,q4 ,why is a ,,halo round the ,,moon a sure indication of ,,rain8 ,a4 ,because the halo is caused by fine rain falling in the upper regions of the air4 ,the larger the halo the nearer the rain-clouds1 and the sooner may rain be expected4 ,q4 ,why does a ,,black ,,mist bring ,,wet weather8 ,a4 ,the mist is black1 because it is overshadowed by dense clouds or masses of vapour2 and1 therefore1 it forebodes wet4 ,q4 ,why does a ,,white ,,mist indicate ,,fine weather8 ,a4 ,the mist is white1 because no clouds blacken it with their shadow2 and 7as the sky is cloudless7 fine weather may be expected4 ,q4 ,why do we ,,feel almost ,,suffocated in a hot cloudy night8 ,a4 ,because the heat of the earth 7being unable to escape into the upper region of the air1 in consequence of the clouds7 floats1 like a sea of heat1 on the surface of the earth4 ,q4 ,why do we feel more ,,sprightly in a clear bright night8 ,a4 ,because the heat of the earth can readily escape into the upper regions of the air1 and is not confined and pent-in by thick clouds4 ,q4 ,why do we ,,feel ,,depressed in ,,spirits on a ,,wet murky ,,day8 ,a4 #ast--,because when the air is laden with vapour1 it has less oxygen4 #bndly--,the air being lighter than usual1 does not balance the air in our body3 and #crdly--,moist air has a tendency to relax the nervous system4 ,q4 ,what is meant by the air balancing the air in our body8 ,a4 ,the human body is filled with air of the same density as that around3 if1 therefore1 we ascend into purer air1 or descend into denser air1 the balance is destroyed1 and we feel oppressed and suffocated4 ,q4 ,why do we feel ,,oppressed and ,,suffocated if the air around is not of the ,,same ,,density as that in our body8 ,a4 ,if the air around be more dense1 it will squeeze our body in by its weight3 if it be less dense1 the air in our body will blow us out4 ,q4 ,why do ,,persons who ,,ascend in ,,balloons ,,feel ,,pain in their eyes1 ears and chest8 ,a4 ,because the air in the upper regions is more rare than the air in their bodies2 and 7till the equilibrium is restored7 great pain is felt in all the more sensitive parts of the body4 ,q4 ,why do ,,persons who ,,descend in ,,diving-,,bells ,,feel ,,pain in their eyes1 ears and chest8 ,a4 ,because the air in the sea is more dense than the air in their bodies2 and 7till the equilibrium is restored7 great pain is felt in all the more sensitive parts of the body4 ,q4 ,why does the ,,sea ,,heave and ,,sigh just ,,previous to a ,,storm8 ,a4 ,the density of the air 7just previous to a storm7 is very suddenly diminished1 but the air in the sea is not so quickly affected2 therefore the sea heaves and sighs in its effort to restore an equilibrium4 ,q4 ,why is the ,,air so universally ,,still just ,,previous to a ,,tempest8 ,a4 ,because the air is suddenly and very greatly rarefied2 and 7as the density of the air is diminished7 its power to transmit sound is diminished also4 ,q4 ,how do you ,,know that ,,rarefied air ,,cannot ,,transmit ,,sound so well as dense air8 ,a4 ,because the sound of a bell 7in the receiver of an air-pump7 cannot be heard at all1 after the air has been partially exhausted2 and a pistol fired on a high mountain would not sound louder than a common cracker4 ,q4 ,why do we ,,feel ,,braced and ,,light-,,hearted on a ,,fine spring or ,,frosty morning8 ,a4 #ast--,because there is more oxygen in the air on a fine frosty morning1 than there is on a wet day3 and #bndly--,a brisk and frosty air has a tendency to brace the nervous system4 ,q4 ,why do ,,dogs and ,,cats 7confined to a room7 feel ,,lazy and ,,drowsy at the approach of rain8 ,a4 #ast--,because the air does not contain its full proportion of oxygen3 and #bndly--,because the damp relaxes their nervous system1 and makes them drowsy4 ,q4 ,why do ,,horses neigh1 ,,cattle low1 ,,sheep bleat1 and ,,asses bray1 at the approach of rain8 ,a4 #ast--,as the air does not contain its full proportion of oxygen1 they feel a difficulty in breathing3 and #bndly--,as damp relaxes their nerves1 they feel languid and uneasy4 ,q4 ,why do ,,candles and ,,fires burn with a ,,bluer ,,flame in ,,wet weather8 ,a4 ,as the air contains less oxygen in wet weather1 the heat of fire is less intense3 and the flame is blue1 because the fuel is not thoroughly consumed4 ,q4 ,why do ,,hills1 c4 appear ,,larger in ,,wet weather8 ,a4 ,because 7when the air is laden with vapour7 the rays of light are more dispersed1 and produce a larger reflection2 objects1 therefore1 seen at a distance1 appear larger4 ,q4 ,why do ,,trees1 c4 in ,,wet weather appear ,,further ,,off than they really are8 ,a4 ,because the fog or mist diminishes the light reflected from the object2 and as the object becomes more dim1 it seems to be further off4 ,q4 ,why does the ,,sun seem ,,larger when he ,,sets and ,,rises1 than he does at noon8 ,a4 ,because the rays pass through more of the vapoury atmosphere which surrounds the earth2 and this vapoury atmosphere acts like a magnifying glass4 ,illustration3 ,it is very manifest that the lines ,d ,c are shorter than the lines ,e ,c3 if1 therefore1 ,a be the earth1 and ,d ,g ,e the boundary of the atmosphere round the earth1 then the rays ,m ,e ,c 7at the horizon7 will pass through more of the atmosphere1 than the rays ,s ,d ,c1 which are more elevated4 ,q4 ,why does the ,,moon appear ,,larger at her ,,rising and ,,setting1 than when above our heads8 ,a4 ,because the rays pass through more of the vapoury atmosphere which surrounds the earth2 and this vapoury atmosphere magnifies the moon1 just like a magnifying glass4 ,q4 ,why do ,,cats ,,rub their ,,ears when it is likely to rain8 ,a4 ,either because the air is full of vapour1 and its humidity 7piercing between the hair of the cat7 produces an itching sensation2 or more probably1 because the air is overcharged with electricity4 ,q4 ,how can the ,,electricity of air produce a sensation of ,,itching8 ,a4 ,if the air is overcharged with electricity1 the hair of the cat is overcharged also2 and this makes her feel as if she were covered with cobwebs4 ,q4 ,why does the ,,cat keep ,,rubbing herself8 ,a4 ,her hair will not lie smooth1 but has a perpetual tendency to become turgid and ruffled2 so the cat keeps rubbing her coat and ears1 to smooth the hair down1 and brush away the feeling of cobwebs4 ,q4 ,why do our ,,heads and ,,skin itch before rain8 ,a4 ,probably because the air is overcharged with electricity2 and1 therefore1 a sensation 7like that of cobwebs7 irritates the skin1 and produces an itching4 ,q4 ,why do we ,,hear distant ,,clocks more distinctly when rain is near at hand8 ,a4 ,because the air is filled with vapour1 and water is a better conductor of sound than dry air4 ,q4 ,why do we hear ,,church-,,bells further1 just previous to rain8 ,a4 ,because the air is filled with vapour1 and vapour is a better conductor of sound than dry air4 ,q4 ,why do ,,doors ,,swell1 when ,,rain is at hand8 ,a4 ,because the air is filled with vapour1 which 7penetrating into the pores of the wood7 forces the parts further apart1 and swells the door4 ,q4 ,why do ,,doors ,,shrink in ,,dry weather8 ,a4 ,because the moisture is absorbed from the wood2 and1 as the particles are brought closer together1 the size of the door is lessened1 7or in other words1 the wood shrinks74 ,q4 ,why is the ,,air filled with offensive ,,smells previous to a coming ,,rain8 ,a4 ,because the volatile parts1 7which rise from dunghills1 sewers1 c471 being laden with vapour1 are unable to rise so readily1 as when they are rarefied by a bright sun4 ,q4 ,why do ,,flowers smell ,,sweeter and ,,stronger just previous to ,,rain8 ,a4 ,because the volatile parts 7which constitute the perfume of flowers7 are laden with vapour2 and 7being unable to rise7 are confined to the lower regions of the air4 ,q4 ,why do ,,horses and other animals stretch out their necks1 and ,,snuff up the ,,air1 just previous to a fall of ,,rain8 ,a4 ,because they smell the odour of plants and hay1 and delight to snuff in their fragrance4 ,q4 ,why does ,,smoke ,,fall when ,,rain is at hand8 ,a4 ,the air being less dense in wet weather1 cannot buoy up smoke so readily1 as when more dry and heavy4 ,q4 ,why do ,,swallows ,,fly ,,low when ,,rain is at hand8 ,a4 ,because the insects 7of which they are in pursuit7 have fled from the cold upper regions of the air1 to the warm air near the earth3 and as their food is low1 the swallows fly low4 ,q4 ,why do these ,,insects seek the lower regions of the air in ,,wet weather1 more than in ,,fine weather8 ,a4 ,because they are forced downward1 by some current of cold air which drives them down4 ,q4 ,why does a ,,downward current of ,,cold ,,air bring ,,rain8 ,a4 ,because it condenses the warm vapour2 which then descends in rain4 ,q4 ,the proverb says1 ,a ,,single ,,magpie in spring1 ,,foul ,,weather will bring3 why is this the case8 ,a4 ,in cold stormy weather1 one magpie alone will leave its warm snug nest in search of food1 while the other stays with the eggs or young ones2 but in fine mild weather 7when their brood will not be injured by cold7 both the magpies will fly out together4 ,q4 ,why is it ,,unlucky for ,,anglers to see a ,,single ,,magpie in spring8 ,a4 ,because when magpies fly abroad singly1 the weather is cold and stormy2 but when both birds fly out together1 the weather is warm and mild1 which is favourable for fishing4 ,q4 ,why do ,,sea ,,gulls fly about the ,,sea in ,,fine weather8 ,a4 ,because they live upon fish1 which are found near the surface of the sea in fine weather4 ,q4 ,why may we expect ,,stormy ,,rains1 when ,,sea ,,gulls assemble on the land8 ,a4 ,because the fish 7on which they live7 leave the surface of the sea in stormy weather1 and go down too deep for the gulls to get at them2 they are obliged1 therefore1 to feed on the worms and larv which are driven out of the ground at such times4 ,q4 ,why does the ,,petrel always fly to the ,,sea during a storm8 ,a4 ,because the petrel lives upon sea insects1 which are always to be found in abundance about the spray of swelling waves4 7,the ,petrel is a bird of the duck-kind1 which lives in the open sea4 ,they run on the top of the sea1 and are called ,petrels1 or rather ,peter-els1 from ,st4 ,peter1 in allusion to his walking on the sea1 to go to ,jesus47 ,q4 ,why do ,,candles and ,,lamps ,,spirt when ,,rain is at hand8 ,a4 ,because the air is filled with vapour1 and the humidity penetrates the wick2 where 7being formed into steam7 it expands suddenly1 and produces a little explosion4 ,q4 ,why does a ,,drop of ,,water sometimes ,,roll along a piece of hot iron without leaving the least trace8 ,a4 ,if the iron be very hot indeed1 the bottom of the drop is turned into vapour1 before the drop can evaporate2 and the vapour thus formed buoys the drop up1 without allowing it to touch the iron at all4 ,q4 ,why does it ,,roll8 ,a4 ,the current of air 7which is always passing over the heated surface7 drives it along4 ,q4 ,why does a ,,laundress put a little ,,saliva on an ,,ironing-,,box to know if it be hot enough8 ,a4 ,if the saliva sticks to the box and is evaporated1 the box is not hot enough2 but if the saliva runs along the box1 it is4 ,q4 ,why is the ,,box ,,hotter if the saliva ,,runs ,,along ,,the ,,box1 than if it adheres to it till it is evaporated8 ,a4 ,if the saliva runs along the box1 the iron is hot enough to convert the bottom of the drop of spittle into vapour2 but if the saliva will not roll1 the box is not hot enough to convert the bottom of the drop of spittle into vapour4 ,,chapter ,,xii4 #d4--;,,evaporation4 ,q4 ,what is meant by ,,evaporation8 ,a4 ,the dissipation of liquid by its being converted into vapour4 ,q4 ,what ,,effects are produced by evaporation8 ,a4 ,the liquid vaporized absorbs heat from the body whence it issues2 and the body deprived of the liquid by evaporation1 loses heat thereby4 ,q4 ,if you ,,wet your ,,finger in your mouth1 and hold it up in the air1 why does it ,,feel ,,cold8 ,a4 ,the saliva quickly evaporates2 and 7as it evaporates7 absorbs heat from the finger1 which makes it feel cold4 ,q4 ,if you ,,bathe your ,,temples with ether1 why does it allay ,,inflammation and feverish heat8 ,a4 ,ether very rapidly evaporates2 and 7as it evaporates7 absorbs heat from the burning head1 producing a sensation of cold4 ,q4 ,why is ,,ether better for this purpose than ,,water8 ,a4 ,because it requires less heat to convert it into vapour2 and therefore it evaporates much more quickly4 7,ether is converted into steam with #ajd degs4 of heat1 but water requires #bab degs4 of heat to convert it into steam47 ,q4 ,why does ,,ether very greatly ,,relieve a ,,scald or ,,burn8 ,a4 ,because it evaporates very rapidly2 and 7while it is converted into vapour7 carries off the heat of the burn4 ,q4 ,why do we ,,feel so ,,cold when we have ,,wet ,,feet or ,,clothes8 ,a4 ,as the wet of our shoes or clothes evaporates1 it keeps absorbing heat from the body1 which makes it feel cold4 ,q4 ,why do ,,wet ,,feet or ,,clothes give us ,,cold8 ,a4 ,because the evaporation absorbs heat from the body so abundantly1 that it is lowered below its natural standard2 and therefore health is injured4 ,q4 ,why is it ,,dangerous to ,,sleep in a ,,damp ,,bed8 ,a4 ,because the heat of the body is continually absorbed in converting the damp of the sheets into vapour2 and as heat is abstracted from the body1 its temperature is reduced below the healthy standard4 ,q4 ,why do we not feel the same sensation of cold1 if we throw a ,,macintosh over our ,,wet ,,clothes8 ,a4 ,the macintosh prevents evaporation1 because the steam cannot escape through the air-tight fabric2 and 7as the wet cannot evaporate from the clothes7 no heat is absorbed from our bodies4 ,q4 ,why do ,,not ,,sailors get ,,cold1 who are so often wet all day with ,,sea-,,water8 ,a4 ,the salt of the sea retards evaporation2 and 7as the heat of the body is drawn off very gradually7 the sensation of cold is prevented4 ,q4 ,why does ,,sprinkling a ,,hot ,,room with water ,,cool ,,it8 ,a4 ,the heat of the room causes a rapid evaporation of the sprinkled water2 and as the water evaporates1 it absorbs heat from the room1 and cools it4 ,q4 ,why does ,,watering the ,,streets and roads ,,cool ,,them8 ,a4 ,the hot streets and roads part with their heat to promote the evaporation of the water sprinkled on them4 ,q4 ,why does a ,,shower of ,,rain seem to ,,cool the ,,air in summer-time8 ,a4 ,the earth 7being wet with the rain7 parts with its heat to promote evaporation2 and as the earth is cooled1 it cools the air also4 ,q4 ,why is ,,linen ,,dried by being exposed to the ,,wind8 ,a4 ,the air 7blowing over the linen7 promotes evaporation1 by removing the vapour from the surface of the wet linen1 as soon as it is formed4 ,q4 ,why is ,,linen ,,dried sooner in the open ,,air1 than in a confined room8 ,a4 ,because the particles of vapour are more rapidly removed from the surface of the linen by evaporation4 ,q4 ,why are ,,wet ,,summers generally ,,succeeded by ,,cold ,,winters8 ,a4 ,because the great evaporation 7carried on through the wet summer7 reduces the temperature of the earth lower than usual1 and produces cold4 ,q4 ,why is ,,england ,,warmer than it used to be1 when ,,agues were so common8 ,a4 ,because it is better drained and better cultivated4 ,q4 ,why does ,,draining land promote ,,warmth8 ,a4 ,because it diminishes evaporation2 in consequence of which less heat is abstracted from the earth4 ,q4 ,why does ,,cultivation increase the ,,warmth of a country8 ,a4 #ast--,because hedges and belts of trees are multiplied2 #bndly--,because the land is better drained2 #crdly--,because the land is dug and ploughed2 and #dthly--,because the vast forests are cut down4 ,q4 ,why do ,,hedges and ,,belts of ,,trees promote ,,warmth8 ,a4 ,because they retard evaporation1 by keeping off the wind4 ,q4 ,if belts of trees promote ,,warmth1 why do ,,forests produce ,,cold8 ,a4 #ast--,because they detain and condense the passing clouds3 #bndly--,they prevent the access of both wind and sun3 #crdly--,the soil of forests is always covered with long damp grass1 rotting leaves1 and thick brushwood3 and #dthly--,there are always many hollows in every forest full of stagnant water4 ,q4 ,why do ,,long ,,grass and ,,rotting ,,leaves promote ,,cold8 ,a4 ,because they are always damp2 and the evaporation which they promote1 is constantly absorbing heat from the earth beneath4 ,q4 ,why do ,,digging and ,,ploughing help to make a country ,,warm8 ,a4 ,digging and ploughing help to pulverize the soil1 by admitting air into it1 and this increases its mean temperature4 ,q4 ,why are ,,france and ,,germany ,,warmer now1 than when the vine would not ripen there8 ,a4 ,chiefly because their vast forests have been cut down2 and the soil is better drained and cultivated4 ,q4 ,what becomes of the ,,water of ,,ponds and ,,tubs in summer-time8 ,a4 ,ponds and tubs in summer-time are often left dry1 because their water is evaporated by the air4 ,q4 ,how is this ,,evaporation ,,produced and carried on8 ,a4 ,the air contains heat1 and changes the surface of the water into vapour2 this vapour 7blending with the air7 is soon wafted away2 while fresh portions of air blow over the water1 and produce a similar evaporation2 till the pond or tub is left quite dry4 ,q4 ,why are the ,,wheels of some machines kept ,,constantly ,,wet with ,,water8 ,a4 ,to carry off the heat 7arising from the rapid motion of the wheels7 by evaporation1 as soon as it is developed4 ,q4 ,why is ,,mould ,,hardened by the ,,sun8 ,a4 ,because 7when the moisture of the mould has been evaporated by the sun7 the earthy particles come into closer contact1 and the mass becomes more solid4 ,q4 ,show the ,,wisdom of ,,god in this arrangement4 ,a4 ,if the soil did not become crusty and hard in dry weather1 the heat and drought would penetrate the soil1 and kill both seeds and roots4 ,q4 ,why is ,,tea cooled ,,faster in a ,,saucer than in a cup8 ,a4 ,because evaporation is increased by increasing the surface2 and as tea in a saucer presents a much larger surface to the air1 its heat is more rapidly carried off by evaporation4 7,the subject of convection will be treated of in a future chapter1 and would scarcely be understood in this place47 ,q4 ,why is not the ,,vapour of the ,,sea ,,salt8 ,a4 ,because the salt is always left behind1 by the process of evaporation4 ,q4 ,why does a ,,white ,,crust appear 7in hot weather7 upon ,,clothes wetted by sea water8 ,a4 ,the white crust is the salt of the water left on the clothes by evaporation4 ,q4 ,why does this ,,white ,,crust always ,,disappear in ,,wet weather8 ,a4 ,in wet weather the moisture of the air dissolves the salt2 and1 therefore1 it no longer remains visible4 ,q4 ,why should ,,not persons1 who take violent exercise1 ,,wear very ,,thick ,,clothing8 ,a4 ,when the heat of the body is increased by exercise1 perspiration reduces the heat 7by evaporation7 to a healthy standard3 as thick clothing prevents this evaporation1 and confines the heat and perspiration to the body1 it is injurious to health4 ,,chapter ,,xiii4 ,,communication ,,of ,,heat4 #a4--;,,conduction4 ,q4 ,how is ,,heat ,,communicated from one body to another8 ,a4 #a4 ,by ,conduction4 #b4 ,by ,absorption4 #c4 ,by ,reflection4 #d4 ,by ,radiation3 and #e4 ,by ,convection4 ,q4 ,what is meant by ,,conduction of heat8 ,a4 ,heat communicated from one body to another1 by actual contact4 ,q4 ,why does a ,,piece of ,,wood 7blazing at ,,one end7 ,,not ,,feel ,,hot at the ,,other end8 ,a4 ,wood is a bad conductor of heat2 and1 therefore1 heat does not traverse freely through it3 hence1 though one end of a stick be blazing-hot1 the other end may be quite cold4 ,q4 ,why do ,,some ,,things feel so much ,,colder than others8 ,a4 ,principally because they are better conductors2 and1 therefore1 draw off the heat from our body 7which touches them7 so much faster4 ,q4 ,what are the ,,best ,,conductors of ,,heat8 ,a4 ,dense solid bodies1 such as metal and stone4 ,q4 ,which ,,metals are the most ,,rapid ,,conductors of ,,heat8 ,a4 ,silver is the best conductor1 then copper1 then gold or tin1 then iron1 then zinc1 and then lead4 ,q4 ,what are the ,,worst ,,conductors of ,,heat8 ,a4 ,all light and porous bodies1 such as hair1 fur1 wool1 charcoal1 and so on4 ,q4 ,why are ,,cooking ,,vessels so often furnished with ,,wooden ,,handles8 ,a4 ,wood is not a good conductor1 like metal2 and1 therefore1 many vessels 7which are exposed to the heat of the fire7 have wooden handles1 lest they should burn our hands when we take hold of them4 ,q4 ,why is the ,,handle ,,of ,a ,,metal ,,tea-,,pot made of ,,wood8 ,a4 ,as wood is a bad conductor1 the heat of the boiling water is not so quickly conveyed to the wooden handle1 nor so quickly poured into the hand by it1 as when the handle is made of metal4 ,q4 ,why would a ,,metal ,,handle ,,burn the ,,hand of the tea-maker8 ,a4 ,as metal is an excellent conductor1 the heat of the boiling water rushes quickly into the metal handle1 and into the hand that touches it4 ,q4 ,how do you know that a ,,metal ,,handle would be ,,hotter than a ,,wooden one8 ,a4 ,by touching the metal collar into which the wooden handle is fixed3 though the wooden handle is quite cold1 this metal collar is intensely hot4 ,q4 ,why do persons use paper or ,,woollen ,,kettle-,,holders to take hold of a kettle with8 ,a4 ,paper and woollen are both very bad conductors of heat2 and1 therefore1 the heat of the kettle does not readily pass through them to the hand4 ,q4 ,does the heat of the boiling kettle ,,never get through the woollen or paper kettle-holder8 ,a4 ,yes2 but though the kettle-holder became as hot as the kettle itself1 it would never feel so hot4 ,q4 ,why would not the kettle-holder ,,feel so hot as the kettle1 when it really is of the same temperature8 ,a4 ,because 7being a very bad conductor7 it disposes of its heat so slowly1 that it is scarcely perceptible2 but metal 7being an excellent conductor7 disposes of its heat so quickly1 that the sudden influx is painful4 ,q4 ,why then does ,,hot ,,metal feel so much ,,more intensely ,,warm than ,,hot ,,wool8 ,a4 ,because it gives out a much greater quantity of heat in the same space of time2 and the influx of heat is1 therefore1 more perceptible4 ,q4 ,why does ,,money in our pocket feel so ,,hot1 when we stand ,,before a ,,fire8 ,a4 ,metal is an excellent conductor2 and1 therefore1 becomes rapidly heated4 ,for the same reason it becomes rapidly cold1 when it comes in contact with a body colder than itself4 ,q4 ,why does a ,,pump-,,handle feel intensely ,,cold in ,,winter8 ,a4 ,as metal is an excellent conductor1 when the hot hand touches the cold pump-handle1 the heat passes rapidly from the hand into the iron2 and this rapid loss of heat produces a sensation of intense coldness4 ,q4 ,is the iron ,,handle of the pump really ,,colder than the wooden ,,pump itself8 ,a4 ,no2 every inanimate substance 7exposed to the same temperature7 possesses the same degree of heat4 ,q4 ,why then does the ,,iron ,,handle seem so ,,much ,,colder than the ,,wooden ,,pump8 ,a4 ,merely because the iron is a better conductor2 and1 therefore1 draws off the heat from our hand much more rapidly than wood does4 ,q4 ,why does a ,,stone or marble ,,hearth feel to the feet so much ,,colder than a ,,carpet or hearth-rug8 ,a4 ,because stone and marble are good conductors1 but woollen carpets and hearth-rugs are very bad conductors4 ,q4 ,why does the ,,stone ,,hearth make our ,,feet ,,cold8 ,a4 ,as soon as the hearth-stone has absorbed a portion of heat from our foot1 it instantly disposes of it1 and calls for a fresh supply2 till the hearth-stone has become of the same temperature as the foot placed upon it4 ,q4 ,do not the woollen ,,carpet and ,,hearth-,,rug1 also1 conduct heat from the human body8 ,a4 ,yes2 7but being very bad conductors7 they convey the heat away so slowly1 that it is scarcely perceptible4 ,q4 ,is the ,,cold ,,hearth-,,stone and ,,warm ,,carpet then of the ,,same ,,temperature8 ,a4 ,yes2 everything in the room is really of the same temperature2 but some feel colder than others because they are better conductors4 ,q4 ,how ,,long will the hearth-stone feel cold to the feet resting on it8 ,a4 ,till the feet and the hearth-stone are both of the same temperature2 and then the sensation of cold in the hearth-stone will go off4 ,q4 ,why would not the ,,hearth-,,stone feel ,,cold1 when it is of the ,,same temperature as our ,,feet8 ,a4 ,because the heat would no longer rush out of our feet into the hearth-stone1 in order to produce an equilibrium4 ,q4 ,why does the ,,hearth-,,stone 7when the fire is lighted7 feel so much ,,hotter than the ,,hearth-,,rug8 ,a4 ,the hearth-stone is an excellent conductor2 and1 therefore1 parts with its heat more readily than the woollen hearth-rug2 which 7being a very bad conductor7 parts with its heat reluctantly4 ,q4 ,why does ,,parting with ,,heat ,,rapidly make the ,,hearth-,,stone feel ,,warm8 ,a4 ,as the heat of the stone rushes quickly into our foot1 it raises its temperature so suddenly1 that we cannot help perceiving the increase of heat4 ,q4 ,why does the non-conducting power of the ,,hearth-,,rug prevent its feeling so ,,hot as it really is8 ,a4 ,because it parts with its heat so slowly and gradually1 that we scarcely perceive its transmission into our feet4 ,q4 ,when we plunge our ,,hands into a basin of ,,water1 why does it produce a sensation of ,,cold8 ,a4 ,though the water 7in which we wash7 is really warmer than the air of our bed-room2 yet because it is a better conductor1 it feels colder4 ,q4 ,why does the ,,conducting power of water make it feel ,,colder than the air1 though in reality it is ,,warmer8 ,a4 ,because it abstracts heat from our hands so rapidly1 that we feel its loss2 but the air abstracts heat so very slowly1 that its gradual loss is hardly perceptible4 ,q4 ,is water a ,,good ,,conductor of heat8 ,a4 ,no2 no liquid is a good conductor of heat2 but yet water is a much better conductor than air4 ,q4 ,why is ,,water a ,,better ,,conductor of heat than ,,air8 ,a4 ,because it is less subtile2 and the conducting power of any substance depends upon its solidity1 or the closeness of its particles4 ,q4 ,how do you know that ,,water is ,,not a ,,good ,,conductor of heat8 ,a4 ,because water may be made to boil at its surface1 without imparting sufficient heat to melt ice a quarter of an inch below the boiling surface4 ,q4 ,why are ,,not ,,liquids ,,good ,,conductors of heat8 ,a4 ,because the heat 7which should be transmitted7 produces evaporation1 and flies off in the vapour4 ,q4 ,why does a ,,poker 7resting on the fender7 feel so much ,,colder than the ,,hearth-,,rug1 which is further off the fire8 ,a4 ,the poker 7being an excellent conductor7 draws heat from the hand much more quickly than the rug1 which is a bad conductor3 and1 therefore1 7though both are equally warm7 the poker seems to be much colder4 ,q4 ,why are ,,hot ,,bricks 7wrapped in cloth7 employed in cold weather to ,,keep the ,,feet ,,warm8 ,a4 ,bricks are bad conductors of heat1 and cloth or flannel still worse3 therefore a hot brick 7wrapped in flannel7 will retain its heat a very long time4 ,q4 ,why is a ,,tin ,,pan 7filled with ,,hot ,,water7 employed as a ,,foot ,,warmer8 ,a4 ,because polished tin 7being a bad radiator of heat7 keeps hot a very long time2 and warms the feet resting upon it4 ,q4 ,what is meant by being a bad ,,radiator of heat8 ,a4 ,to radiate heat is to throw off heat by rays1 as the sun2 a polished tin pan does not throw off the heat of boiling water from its surface1 but keeps it in4 ,q4 ,why is the ,,tin ,,foot-,,warmer covered with ,,flannel8 ,a4 #ast--,to prevent the perspiration of the foot from taking off the polish of the tin3 #bndly--,flannel is a very bad conductor2 and1 therefore1 helps to keep the tin hot longer3 and #crdly--,if the feet were not protected1 the conducting surface of the tin would feel painfully hot4 ,q4 ,what harm would it be if the ,,polish of the tin were injured by the perspiration of our feet8 ,a4 ,polished tin throws off its heat very slowly2 but dull1 scratched1 painted1 or dirty tin1 throws off its heat very quickly3 if1 therefore1 the tin foot-warmer were to lose its polish1 it would get cold in a much shorter time4 ,q4 ,why are ,,furnaces and stoves 7where much ,,heat is required7 built of porous ,,brick8 ,a4 ,as bricks are bad conductors1 they prevent the escape of heat3 and are1 therefore1 employed where great heat is required4 ,q4 ,why are ,,furnace ,,doors1 c4 frequently ,,covered with a paste of ,,clay and ,,sand8 ,a4 ,because this paste is a very bad conductor of heat2 and1 therefore1 prevents the escape of heat from the furnace4 ,q4 ,if a stove be placed in the ,,middle of a room1 should it be made of bricks or ,,iron8 ,a4 ,a stove in the middle of a room should be made of iron2 because iron is an excellent conductor1 and rapidly communicates its heat to the air around4 ,q4 ,why does the ,bible say1 that ,god giveth ,,snow like ,,wool8 ,a4 ,as snow is a very bad conductor of heat1 it protects vegetables and seeds from the frost and cold4 ,q4 ,how does the non-conducting power of ,,snow ,,protect ,,vegetables from the ,,frost and cold8 ,a4 ,as snow is a bad conductor1 it prevents the heat of the earth from being drawn off by the cold air which rests upon it4 ,q4 ,why are ,,woollens and ,,furs used in ,,cold weather for ,,clothing8 ,a4 ,because they are very bad conductors of heat2 and1 therefore1 prevent the warmth of the body from being drawn off by the cold air4 ,q4 ,do not woollens and furs actually ,,impart heat to the body8 ,a4 ,no2 they merely prevent the heat of the body from escaping4 ,q4 ,where would the heat ,,escape to1 if the body were ,,not wrapped in wool or fur8 ,a4 ,the heat of the body would fly off into the air2 for the cold air 7coming into contact with our body7 would gradually draw away its heat1 till it was as cold as the air itself4 ,q4 ,what then is the ,,principal ,,use of ,,clothing in winter-time8 ,a4 ,to keep the body air-tight2 and prevent the external air 7or wind7 from coming into contact with it1 to absorb its heat4 ,q4 ,why are ,,beasts ,,covered with ,,fur1 ,,hair1 or ,,wool8 ,a4 ,because fur1 hair1 and wool are very slow conductors of heat2 and 7as dumb animals cannot be clad like human beings7 ,god has given them a robe of hair or wool1 to keep them warm4 ,q4 ,why are ,,birds covered with ,,down or ,,feathers8 ,a4 ,because down and feathers are very bad conductors of heat2 and 7as birds cannot be clad like human beings7 ,god has given them a robe of feathers to keep them warm4 ,q4 ,why are ,,wool1 ,,fur1 ,,hair1 or ,,feathers such ,,slow ,,conductors of heat8 ,a4 ,because a great quantity of air lurks entangled between their fibres2 and air is a very bad conductor of heat4 ,q4 ,if ,,air be a ,,bad ,,conductor of heat1 why should we not feel as warm ,,without clothing1 as when we are wrapped in wool and fur8 ,a4 ,because the air 7which is cooler than our body7 is never at rest2 and1 therefore1 fresh particles 7perpetually passing over our body7 keep drawing off the heat little by little4 ,q4 ,why does the ceaseless ,,change of air tend to ,,decrease the ,,warmth of a naked body8 ,a4 ,thus3--the air which cases the body absorbs as much heat from it as it can1 while it remains in contact2 it is then blown away1 and makes room for a fresh coat of air1 which does the same4 ,q4 ,does the ,,air 7which encases a naked body7 become by contact as ,,warm as the ,,body itself8 ,a4 ,it would do so1 if it remained motionless2 but as it remains only a very short time1 it absorbs as much heat as it can in the time1 and passes on4 ,q4 ,why do we feel ,,colder in ,,windy ,,weather1 than in a ,,calm day8 ,a4 ,because 7in windy weather7 the particles of air pass over us more rapidly2 and every fresh particle takes from us some portion of heat4 ,q4 ,show the wisdom of ,god in making the ,,air a ,,bad ,,conductor4 ,a4 ,if air were a good conductor 7like iron and stone7 the heat would be drawn so rapidly from our body1 that we must be chilled to death4 ,similar evils would be felt also by all the animal and vegetable world4 ,q4 ,does not the bad conducting power of air enable persons to judge whether an ,,egg be ,,new or ,,stale8 ,a4 ,yes2 touch your tongue against the shell at the larger end2 if it feels warm to the tongue1 the egg is stale2 if not1 it is new-laid4 ,q4 ,why will the ,,shell of a ,,stale ,,egg feel ,,warm to the tongue8 ,a4 ,between the shell and the white of the egg there is a small quantity of air1 which expands in a stale egg1 from the shrinking of the white4 ,q4 ,why does the expansion of air 7at the end of an egg7 make it feel ,,warm to the tongue8 ,a4 ,as air is a very bad conductor1 the more air an egg contains1 the less heat will be drawn from the tongue when it touches the shell4 ,q4 ,why do ladies ,,fan themselves in summer1 to make their ,,faces ,,cool8 ,a4 ,the fan puts the air in motion1 and makes it pass more rapidly over their face2 and 7as the temperature of the air is always lower than that of the human face7 each puff of air carries off some portion of heat from the face4 ,q4 ,does ,,fanning the air make the ,,air itself ,,cooler8 ,a4 ,no2 fanning makes the air hotter and hotter4 ,q4 ,why does ,,fanning the air increase its ,,heat8 ,a4 ,by causing the air continually to absorb heat from the human body which it passes over4 ,q4 ,if fanning makes the ,,air ,,hotter1 how can it make a ,,person feel ,,cooler8 ,a4 ,fanning makes the air hotter1 but the face cooler2 because it keeps taking the heat out of the face1 and giving it to the air4 ,q4 ,why is ,,broth ,,cooled by ,,blowing it8 ,a4 ,the breath causes a rapid change of air to pass over the broth2 and 7as the air is not so hot as the broth7 it keeps absorbing heat1 and thus makes the broth cooler and cooler4 ,q4 ,would not the air absorb heat from the broth just as well ,,without ,,blowing8 ,a4 ,no2 air is a very bad conductor2 unless1 therefore1 the change be rapid1 the air nearest the surface of the broth would soon become as hot as the broth itself4 ,q4 ,but would not the hot air ,,part with its heat instantly to the ,,circumjacent air8 ,a4 ,no2 not instantly4 ,air is so bad a conductor1 that it parts with its heat very slowly3 unless1 therefore1 the air be kept in continual motion1 it would cool the broth very slowly indeed4 ,q4 ,why does ,,wind generally feel ,,cool8 ,a4 ,wind is only air in motion2 and the more quickly the air passes over our body1 the more rapidly it absorbs the heat therefrom4 ,q4 ,why does ,,air ,,absorb heat more ,,quickly by being set in ,,motion8 ,a4 ,because every fresh gust of air absorbs a fresh portion of heat2 and the more rapid the succession of gusts1 the greater will be the quantity of air absorbed4 ,q4 ,if the ,,air were ,,hotter than our body1 would the ,,wind feel ,,cool8 ,a4 ,no2 if the air were hotter than our body1 it would feel insufferably hot4 ,q4 ,why would the ,,air feel ,,intensely ,,hot1 if it were ,,warmer than our ,,blood8 ,a4 ,because then the wind would add to the heat of our body1 instead of diminishing it4 ,q4 ,is the ,,air ,,ever as ,,hot as the human ,,body8 ,a4 ,not in this country3 in the hottest summer's day1 the air is always #aj or #ab degrees cooler than the human body4 ,q4 ,is the ,,earth a ,,good ,,conductor of heat8 ,a4 ,no2 the power of conducting heat depends upon the continuity of matter2 if the particles of which a thing is composed are not continuous1 they have very little power to conduct heat4 ,q4 ,why is the earth 7,,below the ,,surface7 ,,warmer in ,,winter than the surface itself8 ,a4 ,because the earth is a bad conductor of heat2 and1 therefore 7although the ground be frozen7 the frost never penetrates above an inch or two below the surface4 ,q4 ,why is the earth 7,,below the ,,surface7 ,,cooler in ,,summer than the surface itself8 ,a4 ,because the earth is a bad conductor of heat2 and1 therefore1 7although the surface be scorched with the burning sun7 the intense heat cannot penetrate to the roots of the plants and trees4 ,q4 ,shew the ,,wisdom of ,,god in making the ,,earth a ,,bad ,,conductor4 ,a4 ,if the heat and cold could penetrate the earth 7as freely as the heat of a fire penetrates iron71 the springs would be dried up in summer and frozen in winter1 and all vegetation would perish4 ,q4 ,why is ,,water from a ,,spring so ,,cool in ,,summer8 ,a4 ,as the earth is a bad conductor1 the burning rays of the sun can penetrate only a few inches below the surface2 in consequence of which1 the springs of water are not affected4 ,q4 ,why is it ,,cool under a ,,shady tree in a hot summer's day8 ,a4 #ast--,because the overhanging foliage screens off the rays of the sun3 #bndly--,as the rays of the sun are warded off1 the air 7beneath the tree7 is not heated by the reflection of the earth3 and #crdly--,the leaves of trees1 being non-conductors1 allow no heat to penetrate through them4 ,q4 ,why do the ,,laplanders wear ,,skins1 with the ,,fur ,,inwards8 ,a4 ,the dry skin prevents the wind from penetrating to their body2 and as the fur contains a quantity of air between its hairs 7which soon becomes heated by the body7 the ,laplander is clad in a case of hot air1 impervious to the cold and wind4 ,q4 ,why does a ,,linen ,,shirt feel ,,colder than a ,,cotton ,,one8 ,a4 ,linen is a much better conductor than cotton2 and1 therefore1 7as soon as it touches the body7 it more rapidly draws away the heat1 and produces a sensation of cold4 ,q4 ,why is the ,,face ,,cooled by wiping the temples with a fine ,,cambric ,,handkerchief8 ,a4 ,the fine fibres of the cambric have a strong capillary attraction for moisture2 and are excellent conductors of heat3 thus the moisture and heat are both abstracted from the face1 and a sensation of coolness is produced4 ,capillary attraction1 i4 e4 the attraction of a thread or hair4 ,the wick of a candle is wet with grease1 because the melted tallow runs up the cotton from capillary attraction4 ,q4 ,why would not a ,,cotton handkerchief do as well8 ,a4 ,the coarse fibres of cotton have much less capillary attraction1 and are nothing like such good conductors as linen3 and1 therefore1 wiping the face with a cotton handkerchief1 increases the sensation of warmth4 ,,chapter ,,xiv4 #b4--;,,absorption ,,of ,,heat4 ,q4 ,what is the difference between ,,conducting heat1 and ,,absorbing heat8 ,a4 ,to conduct heat1 is to transmit it from one body to another through a conducting medium3 to absorb heat1 is to suck it up1 as a sponge sucks up water4 ,q4 ,give me an example4 ,a4 ,black cloth absorbs1 but does not conduct heat3 thus1 if black cloth be laid in the sun1 it will absorb the rays very rapidly2 but if one end of the black cloth be made hot1 it would not conduct the heat to the other end4 ,q4 ,are good ,,conductors of heat1 good ,,absorbers also8 ,a4 ,no2 every good conductor of heat is a bad absorber of it2 and no good absorber of heat can be a good conductor also4 ,q4 ,is ,,iron a good ,,absorber of heat8 ,a4 ,no2 iron is a good conductor1 but a very bad absorber of heat4 ,q4 ,why do the ,,fender and ,,fire-,,irons 7which lie upon it7 remain ,,cold1 although they are before a good fire8 ,a4 ,because the metal fender and fire-irons have very little capacity for absorbing heat2 although they are soon made hot 7by conduction71 when placed in contact with the hot fire or stove4 ,q4 ,why does a ,,kettle boil faster1 when the bottom and back are ,,covered with ,,soot8 ,a4 ,the black soot absorbs heat very quickly from the fire1 and the metal conducts it to the water4 ,q4 ,why will not a ,,new ,,kettle boil so fast as an ,,old one8 ,a4 ,because the bottom and sides of a new kettle are clean and bright2 but in an old kettle are covered with soot4 ,q4 ,why would the ,,kettle be ,,slower ,,boiling1 if the ,,bottom and ,,back were ,,clean and bright8 ,a4 ,bright metal does not absorb heat1 but reflect it 7i4 e4 throw the heat back again72 and as the heat is thrown off from the surface of bright metal1 therefore1 a new kettle is longer boiling4 ,q4 ,why do we wear ,,white ,,linen and a ,,black outer ,,dress1 if we want to be warm8 ,a4 ,the black outer dress quickly absorbs heat from the sun1 and conveys it to the body2 and the white linen 7being a bad absorbent7 abstracts no heat from the warm body4 ,q4 ,why do persons ,,wear ,,white dresses in ,,summer time8 ,a4 ,white throws off the heat of the sun by reflection1 and is1 therefore1 a very bad absorbent of heat2 in consequence of which1 it never becomes so hot from the scorching sun as dark colours do4 ,q4 ,why do ,,not persons ,,wear ,,white dresses in ,,winter time8 ,a4 ,white will not absorb heat1 like black and other dark colours2 and1 therefore1 white dresses are not so warm as dark ones4 ,q4 ,what ,,colours are ,,warmest for dresses8 ,a4 ,for outside garments black is the warmest1 and then such colours as approach nearest to black 7as dark blue and green74 ,white is the coldest colour for external clothing4 ,q4 ,why are ,,dark ,,colours 7for external wear7 so much ,,warmer than ,,light ,,ones8 ,a4 ,because dark colours absorb heat from the sun more abundantly than light ones4 ,q4 ,how can you prove that ,,dark colours are ,,warmer than ,,light ones8 ,a4 ,if a piece of black cloth and a piece of white were laid upon snow1 in a few hours the black cloth will have melted the snow beneath2 whereas the white cloth will have produced little or no effect upon it at all4 ,n4 ,b4 ,the darker any colour is1 the warmer it is1 because it is a better absorbent of heat4 ,the order may be thus arranged3--#a4 ,black 7warmest of all74--#b4 ,violet4--#c4 ,indigo4--#d4 ,blue4--#e4 ,green4--#f4 ,red4--#h4 ,yellow3 and #i4 ,white 7coldest of all74 ,q4 ,why are ,,black ,,kid ,,gloves so ,,hot in summer time8 ,a4 #ast--,because the black absorbs the solar heat3 and #bndly--,the kid will not allow the heat of the hand to escape through the glove4 ,q4 ,why are ,,lisle ,,thread ,,gloves so ,,cool in summer time8 ,a4 #ast--,because thread absorbs the perspiration of the hands3 and #bndly--,it conducts away the heat of our hot hands4 ,q4 ,are ,lisle thread gloves ,,absorbents of heat8 ,a4 ,as ,lisle thread gloves are generally of a grey or lilac colour1 they do not absorb solar heat4 ,q4 ,why is a ,,plate-,,warmer made of ,,un-,,painted ,,bright ,,tin8 ,a4 ,bright tin reflects 7or throws back7 the heat1 which issues from the fire in rays2 and 7by reflecting the heat upon the meat7 assists greatly in roasting it4 ,q4 ,why would not the tin ,,reflector do as well if it were ,,painted8 ,a4 ,if the tin reflector were painted1 it would be utterly spoiled1 because it would then absorb heat1 and not reflect it at all4 ,a plate-warmer should be kept very clean1 bright1 and free from all scratches4 ,q4 ,why should a ,,reflector be kept so very ,,clean and free from ,,scratches8 ,a4 ,if a reflector be spotted1 dull1 or scratched1 it will absorb heat1 instead of reflecting it2 and1 therefore1 would be of no use whatsoever as a reflector4 ,q4 ,why does ,,hoar-,,frost remain on ,,tombstones1 long after it has melted from the ,,grass and ,,gravel-,,walks of a church-yard8 ,a4 ,tomb-stones being white1 will not absorb heat1 like the darker grass and gravel2 and1 therefore1 the white tombstones 7being so much colder7 retain the hoar-frost after it has melted from other things4 ,q4 ,if black absorbs heat1 why have those who live in ,,hot climates ,,black ,,skins1 and not ,,white skins 7which would not absorb heat at all78 ,a4 ,though the black skin of the negro absorbs heat more plentifully than the white skin of a ,european1 yet the blackness prevents the sun from blistering or scorching it4 ,q4 ,how is it known that the ,,black colour prevents the sun from either ,,blistering or ,,scorching the skin8 ,a4 ,if you put a white glove on one hand1 and a black glove on the other 7when the sun is burning hot71 the hand with the white glove will be scorched1 but not the other4 ,q4 ,which hand will ,,feel the ,,hotter8 ,a4 ,the hand with the black glove will feel the hotter1 but it will not be scorched by the sun2 whereas the hand with the white glove 7though much cooler7 will be severely scorched4 ,q4 ,why does the ,,black skin of a ,,negro ,,never ,,scorch or ,,blister with the hot sun8 ,a4 ,because the black colour absorbs the heat1--conveys it below the surface of the skin1 and converts it to sensible heat and perspiration4 ,q4 ,why does the ,,white ,,european ,,skin ,,blister and ,,scorch when exposed to the hot sun8 ,a4 ,because the white will not absorb the heat2 and1 therefore1 the hot sun rests on the surface of the skin1 and scorches it4 ,q4 ,why has a ,,negro ,,black ,,eyes8 ,a4 ,the black colour of a negro's eyes defends them from the strong light of the tropical sun4 ,if a negro's eyes were not black1 the sun would scorch them1 and every negro would be blind4 ,q4 ,why is ,,water ,,kept ,,cooler 7in summer time7 in a ,,bright ,,tin ,,pot1 than in an ,,earthen one8 ,a4 ,because bright metal will not absorb the heat of the summer sun1 like an earthen vessel4 ,q4 ,why is ,,boiling water ,,kept ,,hot in a ,,bright ,,tin ,,vessel longer1 than in an earthen one8 ,a4 ,because bright tin will not suffer the heat of the boiling water to escape in rays1 as an earthen vessel does4 ,,chapter ,,xv4 #c4--,,reflection ,,of ,,heat4 ,q4 ,what is meant by ,,reflecting ,,heat8 ,a4 ,to reflect heat1 is to throw it back in rays from the surface of the reflecting body1 towards the place from whence it came4 ,q4 ,what are the ,,best ,,reflectors of heat8 ,a4 ,all bright surfaces1 and light colours4 ,q4 ,are ,,good ,,absorbers of heat ,,good ,,reflectors also8 ,a4 ,no2 those things which absorb heat best1 reflect heat worst2 and those which reflect heat worst1 absorb it best4 ,q4 ,why are those things which ,,absorb ,,heat unable to ,,reflect it8 ,a4 ,because if any thing sucks in heat like a sponge1 it cannot throw it off from its surface2 and if any thing throws off heat from its surface1 it cannot drink it in4 ,q4 ,why are ,,reflectors always made of ,,light-,,coloured and highly ,,polished ,,metal8 ,a4 ,because light coloured and highly polished metal makes the best of all reflectors4 ,q4 ,why do not ,,plate-,,warmers ,,blister and scorch the ,,wood behind8 ,a4 ,because the bright tin front throws the heat of the fire back again1 and will not allow it to penetrate to the wood behind4 ,q4 ,if metal be such an excellent ,,conductor of heat1 how can it ,,reflect heat1 or throw it off8 ,a4 ,polished metal is a conductor of heat1 only when that heat is communicated by actual contact2 but whenever heat falls upon bright metal in rays1 it is reflected back again1 and the metal remains quite cool4 ,q4 ,what is meant by heat falling upon metal ,,in ,,rays1 and not by contact8 ,a4 ,if a piece of tin were thrust into a fire1 it would be in actual contact with the fire2 but if it be held before a fire1 the heat of the fire falls upon it in rays4 ,q4 ,what is the use of the ,,tin ,,screen or ,,reflector used in ,,roasting8 ,a4 ,the tin reflector throws the heat of the fire back upon the meat2 and1 therefore1 assists the process of roasting and helps to keep the kitchen cool4 ,q4 ,how does a tin ,,reflector tend to keep the ,,kitchen ,,cool8 ,a4 ,because it confines the heat to the hearth1 and prevents it from being dispersed throughout the kitchen4 ,q4 ,why does a ,,lamp ,,glass ,,diminish the ,,smoke of a ,,lamp8 ,a4 ,as glass is a reflector1 it reflects the heat of the lamp back upon the flame2 in consequence of which1 less carbon escapes unconsumed 7as smoke74 ,q4 ,why are ,,shoes ,,hotter for being ,,dusty8 ,a4 #ast--,because dust absorbs heat3 and #bndly--,as it destroys the blackness of our shoes1 it prevents them from throwing off the heat of our feet in rays4 ,q4 ,why can we not ,,see into the ,,road or ,,street1 when a ,,candle is lighted in a room8 ,a4 ,glass is a reflector2 and1 therefore1 throws the rays of the candle back into the room1 and thus prevents our seeing into the road or street4 ,q4 ,why can persons in the ,,dark ,,street see into a ,,room 7lighted by a candle or lamp78 ,a4 ,the pupil of the eye expands greatly1 when persons are in the dark2 and1 therefore1 when any one in the dark street looks into a light room1 his dilated pupil sees every thing distinctly4 ,q4 ,why does it always ,,freeze on the ,,top of a ,,mountain8 ,a4 ,air is heated by the reflection of the earth1 and not by the rays of the sun2 and1 as there is no earth round a mountain-top to reflect heat1 therefore1 it remains intensely cold4 ,,chapter ,,xvi4 #d4--,,radiation4 ,q4 ,what is meant by ,,radiation8 ,a4 ,radiation means the emission of rays3 thus the sun radiates both light and heat2 that is1 it emits rays of light and heat in all directions4 ,q4 ,when is heat ,,radiated from one body to another8 ,a4 ,when the two bodies are separated by a non-conducting medium3 thus the sun radiates heat towards the earth1 because the air comes between 7which is a very bad conductor74 ,q4 ,on ,,what does ,,radiation ,,depend8 ,a4 ,on the roughness of the radiating surface3 thus if metal be scratched1 its radiating power is increased1 because the heat has more points to escape from4 ,q4 ,does a ,,fire ,,radiate heat8 ,a4 ,yes2 and because burning fuel emits rays of heat1 therefore we feel warm when we stand before a fire4 ,q4 ,why does our ,,face ,,feel uncomfortably ,,hot1 when we approach a ,,fire8 ,a4 ,because the fire radiates heat upon the face2 which 7not being covered7 feels the effect immediately4 ,q4 ,why does the fire catch the ,,face more than the ,,rest of the body8 ,a4 ,the rest of the body is covered with clothing1 which 7being a bad conductor of heat7 prevents the same sudden and rapid transmission of heat to the skin4 ,q4 ,do those substances which ,,radiate heat1 ,,absorb heat also8 ,a4 ,yes4 ,those substances which radiate most1 also absorb most heat3 and those which radiate least1 also absorb the least heat4 ,q4 ,does any thing ,,else radiate heat1 ,,besides the ,,sun and ,,fire8 ,a4 ,yes2 all things radiate heat in some measure1 but not equally well4 ,q4 ,what things ,,radiate heat the ,,next ,,best to the sun and fire8 ,a4 ,all dull and dark substances are good radiators of heat2 but all light and polished substances are bad radiators of heat4 ,q4 ,why does a ,,polished ,,metal ,,tea-,,pot make ,,better ,,tea than a black earthen one8 ,a4 ,as polished metal is a very bad radiator of heat1 it keeps the water hot much longer2 and the hotter the water is1 the better it draws the tea4 ,q4 ,why will not a ,,dull ,,black ,,tea-,,pot make good tea8 ,a4 ,because the heat of the water flies off so quickly through the dull black surface of the tea-pot1 that the water is rapidly cooled1 and will not draw the tea4 ,q4 ,do not pensioners1 and most aged cottagers1 prefer the little ,,black ,,earthen ,,tea-,,pot to the bright ,,metal one8 ,a4 ,yes2 because they set it on the hob to draw2 in which case1 the little black tea-pot will make the best tea4 ,q4 ,why will a ,,black ,,tea-,,pot make better tea than a bright metal one1 if it be set upon the ,,hob to ,,draw8 ,a4 ,because the black tea-pot will absorb heat plentifully from the fire1 and keep the water boiling hot3 whereas1 a bright metal tea-pot 7set upon the hob7 would throw off the heat by reflection4 ,q4 ,then sometimes a ,,black ,,earthen tea-pot is the best1 and sometimes a bright ,,metal one8 ,a4 ,yes2 when the tea-pot is set on the hob to draw1 the black earth is the best1 because it absorbs heat3 but when the tea-pot is not set on the hob1 the bright metal is the best1 because it radiates heat very slowly1 and therefore keeps the water hot4 ,q4 ,why does a ,,saucepan which has been ,,used1 boil ,,quicker than a ,,new ,,one8 ,a4 ,because the bottom and back are covered with soot2 and the black soot rapidly absorbs the heat of the glowing coals4 ,q4 ,why should the ,,front and ,,lid of a ,,saucepan be clean and ,,bright8 ,a4 ,as they do not come in contact with the fire1 they cannot absorb heat2 and 7being bright7 they will not suffer the heat to escape by radiation4 ,q4 ,in what state should a ,,saucepan be1 in order that it may ,,boil ,,quickly8 ,a4 ,all those parts which come in contact with the fire should be covered with soot1 to absorb heat2 but all the rest of the saucepan should be as bright as possible1 to prevent the escape of heat by radiation4 ,q4 ,why is it said that ,,saturday',s ,,kettle ,,boils the ,,fastest8 ,a4 ,because on ,saturday the front and top of the kettle are generally cleaned and polished2 but the bottom and back of the kettle are never cleaned4 ,q4 ,why should ,,not the ,,bottom and ,,back of a kettle be ,,cleaned and polished8 ,a4 ,because they come in contact with the fire1 and 7while they are covered with black soot7 absorb heat freely from the burning coals4 ,q4 ,why should the ,,front and ,,top of a kettle be ,,clean and well polished8 ,a4 ,because polished metal will not radiate heat2 and1 therefore1 7while the front and top of the kettle are well polished7 the heat is kept in1 and not suffered to escape by radiation4 ,q4 ,why is the ,,inside of a ,,kettle and ,,saucepan ,,white8 ,a4 ,white will not radiate heat3 if1 therefore1 the inside of a boiler be white1 the liquor in it is kept hot much longer4 ,q4 ,why is the ,,bottom of a ,,kettle nearly ,,cold1 when the ,,water is ,,boiling ,,hot8 ,a4 ,black soot is a very bad conductor of heat2 and1 therefore1 the heat of the boiling water is some considerable time1 before it gets through the soot which adheres to the bottom of the kettle4 ,q4 ,why is the ,,lid of a ,,kettle so intensely ,,hot1 when the water boils8 ,a4 ,the bright metal lid of the kettle is an admirable conductor of heat2 and1 therefore1 the heat from the boiling water pours into our hand the moment we touch it4 ,q4 ,show the benefit of ,,smoke in ,,cooking4 ,a4 ,the carbon of the fuel 7which flies off in smoke7 naturally blackens all culinary vessels set upon the fire to boil1 and thus renders them fit for use4 7,culinary vessels are vessels used in kitchens for cooking1 as saucepans1 boilers1 kettles1 c47 ,q4 ,how does ,,smoke make culinary vessels ,,fit for ,,use8 ,a4 ,if it were not for the smoke1 7which gathers round a kettle or saucepan7 heat would not be absorbed1 and the process of boiling would be greatly retarded4 ,q4 ,why is boiling water ,,kept ,,hot best in a ,,bright ,,metal pot8 ,a4 ,because bright metal being a bad radiator will not throw off the heat of the boiling water from its surface4 ,q4 ,why is ,,water ,,kept ,,cold in summer-time in a ,,bright ,,metal pot1 better than in an ,,earthen vessel8 ,a4 ,because bright metal will not absorb heat from the hot air1 like an earthen vessel2 in consequence of which1 the water is kept cooler4 ,q4 ,why are ,,dinner-,,covers made of ,,bright ,,tin or ,,silver8 ,a4 ,light-coloured and highly-polished metal is a very bad radiator of heat2 and1 therefore1 bright tin or silver will not allow the heat of the cooked food to escape through the cover by radiation4 ,q4 ,why should a ,,meat-,,cover be very brightly ,,polished8 ,a4 ,if the cover be dull or scratched it will absorb heat from the hot food beneath it2 and 7instead of keeping it hot7 will make it cold4 ,q4 ,why should a ,,silver ,,meat-,,cover be ,,plain1 and not ,,chased8 ,a4 ,if the cover be chased1 it will absorb the heat of the food covered by it2 and instead of keeping it hot1 will make it cold by absorption4 ,q4 ,what is ,,dew8 ,a4 ,dew is the vapour of the air condensed1 by coming in contact with bodies colder than itself4 ,q4 ,why is the ,,ground sometimes ,,covered with ,,dew8 ,a4 ,the earth is more heated by solar rays than the air1 during the day2 but at night1 the earth parts with more heat than the air1 and becomes 7in consequence7 #e or #aj degrees colder4 ,q4 ,how does the ,,earth being ,,colder than the ,,air account for the deposition of ,,dew8 ,a4 ,as soon as the air touches the cold earth1 its warm vapour is chilled1 and condensed into dew4 ,q4 ,why is the surface of the ,,ground ,,colder in a ,,fine clear ,,night1 than in a ,,cloudy one8 ,a4 ,on a fine clear star-light night1 heat radiates from the earth freely1 and is lost in open space3 but on a cloudy night1 the clouds arrest the process of radiation4 ,q4 ,why is ,,dew deposited only on a ,,fine clear ,,night8 ,a4 ,because1 when the night is clear and fine1 the surface of the ground radiates heat most freely2 and 7being cooled down by this loss of heat7 chills the vapour of the air into dew4 ,q4 ,why is there ,,no ,,dew on a dull ,,cloudy ,,night8 ,a4 ,the clouds arrest the radiation of heat from the earth2 and 7as the heat cannot freely escape7 the surface is not sufficiently cooled down to chill the vapour of the air into dew4 ,q4 ,why is a ,,cloudy ,,night ,,warmer than a ,,fine one8 ,a4 ,because the clouds prevent the radiation of heat from the earth2 and1 therefore1 the surface of the earth remains warmer on a dull cloudy night4 ,q4 ,why is ,,dew most ,,abundant in situations most ,,exposed8 ,a4 ,because the radiation of heat is not arrested by houses1 trees1 hedges1 or any other thing4 ,q4 ,why is there scarcely any ,,dew under a shady ,,tree8 ,a4 ,the shady head of the tree both arrests the radiation of heat from the earth1 and also radiates some of its own heat towards the earth2 and1 therefore1 the ground 7underneath a tree7 is not sufficiently cooled down to chill the vapour of the air into dew4 ,q4 ,why is there never much ,,dew at the foot of ,,walls and ,,hedges8 ,a4 #ast--,because the wall or hedge acts as a screen1 to arrest the radiation of heat from the earth3 and #bndly--,the wall or hedge also radiates some portion of heat towards the earth4 ,q4 ,how do these things prevent the deposition of dew8 ,a4 ,as the ground 7beneath a wall1 tree1 or hedge7 is not cooled by the radiation of heat1 it remains of the same temperature as the air above it2 in consequence of which1 the vapours of the air are not chilled by it into dew4 ,q4 ,why is there little or ,,no ,,dew beneath a ,,flower-,,awning1 although that awning be open on all four sides8 ,a4 #ast--,because the awning arrests the radiation of heat from the ground beneath3 and #bndly--,it radiates some of its own heat downwards2 in consequence of which1 the ground beneath an awning is not sufficiently cooled down to chill the vapour of air into dew4 ,q4 ,how can a thin covering of ,,bass or even ,,muslin protect trees from ,,frost8 ,a4 ,because any covering prevents the radiation of heat from the tree2 and if the tree be not cooled down by radiation1 the vapour of the air will not be frozen as it comes in contact with it4 ,q4 ,why is the ,,bass or ,,canvass itself 7which covers the tree7 always ,,drenched with ,,dew8 ,a4 ,the bass or canvass covering radiates heat both upwards and downwards2 and is1 therefore1 so cooled down1 that it readily chills all the vapour of the air 7which passes over it7 into dew4 ,q4 ,why does ,,snow at the foot of a ,,hedge or ,,wall melt sooner1 than in an open field8 ,a4 ,because the hedge or wall radiates heat into the snow beneath1 which melts it4 ,q4 ,why is there ,,no ,,dew after a ,,windy ,,night8 ,a4 #ast--,because the wind evaporates the moisture1 as fast as it is deposited2 and #bndly--,it disturbs the radiation of heat1 and diminishes the deposition of dew thereby4 ,q4 ,why are ,,valleys ,,hollows often thickly covered with ,,dew1 although they are sheltered8 ,a4 ,the surrounding hills prevent the repose of air 7in the valleys7 from being disturbed2 but do not overhang and screen them1 so as to arrest their radiation4 ,q4 ,why does ,,dew ,,fall more ,,abundantly on ,,some ,,things than upon ,,others8 ,a4 ,because some things radiate heat more freely than others1 and therefore become much cooler in the night4 ,q4 ,why are things which ,,radiate ,,heat ,,most ,,freely1 always the most ,,thickly ,,covered with ,,dew8 ,a4 ,because the vapour of the air is chilled into dew1 the moment it comes in contact with them4 ,q4 ,what kind of things ,,radiate ,,heat most ,,freely8 ,a4 ,grass1 wood1 and the leaves of plants1 radiate heat very freely3 but polished metal1 smooth stones1 and woollen cloth1 part with their heat very tardily4 ,q4 ,do the leaves of ,,all plants radiate heat ,,equally ,,well8 ,a4 ,no4 ,rough woolly leaves 7like those of a holly-hock7 radiate heat much more freely1 than the hard smooth polished leaves of a common laurel4 ,q4 ,shew the ,,wisdom of ,,god in making grass1 the leaves of trees1 and ,,all ,,vegetables1 ,,excellent ,,radiators of heat4 ,a4 ,as vegetables require much moisture1 and would often perish without a plentiful deposit of dew1 ,god wisely made them to radiate heat freely1 so as to chill the vapour 7which touches them7 into dew4 ,q4 ,will polished ,,metal1 smooth ,,stones1 and woollen ,,cloth1 readily collect ,,dew8 ,a4 ,no4 ,while grass and the leaves of plants are completely drenched with dew1 a piece of polished metal1 or of woollen cloth 7lying on the same spot7 will be almost dry4 ,q4 ,why would ,,polished ,,metal and ,,woollen ,,cloth be ,,dry1 while grass and leaves are drenched with ,,dew8 ,a4 ,because the polished metal and woollen cloth part with their heat so slowly1 that the vapour of the air is not chilled into dew as it passes over them4 ,q4 ,why is a ,,gravel ,,walk almost ,,dry1 when a grass plat is covered thick with ,,dew8 ,a4 ,grass1 7being a good radiator7 throws off its heat very freely2 but gravel 7being a very bad radiator7 parts with its heat very reluctantly4 ,q4 ,is that the reason why ,,grass is ,,saturated with ,,dew1 and the ,,gravel is ,,not8 ,a4 ,yes4 ,when the vapour of warm air comes in contact with the cold grass1 it is instantly chilled into dew2 but 7as the gravel is not so cold as the grass7 the vapour of air is not so freely condensed as it passes over the gravel4 ,q4 ,why does ,,dew rarely fall upon hard ,,rocks and ,,barren lands8 ,a4 ,rocks and barren lands are so compact and hard1 that they can neither absorb nor radiate much heat2 and 7as their temperature varies but very little7 very little dew distils upon them4 ,q4 ,why does ,,dew fall more abundantly on ,,cultivated soils1 than on ,,barren lands8 ,a4 ,because cultivated soils 7being loose and porous7 absorb heat freely during the day1 and radiate it by night2 and 7being much cooled by the rapid radiation of heat7 as the vapour of the air passes over them1 it is plentifully condensed into dew4 ,q4 ,shew the ,,wisdom of ,,god in this arrangement4 ,a4 ,every plant and inch of land which needs the moisture of dew1 is adapted to collect it2 but not a single drop even of dew is wasted1 where its refreshing moisture is not required4 ,q4 ,shew the ,,wisdom of ,,god in making polished ,,metal and woollen ,,cloth ,,bad ,,radiators of heat4 ,a4 ,if polished metal collected dew as easily as grass1 it could never be kept dry1 and free from rust4 ,again1 if woollen garments collected dew as readily as the leaves of trees1 we should be often soaking wet1 and subject to constant colds4 ,q4 ,shew how this affords a beautiful illustration of ,,gideon',s ,,miracle1 recorded in the book of ,judges1 ,,vi4 #cg1 #ch4 ,a4 ,the fleece of wool 7which is a very bad radiator of heat7 was soaking wet with dew3 when the grass 7which is a most excellent radiator7 was quite dry4 ,q4 ,was not this ,,contrary to the laws of ,,nature8 ,a4 ,yes2 and was1 therefore1 a plain demonstration of the power of ,god1 who could change the very nature of things at his will4 ,q4 ,why do our ,,clothes ,,feel ,,damp1 after walking in a fine evening in ,,spring or ,,autumn8 ,a4 ,because the vapour 7condensed by the cold earth7 lights upon them1 like dew4 ,q4 ,why are ,,windows often covered with thick ,,mist1 and the frames wet with standing ,,water8 ,a4 ,the temperature of the external air always falls at sun-set1 and chills the window-glass1 with which it comes in contact4 ,q4 ,how does this account for the ,,mist and ,,water on a ,,window8 ,a4 ,as the warm vapour of the room touches the cold glass1 it is chilled and condensed into mist2 and the mist 7collecting into drops7 rolls down the window-frame in little streams of water4 ,q4 ,does the ,,glass of a window ,,cool down more ,,rapidly than the ,,air of the room itself8 ,a4 ,yes2 because the air is kept warm by fires1 and the animal heat of the people in the room2 in consequence of which1 the air of a room suffers very little diminution of heat from the setting of the sun4 ,q4 ,whence arises the ,,vapour of a ,,room8 ,a4 #ast--,the very air of the room contains vapour3 #bndly--,the breath and insensible perspiration of the inmates increase this vapour3 and #crdly--,hot dinners1 the steam of tea1 c4 contribute to increase it still more4 ,q4 ,what is meant by the ,,insensible ,,perspiration8 ,a4 ,from every part of the human body an insensible and invisible perspiration issues all night and day2 not only in the hot weather of summer1 but also in the coldest day of winter4 ,q4 ,if the perspiration be both ,,insensible and ,,invisible1 how is it ,,known that there ,,is any such perspiration8 ,a4 ,if you put your naked arm into a clean dry glass cylinder1 the perspiration of your arm will soon condense on the glass1 like mist4 ,q4 ,why are ,,carriage ,,windows very ,,soon covered with thick ,,mist8 ,a4 ,the warm vapour of the carriage is condensed the moment it touches the cold glass1 and covers it over with a thick mist4 ,q4 ,why is the glass window ,,cold enough to condense the vapour of the carriage8 ,a4 ,because the inside of the carriage is much warmer than the outside1 and the glass window is made cold by contact with the external air4 ,q4 ,where does the ,,warm vapour of the carriage come from8 ,a4 ,the warm breath and insensible perspiration of the persons riding in the carriage1 load the air of it with warm vapour4 ,q4 ,what is the cause of the pretty ,,frost-,,work seen on bed-room ,,windows in winter-time8 ,a4 ,the breath and insensible perspiration of the sleeper 7coming in contact with the ice-cold window7 is frozen by the cold glass1 and forms those beautiful appearances seen in our bed-rooms in a winter morning4 ,q4 ,why is the ,,glass of a window colder than the ,,walls of a room8 ,a4 ,glass is a very excellent radiator2 and1 therefore1 most rapidly parts with its heat4 ,q4 ,why is a ,,tumbler of cold ,,water made quite ,,dull with mist1 when brought into a room ,,full of ,,people8 ,a4 ,because the hot vapour of the room 7coming in contact with the cold tumbler7 is condensed upon it2 and changes its invisible and gaseous form for that of a thick mist4 ,q4 ,why is a ,,glass made quite ,,dull1 by laying a ,,hot ,,hand upon it8 ,a4 ,the insensible perspiration of the hot hand is condensed upon the cold glass1 and thus made perceptible4 ,q4 ,why are ,,wine-,,glasses made quite ,,dull when they are brought into a room ,,full of ,,company8 ,a4 ,the hot vapour of the room 7coming in contact with the cold wine-glasses7 is condensed upon them1 and covers them with vapour like dew4 ,q4 ,why does this misty appearance ,,go ,,off after a little time8 ,a4 ,because the glass becomes of the same temperature as the air of the room1 and will no longer chill the vapour which touches it1 and condense it into mist4 ,q4 ,why is a ,,wine-,,glass 7brought out of a ,,cellar into the ,,air7 covered with a thick ,,mist in summer-time8 ,a4 ,the vapour of the hot air is condensed by the cold glass1 and covers it as a thick mist4 ,q4 ,why does ,,breathing on a ,,glass make it quite ,,dull8 ,a4 ,because the hot breath is condensed by the cold glass2 and1 therefore1 covers it with a thick mist4 ,q4 ,why do ,,walls stand thick with ,,wet in a sudden ,,thaw8 ,a4 ,the walls 7being thick7 cannot change their temperature so fast as the thin air can2 and1 therefore1 they retain their cold after the thaw has set in4 ,q4 ,how does ,,retaining their ,,cold account for their being so ,,wet8 ,a4 ,as the vapour of the warm air touches the cold wall1 it is chilled and condensed into water1 which sticks to the wall1 and sometimes trickles down in little streams4 ,q4 ,why does a thick ,,well-,,built ,,house contract more ,,damp of this kind1 than an ,,ordinary one8 ,a4 ,because the walls are much thicker2 and 7if the frost has penetrated far into the bricks7 it takes a long time to reduce them to the same temperature as the air4 ,q4 ,why are ,,banisters1 c4 ,,damp after a ,,thaw8 ,a4 ,the wooden banister 7being made of some very close-grained1 varnished wood7 cannot change its temperature so fast as the air2 and1 therefore1 remains cold some time after the thaw has set in4 ,q4 ,how does ,,this account for the ,,banisters being ,,damp8 ,a4 ,the vapour of the warm air 7coming in contact with the cold banister7 is chilled1 and condensed into water upon it4 ,q4 ,why is our ,,breath ,,visible in ,,winter and ,,not in ,,summer8 ,a4 ,in winter the coldness of the air condenses our breath into visible vapour2 but in summer the air is not cold enough to condense it into visible vapour4 ,q4 ,why are our ,,hair and the ,,brim of our ,,hat often covered with little drops of pearly ,,dew in winter-time8 ,a4 ,the breath 7issuing from our mouth and nose7 is condensed into drops1 as it comes in contact with our cold hair or hat2 and 7being condensed7 hangs there in little dew-drops4 ,q4 ,why does the ,,steam of a ,,railway ,,boiler often pour down1 like fine rain1 when the steam is let off8 ,a4 ,the steam from the steam-pipe 7when the air is cold7 is condensed by contact with the chill air1 and falls like fine rain4 ,q4 ,why is there ,,less ,,dew when the ,,wind is ,,easterly1 than when the wind is ,,westerly8 ,a4 ,easterly winds cross the continent of ,europe1 and1 7as they pass over land7 are dry and arid2 but westerly winds cross the ,atlantic ,ocean2 and 7as they pass over water7 are moist and full of vapour4 ,q4 ,how does the ,,dryness of an eastern wind ,,prevent ,,dew-,,falls8 ,a4 ,as the easterly winds are dry1 they imbibe the moisture of the air2 and1 therefore1 there is very little left to be condensed into dew4 ,q4 ,how does the ,,moistness of a western wind ,,promote dew-falls8 ,a4 ,as the westerly winds are saturated with vapour1 they require a very little reduction of heat to cause a copious deposition of dew4 ,q4 ,when is ,,dew most ,,copiously distilled8 ,a4 ,after a hot day in summer or autumn1 with the wind in the west4 ,q4 ,why is ,,dew distilled most ,,copiously after a ,,hot day8 ,a4 ,because the surface of the earth radiates heat very freely at sunset2 and 7becoming thus much colder than the air7 chills its vapour1 and condenses it into dew4 ,q4 ,does not ,,air radiate heat1 as well as the ,,earth and its various plants8 ,a4 ,no4 ,the air never radiates heat1 nor is the air itself made hot by the rays of the sun4 ,q4 ,how is the ,,air made ,,hot or ,,cold8 ,a4 ,by convection of hot or cold currents4 ,q4 ,what is meant by ,,convection of hot and cold currents8 ,a4 ,the air 7which is heated by the surface of the earth7 ascends1 warming the air through which it passes4 ,other air 7being warmed in a similar way7 also ascends1 carrying heat2 till all the air is made hot4 ,q4 ,is the ,,air made ,,cold in a similar way8 ,a4 ,yes4 ,the air resting on the earth is made cold by contact3 this cold air makes the air above it cold2 and cold currents or winds shake the whole together1 till all becomes of one temperature4 ,q4 ,why is ,,meat very subject to ,,taint on a ,,moon-,,light night8 ,a4 ,in a bright moon-light night1 meat radiates heat very freely2 and is1 therefore1 soon covered with dew1 which produces rapid decomposition4 ,q4 ,why do ,,plants ,,grow ,,rapidly in ,,moon-,,light nights8 ,a4 ,in bright moon-light nights rapid radiation is carried on1 and dew is plentifully deposited on young plants1 which conduces much to their growth and vigour4 ,q4 ,why is evening ,,dew ,,injurious to ,,health8 ,a4 ,because the condensed vapours are always laden with noxious exhalations from the earth3 this is especially the case in marshy countries4 ,q4 ,is ,,honey-,,dew a similar thing to ,,dew8 ,a4 ,no4 ,honey-dew is a sweet liquid shed by a very small insect 7called the aphis71 and deposited in autumn on the under surface of favourite leaves4 ,q4 ,does ,,honey-,,dew ,,injure leaves1 or do them good8 ,a4 ,it injures them very much1 because it fills the pores of the leaf with a thick clammy liquid2 and1 therefore1 prevents the leaf from transpiring and absorbing4 ,q4 ,what ,,effect has honey-dew upon the ,,appearance of a leaf8 ,a4 ,after a little time1 the leaf 7being smothered and starved7 begins to turn a dingy yellow4 ,q4 ,are not ,,ants very ,,fond of ,,honey-,,dew8 ,a4 ,yes2 and they crawl up the loftiest trees1 in order to obtain it4 ,q4 ,what is the cause of ,,mist 7or earth-fog78 ,a4 ,if the night has been very calm1 a rapid radiation of heat has taken place in the earth2 in consequence of which1 the air 7resting on the earth7 is made so cold1 that its vapour is chilled1 and condensed into a thick mist4 ,q4 ,why does not the ,,mist become ,,dew8 ,a4 ,because the chill of the air is so rapid1 that vapour is condensed faster than it can be deposited2 and 7covering the earth in a mist7 prevents any further radiation of heat from the earth4 ,q4 ,when the earth can no longer ,,radiate heat upwards1 does it continue to ,,condense the vapour of the air8 ,a4 ,no2 the air 7in contact with the earth7 becomes about equal in temperature with the surface of the earth itself2 for which reason1 the mist is not condensed into dew1 but remains floating above the earth as a thick cloud4 ,q4 ,why does this ,,mist seem to ,,rise ,,higher and ,,higher1 and yet remain quite as dense below as before8 ,a4 ,the air resting on the earth is first chilled1 and chills the air resting on it2 the air which touches this new layer of mist being also condensed1 layer is added to layer2 and the mist seems to be rising1 when 7in fact7 it is only deepening4 ,q4 ,why does ,,mist and ,,dew ,,vanish as the ,,sun rises8 ,a4 ,because the condensed vapour is again rarefied by the heat of the sun1 and separated into invisible particles4 ,q4 ,why is a ,,dew-,,drop ,,round8 ,a4 ,because every part of the drop is equally balanced2 and1 therefore1 there is no cause why one part of the drop should be further from the centre than another4 ,q4 ,why is the ,,dew-,,drop on a broad leaf sometimes ,,flattened8 ,a4 ,whenever two or more drops of dew roll together1 they make one large spheroid 7or flattened drop74 ,q4 ,why will ,,dew-,,drops ,,roll ,,about ,,cabbage-,,plants1 ,,poppies1 c4 without wetting the surface8 ,a4 ,the leaves of cabbages and poppies are covered with a very fine powder2 and the dew-drop rolls over this fine powder1 as a drop of rain over dust1 without wetting the surface4 ,q4 ,why does not the drop of ,,rain ,,wet the ,,dust over which it rolls8 ,a4 ,because it is driven from grain to grain by capillary repulsion4 ,q4 ,why does not the ,,dew-,,drop ,,wet the ,,powder of the ,,cabbage-plant8 ,a4 ,because it is driven from grain to grain by capillary repulsion4 ,q4 ,why will ,,dew-,,drops ,,roll over ,,roses1 c4 without wetting their petals8 ,a4 ,the leaves of a rose contain an essential oil1 which prevents them from absorbing the dew immediately4 ,q4 ,why can a ,,swan or ,,duck dive under water ,,without being ,,wetted8 ,a4 ,because their feathers are covered with an oily secretion1 which repels the water4 ,q4 ,what is the cause of ,,mist8 ,a4 ,when currents of air from land mix with currents of air from water1 the currents from the water are condensed into mist by the colder currents blowing from the land4 ,q4 ,why are the currents of air from the ,,land ,,colder than those blowing over ,,water8 ,a4 ,because the earth radiates heat very freely1 and 7being greatly cooled down7 cools the air also which comes in contact with it4 ,q4 ,why is not the ,,air1 which passes over ,,water1 so ,,cool as that which passes over ,,land8 ,a4 ,because water does not cool down at sun-set1 so fast as the land does2 and1 therefore1 the air in contact with it is warmer4 ,q4 ,why does not ,,water cool down so fast as ,,land8 ,a4 #ast--,because the surface of water is perpetually changing1 and as fast as one surface is made cold1 another is presented3 and #bndly--,the moment water is made cold it sinks1 and warmer portions of water rise to occupy its place3 therefore1 before the surface of water is cooled1 the whole volume must be made cold2 which is not the case with land4 ,q4 ,what is the cause of a pea-soup ,,london ,,fog8 ,a4 ,these fogs 7which occur generally in the winter time7 are occasioned thus3--,some current of air 7being suddenly cooled7 descends into the warm streets1 preventing the rise of the smoke1 and forcing it back in a mass towards the earth4 ,q4 ,why are there not ,,always ,,fogs every night8 ,a4 ,because the air will always hold in solution a certain quantity of vapour1 7which varies according to its temperature73 and when the air is not saturated with vapour1 it may be condensed without parting with it4 ,q4 ,why are there ,,ever ,,fogs at night8 ,a4 ,if the air be pretty well saturated with vapour during the day1 as soon as its capacity for holding vapour is lessened by the cold night1 it deposits some of the superabundant vapour in the form of dew or fog4 ,q4 ,why is there very ,,often a fog over ,,marshes and ,,rivers at night-time8 ,a4 ,the air of marshes is almost always near saturation2 and1 therefore1 the least depression of temperature1 will compel it to relinquish some part of its moisture in dew or fog4 ,q4 ,what is the ,,difference between ,,dew and ,,rain8 ,a4 ,in dew1 the condensation is made near the earth's surface3 ,in rain1 the drops fall from a considerable height2 but the cause of both is the same1 viz4--,,cold condensing the vapour of the air1 when it is near the point of saturation4 ,q4 ,why does ,,mist and ,,fog ,,vanish at sunrise8 ,a4 ,because the condensed particles are again changed into invisible vapour1 by the heat of the sun4 ,q4 ,what is the difference between a ,,mist and ,,fog8 ,a4 ,,mist is generally applied to vapours condensed on marshes1 rivers1 and lakes4 ,,fog is generally applied to vapours condensed on land1 especially if those vapours are laden with smoke4 ,q4 ,what is the reason why condensed vapour sometimes forms into ,,clouds1 and sometimes into ,,fog8 ,a4 ,if the surface of the ,,earth be hotter than the air1 then the vapour of the earth 7being chilled by the cold air7 becomes ,,fog3 but if the ,,air be hotter than the earth1 the vapour rises through the air1 and becomes ,,cloud4 ,q4 ,if cold air produces ,,fog1 why is it not foggy on a ,,frosty ,,morning8 ,a4 #ast--,because less vapour is formed on a frosty day2 and #bndly--,the vapour is frozen upon the ground before it can rise from the earth1 and becomes ,,hoar-,,frost4 ,q4 ,why are ,,fogs more general in ,,autumn than in spring8 ,a4 ,in spring the earth is not so hot as it is in autumn4 ,in ,,autumn the earth is generally warmer than the air2 and1 therefore1 the vapour 7issuing from the earth7 is condensed into fog by the chill air4 ,q4 ,why are ,,fogs more common in ,,valleys than on ,,hills8 ,a4 #ast--,because valleys contain more moisture than hills3 and #bndly--,they are not exposed to so much wind1 7which dissipates the vapour74 ,q4 ,how does ,,wind dissipate ,,fogs8 ,a4 ,either by blowing them away2 or else by dissolving them into vapour again4 ,q4 ,what is ,,hoar-,,frost8 ,a4 ,there are two sorts of hoar-frost3 #a4--;,,frozen ,,dew3 and #b4--;,,frozen ,,fog4 ,q4 ,what is the cause of the ,,ground hoar-,,frost1 or frozen ,,dew8 ,a4 ,very rapid radiation of heat from the earth2 in consequence of which1 the surface is so cooled down1 that it freezes the dew condensed upon it4 ,q4 ,why is ,,hoar-,,frost seen only after a very ,,clear ,,night8 ,a4 ,unless the night has been very clear indeed1 the earth will not have thrown off heat enough by radiation1 to freeze the vapour condensed upon its surface4 ,q4 ,why does ,,hoar-,,frost very often ,,cover the ,,ground and ,,trees1 when the water of rivers is not frozen8 ,a4 ,hoar-frost is not the effect of cold in the air1 but the cold of the earth 7produced by excessive radiation72 in consequence of which1 the dew 7condensed upon it7 is frozen4 ,q4 ,why is the ,,hoar-,,frost upon ,,grass and ,,vegetables much thicker than that upon lofty ,,trees8 ,a4 ,because the air 7resting on the surface of the ground7 is much colder after sun-set1 than the air higher up2 in consequence of which1 more vapour is condensed and frozen there4 ,q4 ,why is the ,,air 7resting on the surface of the ,,earth7 colder than that in the ,,higher regions8 ,a4 ,because the earth radiates more heat than the leaves of lofty trees2 and1 therefore1 condenses and freezes the vapour of the air more rapidly4 ,q4 ,why are ,,evergreens often ,,frost-,,bitten1 when lofty trees are ,,not8 ,a4 ,evergreens do not rise far above the surface of the earth2 and 7as the air contiguous to the earth is much colder than that in the higher regions7 therefore1 the low evergreen is often frost-bitten1 when the lofty tree is uninjured4 ,q4 ,why are ,,tomb-,,stones covered with ,,hoar-,,frost1 long after it has melted from every object around8 ,a4 ,white is a very bad absorbent of solar heat2 and1 therefore1 the white tomb-stone remains too cold to thaw the frost congealed upon its surface4 ,q4 ,why is there little or ,,no ,,hoar-,,frost under ,,shrubs and shadowy ,,trees8 ,a4 #ast--,because the leafy shrubs and trees arrest the process of radiation from the earth3 and #bndly--,shrubs and trees radiate a little heat towards the earth2 and1 therefore1 the ground beneath is never cold enough to congeal the little dew which rests upon it4 ,q4 ,what is the cause of that ,,hoar-,,frost which arises from ,,frozen ,,fog8 ,a4 ,the thick fog 7which invested the earth during the night7 is condensed by the cold frost of early morning1 and congealed upon every object with which it comes in contact4 ,,chapter ,,xvii4 #e4--;,,convection4 ,q4 ,what is meant by the ,,convection of ,,heat8 ,a4 ,heat communicated by being carried to another thing or place2 as the hot water resting on the bottom of a kettle1 carries heat to the water through which it passes4 7see p4 #bdf74 ,q4 ,are ,,liquids good ,,conductors of heat8 ,a4 ,no2 liquids are bad conductors2 and are1 therefore1 made hot by convection4 ,q4 ,why are ,,liquids ,,bad ,,conductors of heat8 ,a4 ,because heat converts a liquid into steam1 and flies off with the vapour1 instead of being conducted through the liquid4 ,q4 ,explain how ,,water is made ,,hot8 ,a4 ,the water nearest the fire is first heated1 and 7being heated7 rises to the top2 other cold water succeeds1 is also heated1 and rises in turn2 and this interchange keeps going on1 till all the water boils4 ,q4 ,why is ,,water in such continual ,,ferment1 when it is ,,boiling8 ,a4 ,this commotion is mainly produced by the ascending and descending currents of hot and cold water4 ,the escape of air from the water contributes also to increase this agitation4 ,q4 ,how do these two currents ,,pass each other8 ,a4 ,the hot ascending current passes close by the metal sides of the kettle2 while the cold descending current passes down the centre4 ,q4 ,why does ,,boiling ,,water ,,bubble8 ,a4 ,the bubbles are portions of steam 7formed at the bottom of the vessel7 which rise to the surface1 and escape into the air4 ,q4 ,why does a ,,kettle ,,run ,,over1 when the water ,,boils8 ,a4 ,as the heat insinuates itself between the particles of water1 it drives them asunder2 and 7as the particles of water are driven apart from each other7 the same vessel will no longer hold the expanded water1 and some runs over4 ,q4 ,why does a ,,kettle ,,sing1 when it is ,,about to ,,boil8 ,a4 ,water contains a great deal of air1 which 7being expanded by the heat of the fire7 escapes by fits through the spout of the kettle2 which sings in the same way as a trumpet does1 when a person blows in it4 ,q4 ,why does ,,water ,,boil8 ,a4 ,boiling is the effect of a more violent escape of air from the heated water2 when1 therefore1 the air is not permitted to escape1 water will never boil4 ,q4 ,why is ,,heat applied to the ,,bottom1 and not to the top of a ,,kettle8 ,a4 ,because the heated water always ascends to the surface1 heating the water through which it passes3 if1 therefore1 heat were applied to the top of a vessel1 the water below the surface would never be heated4 ,q4 ,as the lower part of a ,,grate is made ,,red-,,hot by the fire ,,above1 why would not the ,,water boil1 if fire were applied to the ,,top8 ,a4 ,the iron of a grate is an excellent conductor2 and1 therefore1 if one part be heated1 the heat is conducted to every other part3 but water is a very bad conductor1 and will not diffuse heat in a similar way4 ,q4 ,how do you know that ,,water is a ,,bad ,,conductor of heat8 ,a4 ,when a blacksmith immerses his red-hot iron in a tank of water1 the water which surrounds the red-hot iron is made boiling hot1 but the water below the surface remains quite cold4 ,q4 ,if you wish to ,,cool ,,liquids1 where should the cold be applied8 ,a4 ,to the top of the liquid2 because the cold portion will always descend1 and allow the warmer parts to come in contact with the cooling substance4 ,q4 ,does ,,boiling water get hotter by being ,,kept on the ,,fire8 ,a4 ,no2 not if the steam be suffered to escape4 ,q4 ,why does not boiling water get ,,hotter1 if the steam be suffered to ,,escape8 ,a4 ,because as fast as the water boils1 it is converted into steam2 and the steam carries away the additional heat1 as fast as it is communicated4 ,q4 ,is ,,steam visible or ,,invisible8 ,a4 ,steam is invisible2 but when it comes in contact with the air 7being condensed into small drops7 it instantly becomes visible4 ,q4 ,how do you know that ,,steam is ,,invisible8 ,a4 ,if you look at the spout of a boiling kettle1 you will find that the steam 7which issues from the spout7 is always invisible for about half an inch2 after which1 it becomes visible4 ,q4 ,why is the steam ,,invisible for only ,,half ,,an ,,inch1 and not either all ,,invisible or all ,,visible8 ,a4 ,the air is not able to condense the steam as it first issues from the spout1 but when it spreads and comes in contact with a larger volume of air1 the invisible steam is readily condensed into visible drops4 ,q4 ,why is our ,,breath ,,visible in winter-time8 ,a4 ,because it is condensed by the cold air into small drops1 which are visible to the eye4 ,q4 ,why do ,,steam-,,engines sometimes ,,burst8 ,a4 ,steam is very elastic2 and this elasticity increases in a greater proportion than the heat which produces it2 unless1 therefore1 some vent be freely allowed1 the steam heaves and swells1 till it bursts the vessel which confined it4 ,q4 ,what ,,becomes of the steam1 after it has been condensed8 ,a4 ,it is dissolved by the air1 and forms a part of its invisible vapour4 ,q4 ,is ,,air a good ,,conductor8 ,a4 ,no2 air is a very bad conductor1 and is heated 7like water7 by convection4 ,q4 ,how is a ,,room ,,warmed by a ,,stove8 ,a4 ,the air nearest the fire is made hot first2 the cold air descends1 is heated also1 and rises in turn2 and this goes on1 till all the air of the room is warmed4 ,q4 ,why are ,,fires placed on the ,,floor of a room1 and not towards the ,,ceiling8 ,a4 ,as heated air always ascends1 if the fire were not near the floor1 the lower part of the air 7which we want to be the warmest7 would never be benefited by the fire at all4 ,q4 ,if you take a ,,poker out of the fire1 and hold the ,,hot ,,end ,,downwards1 why is the ,,handle so intensely ,,hot8 ,a4 ,because the hot end of the poker heats the air around it1 and this hot air 7in its ascent7 scorches the poker1 and the hand which holds it4 ,q4 ,how should a ,,red-,,hot ,,poker be carried so as not to ,,burn our fingers8 ,a4 ,with the hot end upwards2 because then the air 7heated by the poker7 would not pass over our hand to scorch it4 ,q4 ,why is a ,,poker 7resting on the ,,fender7 ,,cold2 but if it leans against the ,,stove1 intensely warm8 ,a4 ,the poker is an excellent conductor2 while1 therefore1 it rests against the hot stove1 the heat of the stove is conducted into the poker2 but when it rests on the fender1 it does not come in contact with the hot stove4 ,q4 ,why does it feel so ,,cold1 when it rests on the ,,fender8 ,a4 ,not being so warm as our hand1 it imbibes the heat from it with such rapidity1 that our loss of heat is palpable1 and produces the sensation of coldness4 ,q4 ,why are ,,flues 7which are carried through a church or room7 always ,,blackened with ,,black ,,lead8 ,a4 ,in order that the heat of the flue may be more readily diffused throughout the room4 ,black lead radiates heat more freely than any other known substance4 ,q4 ,why do country people touch the thick end of an ,,egg with their ,,tongue1 to know if it be ,,stale or not8 ,a4 ,the thick end of an egg always contains a little air 7between the shell and the white72 but1 when the egg is stale1 the white shrinks1 and the air expands4 ,q4 ,how can the ,,tongue tell from this1 whether the egg be ,,stale or ,,fresh laid8 ,a4 ,as air is a very bad conductor1 if the egg be stale1 it will feel much warmer to the tongue1 than if it be new-laid4 ,q4 ,why will the big end of an egg feel ,,warmer to the tongue1 because it contains more ,,air8 ,a4 ,as air is a bad conductor1 it will draw off the heat of the tongue very slowly1 and1 therefore1 appear warm2 but when there is only a very little air in the egg 7as the white is a pretty good conductor71 the heat of the tongue will be more rapidly drawn off1 and the egg appear colder4 ,q4 ,why is the large ,,end of an ,,egg ,,cracked1 when put into a saucepan to boil8 ,a4 ,to let the air out2 if the large end were not cracked1 the air 7expanded by the heat7 would enter the white of the egg1 and give it an offensive taste4 ,,part ,,ii4 ,,air4 ,,chapter ,,xviii4 ,q4 ,of what is atmospheric ,,air composed8 ,a4 ,principally of two gases1 oxygen and nitrogen2 mixed together in the following proportion3 viz4 #a part of oxygen1 to #d parts of nitrogen4 ,q4 ,what are the uses of the ,,oxygen of the air8 ,a4 ,it is the oxygen of the air which supports combustion1 and sustains life4 ,q4 ,what is meant when it is said1 that the ,,oxygen of the air ,,supports ,,combustion8 ,a4 ,it means this2 that it is the oxygen of the air which makes fuel burn4 ,q4 ,how does the ,,oxygen of the air make ,,fuel ,,burn8 ,a4 ,the fuel being decomposed 7by heat7 into hydrogen and carbon2 the carbon combines with the oxygen of the air1 and produces combustion4 ,q4 ,what does the combination of carbon and oxygen produce8 ,a4 ,the carbon of the fuel combining with the oxygen of the air makes ,,carbonic ,,acid ,,gas4 7see pp4 #cf1 #cg74 ,q4 ,what becomes of the ,,hydrogen of the ,,fuel8 ,a4 ,hydrogen 7being very inflammable7 burns with a blaze1 and is the cause of the flame which is produced by combustion4 7see p4 #cd74 ,q4 ,what becomes of the ,,nitrogen of the air1 amidst all these changes and combinations8 ,a4 ,the nitrogen of the air escapes1 and is absorbed by the leaves of grass1 trees1 and various other vegetables4 ,q4 ,what is meant when it is said1 that ,,oxygen ,,sustains ,,life8 ,a4 ,it means this3 if a person could not inhale oxygen1 he would die4 ,q4 ,what ,,good does this inspiration of ,,oxygen do8 ,a4 #ast--,it gives vitality to the blood3 and #bndly--,it is the cause of animal heat4 ,q4 ,how is ,,food converted into ,,blood8 ,a4 ,after it is swallowed1 it is dissolved in the stomach into a grey pulp2 it then passes into the intestines1 and is converted by the bile into a milky substance 7called chyle74 ,q4 ,what ,,becomes of the milky substance1 called ,,chyle8 ,a4 ,it is absorbed by the vessels called lacteals1 and poured into the veins on the left side of the neck4 ,q4 ,what becomes of the chyle ,,after it is ,,poured into the ,,veins8 ,a4 ,it then mingles with the blood1 and is itself converted into blood4 ,q4 ,how does the ,,oxygen we inhale ,,mingle with the ,,blood8 ,a4 ,the oxygen of the air mingles with the blood in the lungs1 and converts it into a bright red colour4 ,q4 ,what colour is the blood ,,before it is oxydized in the lungs8 ,a4 ,a dark purple4 ,the oxygen turns it to a bright red4 ,q4 ,why are ,,persons so ,,pale who live in ,,close ,,rooms and ,,cities8 ,a4 ,the blood derives its redness from the oxygen of the air inhaled2 but1 as the air in close rooms and cities is not fresh1 it is deficient in oxygen1 and cannot turn the blood to a beautiful bright red4 ,q4 ,why are ,,persons who live in the ,,open ,,air and in the country1 of a ,,ruddy complexion8 ,a4 ,as the blood derives its bright red colour from the oxygen of the air inhaled1 therefore1 country-people 7who inhale fresh air7 are more ruddy than citizens4 ,q4 ,why is not the air in ,,cities so ,,fresh as that in the ,,country8 ,a4 ,because it is impregnated with the breath of its numerous inhabitants1 the odour of its sewers1 the smoke of its fires1 and many other impurities4 ,q4 ,how does the ,,combination of ,,oxygen with the ,,blood produce animal ,,heat8 ,a4 ,the principal element of the blood is carbon1 which 7combining with the oxygen of the air inhaled7 produces carbonic acid gas1 7in the same way as burning fuel47 7see pp4 #cc1 #cf74 ,q4 ,what becomes of the ,,nitrogen of the air1 after the oxygen enters the blood8 ,a4 ,the nitrogen is exhaled1 and taken up by the leaves of trees and other vegetables4 7see p4 #ce74 ,q4 ,why does the vitiated air 7after the oxygen has been absorbed7 ,,come ,,out of the ,,mouth1 and not sink into the stomach8 ,a4 ,the vitiated air 7being heated by the heat of the body7 ascends naturally1 and passes by the heavier fresh air 7which we inhale7 without obstruction or injury4 ,q4 ,if 7both in combustion and in respiration7 the ,,oxygen of the air is ,,consumed1 and the ,,nitrogen ,,rejected--,why are not the ,,proportions of the ,,air ,,destroyed8 ,a4 ,because the upper surface of vegetable leaves 7during the day7 gives out oxygen and absorbs nitrogen1 and thus the proper balance is perpetually restored4 ,q4 ,show how ,god has made ,,animal and ,,vegetable life ,,dependent on each other8 ,a4 ,animals require oxygen to keep them alive1 and draw it from the air by inspiration2 the upper surface of leaves 7all day long7 gives out oxygen1 and thus supplies the air with the very gas required by man and other animals4 ,q4 ,do not animals ,,exhale the ,,very ,,gas needed by ,,vegetables8 ,a4 ,yes2 animals reject the nitrogen of the air 7as not suited to the use of animal life71 but vegetables absorb it1 as it is the food they live on2 and thus the vegetable world restores the equilibrium of the air1 disturbed by man and other animals4 ,q4 ,is ,,air a good ,,conductor8 ,a4 ,no2 air is a very bad conductor4 ,q4 ,how is ,,air ,,heated8 ,a4 ,by convective currents4 ,q4 ,what are meant by ,,convective ,,currents8 ,a4 ,when a portion of air is heated1 it rises upward in a current1 carrying the heat with it3 other colder air succeeds1 and 7being heated in a similar way7 ascends also2 and these are called convective currents4 7,convective currents2 so called from the ,latin words1 cum-vectus 7carried with7 because the heat is carried with the current47 ,q4 ,is ,,air ,,heated by the ,,rays of the ,,sun8 ,a4 ,no2 air is not heated 7in any sensible degree7 by the action of the sun's rays passing through it4 ,q4 ,why then is the ,,air ,,hotter on a ,,sunny ,,day1 than on a ,,cloudy one8 ,a4 ,on a fine day1 the sun heats the surface of the earth1 and the air 7resting on the earth7 is heated by contact2 as soon as it is heated it ascends1 and other air succeeding is heated in a similar way1 till all is heated by convection4 ,q4 ,if ,,air be a ,,bad ,,conductor1 why does hot ,,iron get ,,cold1 by being ,,exposed to the ,,air8 ,a4 ,a piece of hot iron exposed to the air1 is made cold--#ast--,by convection2 and #bndly--,by radiation4 ,q4 ,how is hot iron 7exposed to the air7 made cold by ,,convection8 ,a4 ,the air around the iron 7being intensely heated by contact7 rapidly ascends1 carrying some of its heat with it3 other air succeeds1 absorbs more heat1 ascends1 and gives place to that which is colder2 till the hot iron is cooled completely down4 ,q4 ,how is hot iron cooled by ,,radiation8 ,a4 ,while the heat of the iron is being carried off by convection1 it is throwing off heat 7on all sides7 by radiation4 ,q4 ,what is meant by ,,radiation8 ,a4 ,heat emitted 7in all directions7 from any surface1 by innumerable rays4 ,q4 ,why is ,,broth ,,cooled by being left exposed to the ,,air8 ,a4 ,hot broth throws off some heat by radiation2 but it is mainly cooled down by convection4 ,q4 ,how is hot ,,broth cooled down by ,,convection8 ,a4 ,the air resting on the hot broth 7being heated7 ascends2 colder air succeeding absorbs more heat1 and ascends also2 and this process is repeated1 till the broth is made cool4 ,q4 ,why is hot ,,tea and ,,broth ,,cooled faster1 for being ,,stirred about8 ,a4 #ast--,the agitation assists the liquor in bringing its hottest particles to the surface3 #bndly--,the action of stirring agitates the air1 and brings it quicker to the broth or tea3 and #crdly--,as the hottest particles are more rapidly brought into contact with the air1 therefore convection is more rapid4 ,q4 ,why is ,,hot ,,tea1 c4 cooled more rapidly by ,,blowing it8 ,a4 ,because the heated air is blown more rapidly away2 in consequence of which1 cold air more rapidly succeeds to absorb heat from the surface of the tea or broth4 ,q4 ,if a shutter be closed in the day-time1 the stream of light 7piercing through the crevice7 seems in ,,constant ,,agitation4 ,,why is this8 ,a4 ,the air 7in the sun-beam piercing through the shutter-crevice7 is more heated1 than that in its neighbourhood2 the convective current1 therefore1 is distinctly seen1 where little motes and particles of dust are thrown into agitation by the violence of the current4 ,q4 ,why is the ,,gallery of a ,,church or theatre ,,hotter than the ,,aisle or pit8 ,a4 ,the hot air ascends from the bottom to the top of the room1 and cold air 7from the doors and windows7 flies to the bottom to supply its place4 ,q4 ,why does a ,,crowded ,,room produce ,,head-,,ache8 ,a4 ,because we breathe air vitiated by the crowd4 ,q4 ,how does a ,,crowd ,,vitiate the ,,air of a ,,room8 ,a4 ,whenever we breathe1 the elements of the air are separated in the lungs1 some of the oxygen is absorbed by the blood1 and some of it is converted into carbonic acid gas1 and exhaled with the nitrogen4 ,q4 ,is ,,all the ,,nitrogen ,,rejected by the lungs8 ,a4 ,yes2 all the nitrogen of the air is always exhaled4 ,q4 ,what is ,,carbonic ,,acid ,,gas8 ,a4 ,as carbon has a very great affinity for oxygen1 therefore1 whenever they are exposed to heat1 they combine1 and form carbonic acid gas 7or what is vulgarly called fixed air74 ,q4 ,is ,,carbonic ,,acid ,,gas wholesome8 ,a4 ,no2 it is quite fatal to animal life2 and whenever it is inhaled1 it acts like a narcotic poison1 7producing drowsiness which ends in death74 ,q4 ,why is a ,,crowded ,,room ,,unwholesome8 ,a4 ,because the oxygen of the air is either absorbed by the lungs1 or substituted for carbonic acid gas1 which is a noxious poison4 ,q4 ,mention the historical circumstances1 so well known in connection with the ,,black ,,hole of ,,calcutta4 ,a4 ,in the reign of ,george ,,ii1 the ,raja 7or ,prince7 of ,bengal#ab marched suddenly to ,calcutta to drive the ,english from the country2 as the attack was unexpected1 the ,english were obliged to submit1 and #adf persons were taken prisoners4 #ab ,the ,sur ,raja1 at ,dowlat2 a young man of violent passions1 who had but just succeeded to the throne4 ,a4 ,d4 #agef4 ,q4 ,what became of these prisoners8 ,a4 ,they were driven into a place about #ah feet square1 and #ae or #af feet in height1 with only two small grated windows4 #abc of the prisoners died in one night2 and 7of the #bc who survived7 the larger portion died of putrid fevers1 after they were liberated in the morning4 ,q4 ,why were #abc persons ,,suffocated in a few hours1 from confinement in this close hot ,,prison-hole8 ,a4 ,because the oxygen of the air was soon consumed by so many lungs1 and its place supplied by carbonic acid exhaled by the hot breath4 ,q4 ,why do persons in a crowded ,,church feel ,,drowsy8 ,a4 #ast--,because the crowded congregation inhale a large portion of the oxygen of the air1 which alone can sustain vitality and healthy action3 and #bndly--,the air of the church is impregnated with carbonic acid gas1 which 7being a strong narcotic7 produces drowsiness in those who inhale it4 ,q4 ,why did the captives in the ,,black ,,hole die ,,sleeping8 ,a4 #ast--,because the absence of oxygen quickly affects the vital functions1 depresses the nervous energies1 and produces a lassitude which ends in death3 and #bndly--,the carbonic acid gas inhaled by the captives 7being a narcotic poison7 would also produce drowsiness and death4 ,q4 ,why do ,,persons1 who are so much in the ,,open ,,air1 enjoy the best ,,health8 ,a4 ,because the air they inhale is much more pure4 ,q4 ,why is ,,country ,,air more ,,pure than the air in ,,cities8 ,a4 #ast--,because there are fewer inhabitants to vitiate the air3 #bndly--,there are more trees to restore the equilibrium of the vitiated air3 and #crdly--,the free circulation of air keeps it pure and wholesome 7in the same way as running streams are pure and wholesome1 while stagnant waters are the contrary74 ,q4 ,why does the ,,scantiness of a country ,,population render the ,,country ,,air more ,,pure8 ,a4 ,because the fewer the inhabitants1 the less carbonic acid will be exhaled2 and thus country people will inhale pure oxygen1 instead of air impregnated with the narcotic poison1 called carbonic acid gas4 ,q4 ,why do ,,trees and ,,flowers help to make country ,,air ,,wholesome8 ,a4 ,because trees and flowers absorb the carbonic acid generated by the lungs of animals1 putrid substances1 and other noxious exhalations4 ,q4 ,why is the ,,air of ,,cities ,,less wholesome than ,,country air8 ,a4 #ast--,because there are more inhabitants to vitiate the air3 #bndly--,the sewers1 drains1 bins1 and filth of a city1 very greatly vitiate the air3 #crdly--,the streets and alleys prevent a free circulation3 and #dthly--,besides all this1 there are fewer trees to absorb the excess of carbonic acid gas1 and restore the equilibrium4 ,q4 ,why are ,,persons who live in ,,close ,,rooms and crowded ,,cities1 generally ,,sickly8 ,a4 ,because the air they breathe is not pure1 but is both defective in oxygen1 and impregnated with carbonic acid gas4 ,q4 ,where does the ,,carbonic ,,acid of close ,,rooms and ,,cities ,,come from8 ,a4 ,from the lungs of the inhabitants1 the sewers1 drains1 and so on3 besides1 trees and gardens are not numerous enough to absorb the noxious gas as fast as it is generated4 ,q4 ,what ,,becomes of the ,,carbonic ,,acid of crowded cities8 ,a4 ,some of it is absorbed by vegetables1 and the rest is blown away by the wind1 and diffused through the whole volume of the air4 ,q4 ,does not this constant diffusion of carbonic acid affect the ,,purity of the ,,whole ,,air8 ,a4 ,no2 because after it is thus diffused1 it is carried to various lands1 and absorbed in its passage by the vegetable world4 ,q4 ,why do persons who ascend in balloons feel intense pain in their eyes and ears8 ,a4 ,because the air of the upper regions is more rarefied than the air on the earth2 and the air inside their bodies 7seeking to become of the same rarity7 bursts through their eyes and ears1 producing an intense pain4 ,q4 ,why is it often ,,painful1 and difficult to ,,breathe1 on a ,,mountain top8 ,a4 ,because the pressure of air on the mountain top is not so great as on the plain2 and the air inside our bodies 7seeking to become of the same rarity7 bursts through the pores of the body1 and produces great pain4 ,q4 ,why do we feel ,,oppressed just ,,previous to a ,,storm8 ,a4 ,because the air is greatly rarefied by heat and vapour2 and the air inside us 7seeking to become of the same rarity7 produces an oppressive and suffocating feeling4 ,q4 ,why do ,,divers suffer great pain in their eyes and ears under water8 ,a4 ,because the air at the bottom of the sea is more dense than the air on the surface2 and while the air inside the diver's body is settling into the same density1 he feels oppressed with pain1 especially in the ears4 ,q4 ,why is this ,,pain felt especially about the ,,ears of a ,,diver8 ,a4 ,the ear is fitted with a small membrane called the drum 7or tympanum71 through which the dense air bursts1 and the rupture very often produces incurable deafness4 ,q4 ,why do our ,,corns ache just previous to ,,rain8 ,a4 ,previous to rain1 the density of air is greatly lowered 7as every one knows from the fall of the barometer72 in consequence of an unequal pressure1 our feet swell2 but the hard corn1 not being elastic1 is painfully stretched and pressed4 7,some of this pain is due to electricity47 ,q4 ,why do ,,cellars feel ,,warm in ,,winter8 ,a4 ,as the external air has not free access into cellars1 they remain at a pretty even temperature1 which 7in winter time7 is about #aj degrees warmer than the external air4 ,q4 ,why do ,,cellars feel ,,cold in ,,summer time8 ,a4 ,as the external air has not free access into cellars1 they remain at a pretty even temperature1 which 7in summer time7 is about #aj degrees colder than the external air4 ,q4 ,why does lightning strike the ,,oak-tree more frequently than any ,,other tree8 ,a4 #ast--,because the grain of the oak1 being closer than that of any other tree1 renders it a better conductor3 and #bndly--,the sap of the oak contains a large quantity of iron in solution1 which is a most admirable conductor of lightning4 ,q4 ,why does ,,air rust ,,iron8 ,a4 ,the oxygen of the air combines with the surface of the iron1 and produces oxide of iron1 which is generally called rust4 ,this rust is a species of combustion4 ,q4 ,why does hot iron ,,scale and ,,peel off1 when struck with a ,,hammer8 ,a4 ,the oxygen of the air very readily unites with the surface of the hot iron1 and forms a metallic oxide 7or rust7 which scales off when struck with a hammer4 ,q4 ,does iron ,,rust in ,,dry air8 ,a4 ,no2 iron undergoes no change in dry air4 ,q4 ,why do ,,stoves and ,,fire-,,irons become ,,rusty1 in rooms which are not ,,occupied8 ,a4 ,because the air is damp2 and moist air oxidizes 7or rusts7 iron and steel4 ,q4 ,in what part of the year is it most difficult to keep ,,stoves and ,,fire-,,irons ,,bright8 ,a4 ,in autumn and winter2 because the capacity of the air for holding water being on the decrease1 its vapour is deposited on every-thing with which it comes in contact4 ,q4 ,why does ,,greasing iron prevent its becoming ,,rusty8 ,a4 ,because grease prevents the humidity of air from coming in contact with the surface of the iron4 ,q4 ,why do not ,,stoves rust so frequently as ,,pokers and ,,tongs8 ,a4 ,because stoves are generally covered with plumbago1 or black lead4 ,q4 ,what is plumbago1 or black lead8 ,a4 ,a mixture of charcoal and iron filings4 ,a most excellent varnish to prevent rust is made of #a pint of fat oil varnish1 mixed with #e pints of highly rectified spirits of turpentine1 rubbed on the iron or steel with a piece of sponge4 ,this varnish may be applied to bright stoves and even mathematical instruments1 without injuring their delicate polish4 ,q4 ,why does ornamental ,,steel 7of a purple or ,,lilac colour7 rust more readily than polished ,,white steel8 ,a4 ,because the lilac tinge is produced by partial oxidation2 and the process which forms rust has1 therefore1 already commenced4 ,q4 ,how can lilac ,,steel be kept ,,free from ,,rust8 ,a4 ,by keeping it in a very dry place2 for then no additional oxygen will come in contact with it1 to increase its amount of rust4 ,q4 ,do any ,,other metals 7besides iron7 combine rapidly with oxygen8 ,a4 ,yes2 copper1 lead1 mercury1 and even silver to some extent4 ,q4 ,why does ,,copper ,,tarnish8 ,a4 ,the tarnish of copper is caused by its oxidation2 that is1 the oxygen of the air combines with the surface of the copper1 and instead of rusting it1 covers it with a dark tarnish4 ,q4 ,why does ,,lead lose its ,,brightness1 and become ,,dull and of a ,,darker hue1 by being exposed to the air8 ,a4 ,the vapour of the air combines with the lead1 and oxidizes its surface2 but instead of becoming rusty1 the surface becomes dull1 and of a darker colour4 ,q4 ,why is it difficult to keep ,,silver ,,bright8 ,a4 ,because the vapour of the air oxidizes its surface1 and tarnishes it4 ,q4 ,why do silver ,,tea-,,pots and ,,spoons tarnish more quickly than silver ore or bullion8 ,a4 ,because alloy 7of some baser metal7 is used to make it more hard and lasting2 and this alloy oxidizes more quickly than silver itself4 ,q4 ,why does ,,german silver turn a dingy yellow in a few hours8 ,a4 ,german silver has a great affinity for oxygen1 and shows its oxidation by a sickly yellow tarnish1 instead of rust4 ,q4 ,if quicksilver 7or mercury7 is tarnished like copper and lead1--,why does it preserve its ,,brilliancy in ,,barometers and ,,thermometers8 ,a4 ,because air is excluded from it1 and no moisture comes in contact with it to oxidize 7or tarnish it74 ,q4 ,is ,,gold affected by the atmosphere8 ,a4 ,not readily3 gold will never combine with oxygen of itself1 7or without aid74 ,q4 ,which of the ,,metals is capable of resisting oxidation altogether8 ,a4 ,plat'inum2 in consequence of which1 the graduated arcs of delicate instruments for observation are made of plat'inum instead of any other metal4 ,q4 ,why is ,,plat',,inum used for the graduated arcs of delicate mathematical instruments1 instead of any other metal8 ,a4 ,because it will never oxidize2 but retain its bright surface in all weathers free from both rust and tarnish4 ,q4 ,before plat'inum was discovered1 which of the metals was employed for the same purpose8 ,a4 ,gold4 ,platinum1 7a white metal71 so called from plata1 the ,spanish word for silver4 ,it was first introduced into ,england by ,mr4 ,wood1 7,a4 ,d4 #agdi7 from ,south ,america4 ,q4 ,for what other ,,scientific purposes is ,,plat',,inum now used8 ,a4 ,for crucibles in which acids are employed1 and for galvanic batteries4 ,q4 ,why are ,,crucibles 7in which acids are employed7 made of ,,plat',,inum8 ,a4 ,because the acid would act upon other metals1 or upon glass1 and prevent the experimenter's success4 ,q4 ,which of the ,,metals have the ,,greatest affinity to ,,oxygen8 ,a4 ,those called potassium and sodium4 ,potassium and sodium derive their names from potash and soda4 ,potassa is the oxide of potassium2 and soda is the oxide of sodium4 ,q4 ,how is the affinity of potassium and sodium for oxygen shewn8 ,a4 ,they decompose water the moment they are brought into contact with it4 ,q4 ,what effect has ,,potassium on ,,water8 ,a4 ,it catches fire the moment it is thrown into water1 and burns with a vivid flame1 which is still further increased by the combustion of hydrogen separated from the water4 7,n4,b4 ,water is composed of oxygen and hydrogen2 and potassium separates the two gases47 ,q4 ,what effect has ,,sodium on ,,water8 ,a4 ,it does not take fire as potassium does1 but undergoes very rapid oxidation4 ,q4 ,is the ,,furr of ,,kettles an oxide8 ,a4 ,no2 the furr 7or deposit of boiling water7 is a precipitate of lime and mineral salt1 separated from the water by the process of boiling4 ,q4 ,is not this ,,furr of boiling water often ,,dangerous8 ,a4 ,yes2 especially in tubular boilers1 such as those employed in railways4 ,q4 ,why is this ,,furr especially ,,troublesome in ,,railway engines8 ,a4 ,because it is a bad conductor of heat2 in consequence of which1 it hinders the evaporating effect of the fire1 and prevents the economy of fuel4 ,q4 ,why is this ,,furr especially ,,dangerous in ,,railway engines8 ,a4 ,because when it is deposited in the boilers1 they are likely to become over-heated2 and then explosion will take place from the sudden generation of highly elastic steam4 ,q4 ,why cannot ,,railway engines be fed with ,,brackish ,,water8 ,a4 ,because brackish water contains mineral salt1 which makes a much larger deposit of furr1 than that which contains only vegetable matter4 ,,chapter ,,xix4 ,,carbonic ,,acid ,,gas4 ,q4 ,what is ,,choke ,,damp8 ,a4 ,carbonic acid gas accumulated at the bottom of wells and pits1 which renders them noxious1 and often fatal4 ,q4 ,why is not this carbonic acid ,,taken ,,up by the ,,air1 and ,,diffused1 as it is in cities8 ,a4 ,because 7being heavier than common air7 it cannot rise from the well or pit2 and no wind can get to it to blow it away4 ,q4 ,is ,,carbonic ,,acid ,,wholesome8 ,a4 ,no2 it is fatal to animal life1 when inhaled through the mouth2 acting on the stomach1 as a narcotic poison 7i4 e4 a poison which produces death from drowsiness74 ,q4 ,how can any one ,,know1 if a place be infested with ,,carbonic ,,acid ,,gas8 ,a4 ,if a pit or well contain carbonic acid1 a candle 7let down into it7 will be instantly extinguished4 ,the rule1 therefore1 is this--,where a candle will burn1 a man can live2 but what will extinguish a candle1 will also destroy life4 ,q4 ,why does a ,,miner lower a ,,candle into a mine1 before he descends8 ,a4 ,because the candle will be extinguished1 if the mine contains carbonic acid gas3 but if the candle is not extinguished1 the mine is safe1 and the man may fearlessly descend4 ,q4 ,why are ,,persons sometimes ,,killed1 by leaning over ,,beer ,,vats8 ,a4 ,vats 7where beer has been made7 contain a large quantity of carbonic acid gas1 produced by the vinous fermentation of the beer2 and when a man incautiously leans over a beer vat1 and inhales the carbonic acid1 he is immediately killed thereby4 ,q4 ,why are ,,persons often ,,killed1 who enter ,,beer ,,vats to clean them8 ,a4 ,carbonic acid 7being heavier than atmospheric air7 often rests upon the bottom of a vat3 when1 therefore1 a person enters the vat1 and stoops to clean the bottom1 he inhales the pernicious gas1 which kills him4 ,q4 ,why are the ,,jungles of ,jarva and ,hindostan so ,,fatal to life8 ,a4 ,because vast quantities of carbonic acid are thrown off by decaying vegetables2 and 7as the wind cannot penetrate the thick brushwood to blow it away7 it settles there1 and destroys animal life4 ,q4 ,why are ,,persons sometimes ,,killed by having a ,,charcoal ,,fire in their bed-rooms8 ,a4 ,when charcoal is burned1 the carbon of the charcoal unites with the oxygen of the air1 and forms carbonic acid gas1 which is a narcotic poison4 ,q4 ,why does the carbonic acid gas of a ,,charcoal ,,fire ,,rise and ,,disperse itself about the room2 whereas the carbonic acid gas of a ,,beer ,,vat ,,settles near the ,,floor8 ,a4 ,the carbonic acid gas of a charcoal fire is heated by the combustion of the fuel1 and rises2 but the carbonic acid gas of a beer vat is not heated1 and1 therefore1 rests on the bottom of the vat4 ,q4 ,why do persons throw ,,lime into ,,bins to ,,prevent their offensive ,,smell1 in summer time8 ,a4 ,bins contain large quantities of carbonic acid gas1 which readily combines with lime1 and produces carbonate of lime1 which is entirely free from all offensive odour4 ,q4 ,why do persons throw ,,lime into ,,sewers in summer time8 ,a4 ,sewers 7like bins7 contain large quantities of carbonic acid1 which readily combines with lime1 and produces carbonate of lime2 and thus the offensive gas of the sewer is neutralized4 ,q4 ,can carbonic acid be removed in any way ,,besides by ,,lime8 ,a4 ,yes2 water thrown into a pit will disperse the carbonic acid4 ,q4 ,what effect has ,,water on ,,carbonic ,,acid ,,gas8 ,a4 ,water 7under pressure7 absorbs carbonic acid gas2 and parts with it 7when the pressure is removed7 in the form of ,,effervescence4 ,q4 ,why does ,,aerated ,,water effervesce1 when the ,,cork is removed8 ,a4 ,while the cork was fastened down1 the water absorbed the carbonic acid2 but the moment the pressure is removed 7by taking out the cork7 the gas is given out with effervescence4 ,q4 ,why does ,,soda ,,water effervesce8 ,a4 ,soda water contains #h times its own bulk of carbonic acid gas1 which makes its escape in effervescence1 the moment that the cork is removed4 ,q4 ,why does ,,ginger ,,pop fly about in froth1 when the string of the cork is cut8 ,a4 ,all vinous fermentation produces carbonic acid gas4 ,while the cork is fast1 the water of the liquor absorbs the carbonic acid2 but the moment that the pressure is removed1 the gas is given off in effervescence4 ,q4 ,why does ,,bottled ,,ale froth1 more than ,,draught ale8 ,a4 ,because the pressure is greater in a bottle than in a tub which is perpetually tapped3 and effervescence is always produced in proportion to the pressure4 ,q4 ,why does bottled ,,ale and ,,porter become ,,lively and ,,frothy by being ,,set before the ,,fire8 ,a4 ,the heat of the fire expands the air 7between the liquid and the cork71 and as this air expands1 it presses the liquid down1 which causes effervescence4 ,q4 ,what produces the ,,froth of ,,bottled ,,porter8 ,a4 ,the carbonic acid gas1 produced by its vinous fermentation2 which is absorbed by the liquor so long as the bottle is well corked1 but is given off in froth as soon as the pressure of the cork is removed4 ,q4 ,what gives the pleasant ,,acid taste to soda water1 ginger beer1 champagne1 and cider8 ,a4 ,the presence of carbonic acid1 generated by fermentation1 and liberated by effervescence when the pressure of the cork is removed4 ,q4 ,why does fresh ,,spring ,,water ,,sparkle1 when poured from one vessel to another8 ,a4 ,because fresh spring and pump water contain carbonic acid2 and it is the presence of this gas which makes the water sparkle4 ,q4 ,what is the ,,fermentation of ,,beer and ,,wine8 ,a4 ,the production of carbonic acid gas and al'cohol4 ,q4 ,how is ,,carbonic ,,acid ,,gas produced by ,,fermentation8 ,a4 ,malt and fruit both contain sugar2 and sugar consists of carbon1 oxygen1 and hydrogen4 ,in fermentation1 a part of the carbon and oxygen of the sugar escape1 in the form of carbonic acid gas4 ,carbonic acid gas is a compound of carbon and oxygen1 in the following proportions3--#c lbs4 of carbon and #h lbs4 of oxygen will form #aa lbs4 of carbonic acid gas4 ,now1 #ajj lbs4 of white sugar contains #dc lbs4 of carbon2 #ej lbs4 of oxygen2 and #g lbs4 of hydrogen4 ,q4 ,how is ,,al',,cohol produced by ,,fermentation8 ,a4 ,the hydrogen of the sugar combines with the residue of the oxygen and carbon to form ,,al',,cohol4 ,q4 ,what is ,,al',,cohol8 ,a4 ,al'cohol is the spirit of wine or beer1 obtained by fermentation4 7#ajj gallons of alcohol consist of #ch gallons of oxygen2 #dc-a_/b of carbon2 #ae of hydrogen2 and #c-a_/b of nitrogen47 ,q4 ,why is ,,barley ,,malted8 ,a4 ,because germination is produced by the artificial heat2 and in germination the starch of the grain is converted into sugar4 ,q4 ,how is barley malted8 ,a4 ,the barley is moistened with water1 and heaped up2 by which means1 great heat is produced1 which makes the barley sprout4 ,q4 ,why is not the ,,barley suffered to ,,grow1 as well as ,,sprout8 ,a4 ,plants in the germ contain more sugar than in any other state2 as soon as the germ puts forth shoots1 the sugar of the plant is consumed1 to support the shoot4 ,q4 ,how is ,,barley ,,prevented from ,,shooting1 in the process of ,,malting8 ,a4 ,the barley is put into a kiln as soon as it sprouts2 and the heat of the kiln checks or destroys the young shoot4 ,q4 ,why is ,,yeast put into ,,beer to make it ,,work8 ,a4 ,yeast supplies the beer with nitrogen1 which is one of the ingredients of alcohol4 ,alcohol consists of oxygen1 carbon1 and hydrogen1 7obtained from the sugar of malt71 and nitrogen1 7obtained from yeast74 ,q4 ,why is it ,,not needful to put ,,yeast into ,,wine8 ,a4 ,because fruit contains carbon1 hydrogen1 oxygen1 and nitrogen1 in the form of gluten2 and1 therefore1 ferments spontaneously4 7,gluten is explained fully in the ,appendix4--,turn to the word in the ,index47 ,q4 ,does not ,,malt contain carbon1 hydrogen1 oxygen1 and nitrogen1 as well as ,,fruit8 ,a4 ,no2 the sugar of malt contains carbon1 hydrogen1 and oxygen1 but no nitrogen2 in consequence of which1 yeast 7which contains nitrogen7 is added to the wort4 ,q4 ,why do ,,not ,,grapes ferment while they hang on the ,,vine8 ,a4 #ast--,because the skin lets out the water of the pulp1 which causes the grapes to shrivel and dry up3 and #bndly--,the skin prevents the admission of oxygen into the pulp1 from the air without4 ,q4 ,what is the ,,froth or ,,scum of fermented ,,liquors8 ,a4 ,carbonic acid gas1 which 7being heavier than common air7 settles on the top of the liquor1 in the form of scum4 ,q4 ,why does a small piece of raw ,,meat1 or a few ,,raisins improve ,,flat ,,beer8 ,a4 #ast--,because they supply it with nitrogen to form it into al'cohol4 #bndly--,as the raw meat1 c4 putrifies1 it gives off carbonic acid gas into the beer1 which gives it life4 ,q4 ,why is ,,beer ,,flat1 if the cask be open too long8 ,a4 ,because too much of the carbonic acid gas 7produced by fermentation7 is suffered to escape4 ,q4 ,how is the ,,carbonic ,,acid ,,gas of ,,beer generated8 ,a4 ,the saccharine 7or sugar7 of the malt is converted by fermentation into carbonic acid gas and alcohol4 ,q4 ,why does ,,beer turn ,,flat1 if the ,,vent ,,peg be left ,,out of the tub8 ,a4 ,because the carbonic acid gas escapes through the vent hole4 ,q4 ,why will ,,not beer ,,run ,,out of the tub1 till the ,,vent ,,peg is taken out8 ,a4 ,when the tap is turned1 air rushes through the tap into the bottom of the tub1 and holds the liquor in4 ,the upward pressure of air is illustrated by the following simple experiment3--,fill a wine-glass with water2 cover the top of the glass with a piece of writing paper2 turn the glass topsy turvy1 and the water will not run out4 ,the paper is used merely to give the air a medium sufficiently dense to act against4 ,q4 ,why does the ,,beer ,,run ,,freely1 immediately the ,,vent ,,peg is taken out8 ,a4 ,as soon as the vent peg is taken out1 air rushes through the vent hole at the top of the tub1--presses the liquor down1 and forces it through the tap4 ,q4 ,why does liquor flow reluctantly out of a ,,bottle held upside down8 ,a4 ,because the upward pressure of the air prevents the liquor from flowing out4 ,q4 ,why should a bottle be held ,,obliquely1 in order to be emptied of its liquor8 ,a4 ,because air will then flow into the bottle1 and help the liquor out by balancing the upward pressure4 ,q4 ,why does wine 7poured from a bottle ,,quickly7 ,,spirt about without going into the decanter8 ,a4 ,the liquor fills the top of the decanter 7like a cork71 and leaves no room for the air inside to escape2 therefore1 the decanter 7being full of air7 refuses to admit the wine4 ,q4 ,why is ,,beer made ,,stale1 by being exposed to the ,,air8 ,a4 ,because air absorbs its carbonic acid1 which gave it life4 ,q4 ,why is ,,porter made ,,stale1 by being exposed to the ,,air8 ,a4 ,because air absorbs its carbonic acid1 which gave it life4 ,q4 ,why does the ,,effervescence of soda water and ginger beer so soon go off8 ,a4 ,because air absorbs the carbonic acid1 which produced the effervescence4 ,q4 ,why is ,,boiled ,,water ,,flat and insipid8 ,a4 ,because the whole of the carbonic acid is expelled by boiling1 and absorbed by the air4 ,q4 ,why does ,,water become ,,flat and insipid1 after it has been ,,drawn some time8 ,a4 ,because air absorbs its carbonic acid2 and when its carbonic acid is absorbed1 the water is flat and insipid4 ,q4 ,why should spring ,,water 7used for ,,washing7 be exposed to the ,,air8 ,a4 ,spring water contains carbonic acid2 but 7by being exposed to the air7 this carbonic acid is absorbed1 and the water becomes more soft4 ,q4 ,why does ,,yeast make ,,bread ,,light8 ,a4 ,flour contains a small portion of saccharine matter 7or sugar72 and the yeast 7mixing with this7 produces fermentation1 as it does in brewing4 ,q4 ,how does ,,fermentation make the ,,dough ,,rise8 ,a4 ,during fermentation1 carbonic acid gas is evolved2 but the sticky texture of the dough will not allow it to escape1 so it forces up little bladders all over the dough4 ,q4 ,why is ,,dough placed ,,before the ,,fire8 ,a4 #ast--,because the heat of the fire increases the fermentation3 and #bndly--,it expands the gas which is confined in the little bladders2 in consequence of which1 the bladders are blown up larger1 and the dough becomes lighter and more porous4 ,q4 ,why is ,,bread ,,heavy1 if the dough be removed from the fire8 ,a4 ,because the dough gets cold1 and then the air in the bladders condenses1--the paste falls1--and the bread is close and heavy4 ,q4 ,whence does the ,,heat of ,,fire arise8 ,a4 ,the carbon of fuel 7when heated7 combines with the oxygen of the air1 and produces carbonic acid gas3 again1 the hydrogen of the fuel combining with other portions of oxygen1 condenses into water2 by which chemical actions heat is evolved4 ,q4 ,whence does the ,,heat of our own ,,body arise8 ,a4 ,the carbon of the blood combines with the oxygen of the air inhaled1 and produces carbonic acid gas2 which produces heat in a way similar to burning fuel4 ,q4 ,whence does the ,,heat of a ,,dunghill arise8 ,a4 ,the straw1 c4 of the dunghill undergoes fermentation as it decays3 the fermentation produces carbonic acid gas1 and heat is evolved by a species of combustion 7as in the two former cases74 ,q4 ,what changes do ,,vegetables undergo from ,,putrefaction8 ,a4 ,the hydrogen of the vegetables combines with the oxygen of the air1 and forms water3 again1 the carbon of the vegetables combines with oxygen of the air1 and forms carbonic acid gas4 ,putrefaction1 therefore1 is only another species of combustion4 ,q4 ,what changes do ,,animal bodies undergo from ,,putrefaction8 ,a4 ,the same as vegetables1 with this addition--they give out ammonia1 sulphur1 and phosphorus also2 which causes the offensive smell of putrefying animal bodies4 ,q4 ,why is ,,lime heated by a ,,kiln8 ,a4 ,all marl and chalk abound in carbonic acid2 and 7when heated by a fire7 the carbonic acid flies off in gas1 producing great heat4 ,q4 ,what is ,,mortar8 ,a4 ,lime mixed with sand and water4 ,q4 ,what is ,,lime8 ,a4 ,lime-stone burnt produces lime4 ,q4 ,why is the lime-stone ,,burnt1 in order to make it into ,,lime8 ,a4 ,the fire expels the carbonic acid1 and converts the hard lime-stone into a loose powder4 ,q4 ,why does ,,mortar become ,,hard1 after a few days8 ,a4 ,because the lime re-imbibes the carbonic acid of the air1 which was expelled by fire2 and the loose powder again becomes as hard as the original lime-stone4 ,q4 ,why is ,,mortar adhesive8 ,a4 ,when the carbonic acid is expelled1 the hard lime-stone is converted into a loose powder1 which 7being mixed with sand and water7 becomes a soft and sticky plaster2 but1 as soon as it is placed between bricks1 it imbibes carbonic acid again1 and hardens into lime-stone4 ,,chapter ,,xx4 ,,carburetted ,,hydrogen ,,gas4 ,q4 ,what is ,,choke-,,damp8 ,a4 ,carbonic acid gas accumulated at the bottom of wells and pits4 ,it is called ,,choke damp1 because it chokes 7or suffocates7 every animal that inhales it4 7see p4 #bfd74 ,q4 ,what is marsh-gas or ,,fire-,,damp8 ,a4 ,carburetted hydrogen gas accumulated on marshes1 in stagnant waters1 and coal pits2 it is frequently called inflammable air4 ,q4 ,what is ,,carburetted ,,hydrogen ,,gas8 ,a4 ,carbon combined with hydrogen4 ,q4 ,how may ,,carburetted ,,hydrogen ,,gas be ,,procured on marshes8 ,a4 ,by stirring the mud at the bottom of any stagnant pool1 and collecting the gas 7as it escapes upwards7 in an inverted glass vessel4 ,q4 ,what is ,,coal ,,gas8 ,a4 ,carburetted hydrogen extracted from coals1 by the heat of fire4 ,q4 ,why is carburetted hydrogen gas called ,,fire-,,damp1 or inflammable air8 ,a4 ,because it very readily catches fire and explodes1 when a light is introduced to it4 ,q4 ,why is carburetted hydrogen gas frequently called ,,marsh ,,gas8 ,a4 ,because it is generated in meadows and marshes from putrefying vegetable substances4 7,see ignis fatuus1 p4 #bhe74 ,q4 ,what gas is evolved by the ,,wick of a burning ,,candle8 ,a4 ,carburetted hydrogen gas3 that is1 the carbon and hydrogen of the tallow combine into a gas from the heat of the flame2 and this gas is carburetted hydrogen1 or inflammable air4 ,q4 ,why do ,,coal-,,mines so frequently ,,explode8 ,a4 ,because the carburetted hydrogen gas 7which is generated in these mines by the coals7 explodes1 when a light is incautiously introduced4 ,q4 ,how can miners ,,see in the coal-pits1 if they may ,,never introduce a ,,light8 ,a4 ,sir ,humphrey ,davy invented a lantern for the use of miners1 called the ,safety ,lamp1 which may be used without danger4 ,q4 ,who was ,,sir ,,humphrey ,,davy8 ,a4 ,a very clever chemist1 born in ,cornwall4 7#aggh--ahbi74 ,q4 ,what kind of thing is the ,,safety ,,lamp8 ,a4 ,it is a kind of lantern covered with a fine gauze wire1 instead of glass or horn4 ,q4 ,how does this fine ,,gauze ,,wire prevent an ,,explosion in the coal mine8 ,a4 #ast--,because flame will never pass through fine gauze wire3 and #bndly--,though the wire get red-hot1 it will not ignite the gas2 for carburetted hydrogen gas can be ignited only by flame4 7,n4 ,b4 ,the interstices of the gauze wire must not exceed the #gth of an inch in diameter47 ,q4 ,why will not ,,flame ,,pass ,,through very fine wire-,,gauze8 ,a4 ,because the metal wire is a very rapid conductor of heat2 and when the flame of burning gas in the lamp reaches the wire gauze1 the heat 7which is needful to produce flame7 is conducted away by the wire1 and the flame is extinguished4 ,q4 ,does the gas of the ,,coal-,,pit get ,,through the wire gauze ,,into the ,,lantern8 ,a4 ,yes2 but the inflammable gas ignites and burns inside the lamp3 as soon1 however1 as this is the case1 the miner is in danger1 and should withdraw4 ,q4 ,why is the miner in ,,danger1 if the gas ignites and burns in the ,,inside of the safety-lamp8 ,a4 ,because the heat of the burning gas will soon destroy the wire gauze1 and then the flame 7being free7 will set fire to the mine4 ,,chapter ,,xxi4 ,,phosphuretted ,,hydrogen ,,gas4 ,q4 ,from what does the very ,,offensive ,,effluvia of ,,church-,,yards arise8 ,a4 ,from a gas called ,,phosphuretted ,,hydrogen2 which is phosphorus combined with hydrogen gas4 ,q4 ,what is ,,phosphorus8 ,a4 ,a pale amber-coloured substance1 resembling wax in appearance4 ,the word is derived from two ,greek words1 which mean to produce or carry light4 7,greek3 phs-pherein74 ,q4 ,how is ,,phosphorus ,,obtained8 ,a4 ,by heating bones to a white heat2 by which means the animal matter and charcoal are consumed1 and what is left is called phosphate of lime4 ,q4 ,how is ,,phosphate ,,of ,,lime converted into ,,phosphorus8 ,a4 ,it is reduced to powder1 and mixed with sulphuric acid2 which 7being heated and filtered7 is converted into phosphorus4 ,q4 ,of what are ,,lucifer ,,matches made8 ,a4 ,of phosphorus2 and above #bej thousand lbs4 of phosphorus are used every year in ,london alone1 merely for the manufacture of lucifer matches4 ,q4 ,why does a ,,putrefying dead ,,body ,,smell so offensively8 ,a4 ,from the phosphuretted hydrogen gas1 which always arises from putrefying animal substances4 ,the escape of ammonia and sulphur contributes also to this offensive effluvia4 ,q4 ,what is the cause of the ,,ignis ,,fatuus1 ,jack o',lantern1 or ,will o'the ,wisp8 ,a4 ,this luminous appearance 7which haunts meadows1 bogs1 and marshes7 arises from the gas of putrefying animal and vegetable substances2 especially decaying fish4 ,q4 ,what gases arise from these ,,putrefying substances8 ,a4 ,phosphuretted hydrogen gas from putrefying animal substances3 and ,carburetted hydrogen1 7or inflammable gas7 from fermenting vegetable matters4 ,some persons erroneously think that the ,,aurora ,,borealis1 or ,northern ,lights1 may be attributed to the same gases1 burning in the upper regions of the air4 ,q4 ,how are these gases ,,ignited on bogs and meadows8 ,a4 ,by the electricity of the air1 the rays of the sun1 some accidental spark1 the lamp of some traveller1 or in some similar way4 ,and sometimes from the spontaneous combustion of some dung-heaps1 c4 in the locality4 ,q4 ,why does an ignis fatuus or ,will o'the ,wisp ,,fly from us when we ,,run to ,,meet it8 ,a4 ,when we run towards an ignis fatuus1 we produce a current of air1 which drives the light gas forwards4 ,q4 ,why does an ignis fatuus run ,,after us1 when we ,,flee from it in fright8 ,a4 ,when we run away from the ignis fatuus1 we produce a current in the way we run1 which attracts the light inflammable gas in the same course4 ,q4 ,is not a kind of ,jack o',lantern sometimes produced by an ,,insect8 ,a4 ,yes2 a swarm of luminous insects sometimes passes over a meadow1 and produces an appearance exactly like that of the ignis fatuus4 ,q4 ,may this meteoric appearance be attributed to any ,,other cause1 besides those mentioned8 ,a4 ,yes2 if many horses1 sheep1 pigs1 or oxen1 are pastured on a meadow1 the animal vapour arising from them 7strongly electrified by the air7 will ignite1 and produce a luminous appearance4 ,q4 ,may not many ,,ghost stories have risen from some ignis fatuus lurking about church-yards8 ,a4 ,perhaps all the ghost stories 7which deserve any credit at all7 have arisen from the ignited gas of church-yards lurking about the tombs1 to which fear has added its own creations4 ,,chapter ,,xxii4 ,,wind4 ,q4 ,what is ,,wind8 ,a4 ,wind is air in motion4 ,q4 ,what ,,puts the air in motion1 so as to produce ,,wind8 ,a4 ,the principal causes are the variations of heat and cold1 produced by the succession of day and night1 and the four seasons4 ,q4 ,what effect has ,,heat upon the air8 ,a4 ,heat rarefies the air1 and causes it to expand4 ,q4 ,how do you ,,know that heat causes the air to ,,expand8 ,a4 ,if a bladder half full of air 7tied tight round the neck71 were laid before a fire1 the heat of the fire would expand the air so much1 that the bladder would soon be entirely inflated2 7in this case1 the air in the bladder is expanded to twice its original bulk1 by the heat of the fire74 ,q4 ,what ,,effect is produced upon air by ,,rarefaction8 ,a4 ,it causes the air to ascend through colder strata1 as a cork 7put at the bottom of a basin of water7 would ascend through the water4 ,q4 ,how do you ,,know that rarefied air ,,ascends8 ,a4 ,when a boy sets fire to the cotton of his balloon1 the flame heats the air inside the balloon2 and the air becomes so light1 that it ascends1 and carries the balloon with it4 ,q4 ,what effect is produced upon ,,air by ,,cold8 ,a4 ,air is condensed by cold1 or squeezed into a smaller compass2 in consequence of which1 it becomes heavier1 and descends towards the ground4 ,q4 ,how do you ,,know that air is ,,condensed by ,,cold8 ,a4 ,after the bladder is fully inflated1 7by lying before the fire71 if it be taken away from the fire1 the bladder will collapse1 and show that it is not half full4 ,q4 ,what is meant by the bladder ,,collapsing8 ,a4 ,the skin will become wrinkled1 shrivelled1 and flabby1 because there is not sufficient air inside to fill it out4 ,q4 ,how do you ,,know that ,,condensed air will ,,descend8 ,a4 ,as soon as the cotton of the balloon is burnt out1 the air inside becomes cold again1 and the balloon falls to the earth4 ,q4 ,does the ,,sun ,,heat the ,,air as it does the ,,earth8 ,a4 ,no2 the air is not heated by the rays of the sun1 because air 7like water7 is a very bad conductor4 ,q4 ,how is the ,,air ,,heated8 ,a4 ,by convection1 thus3--,the sun heats the earth1 and the earth heats the air resting upon it2 the air thus heated rises1 and is succeeded by other air1 which is heated in a similar way1 till all is warmed by convective currents4 ,q4 ,what is meant by ,,convective ,,currents of air8 ,a4 ,streams of air heated by the earth1 which rise upwards and carry heat with them1 are called convective currents of hot air4 ,q4 ,is the air in a ,,room in perpetual motion1 as the air ,,abroad is8 ,a4 ,yes2 there are always two currents of air in the room we occupy1 one of hot air flowing out of the room1 and another of colder air flowing into the room4 ,q4 ,how do you ,,know1 that there are these ,,two currents of air in every occupied ,,room8 ,a4 ,if ,i hold a lighted candle near the crevice at the top of the door1 the flame will be blown outward 7towards the hall72 but if ,i hold the candle at the bottom of the door1 the flame will be blown inwards 7into the room74 ,q4 ,why would the flame be blown ,,outwards 7towards the ,,hall71 if the candle were held at the ,,top of the door8 ,a4 ,because as the air of the room is warmed by the fire1 c41 it ascends2 and 7floating about the upper part of the room7 some of it escapes through the crevice at the top of the door1 and thus produces a current of air outwards 7into the hall74 ,q4 ,why would the flame be blown ,,inwards 7into the ,,room71 if the candle were held at the ,,bottom of the door8 ,a4 ,because after the warm air of the room has ascended to the ceiling1 or made its escape into the hall1 c41 a partial vacuum is made at the bottom of the room2 and cold air 7from the hall7 rushes under the door to supply the void4 ,q4 ,what is meant by a partial ,,vacuum being made1 at the ,,bottom of the ,,room8 ,a4 ,a vacuum means a place from which the air has been taken3 and a partial vacuum means1 a place from which a part of its air has been taken away4 ,thus when the air on the floor ascends to the ceiling1 a partial vacuum is made on the floor4 ,q4 ,and how is the ,,vacuum filled ,,up again8 ,a4 ,it is filled up by colder air1 which rushes 7under the door1 and through the window crevices7 into the room4 ,q4 ,give me an ,,illustration4 ,a4 ,if ,i dip a pail into a pond and fill it with water1 a hole 7or vacuum7 is made in the pond as big as the pail2 but the moment ,i draw the pail out1 the hole is filled up by the water around4 ,q4 ,show how this illustration ,,applies4 ,a4 ,the heated air which ascends from the bottom of a room1 is as much taken away1 as the water in the pail2 and 7as the void was instantly supplied by other water in the pond7 so the void of air is supplied by a current from without4 ,q4 ,what is the ,,cause of ,,wind8 ,a4 ,the sun heats the earth1 and the earth heats the air resting upon it2 as the warm air ascends1 the void is filled up by a rush of cold air to the place1 and this rush of air we call ,,wind4 ,q4 ,does the ,,wind ,,always blow8 ,a4 ,yes2 there is always some motion in the air2 but the violence of the motion is perpetually varying4 ,q4 ,why is there always ,,some motion in the air8 ,a4 ,as the earth is always turning round1 the vertical rays of the sun are always varying4 ,q4 ,what do you mean by the ,,vertical ,,rays of the ,,sun8 ,a4 ,the rays made at noon-day3 when the sun is in a direct line above any place1 his rays are said to be vertical to that place4 ,q4 ,how are the ,,vertical rays of the sun always ,,varying8 ,a4 ,suppose the brass meridian of a globe to represent the vertical rays of the sun2 as you turn the globe round1 different parts of it will pass under the brass rim1 in constant succession4 ,q4 ,and is it ,,noon-,,day to the place over which the ,,sun is ,,vertical8 ,a4 ,yes2 as each place passes under the brass meridian1 it is noon-day to one half1 and mid-night to the other4 ,q4 ,show how this ,,rotation of the earth affects the ,,air4 ,a4 ,if we suppose the brass meridian to be the vertical sun1 the whole column of air beneath will be heated by the noon-day rays2 that part which the sun has left1 will become gradually colder and colder2 and that part to which the sun is approaching1 will grow constantly warmer and warmer4 ,q4 ,then there are ,,three qualities of air about this spot8 ,a4 ,yes2 the air over the place which has passed the meridian is cooling3 the air under the vertical sun is the hottest2 and the air which is over the place about to pass under the meridian1 is increasing in heat4 ,q4 ,how does this ,,variety in the ,,heat of ,,air produce ,,wind8 ,a4 ,the air always seeks to preserve an equilibrium2 so the cold air rushes to the void1 made by the upward current of the warmer air4 ,q4 ,why does not the wind ,,always ,,blow ,,one way1 following the direction of the ,,sun8 ,a4 ,because the direction of the wind is subject to perpetual interruptions from hills and valleys1 deserts and seas4 ,q4 ,how can ,,hills and ,,mountains ,,alter the course of the ,,wind8 ,a4 ,suppose a wind1 blowing from the north1 comes to a mountain1 as it cannot pass through it1 it must either rush back again1 or fly off at one side 7as a marble when it strikes against a wall74 ,q4 ,do ,,mountains affect the wind in any ,,other way8 ,a4 ,yes2 many mountains are capped with snow1 and the warm air is condensed as it comes in contact with them2 but as soon as the temperature of the wind is changed1 its direction may be changed also4 ,suppose ,a ,b ,c to be three columns of air4 ,a1 the column of air which is cooling down2 ,b1 the column to which the sun is vertical2 and ,c1 the column which is to be heated next4 ,in this case the cold air of ,a will rush towards ,b ,c1 because the air of ,b and ,c is hotter than ,a4 ,but suppose now ,c to be a snow-capped mountain4 ,as the hot air of ,b reaches ,c1 it is chilled2 and 7being now colder than the air behind7 it rushes back again towards ,a1 instead of following the sun4 ,q4 ,how can the ,,ocean affect the direction of the ,,wind8 ,a4 ,when the ocean rolls beneath the vertical sun1 the water is not made so hot as the land2 and 7as another change of temperature is produced7 another obstacle is offered to the uniform direction of the wind4 ,q4 ,why is not the ,,water of the sea made so ,,hot by the vertical sun1 as the surface of the ,,land8 ,a4 #ast--,because the evaporation of the sea is greater than that of the land3 #bndly--,the waters are never still3 and #crdly--,the rays of the sun strike into the water1 and are not reflected from its surface1 as they are by land4 ,q4 ,why does the ,,evaporation of the sea prevent its surface from being ,,heated by the vertical sun8 ,a4 ,as water absorbs heat by being converted into vapour2 the surface of the sea is continually losing heat by evaporation4 ,q4 ,how does the ,,motion of the sea prevent its surface from being ,,heated by the vertical sun8 ,a4 ,as one portion is heated it rolls away1 and is succeeded by another2 and this constant motion prevents one part of the sea from being heated more than another4 ,q4 ,how is the ,,wind affected by the ,,sea8 ,a4 ,when air from the hot earth reaches the sea1 it is often condensed1 and either rushes back again1 or else its violence is very greatly abated4 ,q4 ,do ,,clouds affect the ,,wind8 ,a4 ,yes4 ,as passing clouds screen the direct heat of the sun from the earth1 they diminish the rarefication of the air also3 and this is another cause why neither the strength nor direction of the wind is uniform4 ,q4 ,would the winds blow regularly from east to west1 if these ,,obstructions were ,,removed8 ,a4 ,without doubt they would4 ,if the whole earth were covered with water1 the winds would always follow the sun1 and blow from east to west4 ,their irregularity is owing to the interspersion of sea and land1 and the irregularities of the earth's surface4 ,q4 ,do winds ,,never blow ,,regularly8 ,a4 ,yes2 in those parts of the world1 where these obstructions do not exist2 as on the ,atlantic and ,pacific ,ocean1 the winds are pretty uniform4 ,q4 ,what are the winds1 which blow over the ,,atlantic and ,,pacific ,ocean1 called8 ,a4 ,they are called ,trade ,winds4 ,q4 ,why are they called ,,trade ,,winds8 ,a4 ,because 7as they blow uniformly in one direction7 they are very convenient to those who carry on trade by means of these oceans4 ,q4 ,in what ,,direction do the ,,trade ,,winds blow8 ,a4 ,that in the northern hemisphere blows from the north-east3 that in the southern hemisphere from the south-east4 ,q4 ,why do they not blow from the ,,full ,,north and ,,south8 ,a4 ,because the polar current1 combining with the equatorial current1 give the wind a new direction4 ,q4 ,what is the ,,cause of the ,,equatorial current8 ,a4 ,the rotation of the earth upon its axis4 ,q4 ,what is the cause of the ,,polar ,,current8 ,a4 ,as the heat in the torrid zone is always greatest1 and at the poles the least1 therefore a constant current of air rushes from the poles towards the equator4 ,q4 ,how does the ,,combination of these two currents give a new direction to them both8 ,a4 ,when these currents of air meet at the equator1 they clash together1 and fly off in a new direction4 ,q4 ,do trade winds blow from the north-east and south-east ,,all the ,,year ,,round8 ,a4 ,yes1 in the open sea2 that is1 in the ,atlantic and ,pacific ,oceans for about #cj degs4 each side of the equator4 ,q4 ,do the ,,trade ,,winds blow uniformly from north-east and south-east in the ,,indian ,,ocean8 ,a4 ,no2 nor yet in those parts of the ,atlantic and ,pacific which verge on the land4 ,q4 ,why do not the trade winds blow uniformly from north-east and south-east in the ,,indian ,,ocean8 ,a4 ,because when ,arabia1 ,persia1 ,india1 and ,china1 are exposed to the enormous heat of their summer sun1 the air is so rarefied1 that the colder air from the south pole rushes towards these nations1 and not to the equator2 in consequence of which1 a ,,south-,,west wind is produced for six months of the year4 ,q4 ,how does it blow for the ,,other #f months8 ,a4 ,when the sun has left the northern side of the equator for the southern1 then the southern part of the torrid zone is most heated2 and the cold air from the north 7rushing towards the southern tropic7 is diverted to the ,,north-,,east1 where it continues for the other six months of the year4 ,q4 ,what are the six-month trade winds called8 ,a4 ,they are called ,,monsoons2 and blow from the north-east from ,september to ,april1 and from the south-west for the other six months of the year4 ,q4 ,have ,,we any regular winds in ,,england8 ,a4 ,no2 our island 7having a continent on one side1 and a sea on the other7 has a most variable climate4 ,q4 ,have the winds in ,england ,,no general direction throughout the year8 ,a4 ,we generally find that easterly winds prevail during the spring of the year1 and westerly winds are most common in the summer and autumn4 ,s-,west winds are most frequent in ,july and ,august4 ,n-,east winds in ,january1 ,march1 ,april1 ,may1 ,june2 and most seldom in ,july1 ,september1 and ,december4 ,q4 ,when are the ,,winds in ,,england generally the ,,highest8 ,a4 ,the winds in ,december and ,january are generally the highest4 ,those in ,february and ,november the next2 and those in ,august and ,september the least boisterous4 ,q4 ,why are the winds of ,europe generally ,,highest in ,,december and ,,january8 ,a4 ,because the sun is furthest south in those months2 and 7as the heat in these northern regions rapidly decreases7 the contrast between our temperature and that of the torrid zone is greater in ,december and ,january1 than in any other two months throughout the year4 ,q4 ,why does this ,,contrast of heat increase the ,,violence of the ,,winds8 ,a4 ,as the air always seeks to preserve an equilibrium1 therefore the greater the contrast1 the more violent will be the rush of air to equalize the two volumes4 ,q4 ,why are the winds in ,europe generally the most ,,placid during the months of ,,september and ,,august8 ,a4 ,august and ,september are our warmest months1 when we approach nearer to the heat of the torrid zone than in any other two months2 therefore1 the air 7to and from the equator7 moves with less velocity in our northern hemisphere4 ,q4 ,show the ,,goodness and ,,wisdom of ,,god in the constant tendency of air to equilibrium4 ,a4 ,if the cool air of the polar regions did not rush into the torrid zone1 it would become so hot1 that no human being could endure it4 ,if 7on the other hand7 the hot air from the torrid zone did not modify the polar regions1 they would soon become insufferably cold4 ,q4 ,why are ,,east ,,winds in ,england generally ,,dry8 ,a4 ,because1 as they come over the vast continents of ,asia and ,europe1 they absorb very little water4 ,q4 ,why does their imbibing so little water make them ,,dry winds8 ,a4 ,being thirsty when they reach our island1 they readily imbibe moisture from the air and clouds2 and1 therefore1 bring dry weather4 ,q4 ,why is the ,,north ,,wind in ,england generally ,,cold8 ,a4 ,the north wind comes from the polar regions1 over mountains of snow1 and seas of ice2 in consequence of which1 it is very cold4 ,q4 ,why are ,,north ,,winds in ,england generally ,,dry and biting8 ,a4 ,as they come from regions colder than our own1 they are warmed by the heat of our island2 and 7as their temperature is raised7 they absorb moisture from every thing they touch2 in consequence of which1 they are both dry and parching4 ,q4 ,why is the ,,south ,,wind generally ,,warm in ,england8 ,a4 ,the south wind comes over the hot sandy deserts of ,africa1 and is heated by the land it traverses4 ,q4 ,why does the ,,south ,,wind often bring us ,,rain8 ,a4 ,the south wind 7being much heated by the hot sands of ,africa7 imbibes water very plentifully1 as it passes over the ,mediterranean ,sea and ,british ,channel4 ,q4 ,why does the ,,saturation of the south wind cause ,,rain8 ,a4 ,as soon as it reaches our cold climate1 it is condensed1 and its vapour is squeezed out 7as water from a wet sponge74 ,q4 ,why are ,,west ,,winds in ,england generally ,,rainy8 ,a4 ,the west winds come over the ,atlantic ,ocean1 and are laden with vapour3 if1 therefore1 they meet with the least chill1 some of the vapour is squeezed out4 ,q4 ,why is a fine ,,clear ,,day sometimes ,,overcast in a few minutes8 ,a4 ,because some sudden change of temperature has condensed the vapour of the air into clouds4 ,q4 ,why are ,,clouds sometimes ,,dissipated quite as suddenly8 ,a4 ,because some dry wind 7blowing over the clouds7 has imbibed their moisture1 and carried it off in invisible vapour4 ,q4 ,why does a ,,south-,,west wind bring us ,,rain8 ,a4 ,as it comes from the torrid zone1 and crosses the ocean1 the hot wind is laden with vapour2 and as some of the heat escapes 7as soon as it reaches our northern island7 the vapour is condensed1 and precipitated as rain4 ,q4 ,why does a ,,north-,,east wind ,,rarely bring ,,rain8 ,a4 ,as it comes from a climate colder than our own1 its capacity for imbibing vapour is increased when it reaches our island2 in consequence of which1 it dries the air1 dispels the clouds1 and promotes evaporation4 ,q4 ,why does ,,wind sometimes bring ,,rain1 and sometimes ,,fine weather8 ,a4 ,if the wind be colder than the clouds1 it will condense their vapour into rain3 if the wind be warmer than the clouds1 it will dissolve them1 and cause them to disappear4 ,q4 ,why are ,,march winds ,,dry8 ,a4 ,because they generally blow from the east or north-east2 and1 therefore1 sweep over the continent of ,europe4 ,q4 ,what is the ,,use of ,,march winds8 ,a4 ,they dry the soil 7which is saturated with the floods of ,february71 break up the heavy clods1 and fit the land for the seeds which are committed to it4 ,q4 ,why does ,,march ,,come ,,in like a ,,lion8 ,a4 ,because it comes in with blustering east winds1 which are essential to dry the soil1 which would otherwise rot the seed committed to it4 ,q4 ,why does ,,march ,,go ,,out like a ,,lamb8 ,a4 ,because the water 7evaporated by the high winds7 falls again in showers to fertilize the earth1 and breaks the violence of the winds4 ,q4 ,why is it said that ,a bushel of ,,march ,,dust is worth the king's ransom8 ,a4 ,because it indicates that there has been a continuance of dry weather2 and unless ,march be dry1 the seed will rot in the wet soil4 ,q4 ,why is it said ,a ,,dry cold ,,march never ,,begs ,,bread8 ,a4 ,because the dry cold winds of ,march prepare the soil for seeds1 which germinate1 and produce fruit in the autumn4 ,q4 ,why is it said that ,a ,,wet ,,march makes a ,,sad autumn8 ,a4 ,because1 if ,march be wet1 so much of the seed rots in the ground1 that the autumn crops are spoiled4 ,q4 ,why is it said that ,,march ,,flowers make ,,no summer ,,bowers8 ,a4 ,because1 if the spring be very mild1 vegetation gets too forward1 and is pinched by the nightly frosts1 so as to produce neither fruits nor flowers4 ,q4 ,why is it said ,a ,,late ,,spring makes a ,,fruitful ,,year8 ,a4 ,because if the vegetation of spring be backward1 the frosty nights will do no harm2 for the fruits and flowers will not put forth their tender shoots1 till the nights become too warm to injure them4 ,q4 ,why is it said that ,,april ,,showers bring ,,may ,,flowers8 ,a4 ,before seeds can germinate1 three things are essential3--,darkness1 ,heat1 and ,moisture4 ,april showers supply the principal nourishment on which seeds depend for existence4 ,q4 ,does ,,rain-water possess any fertilizing properties ,,besides that of mere ,,moisture8 ,a4 ,yes2 rain-water contains ,,ammonia1 to which much of its fertilizing power may be attributed4 7,ammonia is a compound of nitrogen and hydrogen4 ,common hartshorn is only ammonia and water47 ,q4 ,why has ,god made ,,november a very ,,rainy month8 ,a4 ,because the rain hastens the putrefaction of the fallen leaves1 and this makes the earth fertile4 ,q4 ,why is there ,,more rain ,,from ,,september to ,,march than from ,march to ,september8 ,a4 ,from ,september to ,march1 the temperature of the air is constantly decreasing2 on which account1 its capacity for holding vapour is on the decrease1 and the vapour is precipitated as rain4 ,q4 ,why is there ,,less rain ,,from ,,march to ,,september1 than from ,september to ,march8 ,a4 ,from ,march to ,september1 the temperature of the air is constantly increasing2 on which account1 its capacity for holding vapour is on the increase1 and very little is precipitated as rain4 ,q4 ,why is the ,,rising ,,sun in summer accompanied with a ,,breeze8 ,a4 ,because the heat of the rising sun stops the radiation of heat from the earth1 and warms its surface4 ,q4 ,how does this ,,warmth produce a ,,breeze8 ,a4 ,the air 7resting on the earth's surface7 is warmed by contact1 ascends upwards1 and colder air rushes in to fill up the void1 which is the cause of the morning breeze4 ,q4 ,why is there often an ,,evening ,,breeze during the summer months8 ,a4 ,the earth radiates heat at sun-set1 and the air is cooled down quickly by contact3 this condensation causes a motion in the air1 which is the evening breeze4 ,q4 ,why are ,,tropical ,,islands always subject to a ,,sea-breeze every ,,morning 7i4 e4 a breeze blowing from the sea to the land78 ,a4 ,the solar rays are unable to heat the surface of the sea as they do the earth2 therefore1 the air resting on the earth is more heated than the air resting on the sea2 and the colder sea air blows inland to restore the equilibrium4 ,q4 ,why is the ,,land ,,breeze ,,unhealthy8 ,a4 ,because it is frequently loaded with exhalations from putrefying animal and vegetable substances4 ,q4 ,why is the ,,sea ,,breeze fresh and ,,healthy8 ,a4 ,because it passes over the fresh sea1 and is not laden with noxious exhalations4 ,it is healthy1 therefore1 to walk on the sea-beach before ten o'clock in the morning2 but unhealthy after sun-set4 ,q4 ,why is there generally a fresh breeze from the ,,sea 7in ,english watering places7 during the summer and autumn ,,mornings8 ,a4 ,as the land is more heated by the sun than the sea2 therefore1 air resting on the land is hotter than air resting on the sea2 in consequence of which1 cooler sea air glides inland1 to restore the equilibrium4 ,q4 ,why does the ,,sea ,,breeze feel ,,cool8 ,a4 ,as the sun cannot make the surface of the sea so hot as the surface of the land2 therefore1 the air which blows from the sea1 feels cooler than the air of the land4 ,q4 ,why are ,,tropical ,,islands subject to a ,,land ,,breeze every ,,evening 7i4 e4 a breeze blowing from the land towards the sea78 ,a4 ,the surface of land cools down faster 7after sun-set7 than the surface of the sea3 in consequence of which1 the air of the cold land is condensed1 sinks down1 and spreads itself into the warmer sea air1 causing the ,,land ,,breeze4 ,q4 ,why is the ,,land ,,breeze ,,cool8 ,a4 ,as the surface of the land is cooled at sun-set quicker than the surface of the sea2 therefore1 the seaman feels the air from the land to be chill4 ,q4 ,why is the ,,temperature of ,,islands more ,,equable than that of ,,continents8 ,a4 ,because the water around the island absorbs the extreme heat of summer1 and gives out heat to mitigate the extreme cold of winter4 ,q4 ,why does the sea round an island ,,give ,,out heat in winter8 ,a4 ,unless the sea be frozen 7which is rarely the case71 it is warmer than the frozen land2 and1 therefore1 the warmth of the sea air 7mixing with the cold land air7 helps to mitigate the intense cold4 ,q4 ,why are there ,,waves in the sea8 ,a4 ,the wind 7acting on the surface of the sea7 piles up ridges of water1 which leave behind an indentation3 as the water on all sides rushes to fill up this indentation1 the disturbance spreads on all sides1 and billow rolls after billow4 ,q4 ,why does ,,wind in ,england generally feel ,,cold8 ,a4 ,because a constantly changing surface comes in contact with our body1 to draw off its heat4 ,q4 ,why is a ,,room 7even without a fire7 generally ,,warmer than the ,,open ,,air8 ,a4 ,as the air in a room is not subject to much change1 it soon becomes of the same temperature as our skin1 and no longer feels cold4 ,q4 ,why do we generally feel ,,colder out-of-doors8 ,a4 ,because the air 7which surrounds us7 is always changing2 and as fast as one portion of air has become warmer by contact with our body1 another colder portion surrounds us to absorb more heat4 ,q4 ,why are ,,hot ,,foods made ,,cool by ,,blowing them8 ,a4 ,blowing causes the air 7which covers the hot food7 to change more rapidly2 in consequence of which1 the hot air is quickly blown away1 and gives place to fresh cold air4 ,q4 ,why do ladies ,,fan ,,themselves in hot weather8 ,a4 ,by the action of the fan1 fresh particles of air are perpetually brought in contact with the face1 and every fresh particle of air absorbs some heat from the skin4 ,q4 ,does the fan ,,cool the ,,air8 ,a4 ,no2 it makes the air hotter1 by imparting to it the heat out of our face3 but it cools the face blown upon1 by transferring its heat to the air4 ,q4 ,is the ,,air in ,,summer time ever so hot as our bodies8 ,a4 ,no1 not in ,england4 ,in the hottest day in summer1 the air of ,england is #ae or #bj degrees cooler than the human body4 ,q4 ,how fast does wind travel8 ,a4 ,a gentle breeze goes at about the rate of #e miles an hour4 ,a high wind from #bj to #fj4 ,a hurricane from #hj to #ajj miles an hour4 ,q4 ,how is the ,,velocity of ,,winds ascertained8 ,a4 ,by observing the velocity of the clouds1 and by an instrument for the purpose4 ,this instrument is called an ,,anemometer4 ,q4 ,how is the ,,velocity of the ,,clouds ascertained8 ,a4 ,by observing the speed of their shadow along the ground2 which is found in a high wind to vary from #bj to #fj miles an hour4 ,q4 ,why is there always a strong ,,draught through the ,,keyhole of a door8 ,a4 ,as the air of the room we occupy is warmer than the air in the hall1 therefore the cold hall air rushes through the keyhole into the room1 and causes a draught4 ,q4 ,why is there always a strong ,,draught ,,under the ,,door1 and through the crevice on each side8 ,a4 ,the cold air rushes from the hall under the door1 c4 into the room1 to supply the void caused in the room 7by the escape of warm air up the chimney1 c47 ,q4 ,why is there always a ,,draught through the ,,window crevices8 ,a4 ,the external air 7being colder than the air of the room we occupy7 rushes through the window crevices to supply the deficiency1 caused by the escape of air up the chimney1 c4 ,q4 ,why is there more ,,draught if you open the ,,lower ,,sash of a window1 than if you open the ,,upper sash8 ,a4 ,if the lower sash be open1 the cold external air will rush more freely into the room2 but if the upper sash be open the heated air of the room will rush out2 and 7of course7 there will be less draught4 ,q4 ,by which means is the ,,room better ,,ventilated1 by opening the lower or the upper sash8 ,a4 ,a room is better ventilated by opening the upper sash2 because the hot vitiated air 7which always ascends towards the ceiling7 can better escape4 ,q4 ,by which means is a ,,hot ,,room more quickly ,,cooled--,by opening the upper or the lower sash8 ,a4 ,a hot room is cooled more quickly by opening the lower sash2 because the cold air can enter more freely by an under current1 than by one higher up4 ,q4 ,why does ,,wind ,,dry damp ,,linen8 ,a4 ,because dry wind 7like a dry sponge7 imbibes the particles of vapour from the surface of the linen1 as fast as they are formed4 ,q4 ,which is the ,,hottest ,,place in a church1 chapel1 or theatre8 ,a4 ,the gallery4 ,q4 ,why is the ,,gallery of all public places ,,hotter than the lower parts of the building8 ,a4 ,because the heated air of the room ascends1 and all the cold air 7which can enter through the doors and windows7 keeps to the floor1 till it has become heated4 ,q4 ,why do ,,plants often grow out of ,,walls and ,,towers8 ,a4 ,because sometimes the wind blows the seed there with the dust2 and sometimes birds 7flying over7 drop the seed which they had formerly eaten4 ,,chapter ,,xxiii4 ,,barometer4 ,q4 ,what is a ,,barometer8 ,a4 ,a weather-glass1 or instrument to show the changes of the weather1 by marking the variations in the weight of air4 ,q4 ,what is a ,,thermometer8 ,a4 ,an instrument to show how hot or cold anything is4 ,q4 ,what is the ,,difference between a ,,thermometer and a ,,barometer8 ,a4 ,in a ,,thermometer the mercury is sealed up from the air3 ,in a ,,barometer the mercury is left exposed 7or open7 to the air4 ,q4 ,if the mercury of the thermometer be ,,sealed ,,up from the air1 how can the air ,,affect it8 ,a4 ,the heat of the air passing through the glass tube into the mercury1 causes it to expand more or less1 and rise in the tube accordingly4 ,q4 ,why is the ,,tube of a ,,barometer left ,,open8 ,a4 ,that the air may press upon it freely2 and as this pressure is more or less1 the mercury rises or falls in the tube4 ,q4 ,how can weather be affected by the ,,weight of the air8 ,a4 ,when air is warm or moist1 it is lighter than usual3 ,when it is cold or dry1 it is heavier3 and as a barometer marks whether the air be light or heavy1 it indicates these changes4 ,q4 ,how can you tell 7by looking at a ,,barometer7 what ,,kind of ,,weather it will be8 ,a4 ,because the mercury in the tube rises and falls1 as the air becomes lighter or heavier3 and we can generally tell by the weight of the air1 what kind of weather to expect4 ,q4 ,does the ,,weight of the air ,,vary ,,much8 ,a4 ,yes2 the atmosphere in ,england varies as much as one-tenth part more or less4 ,q4 ,what is the chief ,,use of a ,,barometer8 ,a4 ,to warn sailors how to regulate their ships1 before squalls come on4 ,q4 ,how can a ,,barometer warn ,,sailors to regulate their ,,ships8 ,a4 ,as the barometer will tell when wind1 rain1 or storm is at hand1 the sailor can make his ship trim before it overtakes him4 ,q4 ,are there any ,,rules which can be depended on8 ,a4 ,yes2 there are ten special rules to direct us how to know the changes of weather1 by marking the mercury of a barometer4 ,q4 ,what is the #a,,st ,,special ,,rule in regard to the barometer8 ,a4 ,the barometer is highest of all during a long frost2 and it generally rises with a north-east wind4 ,q4 ,why is the barometer ,,highest of all during a long ,,frost8 ,a4 ,because long frost condenses the air very greatly2 and the more air is condensed1 the greater is its pressure on the mercury of the barometer4 ,q4 ,why does the barometer generally ,,rise with a ,,north-,,east wind8 ,a4 ,because ,,north-,,east winds make the air both cold and dry3 the air1 therefore1 is both condensed1 and without vapour4 ,q4 ,what is the #b,,nd ,,special ,,rule in regard to the barometer8 ,a4 ,the barometer is lowest of all during a thaw which follows a long frost3 it generally falls with ,,south and ,,western winds4 ,q4 ,why does the barometer fall ,,lowest of all at the ,,breaking ,,up of a long ,,frost8 ,a4 #ast--,because the air 7which had been much dried by the frost7 absorbs the moisture of the fresh warm current of wind from the south or south-west3 and #bndly--,the air 7which had been much condensed by the frost7 is suddenly expanded by the warm wind which is introduced4 ,q4 ,why does the barometer fall very low with ,,south and ,,west winds8 ,a4 ,because ,,south and ,,west winds come heavily laden with vapour2 and vaporized air is lighter than dry air4 ,q4 ,what effect has ,,wind on the mercury8 ,a4 ,all winds make the barometer drop1 except ,,eastern winds3 those winds which blow from the ,,south1 and ,,south-,,west make it drop the lowest4 ,q4 ,why do ,,winds generally make the mercury of a barometer ,,drop8 ,a4 ,wind is caused by a partial vacuum in some parts of the globe2 and as the air rushes in to supply this deficiency1 its general pressure is lessened1 and the barometer falls4 ,q4 ,what is the #c,,rd ,,special ,,rule in regard to the barometer8 ,a4 ,while the barometer stands above #cj1 the air must be very dry or very cold1 or perhaps both1 and no rain may be expected4 ,q4 ,why will there be ,,no ,,rain if the ,,air be very ,,dry8 ,a4 ,if the air be very dry it will absorb moisture1 and not part with what it has in rain4 ,q4 ,why will there be ,,no ,,rain if the ,,air be very ,,cold8 ,a4 ,if the air be very cold it is so much condensed1 that it has already parted with as much moisture as it can spare4 ,q4 ,what is the #d,,th ,,special ,,rule in regard to the barometer8 ,a4 ,when the barometer stands very low indeed1 there is never much rain1 although a fine day will seldom occur at such times4 ,q4 ,what kind of ,,weather will it be when the barometer is ,,unusually ,,low8 ,a4 ,there will be short heavy showers1 with sudden squalls of wind from the west4 ,q4 ,why will there be ,,very ,,little ,,rain if the barometer be ,,unusually ,,low8 ,a4 ,because the air must be very warm1 or very moist1 or perhaps both4 ,q4 ,why will there be little or no rain1 if the ,,air be very ,,warm8 ,a4 ,if the air be very warm it will have a tendency to imbibe more moisture1 and not to part with what it has4 ,q4 ,why will there be little or no rain if the air be ,,moist1 and the barometer remains very ,,low8 ,a4 ,if the air be ever so moist1 rain will never fall till cold air has been introduced to condense the vapour2 and the moment that the cold air is introduced1 the barometer will rise4 ,q4 ,what is the #e,,th ,,special ,,rule in regard to the barometer8 ,a4 ,in summer-time 7after a long continuance of fair weather7 the barometer will fall gradually for #b or #c days before rain comes2 but if the fall of the mercury be very sudden1 a thunder-storm is at hand4 ,q4 ,what is the #f,,th ,,special ,,rule in regard to the barometer8 ,a4 ,when the sky is cloudless1 and seems to promise fair weather1 if the barometer be low1 the face of the sky will soon be suddenly overcast4 ,q4 ,what is the #g,,th ,,special ,,rule in regard to the barometer8 ,a4 ,dark dense clouds will pass over without rain1 when the barometer is high2 but if the barometer be low1 it will often rain without any gathering of clouds4 ,q4 ,what is the #h,,th ,,special ,,rule in regard to the barometer8 ,a4 ,the higher the barometer1 the greater is the probability of fair weather4 ,q4 ,why is the barometer ,,high in ,,fine weather8 ,a4 ,because the air contains but very little vapour4 ,the drier the air1 the higher does the mercury of the barometer rise4 ,q4 ,what is the #i,,th ,,special ,,rule in regard to the barometer8 ,a4 ,when the mercury is in a rising state1 fine weather is at hand2 but when the mercury is in a sinking state1 foul weather is near4 ,q4 ,why does the mercury ,,rise at the approach of ,,fine weather8 ,a4 ,because the air is becoming more dry1 and therefore its pressure is greater4 ,q4 ,why does the mercury ,,sink at the approach of ,,foul weather8 ,a4 ,because the air is laden with vapour1 or disturbed by wind4 ,q4 ,why does ,,vapour in the air make the mercury ,,sink8 ,a4 ,because vaporized air is lighter than dry air1 and therefore its pressure is less on the mercury of the barometer4 ,q4 ,what is the #aj,,th ,,special ,,rule in regard to the barometer8 ,a4 ,if 7in frosty weather7 it begins to snow1 the barometer generally rises to #cb1 where it remains as long as the snow continues to fall2 if1 after this1 the weather clear up1 you may expect very severe cold4 ,q4 ,how can you know if the ,,mercury of the barometer be ,,rising8 ,a4 ,if it be convex 7i4 e4 higher in the middle than at the sides27 it is in a rising state4 ,q4 ,how can you tell if the ,,mercury of the barometer be about to ,,fall8 ,a4 ,if it be concave 7i4 e4 hollow in the middle7 it is in a falling state4 ,q4 ,why is the mercury ,,convex when it is ,,rising8 ,a4 ,the sides of the mercury rub against the glass tube1 and are delayed by it1 so that the middle part rises faster than the sides4 ,q4 ,why is the mercury ,,concave when it is ,,falling8 ,a4 ,the sides of the mercury rub against the glass tube1 and are delayed by it1 so that the middle part sinks faster than the sides4 ,q4 ,what effect does a ,,thunder-,,storm produce on the weather8 ,a4 ,thunder is generally preceded by hot weather1 and followed by cold and showery weather4 ,q4 ,what effect does a ,,sudden ,,change produce on the weather8 ,a4 ,a great and sudden change 7either from hot to cold1 or from cold to hot7 is generally followed by rain within #bd hours4 ,q4 ,why is a sudden ,,change from ,,hot to ,,cold followed by ,,rain8 ,a4 ,the cold condenses the air and its vapour2 which1 being condensed and squeezed out1 falls in rain4 ,q4 ,why is a sudden ,,change from ,,cold to ,,hot followed by ,,rain8 ,a4 ,because the air is quickly saturated with moisture2 and as soon as night comes on1 the temperature is lowered again1 and some of the abundant moisture falls in rain4 ,q4 ,why is the air quickly ,,saturated with ,,moisture1 when ,,heat succeeds rapidly from ,,cold8 ,a4 ,because the evaporation 7which was checked by the cold7 is carried on very rapidly1 in consequence of the diminished pressure of the air4 7,n4 ,b4 ,the less the pressure of the air1 the more rapidly it evaporates moisture47 ,q4 ,when does the barometer ,,vary ,,most8 ,a4 ,in winter time4 ,q4 ,why does the barometer vary ,,more in ,,winter than in ,,summer time8 ,a4 ,because the difference of temperature between the torrid and temperate zones is so great1 that the state of the air is perpetually disturbed by their mixing together4 ,q4 ,when does the barometer ,,vary ,,least8 ,a4 ,in summer time4 ,q4 ,why does the barometer vary ,,less in ,,summer than in ,,winter time8 ,a4 ,because the temperature of our island is so nearly equal to that of the torrid zone1 that its state is not much disturbed by interchange of currents4 ,q4 ,what effect has ,,wind on the barometer8 ,a4 ,,north and ,,east winds make the mercury rise2 all other winds make it sink2 but ,,south and ,,west winds make it sink lower than any other winds4 ,q4 ,have ,,heat and ,,cold any effect on the barometer8 ,a4 ,no1 not of themselves2 but because cold weather is generally either dry1 or rough with north-east winds1 therefore the mercury rises in cold weather2 and because warm weather is often moist or fanned by south-west winds1 therefore1 the mercury sinks4 ,q4 ,why is the mercury of a barometer ,,lower in the ,,torrid than in the ,,frigid zones8 ,a4 ,because the warm air of the torrid zone contains much more vapour than the condensed air of the frigid zone2 and the moister the air1 the less is its pressure4 ,q4 ,in what ,,months is the barometer ,,highest8 ,a4 ,in ,may and ,august2 next to these1 in ,june1 ,march1 ,september1 and ,april4 ,q4 ,in what ,,months is the barometer ,,lowest8 ,a4 ,in ,november and ,february2 then in ,october1 ,july1 ,december1 and ,january4 ,q4 ,what are the ,,driest months8 ,a4 ,march and ,june2 then ,may and ,august2 then ,april and ,november4 ,q4 ,what are the ,,wettest months8 ,a4 ,october and ,february2 then ,july and ,september2 then ,january and ,december4 ,q4 ,why is there ,,less wet from ,,march to ,,august1 than there is from ,august to ,march8 ,a4 ,because the heat is constantly increasing2 and the capacity of the air to absorb and retain moisture increases likewise4 ,q4 ,why is there ,,more wet from ,,august to ,,march1 than there is from ,march to ,august8 ,a4 ,because the heat is constantly decreasing1 and the capacity of the air to retain moisture decreases also2 so that 7although it often rains7 yet the air is always on the point of saturation4 ,q4 ,why does the mercury of a barometer ,,rise in a ,,frost8 ,a4 ,because frost condenses the air2 and condensed air is heavier than rarefied air4 ,q4 ,why does the mercury of a barometer ,,fall in a ,,thaw8 ,a4 ,because the air is both warmer 7or more rarefied71 and also filled with vapour4 ,q4 ,what does a ,,sudden rise or fall of the barometer indicate8 ,a4 ,if the rise be sudden1 fine weather will not continue long3 ,if the fall be sudden1 foul weather will not continue long4 ,q4 ,what sort of weather may we expect if the barometer be very ,,fluctuating8 ,a4 ,if the mercury fluctuates much1 the weather will be very changeable and unsettled4 ,the ,,fall of the barometer4 ,in very hot weather1 the fall of the mercury denotes thunder4 ,except in very hot weather1 the sudden falling of the barometer denotes high wind4 ,in frosty weather1 the fall of the barometer denotes thaw4 ,if wet weather happens soon after the fall of the barometer1 expect but little of it4 ,in wet weather if the barometer falls1 expect much wet4 ,in fair weather1 if the barometer falls much and remains low1 expect much wet in a few days1 and probably wind4 ,n4 ,b4 ,the barometer sinks lowest of all for wind and rain together1 next to that for wind 7except it be an east or north-east wind74 99 99 99 99 99 ,the ,,rise of the barometer4 ,in winter the rise of the barometer presages frost4 ,in frosty weather1 the rise of the barometer presages snow4 ,if fair weather happens soon after the rise of the barometer1 expect but little of it4 ,in wet weather1 if the mercury rises high and remains so1 expect continued fine weather in a day or two4 ,in wet weather1 if the mercury rises suddenly very high1 fine weather will not last long4 ,n4 ,b4 ,the barometer rises highest of all for north and east winds2 for all other winds it sinks4 99 99 99 99 99 ,if the barometer be ,,unsettled4 ,if the motion of the mercury be unsettled1 expect unsettled weather4 ,if it stand at ,,much ,,rain and rise to ,,changeable1 expects fair weather of short continuance4 ,if it stand at ,,fair and fall to ,,changeable1 expect foul weather4 ,n4 ,b4 ,its motion upwards indicates the approach of fine weather3 its motion downwards indicates the approach of foul weather4 ,,chapter ,,xxiv4 ,,snow4 ,,hail4 ,,rain4 ,q4 ,what is ,,snow8 ,a4 ,the condensed vapour of the air frozen1 and precipitated to the earth4 ,q4 ,what is the ,,cause of ,,snow8 ,a4 ,when the air is nearly saturated with vapour1 and condensed by a current of air below freezing point1 some of the vapour is squeezed out1 and frozen into snow4 ,a few years ago1 some fishermen 7who wintered at ,nova-,zembla71 after they had been shut up in a hut for several days1 opened the window1 and the cold external air rushing in1 instantly condensed the air of the hut1 and the vapour 7which was squeezed out7 fell on the floor in a shower of snow4 ,q4 ,why does ,,snow fall in ,,winter time8 ,a4 ,because the sun's rays are too oblique to heat the surface of the earth2 and 7as the earth has no heat to radiate into the air7 the air is very cold4 ,q4 ,what is ,,sleet8 ,a4 ,when flakes of snow 7in their descent7 pass through a bed of air above freezing point1 they melt2 and fall to the earth as half-melted snow or sleet4 ,q4 ,what is the ,,use of ,,snow8 ,a4 ,to keep the earth warm1 and to nourish it4 ,q4 ,how can snow keep the ,,earth ,,warm8 ,a4 ,because it is a very bad conductor2 in consequence of which1 the earth which is covered with snow1 very rarely descends below freezing point1 even when the air is #ae or #bj degrees colder4 ,q4 ,why is ,,snow a ,,bad ,,conductor of heat and cold8 ,a4 ,because air is confined and entangled between the crystals1 and air is a very bad conductor2 when1 therefore1 the earth is covered with snow1 it cannot throw off its heat by radiation4 ,q4 ,tell me the words of the ,,psalmist 7cxlvii4 #af47 respecting snow1 and explain what he means4 ,a4 ,the ,psalmist says--,the ,lord giveth snow like wool3 and he means not only that snow is as white as wool1 but that it is also as warm as wool4 ,q4 ,why is ,,wool ,,warm8 ,a4 ,because air is entangled between the fibres of the wool1 and air is a bad conductor4 ,q4 ,why is ,,snow ,,warm8 ,a4 ,because air is entangled between the crystals of the snow1 and air is a bad conductor4 ,q4 ,why does ,,snow ,,nourish the earth8 ,a4 ,because it supplies it with moisture for a considerable time2 which penetrates slowly into the soil1 and insinuates itself through every clod1 ridge1 and furrow4 ,q4 ,why is there ,,no ,,snow in ,,summer time8 ,a4 ,no snow reaches the general surface of the earth in summer time1 because the heat of the earth melts it in its descent4 ,q4 ,why are some ,,mountains ,,always ,,covered with ,,snow8 ,a4 #ast--,because the air is more rarefied2 and rarefied air abstracts heat which it holds in a latent state3 #bndly--,as the mountain top is not surrounded by earth to radiate heat into the air2 therefore1 the snow is not melted in its descent1 but falls on the mountain1 and lies there4 ,q4 ,why is ,,snow ,,white8 ,a4 ,snow is formed of an infinite number of very minute crystals and prisms1 which reflect all the colours of the rays of light2 and these colours uniting before they meet the eye1 cause snow to appear white4 ,q4 ,what is ,,hail8 ,a4 ,rain1 which has passed in its descent through some cold bed of air1 and has been frozen into drops of ice4 ,q4 ,why is ,,one bed of air ,,colder than another8 ,a4 ,this is frequently caused by electricity in the air1 unequally distributed4 ,q4 ,why is ,,hail frequently accompanied with ,,thunder and ,,lightning8 ,a4 #ast--,because the congelation of water into hail disturbs the electricity of the air3 and #bndly--,the friction 7produced by the fall of hail7 excites it still more4 ,q4 ,why does ,,hail fall generally in ,,summer and ,,autumn8 ,a4 #ast--,because the air is more highly electrified in summer and autumn3 and #bndly--,the vapours 7being rarefied7 ascend to the more elevated regions1 where the cold is greater than it is nearer the earth4 ,q4 ,what ,,two things are essential to cause ,,hail8 ,a4 ,two strata of clouds having opposite electricities1 and two currents of wind4 ,the lower cloud 7being negative7 is the one precipitated4 ,q4 ,what is ,,rain8 ,a4 ,the vapour of the clouds or air condensed1 and precipitated to the earth4 ,q4 ,why is the vapour of the air or clouds ,,precipitated8 ,a4 ,when the air is saturated with vapour1 if a cold current condenses it1 it is no longer able to hold all its vapour in solution1 and some of it is squeezed out1 and falls as rain4 ,q4 ,why does ,,rain fall in ,,drops8 ,a4 ,the vapoury particles in their descent attract each other2 and those which are sufficiently near1 unite and form into a drop4 ,q4 ,why does not the ,,cold of ,,night ,,always cause rain8 ,a4 ,when the air is not near saturation 7although condensed by the chill of evening71 it will still be able to hold its vapour in solution4 ,q4 ,why does a ,,passing ,,cloud often drop ,,rain8 ,a4 ,because the cloud 7travelling about on the wind7 comes into contact with something that chills it2 and its vapour being squeezed out1 falls to the earth as rain4 ,q4 ,why are ,,rain-,,drops sometimes much ,,larger than at ,,other times8 ,a4 ,when the rain-cloud is floating near the earth1 the drops are large1 because such a cloud is much more dense than one which is more elevated4 ,the size of the rain-drop is increased according to the rapidity with which the vapours are condensed4 ,q4 ,does not ,,wind sometimes ,,increase the ,,size of rain-drops8 ,a4 ,yes2 by blowing two or more drops into one4 ,q4 ,why do ,,clouds ,,fall in ,,rainy weather8 ,a4 #ast--,because the clouds are heavy with abundant vapour3 and #bndly--,as the density of the air is diminished1 it is less able to buoy the clouds up4 ,q4 ,how do you ,,know that the ,,density of the air is ,,diminished in ,,rainy weather8 ,a4 ,because the mercury of a barometer falls4 ,q4 ,why is ,,rain-water more ,,fertilizing than ,,pump-water8 ,a4 ,because it contains a compound of hydrogen and nitrogen 7called ammonia71 which is a very excellent food for young plants4 ,q4 ,why is ,,november made by ,god to be a ,,rainy ,,month8 ,a4 ,because rain hastens the putrefaction of the fallen leaves by causing fermentation4 ,q4 ,why does ,,rain ,,purify the ,,air8 ,a4 #ast--,because it beats down the noxious exhalations collected in the air1 and dissolves them3 #bndly--,it mixes the air of the upper regions with that of the lower regions3 and #crdly--,it washes the earth1 and sets in motion the stagnant sewers and ditches4 ,q4 ,why are ,,mountainous countries more ,,rainy than flat ones8 ,a4 ,the air 7striking against the side of the mountains7 is carried up the inclined plane1 and brought in contact with the cold air of the higher regions1 by which it is condensed1 and its vapour squeezed out4 ,q4 ,why does a ,,sponge ,,swell when it is ,,wetted8 ,a4 ,because the water penetrates the pores of the sponge1 and drives the particles of the sponge further from each other2 in consequence of which1 the bulk of the sponge is greatly increased4 ,q4 ,why do ,,fiddle-strings ,,snap in ,,wet weather8 ,a4 ,because the moisture of the air 7penetrating the string7 causes it to swell2 and 7as the cord thickens7 its tension is increased1 and the string snaps4 ,q4 ,why does ,,paper ,,pucker when it is ,,wetted8 ,a4 ,because the moisture 7penetrating the paper7 drives its particles further apart2 and 7as the moisture is absorbed unequally by the paper7 some parts are more enlarged than others2 in consequence of which1 the paper blisters or puckers4 ,q4 ,why do the weather toys called ,,capu',,chins lift the cowl over the figures in wet weather1 and remove it in dry8 ,a4 ,the cowl of the capu'chin is fastened to a piece of cat-gut4 ,when the weather is wet1 the moisture swells the cat-gut and it is shortened1 by which means the cowl is pulled up2 but in dry weather1 the string is loosened1 and the cowl falls down4 ,q4 ,in another weather toy1 the ,,man comes out in ,,wet weather1 and the ,,lady in ,,fine3--,why is this8 ,a4 ,the two figures are attached to a piece of cat-gut in such a manner1 that when the cat-gut is shortened by moisture1 it pulls the man out2 but when it is loose1 the woman falls out by her own weight4 ,q4 ,why are ,,wet ,,stockings ,,difficult to ,,pull ,,on8 ,a4 ,the moisture 7by penetrating the threads of the stockings7 causes them to shrink in size4 ,q4 ,what is the ,,most ,,rainy spot in ,,england8 ,a4 ,keswick 7in ,cumberland72 and then ,kendal 7a market town in ,westmoreland74 7,in ,keswick1 about #fc inches of rain fall in a year4 ,in ,kendal1 #eh2 ,manchester1 #ch2 ,liverpool1 #cd2 ,dublin and ,cambridge1 #be2 ,lincoln1 #bd2 ,london1 #ba2 and in ,paris1 only #ah47 ,q4 ,in which ,,part of the ,,day does the ,,most ,,rain fall8 ,a4 ,more rain falls by night than by day2 because the cold night condenses the air1 and diminishes its capacity for holding vapour in solution4 ,q4 ,does more rain fall in ,,summer or in ,,winter time8 ,a4 ,there are more rainy days from ,september to ,march2 but heavier rains between ,march and ,september4 ,q4 ,why are there ,,more ,,rainy ,,days from ,september to ,march1 than from ,march to ,september8 ,a4 ,because the temperature of the air is constantly decreasing1 and its capacity for vapour decreases also2 in consequence of which1 it is perpetually obliged to part with some of its vapour in rain4 ,q4 ,in what ,,part of the ,,world does ,,rain fall ,,most ,,abundantly8 ,a4 ,near the equator2 and the quantity of rain decreases as we approach the poles4 ,q4 ,why does ,,more ,,rain fall at the ,,equator than at the ,,poles8 ,a4 ,because the contrast between the night and day is very great4 ,the hot air absorbs moisture very abundantly during the day2 and when the cold night condenses the air1 it is unable to retain the moisture imbibed1 and some of it falls in rain4 ,,chapter ,,xxv4 ,,water4 ,q4 ,what is ,,water8 ,a4 ,water is composed of two gases1 oxygen and hydrogen4 7,in #i lbs4 of water1 #h are oxygen1 and #a is hydrogen47 ,q4 ,why is ,,water ,,fluid8 ,a4 ,because its particles are kept separate by latent heat2 but when a certain quantity of this latent heat is driven out1 water becomes solid1 and is called ice4 ,q4 ,how can ,,water be converted into a ,,gas8 ,a4 ,by increasing its latent heat1 the particles1 of water are again subdivided into invisible steam4 ,q4 ,why is ,,pump water called ,,hard water8 ,a4 ,because it is laden with foreign matters1 and will not readily dissolve substances immersed in it4 ,q4 ,what makes ,,pump-water ,,hard8 ,a4 ,because when it filters through the earth1 it becomes impregnated with sulphate of lime1 and many other impurities from the earths and minerals with which it comes in contact4 ,q4 ,why is it difficult to ,,wash our ,,hands clean with ,,hard water8 ,a4 ,because the soda of the soap combines with the sulphuric acid of the hard water1 and the oil of the soap with the lime1 and float in flakes on the top of the water4 ,n4,b4 ,sulphate of lime consists of sulphuric acid and lime4 ,q4 ,why is it difficult to wash in ,,salt ,,water8 ,a4 ,because salt water contains muriatic acid2 and the soda of soap combines with the muriatic acid of the salt water1 and produces a cloudiness4 ,q4 ,why does a ,,black ,,hat turn ,,red at the ,,sea ,,side8 ,a4 ,the muriatic acid of the sea-water disturbs the gallic acid of the black dye1 and turns it red4 ,q4 ,of what is ,,soap made8 ,a4 ,of kelp 7or the ashes of sea-weed dried and burnt in a pit7 mixed with oil or fat4 ,,yellow ,,soap is made of whale-oil1 soda1 and resin4 ,,soft ,,soap is made of oil and potash4 ,,hard ,,soap of oil and soda4 ,q4 ,why does ,,water ,,clean dirty ,,linen8 ,a4 ,because the oxygen of the water attaches itself to the stains of the linen1 and dissolves them2 as oxalic acid dissolves ink spots4 ,q4 ,why does ,,soap greatly ,,increase the cleansing power of water8 ,a4 #ast--,because soap increases the oxygen of the water3 and #bndly--,it neutralizes the grease of the things washed4 ,q4 ,why is ,,rain ,,water ,,soft8 ,a4 ,because it has not come in contact with earths and minerals4 ,q4 ,why is it ,,more ,,easy to ,,wash with ,,soft water than with ,,hard8 ,a4 ,because it unites freely with the soap1 dissolving it instead of decomposing it1 as hard water does4 ,q4 ,why do ,,wood ,,ashes make ,,hard water ,,soft8 ,a4 #ast--,because the carbonic acid of the wood ashes combines with the sulphate of lime in the hard water1 and converts it into chalk3 and #bndly--,the sulphuric acid of the water combines with the potash of the wood ashes1 and prevents it from neutralizing the oily matter of the soap4 ,q4 ,why has ,,rain water such an ,,unpleasant ,,smell1 when it is collected in a rain water tub or tank8 ,a4 ,because it is impregnated with decomposed organic matter1 washed from roofs1 trees1 or the casks in which it is collected4 ,q4 ,why does ,,water ,,melt ,,sugar8 ,a4 ,because very minute particles of water insinuate themselves into the pores of the sugar1 and force the crystals apart from each other4 ,q4 ,why does ,,water ,,melt ,,salt8 ,a4 ,because very minute particles of water insinuate themselves into the pores of the salt1 and force the crystals apart from each other4 ,q4 ,why does melted ,,sugar or ,,salt give a ,,flavour to the ,,water8 ,a4 ,because the sugar or salt 7being disunited into very minute pieces7 floats about the water1 and mixes with every part4 ,q4 ,why does ,,hot water melt sugar and salt ,,quicker than ,,cold water8 ,a4 #ast--,because the heat of the water entering the pores of the sugar or salt1 opens a passage for the water3 and #bndly--,the particles of hot water being smaller than those of cold1 can more readily penetrate the pores of salt or sugar4 ,q4 ,why is ,,sea-water ,,salt8 ,a4 #ast--,because it contains mines of salt at the bottom of its bed3 #bndly--,it is impregnated with bituminous matter1 which is brackish3 and #crdly--,it contains many putrid substances1 which increase its brackishness4 ,q4 ,why is ,,not ,,rain-water ,,salt1 although most of it is evaporated from the ,,sea8 ,a4 ,because salt will not evaporate2 and1 therefore1 when sea-water is turned to vapour1 its salt is left behind4 ,q4 ,why does ,,stagnant water ,,putrefy8 ,a4 ,because leaves1 plants1 insects1 c4 are decomposed in it4 ,q4 ,why is ,,stagnant water full of ,,worms1 ,,eels1 c48 ,a4 ,because numberless insects lay their eggs in the leaves and plants which float on the surface2 these eggs are soon hatched1 and produce swarms of worms1 eels1 and insects4 ,q4 ,why are ,,flowing waters ,,free from these ,,impurities8 ,a4 #ast--,because the motion of running water prevents its fermentation3 #bndly--,it dissolves the putrid substances which happen to fall into it3 and #crdly--,it casts on the bank 7by its current7 such substances as it cannot dissolve4 ,q4 ,why does ,,running water ,,oscillate and ,,whirl in its current8 ,a4 #ast--,because it impinges against its banks1 and is perpetually diverted from its forward motion3 and #bndly--,because the centre of a river flows faster than its sides4 ,q4 ,why do the ,,sides of a river flow more ,,tardily than its ,,centre8 ,a4 ,because they rub against the banks1 and are delayed in their current thereby4 ,q4 ,why does ,,soapy water ,,bubble8 ,a4 ,because the soap makes the water tenacious1 and prevents the bubbles from bursting as soon as they are formed4 ,q4 ,why will not water bubble ,,without ,,soap8 ,a4 ,because it is not tenacious enough to hold together the bubbles that are formed4 ,q4 ,when ,,soap ,,bubbles are blown from a pipe1 why do they ,,ascend8 ,a4 ,because they are filled with warm breath1 which is lighter than air4 ,,chapter ,,xxvi4 ,,ice4 ,q4 ,what is ,,ice8 ,a4 ,,frozen ,,water4 ,when the air is reduced to #cb degrees of heat1 water will no longer remain in a fluid state4 ,q4 ,why is ,,solid ,,ice ,,lighter than ,,water8 ,a4 ,because water expands by freezing2 and as the bulk is increased1 the gravity must be less4 ,nine cubic inches of water become ten when frozen4 ,q4 ,why do ,,ewers ,,break in a ,,frosty ,,night8 ,a4 ,because the water in them freezes2 and as the water is expanded by frost1 it bursts the ewers to make room for its increased volume4 ,q4 ,why does it not expand ,,upwards 7like boiling water71 and ,,run ,,over8 ,a4 ,because the surface is first frozen1 and the frozen surface acts as a plug1 which is more difficult to burst than the earthen ewer itself4 ,q4 ,why do ,,tiles1 ,,stones1 and ,,rocks often ,,split in winter8 ,a4 ,because the moisture 7which they imbibed7 freezes1 and by its expansion splits the solid mass4 ,q4 ,in winter time1 ,,foot-,,marks and ,,wheel-,,ruts are often covered with an icy ,,net-,,work1 through the interstices of which the soil is clearly seen1--,,why does the water freeze in ,,net-,,work8 ,a4 ,the water in these hollows froze first at the sides of the foot-prints3 other crystals gradually shot across the water1 and would have covered the whole surface1 had not the earth absorbed the water before it had time to freeze4 ,q4 ,in winter time these ,,foot-,,marks and ,,wheel-,,ruts are sometimes covered with a perfect ,,sheet of ice1 and not an icy net-work1--,why is ,,this8 ,a4 ,the air being colder and the earth harder 7than in the former case71 the entire surface of the foot-print is frozen over1 before the earth can draw the water in4 ,q4 ,why is not the ice ,,solid in these ruts8--,,why is there only a very thin ,,film or ,,net-,,work of ice8 ,a4 ,because the earth absorbs the water1 and leaves the icy film behind4 ,q4 ,does not water expand by ,,heat as well as ,,cold8 ,a4 ,yes2 it expands as soon as it is more than #db degrees till it boils1 and then it flies off in steam4 ,illustration3 ,here ,a ,b measures the bulk of a portion of water at #db degrees4 ,it goes on increasing in bulk to ,c ,d1 when it boils4 ,it also goes on increasing in bulk to ,e ,f1 when it freezes4 ,q4 ,why do ,,water-,,pipes frequently ,,burst in ,,frosty weather8 ,a4 ,because the water in them freezes2 and as the water expands by frost1 it bursts the pipes to make room for its increased volume4 ,q4 ,when does ,,water begin to ,,expand from cold8 ,a4 ,water 7which is wisely ordained by ,god to be an exception to a very general rule7 contracts till it is reduced to #db degrees1 and then it expands till it freezes4 7,water freezes at #cb47 ,q4 ,why does water expand when it freezes8 ,a4 ,because it is converted into solid crystals1 which do not fit close1 like the particles of water4 ,q4 ,why is the water at the ,,bottom of a river ,,never ,,frozen8 ,a4 ,because when water is colder than #db degrees1 it instantly ascends to the surface2 and 7if it freezes7 floats there till it is melted4 7,when a river is frozen1 the water below the surface is never less than #db47 ,q4 ,show the ,,wisdom of ,,god in this wonderful exception to a general law4 ,a4 ,if ice were heavier than water1 it would sink2 and a river would soon become a solid block of ice1 which could never be dissolved4 ,q4 ,why does not the cold ,,ice on the ,,surface of a river ,,chill the water ,,beneath1 and make it freeze8 ,a4 #ast--,water is a very bad conductor1 and is heated or chilled by ,,convection only3 #bndly--,if the ice on the surface were to communicate its coldness to the water beneath1 the water beneath must communicate its heat to the ice1 and the ice would instantly melt3 and #crdly--,the ice on the surface acts as a shield to prevent the cold air from penetrating the river to freeze it below the mere crust4 ,q4 ,why does ,,water ,,freeze at the ,,surface first8 ,a4 ,because the surface is in contact with the air1 and the air carries away its heat4 ,q4 ,why does the coat of ice grow ,,thicker and ,,thicker1 if the frost ,,continues8 ,a4 ,because the heat of the water 7immediately below the frozen surface7 passes through the pores of the ice into the cold air4 ,q4 ,why then are not ,,whole ,,rivers ,,frozen 7layer by layer7 till they become solid ice8 ,a4 ,because water is so slow a conductor1 that our frosts never continue long enough to convert a whole river into a solid mass of ice4 ,q4 ,why does not ,,running water freeze so fast as ,,still water8 ,a4 #ast--,because the motion of the current dissolves the crystals as fast as they are formed2 and #bndly--,the heat of the under surface is more freely distributed to the upper surface by the rolling water4 ,q4 ,when ,,running water is ,,frozen1 why is the ,,ice generally very ,,rough8 ,a4 ,because little flakes of ice are first formed and carried down the stream1 till they meet some obstacle to stop them2 other flakes of ice 7impinging against them7 are arrested in like manner2 and the edges of the different flakes overlapping each other1 make the surface rough4 ,q4 ,why do ,,some parts of a ,,river ,,freeze ,,less than ,,others8 ,a4 ,because springs issue from the bottom1 and 7as they bubble upwards7 thaw the ice1 or make it thin4 ,q4 ,when persons ,,fall into a ,,river in winter time1 why does the ,,water feel remarkably ,,warm8 ,a4 ,because the frosty air is at least #aj or #ab degrees colder than the water4 7,the water below the surface is at least #db2 but the air #cb1 or even less47 ,q4 ,why is ,,shallow water ,,frozen ,,quicker than ,,deep water8 ,a4 ,because 7as the whole volume of water must be cooled to #db degrees before the surface can be frozen7 it will take a longer time to cool down a deep bed of water than a shallow one4 ,q4 ,why is ,,sea-,,water ,,rarely ,,frozen8 ,a4 #ast--,because the mass of water is so great that it requires a very long time to cool the whole volume down to #db degrees3 #bndly--,the ebb and flow of the sea interfere with the cooling influence of the air3 and #crdly--,salt never freezes till the surface is cooled down at least #be degrees below the freezing point4 ,q4 ,why do some ,,lakes ,,rarely if ever ,,freeze8 ,a4 #ast--,because they are very deep3 #bndly--,because their water is supplied by springs1 which bubble from the bottom4 ,q4 ,why does the ,,depth of the water ,,retard its ,,freezing8 ,a4 ,as the whole volume of water must be reduced to #db degrees before the surface will freeze1 the deeper the water1 the longer it will be before the whole volume is thus reduced4 ,q4 ,why do ,,springs at the bottom of a lake ,,prevent its ,,freezing8 ,a4 ,because they keep continually sending forth fresh water1 which prevents the lake from being reduced to the necessary degree of coldness4 ,q4 ,why is it ,,colder in a ,,thaw than in a ,,frost8 ,a4 ,when frozen water is thawed1 it absorbs heat from the air and objects around to melt its ice1 in consequence of which the cold is greatly increased4 ,q4 ,why is it ,,warmer in a ,,frost than in a ,,thaw8 ,a4 ,when water freezes it gives out its latent heat1 in order that it may be converted into solid ice2 and as much heat is liberated from the water into the air1 we feel warmer4 ,q4 ,why does ,,salt ,,dissolve ,,ice8 ,a4 ,water freezes at #cb1 but salt and water will not freeze till the air is #be colder3 if1 therefore1 salt be added to frozen water it becomes liquid1 unless the thermometer stands below #g1 7which it never does in our island74 ,q4 ,will any thing do ,,instead of ,,salt8 ,a4 ,yes2 any acid1 such as sulphuric1 nitric1 c4 ,q4 ,why are ,,salt and ,,snow mixed together1 colder than ,,snow8 ,a4 ,when salt is mixed with snow1 it dissolves the crystals into a fluid2 and whenever a solid is converted to a liquid1 heat is absorbed1 and the cold made more intense4 ,q4 ,why does ,,frost make the ,,earth ,,crack8 ,a4 ,during the warm weather the earth absorbed abundance of moisture1 which the winter freezes3 and 7as water expands by frost7 the expanding water thrusts the particles of earth apart from each other1 and leaves a chink or crack behind4 ,q4 ,show the ,,wisdom of ,,god in this arrangement4 ,a4 ,these cracks in the earth let in the air1 the dew and rain1 and many gases favourable to vegetation4 ,q4 ,why does the ,,earth ,,crumble in ,,spring8 ,a4 ,in spring the ice of the clods dissolves1 and the particles of earth 7which had been held apart by the expanded ice7 are left unsupported1 and tumble into minute parts 7because their cement is dissolved74 ,q4 ,why does ,,mortar ,,crumble away in ,,frost8 ,a4 ,if the mortar was not dried in the warm weather1 its moisture freezes1 expands1 and thrusts the particles of the mortar away from each other2 but 7as soon as the frost goes7 the water condenses and leaves the mortar full of cracks and chinks4 ,q4 ,why does ,,stucco ,,peel from a ,,wall in ,,frosty weather8 ,a4 ,if the stucco was not dried in the warm weather1 its moisture freezes1 expands1 and thrusts its particles away from the wall2 but as soon as the water condenses again by the thaw1 the stucco 7being unsupported7 falls by its own weight4 ,q4 ,why cannot ,,bricklayers and ,,plasterers work in ,,frosty weather8 ,a4 ,because the bricks and plaster would start from their position as soon as the frost came and expanded the mortar4 ,q4 ,why do ,,bricklayers ,,cover their work with ,,straw in spring and autumn8 ,a4 ,because straw is a non-conductor1 and prevents the mortar of their new work from freezing during the cold nights of spring and autumn4 ,q4 ,why are ,,water-,,pipes often covered with ,,stall-,,litter in winter time8 ,a4 ,because straw 7being a non-conductor7 prevents the water of the pipes from freezing1 and the pipes from bursting4 ,q4 ,why are delicate ,,trees covered with ,,straw in ,,winter8 ,a4 ,because straw 7being a non-conductor7 prevents the sap of the tree from being frozen4 ,q4 ,can ,,water be ,,frozen in any way ,,besides by frosty weather8 ,a4 ,yes2 in very many ways4 ,for example--a bottle of water wrapped in cotton1 and frequently wetted with ether1 will soon freeze4 ,q4 ,why would ,,water ,,freeze if the bottle were kept constantly wetted with ,,ether8 ,a4 ,because evaporation would carry off the heat of the water1 and reduce it to freezing point4 ,q4 ,why does ,,ether freeze under the ,,receiver of an ,,air-pump1 when the air is exhausted8 ,a4 ,because evaporation is very greatly increased by the diminution of atmospheric pressure2 and the ether freezes by evaporation4 ,,freezing ,,mixtures4 #a4 ,if nitre be dissolved in water1 the heat of the liquid will be reduced #af degrees4 #b4 ,if #e oz4 of nitre1 and #e of sal-ammoniac 7both finely powdered7 be dissolved in #ai oz4 of water1 the heat of the liquid will be reduced #dj degrees4 #c4 ,if #c lbs4 of snow be added to #a lb4 of salt1 the mixture will fall to #j 7or #cb degrees below freezing point74 ,the two following are the coldest mixtures yet known3-- #a4 ,mix #c lbs4 of muriate of lime with #a lb4 of snow4 #b4 ,mix #e lbs4 of diluted sulphuric acid with #d lbs4 of snow4 ,q4 ,why is it more easy to ,,swim in the ,,sea than in a ,,river8 ,a4 ,because the specific gravity of salt water is greater than that of fresh1 and therefore it buoys up the swimmer better4 ,q4 ,how do cooks ascertain if their ,,brine be ,,salt ,,enough for pickling8 ,a4 ,they put an egg into their brine4 ,if the egg sinks the brine is not strong enough1 if the egg floats it is4 ,q4 ,why will the ,,egg ,,sink if the brine be ,,not ,,strong enough for pickling8 ,a4 ,as an egg is heavier than water1 it will sink if immersed therein2 but if as much salt be added as the water can dissolve1 the egg will float4 ,q4 ,why will the ,,egg ,,float in strong ,,brine8 ,a4 ,because the specific gravity of salt and water is greater than that of water only4 ,q4 ,why do persons ,,sink in water when they are ,,unskilful ,,swimmers8 ,a4 #ast--,because 7in their floundering about7 they take in water at their nose and mouth1 which makes them heavier3 #bndly--,,fear contracts the body2 and as the body is compressed by fear into a smaller compass1 it becomes heavier3 and #crdly--,the water and fear take away the breath2 and when the breath is taken from the body1 its bulk is reduced1 and it becomes heavier4 ,q4 ,why can ,,quadrupeds swim ,,more ,,easily than ,,man8 ,a4 #ast--,because the trunk of a quadruped is lighter than water1 and this is the greatest part of them3 #bndly--,the position of a beast in water is a natural one4 ,q4 ,why is it ,,more ,,difficult for a ,,man to swim than for a ,,beast8 ,a4 ,because the head and limbs of a man 7like those of a beast7 are heavier than water1 and these compose more than half his body3 #bndly--,the position of a man in water is unnatural to him4 ,q4 ,why can ,,fat men ,,swim more ,,easily than ,,spare men8 ,a4 ,fat is lighter than water2 and the fatter a man is1 the more buoyant will he be4 ,q4 ,how are ,,fishes able to ,,ascend to the ,,surface of water8 ,a4 ,fishes have an air-bladder near their abdomen3 when this bladder is filled with air1 the fish increases in size2 and 7being lighter7 ascends through the water to its surface4 ,q4 ,how are fishes able to ,,dive in a minute to the ,,bottom of a stream8 ,a4 ,they expel the air from their air-bladder2 in consequence of which1 their size is diminished1 and they sink instantly4 ,,chapter ,,xxvii4 ,,light4 ,q4 ,what is ,,light8 ,a4 ,rapid undulations of a fluid called ether1 striking on the optic nerve of the eye4 7,see p4 #df47 ,the heat of fire or of the sun sets the atoms of matter in motion2 and these atoms1 striking against the fluid ether1 cause it to undulate4 ,q4 ,how ,,fast does ,,light ,,travel8 ,a4 ,light travels so fast1 that it would go eight times round the earth1 while a person counts ,,one4 ,q4 ,does ,,all light travel equally fast8 ,a4 ,yes2 the light of the sun1 or the light of a candle1 or the light from houses1 trees1 and fields4 ,q4 ,where does the ,,light of ,,houses1 ,,trees1 and ,,fields come from8 ,a4 ,the light of the sun 7or of some lamp or candle7 is reflected from their surfaces4 ,q4 ,why are ,,some surfaces ,,brilliant like glass and steel1 and ,,others ,,dull like lead8 ,a4 ,those surfaces which reflect the most light1 are the most brilliant2 and those which absorb light are dull4 ,q4 ,what is meant by ,,reflecting ,,light8 ,a4 ,throwing the rays of light back again1 from the surface on which they light4 ,q4 ,what is meant by ,,absorbing ,,light8 ,a4 ,letting the rays of light sink below the surface which they touch1 so as not to be seen4 ,q4 ,why can a ,,thousand persons ,,see the ,,same ,,object at the same time8 ,a4 ,because it throws off from its surface an infinite number of rays in all directions2 and one person sees one portion of these rays1 and another person another4 ,q4 ,why is the ,,eye ,,pained by a ,,sudden light8 ,a4 ,because the pupil of the eye is burdened with rays1 before it has had time to contract4 ,q4 ,why does it give us ,,pain1 if a ,,candle be brought suddenly towards our ,,bed at night time8 ,a4 ,in the dark the pupils of the eyes dilate very much1 in order to admit more rays4 ,when a candle is brought before them1 the enlarged pupil is overladen with rays1 and feels pained4 ,q4 ,why ,,can we ,,bear the candle-light after a few moments8 ,a1 ,because the pupil contracts again almost instantly1 and adjusts itself to the quantity of light which falls upon it4 ,q4 ,why can we ,,see ,,nothing1 when we leave a ,,well-,,lighted room1 and go into the ,,dark ,,road or street8 ,a4 ,because the pupil 7which contracted in the bright room7 does not dilate instantaneously2 and the contracted pupil is not able to collect rays enough 7from the dark road or street7 to enable us to see before us4 ,q4 ,why do we ,,see ,,better1 when we get ,,used to the dark8 ,a4 ,because the pupil dilates again1 and is able to gather together more rays2 in consequence of which1 we see more distinctly4 ,q4 ,if we look at the ,,sun for a few moments1 why do all ,,other things appear ,,dark8 ,a4 ,because the pupil of the eye 7which was very much contracted by looking at the sun7 is too small to collect sufficient rays from other objects1 to enable us to distinguish their colours4 7,see accidental colours47 ,q4 ,if we watch a bright ,,fire for a few moments1 why does the ,,room seem ,,dark8 ,a4 ,because the pupil of the eye 7which was very much contracted by looking at the fire7 is too small to collect sufficient rays from the objects around1 to enable us to distinguish their colours4 ,q4 ,why can we see the ,,proper ,,colour of every object again1 after a few minutes8 ,a4 ,because the pupil dilates again1 and accommodates itself to the light around4 ,q4 ,why can ,,tigers1 ,,cats1 and ,,owls see in the ,,dark8 ,a4 ,because they have the power of enlarging the pupil of their eyes1 so as to collect several scattered rays of light2 in consequence of which1 they can see distinctly when it is not light enough for us to see any thing at all4 ,q4 ,why do ,,cats and ,,owls ,,sleep almost all ,,day8 ,a4 ,as the pupil of their eyes is very broad1 daylight fatigues them2 so they close their eyes for relief4 ,q4 ,why do ,,cats keep ,,winking1 when they sit before a ,,fire8 ,a4 ,as the pupil of their eyes is very broad1 the light of the fire pains them2 and they keep shutting their eyes to relieve the sensation of too much light4 ,q4 ,why do ,,tigers1 ,,cats1 ,,owls1 c4 ,,prowl by ,,night for prey8 ,a4 ,as these animals cannot see distinctly in strong daylight1 they sleep during the day3 and as they can see clearly in the dark1 they prowl then for prey4 ,q4 ,why do ,,glow-,,worms glisten by ,,night only8 ,a4 ,because the light of day is so much stronger1 that it eclipses the feeble light of a glow-worm2 in consequence of which1 glow-worms are invisible by day4 ,q4 ,why can we not see the ,,stars in the ,,day-,,time8 ,a4 ,because the light of day is so powerful1 that it eclipses the feeble light of the stars3 in consequence of which1 they are invisible by day4 ,q4 ,why can we see the ,,stars even at ,,mid-,,day1 from the bottom of a deep ,,well8 ,a4 ,as the rays of the sun never come directly over a well1 but the rays of the stars do2 therefore the light from those stars 7in such a situation7 is more clear than the light of the sun4 ,q4 ,what is the ,,use of ,,two ,,eyes1 since they present only one image of any object8 ,a4 ,the use of two eyes is to increase the light1 or take in more rays of light from the object looked at1 in order that it may appear more distinct4 ,q4 ,why do we ,,not see things ,,double1 with ,,two ,,eyes8 ,a4 #ast--,because the axis of both eyes is turned to one object2 and1 therefore1 the same impression is made on the retina of each eye4 #bndly--,the nerves 7which receive the impression7 have one point of union1 before they reach the brain4 ,q4 ,why do we ,,see ,,ourselves in a ,,glass8 ,a4 ,the rays of light from our face strike against the surface of the glass1 and 7instead of being absorbed7 are reflected1 or sent back again to our eye4 ,q4 ,why are the rays of light ,,reflected by a ,,mirror8 ,a4 ,because they cannot pass through the impenetrable metal with which the back of the glass is covered2 so they rebound back1 just as a marble would do if it struck against a wall4 ,q4 ,when a marble is rolled towards a wall1 what is that path ,,through ,,which ,,it ,,runs called8 ,a4 ,the line of the angle of incidence4 ,q4 ,when a marble ,,rebounds back again1 what is the path it ,,then describes called8 ,a4 ,the line of the angle of reflection4 ,q4 ,when the light of our face goes ,,to the ,,glass1 what is the path through which it goes ,,called8 ,a4 ,the line of the angle of incidence4 ,q4 ,when the light of our face is reflected ,,back again from the mirror1 what is this ,,returning path called8 ,a4 ,the line of the angle of reflection4 ,q4 ,why does our reflection in a mirror seem to ,,approach us as we walk ,,towards it1 and to ,,retire ,,from us as ,,we retire8 ,a4 ,because the line of the angle of incidence is always equal to the line and angle of reflection4 ,illustration3 ,here ,,ca1 ,,ea and ,,db1 ,,fb are the lines of the angle of incidence2 and ,,ga1 ,,ka and ,,hb1 ,,lb are the lines of the angle of reflection4 ,when the arrow is at ,,cd1 its shadow will appear at ,,gh1 because the line ,,ca,,ga and the angle ,,cabangle ,,gab1 c42 and the same may be said about the point ,d4 ,q4 ,why can a man see his ,,whole ,,person reflected in a ,,little ,,mirror not #f inches in length8 ,a4 ,because the line of the angle of incidence is always equal to the line and angle of reflection4 ,take the last figure--,,cd is much larger than the mirror ,,ab2 but the head of the arrow ,c is reflected obliquely behind the mirror to ,g2 and the barb ,d appears at ,h4--,why8 ,because the line ,,ca,,ag and the angle ,,cabangle ,,gab1 c4 ,the same may be said of the point ,d4 ,q4 ,why does a ,,shadow in ,,water always appear ,,topsy-,,turvy8 ,a4 ,because the line of the angle of incidence is always equal to the line and angle of reflection4 ,illustration3 ,here the arrow-head ,a strikes the water at ,f1 and is reflected to ,d2 and the barb ,b strikes the water at ,e1 and is reflected to ,c4 ,if a spectator stands at ,g1 he will see the reflected lines ,,ce and ,,df1 produced as far as ,g4 ,it is very plain that the more elevated object ,a will strike the water1 and be projected from it more perpendicularly than the point ,b1 and therefore the shadow will seem inverted4 ,q4 ,when we see our ,,shadow in ,,water1 why do we seem to ,,stand on our ,,head8 ,a4 ,because the line of the angle of incidence is always equal to the line and angle of reflection4 ,suppose our head to be at ,a1 and our feet at ,b2 then the shadow of our head will be seen at ,d1 and the shadow of our feet at ,c4 7,see last figure47 ,q4 ,why do ,,windows seem to ,,blaze at ,,sun-,,rise and ,,sun-,,set8 ,a4 ,because glass is a good reflector of light2 and the rays of the sun 7striking against the window glass7 are reflected1 or thrown back4 ,q4 ,why do ,,not windows reflect the ,,noon-,,day rays also8 ,a4 ,they do1 but the reflection is not seen4 ,q4 ,why is the reflection of the ,,rising and ,,setting sun seen in the window1 and ,,not that of the ,,noon-,,day sun8 ,a4 ,as the angle of incidence always equals the angle of reflection1 therefore the rays of the noon-day sun enter the glass too perpendicularly for their reflection to be seen4 ,illustration3 ,here ,,ab represents a ray of the noon-day sun striking the window at ,b2 its reflection will be at ,c3 ,but ,,db 7a ray of the rising or setting sun7 will be reflected to ,e 7the eye of the spectator74 ,q4 ,why can we not see the ,,reflection of the ,,sun in a ,,well1 during the day-time8 ,a4 ,because the rays of the ,,sun fall so obliquely1 that they never reach the surface of the water at all1 but strike against the brick sides4 ,illustration3 ,let ,,bdec be the well1 and ,,de the water4 ,the ray ,,ab strikes against the brick-work inside the well2 and ,the ray ,,ac strikes against the brick-work outside the well4 ,none will ever touch the water ,,de4 ,q4 ,why do we see the ,,moon reflected in a ,,well very ,,often8 ,a4 ,as the rays of the ,,moon are not so oblique as those of the sun1 they will often reach the water4 7,see next figure47 ,q4 ,why are the ,,stars ,,reflected in a ,,well1 although the ,,sun is ,,not8 ,a4 ,as the rays of the ,,stars are not so oblique as those of the sun1 they will often reach the water4 ,illustration3 ,here the moon's rays ,,ab1 ,,ac1 both strike the water ,,de1 and are reflected by it4 ,q4 ,in a sheet of water at noon1 the sun appears to shine upon only ,,one spot1 and all the ,,rest of the water seems ,,dark1--,,why is this8 ,a4 ,because the rays 7which fall at various degrees of obliquity on the water7 are reflected at similar angles2 but as only those which meet the eye of the spectator are visible1 all the sea will appear dark but that one spot4 ,illustration3 ,here of the rays ,,sa1 ,,sb1 and ,,sc1 only the ray ,,sc meets the eye of the spectator ,d4 ,the spot ,c1 therefore1 will appear luminous to the spectator ,d1 but no other spot of the water ,,abc4 ,q4 ,at night the ,,moon seems to be reflected from only ,,one ,,spot of a lake of water1 while all the ,,rest seems ,,dark1--,,why is this8 ,a4 ,because the rays 7which fall at various degrees of obliquity on the lake7 are reflected at similar angles2 but as only those which enter the eye of the spectator will be visible1 all the water will appear dark but that one spot4 7,see last figure47 ,q4 ,why are ,,more ,,stars visible from a ,,mountain1 than from a ,,plain8 ,a4 ,as the air absorbs and diminishes light1 the higher we ascend1 the less light will be absorbed4 ,q4 ,why does the ,,sun seem ,,larger at his ,,rise and ,,set1 than it does at ,,noon8 ,a4 ,because the earth is surrounded by air1 which acts like a magnifying glass2 and when the sun is near the horizon 7as its rays pass through more of this air71 it is more magnified4 ,illustration3 ,here ,,sc represents a ray of the sun at noon1 and ,,mc a ray of the sun near the horizon4 ,,deg represents the air or atmosphere around the earth4 ,because ,,ec is longer than ,,dc1 therefore the rays of the sun at ,m pass through more air than the rays of the sun at ,s1 and the sun is more magnified4 ,q4 ,why does the ,,rising and ,,setting ,,moon appear so much ,,larger1 than after it is risen higher above our heads8 ,a4 ,because the earth is surrounded by air1 which acts like a magnifying glass2 and when the moon is near the horizon 7as its rays pass through more of this air7 it is more magnified4 7,see last figure47 ,q4 ,when ,,candles are ,,lighted1 we ,,cannot ,,see into the ,,street or road1--,,why is this8 ,a4 #ast--,because glass is a reflector1 and throws the candle-light back into the room again2 and #bndly--,the pupil of the eye 7which has become contracted by the light of the room7 is too small to collect rays enough from the dark street1 to enable us to see into it4 ,q4 ,why can't persons in the street ,,see into a ,,well-,,lighted ,,room8 ,a4 ,because the pupil of their eyes is much dilated by the dark1 and cannot collect from the window sufficient rays to enable them to see into the room4 ,q4 ,why do we often see the ,,fire ,,reflected in our parlour ,,window in winter time8 ,a4 ,because glass is a good reflector2 and the rays of the fire 7striking against the window-glass7 are reflected back into the room again4 ,q4 ,why do we often see the shadow of our ,,candles in the window1 while we are sitting in our parlour8 ,a4 ,because the rays of the candle 7striking against the glass7 are reflected back into the room3 and the darker the night1 the clearer the reflection4 ,q4 ,why is this reflection more clear1 if the external ,,air be ,,dark8 ,a4 ,because the reflection is not then eclipsed by the brighter rays of the sun striking on the other side of the window4 ,q4 ,why is the ,,shadow of an object 7thrown on the wall7 ,,larger and larger1 the ,,closer any object be held to the ,,candle8 ,a4 ,because the rays of light diverge 7from the flame of a candle7 in straight lines1 like lines drawn from the centre of a circle4 ,illustration3 ,here the arrow ,a held close to the candle1 will cast the shadow ,,bf on the wall3 while the same arrow held at ,c1 would cast only the little shadow ,d ,e4 ,q4 ,when we enter a long ,,avenue of ,,trees1 ,,why does the avenue seem to get ,,narrower and narrower till it appears to ,,meet8 ,a4 ,because the further the trees are off1 the more acute will be the angle that any two will make with our eye4 ,illustration3 ,here the width between the trees ,a and ,b will seem to be as great as the line ,,ab3 ,but the width between the trees ,c and ,d will seem to be no more than ,,ef4 ,q4 ,in a long straight ,,street1 ,,why do the houses seem to ,,approach ,,nearer and nearer as they are more ,,distant8 ,a4 ,because the more distant the houses are1 the more acute will be the angle which any two make with our eye4 ,thus in the last figure-- ,if ,a and ,b were two houses at the top of the street1 the street would seem to be as wide as the line ,a ,b3 ,and if ,c and ,d were two houses at the bottom of the street1 the street at the bottom would seem to be no wider than ,e ,f4 ,q4 ,in an ,,avenue of ,,trees1 ,,why do they seem to be ,,smaller as their distance increases8 ,a4 ,because the further the trees are off1 the more acute will be the angle made by their perpendicular height with our eye4 ,illustration3 ,here the first tree ,a ,b will appear the height of the line ,a ,b2 but the last tree ,c ,d will appear only as high as the line ,e ,f4 ,q4 ,in a long straight ,,street1 ,,why do the houses seem to be ,,smaller and smaller the ,,further they are ,,off8 ,a4 ,because the further any house is off1 the more acute will be the angle made by its perpendicular height with our eye4 ,thus in the last figure-- ,if ,a ,b be a house at the top of the street1 its perpendicular height will be that of the line ,a ,b4 ,if ,c ,d be a house at the bottom of the street1 its perpendicular height will appear to be that of ,e ,f4 ,q4 ,why does a man on the ,,top of a ,,mountain or church spire seem to be no ,,bigger than a ,,crow8 ,a4 ,because the angle made by the perpendicular height of the man 7at that distance7 with our eye1 is no bigger than the perpendicular height of a crow close by4 ,illustration3 ,let ,,ab be a man on a distant mountain or spire1 and ,,cd a crow close by3 ,the man will appear only as high as the line ,,cd1 which is the height of the crow4 ,q4 ,why does the ,,moon appear to us so much ,,bigger than the ,,stars1 though in fact it is a great deal ,,smaller8 ,a4 ,because the moon is very much nearer to us than any of the stars4 ,illustration3 ,let ,,ab represent a fixed star1 and ,,cd the moon4 ,,ab1 though much the larger body1 will appear no bigger than ,,ef2 whereas the moon 7,,cd7 will appear as big as the line ,,cd to the spectator ,g4 ,the moon is #bdj1jjj miles from the earth1 not quite a quarter of a million of miles4 ,the nearest fixed stars are #bj1jjj1jjj1jjj1jjj4 7i4 e4 #bj billions47 ,if a ball went #ejj miles an hour1 it would reach the moon in twenty days3 but it would not reach the nearest fixed star in #d1ejj1jjj years4 ,had it begun1 therefore1 when ,adam was created1 it would be no further on its journey than a coach 7which has to go from the bottom of ,cornwall to the top of ,scotland7 after it has past about three-quarters of a mile4 ,q4 ,why does the ,,moon 7which is a sphere7 ,,appear to be a ,,flat surface8 ,a4 ,it is so far off1 that we cannot distinguish any difference between the length of the rays which issue from the edge1 and those which issue from the centre4 ,illustration3 ,the rays ,,ad and ,,cd appear to be no longer than the ray ,,bd2 but if all the rays seem of the same length1 the part ,b will not seem to be nearer to us than ,a and ,c1 and therefore ,,abc will look like a flat or straight line4 ,the rays ,,ad and ,,cd are #bdj1jjj miles long4 ,the ray ,,bd is #bch1iaj miles long4 ,q4 ,why do the ,,sun and ,,stars 7which are spheres7 appear to be ,,flat surfaces8 ,a4 ,because they are such an immense way off1 that we can discern no difference of length between the rays which issue from the edge1 and those which issue from the centre of these bodies4 ,the rays ,,ad and ,,cd appear no longer than ,,bd2 and as ,b appears to be no nearer than ,a or ,c1 therefore ,,abc must all seem equally distant2 and ,,abc will seem a flat or straight line4 7,see last figure47 ,q4 ,why does ,,distance make an object ,,invisible8 ,a4 ,because the angle 7made by the perpendicular height of the distant object with our eye7 is so very acute1 that one line of the angle merges in the other4 ,illustration3 ,here the tree ,,ad would not be visible to the spectator ,c1 even if he were to approach as far as ,b2 because no visible perpendicular can be inserted between the two lines ,,ac1 ,,dc1 till after the point ,b is past2 when the tree will appear like a very little speck4 ,q4 ,why do ,,telescopes enable us to ,,see objects ,,invisible to the naked eye8 ,a4 ,because they concentrate several rays within the tube of the telescope1 and bend them upon the mirror or lens1 which acts as a magnifying glass4 ,q4 ,when a ,,ship 7out at sea7 is approaching the shore1 why do we ,,see the small ,,masts before we see the bulky ,,hull8 ,a4 ,because the earth is round1 and the curve of the sea hides the hull from our eyes1 after the tall masts have become visible4 ,illustration3 ,here only that part of the ship above the line ,,ac can be seen by the spectator ,a2 the rest of the ship is hidden by the swell of the curve ,,de4 ,q4 ,what is meant by ,,refraction8 ,a4 ,the bending of a ray of light1 as it passes from one medium to another4 ,q4 ,how is a ray of light ,,bent1 as it passes from one medium to another8 ,a4 ,when a ray of light passes into a denser medium1 it is bent towards the perpendicular4 ,when it passes into a rarer medium1 it is bent from the perpendicular4 ,illustration3 ,suppose ,,de to be a perpendicular line4 ,if ,,ab 7a ray of light17 enters the water1 it will be bent towards the perpendicular to ,c4 ,if 7on the other hand7 ,,cb 7a ray of light7 emerges from the water1 it would be bent away from the perpendicular towards ,a4 ,q4 ,why does a ,,spoon 7in a glass of water7 always appear ,,bent8 ,a4 ,because as the light of the spoon emerges from the water1 it is refracted4 ,and the spoon looks like ,,abc4 7,see the last figure47 ,q4 ,why does a river always appear more shallow than it really is8 ,a4 ,because the light of the bottom of the river is ,,refracted as it emerges out of the water3 and 7as a stick is not so long when it is bent1 as it is when it is straight7 so the river seems less deep than it really is4 ,q4 ,how much deeper is a river than it seems to be8 ,a4 ,one-third4 ,if1 therefore1 a river seems only #d feet deep1 it is really #f feet deep4 ,n4 ,b4 ,many boys get out of their depth in bathing1 in consequence of this deception4 ,remember1 a river is always one-third deeper than it appears to be3--thus1 if a river seems to be #d feet deep1 it is in reality #f feet deep1 and so on4 ,q4 ,why do fishes always seem to be nearer the surface of a river than they really are8 ,a4 ,because the rays of light from the fish are refracted as they emerge from the eye3 and 7as a bent stick is not so far from end to end as a straight one7 so the fishes appear nearer our eye than they really are4 ,q4 ,why are some persons ,,near-,,sighted8 ,a4 ,because the ,,cor,,nea of their eye is so prominent1 that the image of distant objects is reflected before it reaches the ,,ret',,ina2 and1 therefore1 is not distinctly seen4 ,n4,b4 ,the cornea shields the ,,crystalline ,,lens1 and is more or less convex according to the lens which it covers4 ,q4 ,what is meant by the ,,cor',,nea of the ,,eye8 ,a4 ,all the outside of the visible part of the eye-ball4 ,illustration3 ,the curve ,a ,b ,c is called the ,,cor',,nea4 ,if this curve be too prominent 7or convex71 the eye is near-sighted4 ,if too flat 7or concave71 the eye is far-sighted4 ,q4 ,what is meant by the ,,ret',,ina of the ,,eye8 ,a4 ,the net-work which lines the back of the eye1 is so called4 ,illustration3 ,the net-work ,,abc is called the ret'ina1 and the projecting part ,,def is called the cor'nea4 ,q4 ,what sort of ,,glasses do ,,near-,,sighted persons wear8 ,a4 ,if the cor'nea be too convex 7or projecting71 the person must wear double concave glasses1 to counteract it4 ,q4 ,what is meant by ,,double ,,concave ,,glasses8 ,a4 ,glasses hollowed in on both sides4 ,illustration3 ,the figure ,a is double concave1 or concave on both sides4 ,q4 ,what is meant by the ,,image of objects being reflected ,,before it reaches the ,,ret',,ina8 ,a4 ,if the cor'nea be too convex1 the image of a distant object is reflected 7on the vitreous humours of the eye7 before it reaches the ret'ina4 ,illustration3 ,thus the image is reflected at ,,de1 instead of on ,,abc 7the ret'ina74 ,q4 ,what is the use of ,,double ,,concave ,,spectacle glasses8 ,a4 ,near-sighted spectacles cast the reflection further back2 and the image 7being thrown upon the ret'ina7 becomes visible4 ,q4 ,why are ,,old people ,,far-,,sighted8 ,a4 ,because the humours of their eyes are dried up by age1 and the ,,cor',,nea sinks in1 or becomes flattened4 ,q4 ,why does the ,,flattening of the ,,cor',,nea prevent persons seeing objects which are ,,near8 ,a4 ,as the cor'nea is too flat1 the image of any near object is formed behind the ,,ret',,ina of the eye1 and is not seen at all4 ,illustration3 ,the reflection is made at ,,de1 instead of at ,,abc 7the retina74 ,q4 ,what sort of ,,glasses do ,,old people ,,wear8 ,a4 ,as their cor'nea is not sufficiently convex1 they must use double convex glasses1 to enable them to see objects near at hand4 ,q4 ,what sort of glasses are ,,double ,,convex ,,spectacle-,,glasses8 ,a4 ,glasses which curve outwards on both sides4 ,illustration3 ,the figure ,a is double convex1 or convex on both sides4 ,q4 ,what is the ,,use of ,,double ,,convex spectacle-glasses8 ,a4 ,as the image of near objects is reflected behind the ,,ret',,ina1 these double convex glasses shorten the focus of the eye1 and bring the image into the eye 7upon the ret'ina74 ,q4 ,why do ,,near-,,sighted persons bring objects ,,close to the eye1 in order to ,,see ,,them8 ,a4 ,as the distance between the front and back of their eye is too great1 distant objects are reflected before they reach the ret'ina2 therefore1 near-sighted persons bring the objects closer1 in order that the reflection may be cast further back1 7to reach the ret'ina74 ,q4 ,why do ,,old people ,,hold objects ,,further ,,off1 in order to see them better8 ,a4 ,as the distance between the front and back of their eye is not great enough1 the reflection of near objects is thrown beyond the ret'ina2 therefore1 they hold objects a long way off1 in order to bring their images forward 7so as to cast it on the ret'ina74 ,q4 ,why are ,,hawks able to see such an ,,immense way off8 ,a4 ,because they have a muscle in the eye which enables them to flatten their cor'nea1 by drawing back the crystalline lens4 ,this muscle is called the marsupium4 ,q4 ,why can ,,hawks not only see such a long way off1 but also objects within half-an-inch of their eye8 ,a4 ,because their eyes are furnished with a broad circular rim which confines the action of this muscle1 and throws the cor'nea forward4 ,q4 ,into how many ,,parts may a ,,ray of ,,light be ,,divided8 ,a4 ,into three parts3 ,,blue1 ,,yellow1 and ,,red4 ,n4,b4 ,these #c colours1 by combination1 make seven4 #a4--,,red4 #b4--,red and yellow form ,,orange4 #c4--,,yellow4 #d4--,yellow and blue make ,,green4 #e4--;,,blue4 #f and #g4--,shades of blue called ,,indigo and ,,violet4 ,q4 ,how is it ,,known1 that a ray of light consists of several different colours8 ,a4 ,because1 if a ray of light be cast upon a triangular piece of glass 7called a prism71 it will be distinctly divided into seven colours3 #a4--,red2 #b4--,orange2 #c4--,yellow2 #d4--;,green2 #e4--;,blue2 #f4--;,indigo2 and #g4--,violet4 ,q4 ,why does a ,,prism ,,divide a ray of light into ,,various ,,colours8 ,a4 ,because all these colours have different refractive powers4 ,red is refracted least1 and blue the most2 therefore1 the blue colour of the ray will be bent to the top of the prism1 and the red will remain at the bottom4 ,illustration3 ,here the ray ,,ab received on a prism1 would have the blue part bent up to ,c2 the yellow part to ,d2 and the red part no further than ,e4 ,q4 ,what is meant by the ,,refraction of a ray8 ,a4 ,bending it from its straight line4 ,thus the ray ,,ab of the last figure is refracted at ,b into three courses1 ,c1 ,d1 and ,e4 ,q4 ,what is the cause of a ,,rainbow8 ,a4 ,when the clouds opposite the sun are very dark1 and rain is still falling from them1 the rays of the bright sun are divided by the rain-drops1 as they would be by a prism4 ,illustration3 ,let ,a1 ,b1 and ,c be three drops of rain2 ,,sa1 ,,sb1 and ,,sc three rays of the sun4 ,,sa is divided into the #c colours2 the blue and yellow are bent above the eye ,d1 and the red enters it4 ,the ray ,,sb is divided into the three colours2 the blue is bent above the eye1 and the red falls below the eye ,d2 but the yellow enters it4 ,the ray ,,sc is also divided into the three colours4 ,the blue 7which is bent most7 enters the eye2 and the other two fall below it4 ,thus the eye sees the blue of ,c1 and all drops in the position of ,c2 the yellow of ,b1 and of all drops in the position of ,b2 and the red of ,a1 c42 and thus it sees a rainbow4 ,q4 ,does ,,every person see the ,,same colours from the ,,same ,,drops8 ,a4 ,no2 no two persons see the same rainbow4 ,to another spectator the rays from ,,sb might be red instead of yellow2 the ray from ,,sc1 yellow2 and the blue might be reflected from some drop below ,c4 ,to a third person the red may issue from a drop above ,a1 and then ,a would reflect the yellow1 and ,b the blue1 and so on4 ,q4 ,why are there often ,,two ,,rainbows at one and the same time8 ,a4 ,in one rainbow we see the rays of the sun entering the rain-drops at the top1 and reflected to the eye from the bottom4 ,in the other rainbow1 we see the rays of the sun entering the rain-drops at the bottom1 and reflected to the top1 whence they reach the eye4 ,illustration3 ,here the ray ,,sa strikes the drop at ,a1--is refracted or bent to ,b1--is then reflected to ,c1 where it is refracted again1 and reaches the eye of the spectator4 ,illustration3 ,here the ray ,,sb strikes the drop at ,b1--is refracted to ,a1--is then reflected to ,c1--is again reflected to ,d1 when it is again refracted or bent till it reaches the eye of the spectator4 ,q4 ,why are the ,,colours of the ,,second bow all ,,reversed8 ,a4 ,because in one bow we see the rays which enter at the top of the raindrops1 refracted from the bottom3 ,but in the other bow we see the rays which enter at the bottom of the raindrops 7after two reflections71 refracted from the top4 ,illustration3 ,here ,a1 ,b1 ,c1 represent three drops of rain in the ,,primary 7or inner7 ,,rainbow4 ,the least refracted line is ,,red1 and ,,blue the most4 ,so the ,,red 7or least refracted rays7 of all the drops in the position of ,a1--the ,,yellow of those in the position of ,b1--and the ,,blue 7or the most refracted rays7 of the lowest drops1 all meet the eye ,d1 and form a rainbow to the spectator4 ,the reason why the primary bow exhibits the stronger colours is this--because the colours are seen after one reflection and two refractions2 but the colours of the secondary 7or upper7 rainbow undergo two reflections and three refractions4 ,illustration3 ,here also the least refracted ray is ,,red1 and the most refracted ,,blue 7as in the former case72 but the position of each is reversed4 ,q4 ,why does a ,,soap ,,bubble exhibit such ,,variety of ,,colours8 ,a4 ,the changing colour of the bubble depends upon the changing thickness of the film through which the ray passes4 ,q4 ,how does the ,,thickness of the ,,film affect the ,,colour of the soap bubble8 ,a4 ,because different degrees of thickness produce different angles of refraction1 and1 therefore1 different colours reach the eye4 ,q4 ,why is the ,,soap ,,bubble so constantly ,,changing its ,,thickness8 ,a4 ,as the bubble is suspended1 the water keeps running down from the top to the bottom of the bubble1 till the crown becomes so thin as to burst4 ,q4 ,why are the late ,,evening ,,clouds ,,red8 ,a4 ,because ,,red rays 7being the least refrangible7 are the last to disappear4 ,illustration3 ,here it will be seen that the red ray ,,pa1 being reflected on the horizon at ,a1 will be visible to us2 but the ,,yellow and ,,blue rays will be hidden by the curve of the earth4 ,q4 ,why are the early ,,morning clouds ,,red8 ,a4 ,because ,,red rays 7being the least refrangible7 are the first to appear4 ,see last figure4--,it is evident that ,,pa 7the red rays7 will be reflected on the horizon before either the yellow or blue ones4 ,q4 ,what becomes of the ,,blue and ,,yellow rays8 ,a4 ,they are refracted below the horizon1 and are soon made invisible by the curve of the earth4 7,see last figure47 ,q4 ,why are the ,,edges of ,,clouds more ,,luminous than their ,,centres8 ,a4 ,because the body of vapour is thinnest at the edges of the clouds4 ,q4 ,what is the cause of morning and evening ,,twilight8 ,a4 ,when the sun is below the horizon1 the rays 7which strike upon the atmosphere or clouds7 are bent down towards the earth1 and produce a little light called twilight4 ,see figure on p4 #cii4--;,here the rays of ,,pa will give some light4 ,q4 ,why is a ray of ,,light composed of ,,various ,,colours8 ,a4 ,if solar light were of one colour only1 all objects would appear of that one colour 7or else black47 ,q4 ,why are some things of ,,one ,,colour1 and some of ,,another8 ,a4 ,as every ray of light is composed of all the colours of the rainbow1 some things reflect one of these colours1 and some another4 ,q4 ,why do some things reflect ,,one ,,colour1 and some ,,another8 ,a4 ,because the surface of things is so differently constructed1 both physically and chemically2 and1 therefore1 some things reflect one ray2 some two rays2 some all the rays2 and some none4 ,q4 ,what mainly determines the ,,colour of any object8 ,a4 ,the fluid or gas either in the body1 or on its surface4 ,n4 ,b4 ,nitrogen gives green1--,oxygen gives red1--,hydrogen gives blue colours4 ,q4 ,why does ,,dying a silk1 c4 ,,change its ,,colour8 ,a4 ,because the materials used in dyeing alter the chemical construction of the substance dyed4 ,q4 ,why is a ,,rose ,,red8 ,a4 ,because the surface of a rose absorbs the blue and yellow rays of light1 and reflects only the red ones4 ,q4 ,why does a rose absorb the yellow and blue rays1 and reflect the ,,red8 ,a4 ,because the action of the sun's rays on the oxygen 7accumulated in the petals7 produces an acid which turns them red4 ,the leaves which compose a flower1 are called ,,petals4 ,q4 ,why is a ,,violet ,,blue8 ,a4 ,because the surface of the violet absorbs the red and yellow rays of the sun1 and reflects the blue only4 ,q4 ,why do violets absorb the red and yellow rays1 and reflect the ,,blue8 ,a4 ,because the petals of the violet contain an alkali1 which gives them a purple tinge4 ,q4 ,why is a ,,primrose ,,yellow8 ,a4 ,because the surface of the primrose absorbs the blue and red rays of solar light1 and reflects the yellow ones4 ,all plants which have much alkali in their ash1 have blue or yellow flowers4 ,those which have acid in their ash1 have orange1 pink1 or red flowers4 ,n4 ,b4 ,anti-acids 7like soda7 are called ,,alkalis4 ,q4 ,why are some things ,,black8 ,a4 ,because they absorb all the rays of light1 and reflect none4 ,q4 ,why are some things ,,white8 ,a4 ,because they absorb none of the rays of light1 but reflect them all4 ,q4 ,why are ,,coals ,,black8 ,a4 ,because they absorb all the rays of the sun which impinge upon them1 and stifle their reflection4 ,q4 ,why is ,,snow ,,white8 ,a4 ,snow consists of a vast number of crystals 7or small prisms71 which separate the rays into their elemental colours2 but as these crystals are very numerous1 the colours unite again before they meet the eye1 and appear white4 ,n4 ,b4 ,the combination of all colours makes ,,white4 ,q4 ,why is ,,sugar ,,white8 ,a4 ,sugar consists of a vast number of small crystals1 which separate the rays into their elemental colours2 but as these crystals are very numerous1 the colours unite again before they meet the eye1 and appear white4 ,q4 ,why is ,,salt ,,white8 ,a4 ,salt consists of a vast number of small crystals1 which reflect the various rays of light from different points of the salt2 and as these colours unite before they meet the eye1 the salt appears to be white4 ,n4 ,b4 ,the combination of all colours makes ,,white4 ,q4 ,why are the ,,leaves of plants ,,green8 ,a4 ,because the carbon of the leaves is a bluish olive1 and the sap and tissue of the cells1 ,,yellow2 when1 therefore1 the yellow sap flows into the blue carbon1 it produces a green leaf4 ,q4 ,why are leaves a ,,light green in ,,spring8 ,a4 ,because the young leaves of spring have more sap than carbon2 and1 therefore1 the yellow of the green prevails4 ,q4 ,why are leaves a ,,yellowish ,,brown in ,,autumn8 ,a4 ,because the carbon of the leaves is dying away1 and the yellow tinge of the tissue and falling sap prevails over the blue4 ,q4 ,why are plants a ,,pale ,,yellow when kept in the ,,dark8 ,a4 ,solar light is essential for the production of carbon2 and as plants kept in the dark lose their carbon1 they lose the blue colour which should convert their yellow sap to green4 ,q4 ,why are ,,potatoes ,,yellow8 ,a4 ,potatoes are grown underground1 and1 therefore1 contain very little carbon 7or blue colour72 hence the yellow sap of the potato is not converted to green by carbon4 ,q4 ,why are potatoes 7which grow ,,exposed to the air and light7 ,,green8 ,a4 ,because the sun-light increases their carbon2 which 7mingling with the yellow sap7 turns the potato green4 ,q4 ,why is it ,,dangerous to ,,sleep in a room which contains ,,living ,,plants8 ,a4 ,because they exhale carbon in the dark in the form of ,,carbonic ,,acid ,,gas1 which is destructive to animal life4 ,q4 ,why are ,,some things 7like glass7 ,,transparent8 ,a4 ,in transparent bodies 7like glass7 all the rays of light emerge on the opposite side4 ,q4 ,why are ,,some things ,,shining and splendid8 ,a4 ,those objects which reflect the most rays are the most splendid2 and those which absorb them most1 are dull4 ,q4 ,why are ,,deserts so ,,dazzling in summer time8 ,a4 ,because each separate grain of sand reflects the rays of the sun like a mirror4 ,q4 ,if you move a stick 7burnt at one end7 ,,round pretty briskly1 it seems to make a ,,circle ,,of ,,fire1--,,why is this8 ,a4 ,because the eye retains the image of any bright object1 after the object itself is withdrawn2 and as the spark of the stick returns before the image has faded from the eye1 therefore1 it seems to form a complete circle4 ,q4 ,if separate figures 7as a man and a horse7 be drawn on separate sides of a card1 and the card ,,twisted quickly1 the man seems to be seated on the horse1--,,why is this8 ,a4 ,because the image of the horse remains upon the eye till the man appears4 ,the ,thaumatrope is constructed on this principle4 ,q4 ,why do the ,,stars ,,twinkle8 ,a4 ,fixed stars are so far off1 that their rays of light do not strike upon the eye in a continuous flow1 but at intervals3 when their rays reach the eye1 the star becomes visible1 and then is obscured till the next batch of rays arrive2 and this perpetually occurring1 makes a kind of twinkling4 ,q4 ,if we look at a ,,red-hot ,,fire for a few minutes1 ,,why does every thing seem ,,tinged with a ,,bluish ,,green colour8 ,a4 ,because bluish green is the ,,accidental ,,colour of red3 and if we fix our eye upon any colour whatsoever1 when we turn aside1 we see every object tinged with its accidental colour4 ,q4 ,if we wear ,,blue ,,glasses1 7when we take them off17 every thing appears tinged with ,,orange1--,,why is this8 ,a4 ,because orange is the accidental colour of blue3 and if we look through blue glasses1 we shall see its accidental colour1 when we lay our glasses aside4 ,q4 ,if we look at the ,,sun for a few moments1 every thing seems tinged with a ,,violet colour1--,,why is this8 ,a4 ,because violet is the accidental colour of yellow light2 and as the sun is yellow1 we shall see its accidental colour blue1 when we turn from gazing at it4 ,q4 ,does not the ,,dark ,,shadow 7which seems to hang over every thing after we turn from looking at the sun7 arise from our eyes being ,,dazzled8 ,a4 ,partly so3 the pupil of the eye is very much contracted by the brilliant light of the sun1 and does not adjust itself immediately to the feebler light of terrestrial objects2 but1 independent of this1 the ,,accidental ,,colour of the sun being dark violet1 would tend to throw a shadow upon all things4 7,see p4 #cff47 ,q4 ,why is ,,black glass for spectacles the ,,best for wear8 ,a4 ,because white is the accidental colour of black2 and if we wear black glasses1 every thing will appear in white light1 when we take them off4 ,q4 ,why does every thing seem shadowed with a ,,black ,,mist1 when we take off our common ,,spectacles8 ,a4 ,because the glasses are white1 and black being its accidental colour1 every thing appears in a black shade1 when we lay our glasses down4 ,the accidental colour of red is bluish green4 of orange blue4 of violet yellow4 of black white4 ,and the converse of this is true3-- ,the accidental colour of bluish green is red4 of blue orange4 of yellow violet4 of white black4 7,the law of an accidental colour is this--,the accidental colour is always half the spectrum4 ,thus1 if we take half the length of the spectrum by a pair of compasses1 and fix one leg in any colour1 the other leg will hit upon its accidental colour47 ,n4 ,b4 ,the spectrum means the seven colours--,red1 orange1 yellow1 green1 blue1 indigo1 and violet1 divided into seven equal bands1 and placed side by side in the order just mentioned4 ,,chapter ,,xxviii4 ,,sound4 ,q4 ,what is ,,sound8 ,a4 ,the vibration of some sonorous substance produces motion in the air called ,,sound ,,waves1 which strike upon the drum of the ear1 and give the sensation of sound4 ,q4 ,what are ,,musical ,,sounds8 ,a4 ,regular and uniform successions of vibrations1 which are always pleasing to the ear4 ,q4 ,how ,,fast does ,,sound ,,travel8 ,a4 ,about #ac miles in a minute1 or #aadb feet in a second of time4 ,q4 ,how fast does ,,light ,,travel8 ,a4 ,light would go #h times round the whole earth1 while sound is going its #ac miles4 ,q4 ,why are ,,some things ,,sonorous1 and others ,,not8 ,a4 ,the sonorous quality of any substance depends upon its hardness and elasticity4 ,q4 ,why are ,,copper and ,,iron ,,sonorous1 and not ,,lead8 ,a4 ,copper and iron are hard and elastic2 but as lead is neither hard nor yet elastic1 it is not sonorous4 ,q4 ,of what is ,,bell-,,metal made8 ,a4 ,of copper and tin in the following proportions3--,in every #e pounds of bell-metal1 there should be #a lb4 of tin1 and #d lbs4 of copper4 ,q4 ,why is this mixture of tin and copper used for ,,bell-,,metal8 ,a4 ,because it is much harder and more elastic than either of the pure metals4 ,q4 ,why is the ,,sound of a bell ,,stopped by ,,touching the bell with our finger8 ,a4 ,the weight of the finger stops the vibrations of the bell2 and as soon as the bell ceases to vibrate1 it ceases to make sound-waves in the air4 ,q4 ,why does a ,,split ,,bell make a ,,hoarse disagreeable sound8 ,a4 ,the split of the bell causes a double vibration2 and as the sound-waves clash and jar1 they impede each other's motion1 and produce discordant sounds4 ,q4 ,why does a ,,fiddle-,,string give a musical sound8 ,a4 ,the bow drawn across the string causes it to vibrate1 and this vibration of the string sets in motion the sound-waves of the air1 and produces musical notes4 ,q4 ,why does a ,,drum sound8 ,a4 ,the parchment head of the drum vibrates from the blow of the drum-stick1 and sets in motion the sound-waves of the air4 ,q4 ,why do ,,musical ,,glasses give sounds8 ,a4 ,because the glasses vibrate as soon as they are struck1 and set in motion the sound-waves of the air4 ,q4 ,why do ,,flutes1 c4 produce musical sounds8 ,a4 ,the breath of the performer causes the air in the flute to vibrate1 and sets in motion the sound-waves of the air4 ,q4 ,why do ,,piano-,,fortes produce musical sounds8 ,a4 ,the keys of the piano 7being struck with the finger7 lift up a little hammer which knocks against a string2 and the vibration thus produced1 sets in motion the sound-waves of the air4 ,q4 ,why are ,,some notes ,,bass and some ,,treble8 ,a4 ,slow vibrations produce bass or deep sounds2 whereas1 quick vibrations produce shrill or treble sounds4 ,q4 ,why is an instrument ,,flat when the ,,strings are ,,unstrung8 ,a4 ,because the vibrations are too slow2 in consequence of which1 the sounds produced are not shrill or sharp enough4 ,q4 ,why can persons living a mile or two from a town ,,hear the ,,bells of the town-church ,,some ,,times1 and not at ,,others8 ,a4 ,fogs1 rain1 and snow1 obstruct the passage of sound2 but when the air is cold and clear1 sound is propagated more easily4 ,q4 ,why can we ,,not hear sounds 7as distant church bells7 in ,,rainy weather1 so well as in ,,fine weather8 ,a4 ,because the falling rain interferes with the undulations of the sound-waves1 and breaks them up4 ,q4 ,why can we not hear sounds 7as distant church bells7 in ,,snowy weather1 so well as in ,,fine weather8 ,a4 ,because the falling snow interferes with the undulations of the sound-waves1 and stops their progress4 ,q4 ,why can we ,,hear distant clocks ,,most distinctly in ,,clear ,,cold weather8 ,a4 ,because the air is most uniform then3 there are not two currents of air 7one up and one down7 to interrupt the sound-waves4 ,q4 ,why can persons hear the ,,voices of men in conversation for a ,,mile distant1 near the ,,poles1 in winter time8 ,a4 ,because the air is very cold and very clear2 in consequence of which1 there are not two currents of air 7one up and one down7 to interrupt the sound-waves4 ,captain ,ross heard the voices of his men in conversation1 a mile and a half from the spot where they stood4 ,q4 ,why are not ,,sounds 7such as distant church bells7 heard so distinctly on a ,,hot ,,day as in ,,frosty weather8 ,a4 ,because there are two currents of air2 the current of hot air ascending from the earth1 and the current of colder air falling towards the earth2 and these two currents break up the sound-waves4 ,q4 ,why can we not hear ,,sounds 7such as distant clocks7 so distinctly in a thick ,,mist or ,,haze1 as in a ,,clear night8 ,a4 ,because the mist diminishes the velocity of the sound-waves1 and 7by overburdening them with vapour7 limits their length4 ,q4 ,why do we hear ,,sounds better by ,,night than by ,,day8 ,a4 #ast--,night air is more uniform1 because the ascending currents of air 7raised by the action of the sun's rays7 cease as the evening advances2 and #bndly--,night is more still from the suspension of business1 and the cessation of the hum of men4 ,q4 ,how should ,,partition ,,walls be made to ,,prevent the voices in adjoining rooms from being ,,heard8 ,a4 ,the space between the laths 7or canvass7 should be filled with shavings or saw-dust2 and then no sound would ever pass from one room to another4 ,q4 ,why would ,,shavings or saw-dust ,,prevent the transmission of sound from room to room8 ,a4 ,because there would be several different media for the sound to pass through3 #ast--the air2 #bndly--the laths and paper2 #crdly--the saw-dust or shavings2 #dthly--the air again3 and every variety diminishes the strength of the sound-waves4 ,q4 ,why can ,,deaf people hear through an ,,ear ,,trumpet8 ,a4 ,the ear trumpet restrains the spread of the voice1 and limits the diameter of the sound-waves2 in consequence of which1 their strength is increased4 ,q4 ,why are ,,mountains so ,,noiseless and quiet8 ,a4 ,because the air of mountains is very rarefied2 and as the air becomes rarefied1 sound becomes less intense4 ,q4 ,how do you know that the ,,rarety of air ,,diminishes the intensity of ,,sound8 ,a4 ,if a bell be rung in the receiver of an air-pump1 the sound becomes fainter and fainter as the air is exhausted1 till at last it is quite inaudible4 ,q4 ,what is the cause of ,,echo8 ,a4 ,whenever a sound-wave strikes against any obstacle 7such as a wall or hill71 it is reflected 7or thrown back72 and this reflected sound is called an ,,echo4 ,the same laws govern echo as light4 7,see p4 #cgj47 ,q4 ,what places are most ,,famous for ,,echoes8 ,a4 ,caverns1 grottoes1 and ruined abbeys2 the areas of antique halls2 the windings of long passages2 the aisles of cathedral churches2 mountains1 and ice-bergs4 ,q4 ,why are caverns1 grottoes1 and ruined abbeys ,,famous for ,,echoes8 ,a4 #ast--,because the sound-waves cannot pass beyond the cavern or grotto1 and must flow back3 #bndly--,the return waves 7being entangled by the cavern7 are detained for a short time1 and come deliberately to the ear4 ,q4 ,why are antique halls1 winding passages1 and cathedral aisles ,,famous for ,,echoes8 ,a4 ,because the sound-waves cannot flow freely forward1 but strike against the winding walls perpetually1 and are beaten back4 ,q4 ,why are ,,mountains and ice-bergs ,,famous for ,,echoes8 ,a4 ,because they present a barrier to the sound-waves which they cannot pass2 and are sufficiently elastic to throw them back4 ,q4 ,why do not the walls of a ,,room or church produce ,,echo8 ,a4 ,because sound travels with such velocity1 that the echo is blended with the original sound1 and produce but one impression on the ear4 ,sound travels #ac miles in a minute4 ,q4 ,why do very ,,large buildings 7as cathedrals71 often ,,reverberate the voice of the speaker8 ,a4 ,because the walls are so far off from the speaker1 that the echo does not get back in time to blend with the original sound2 and1 therefore1 each is heard separately4 ,q4 ,why do ,,some echoes repeat only ,,one syllable8 ,a4 ,the further the echoing body is distant1 the more sound it will reflect4 ,if1 therefore1 the echoing body be near1 it will repeat but one syllable4 ,q4 ,why does an ,,echo sometimes repeat ,,two or more syllables8 ,a4 ,because the echoing body is far off2 and1 therefore1 there is time for one reflection to pass away before another reaches the ear4 ,q4 ,why do ,,windows ,,rattle when ,,carts pass by a house8 ,a4 #ast--,glass is sonorous2 and the air communicates its vibrations to the glass1 which echoes the same sound3 and #bndly--,the window-frame is shaken by the sound-waves impinging against the window1 and contributes to the noise4 ,,chapter ,,xxix4 ,,miscellaneous4 ,q4 ,why do the ,,bubbles in a ,,cup ,,of ,,tea range round the ,,sides of the ,,cup8 ,a4 ,because the cup attracts them4 ,q4 ,why do all the ,,little ,,bubbles tend towards the ,,large ones8 ,a4 ,because the large bubbles 7being the superior masses7 attract them4 ,q4 ,why do the ,,bubbles of a ,,cup ,,of ,,tea ,,follow a ,,tea-,,spoon8 ,a4 ,because the tea-spoon attracts them4 ,q4 ,why are the ,,sides of a pond covered with ,,leaves1 while the ,,middle of the pond is quite ,,clear8 ,a4 ,because the shore attracts the leaves to itself4 ,q4 ,why do all fruits1 c4 7when severed from the tree7 ,,fall to the ,,earth8 ,a4 ,because the earth attracts them4 ,q4 ,why do persons 7who water ,,plants7 very often pour the water into the ,,saucer1 and not ,,over the ,,plants8 ,a4 ,because the water in the saucer is supped up by the mould 7through the hole at the bottom of the flower-pot71 and is transferred to the stem and leaves of the plant by ,,capillary ,,attraction1 7,see p4 #hd74 ,q4 ,why is vegetation on the ,,margin of a ,,river more ,,luxuriant than in an open ,,field8 ,a4 ,because the porous earth on the bank sups up water to the roots of the plants by ,,capillary ,,attraction4 ,q4 ,why is a ,,lump of ,,sugar 7left at the bottom of a cup7 so ,,long in ,,melting8 ,a4 ,because as it melts1 it makes the tea above it heavier2 and 7so long as it remains at the bottom7 is surrounded by tea fully saturated with sugar2 in consequence of which1 the same portions of liquid will hold no more sugar in solution4 ,q4 ,why does the ,,lump of ,,sugar ,,melt more ,,quickly when ,,stirred ,,about8 ,a4 ,because fresh portions of unsaturated tea keep coming in contact with the lump1 and soon dissolve it4 ,q4 ,why does a ,,piece ,,of ,,sugar 7held in a spoon at the ,,top of our tea7 melt very ,,rapidly8 ,a4 ,because as the tea becomes sweetened1 it descends to the bottom of the cup by its own gravity2 and fresh portions of unsweetened tea are brought constantly into contact with the sugar1 till the lump is entirely dissolved4 ,q4 ,how can a ,,sick ,,room be kept ,,free from unhealthy ,,effluvia8 ,a4 ,vinegar boiled with myrrh1 or camphor1 sprinkled in a sick room1 will entirely correct putridity4 ,q4 ,why does ,,lime destroy the offensive smells of ,,bins1 ,,sewers1 c48 ,a4 ,because it combines with the carbonic acid of these places1 and converts it into ,,carbonate ,,of ,,lime1 which is entirely free from smell4 ,q4 ,why does ,,chloride of ,,lime fumigate a sick room8 ,a4 ,because the chlorine absorbs the hydrogen of the stale air2 and by this means removes both the offensive smell and the infection of a sick room4 ,q4 ,how can the ,,taint of ,,meat be removed8 ,a4 ,either by washing with ,,pyroligneous ,,acid1--covering it for a few hours with common ,,charcoal1--or by putting a few lumps of charcoal into the water in which it is boiled4 ,q4 ,why do these things ,,destroy the ,,taint of meat8 ,a4 ,because they combine with the putrescent particles1 and neutralize their offensive taste and smell4 ,q4 ,why should ,,bed-,,rooms1 ,,cottages1 ,,hospitals1 and ,,stables1 be washed occasionally with ,,lime-,,white8 ,a4 ,because the lime is very caustic1 and removes all organic matters adhering to the walls4 ,q4 ,how can ,,mouldiness be prevented8 ,a4 ,the perfume of any essential oil will prevent mouldiness from ink1 paste1 preserves1 c4 ,alum1 salt of amber1 borax1 nitre1 salt1 camphor1 charcoal1 and pyroligneous acid1 are all excellent antiseptics4 ,salt1 corrosive sublimates1 copperas1 and alum1 all arrest the decay of timber4 7,see p4 #dbf47 ,q4 ,why will strong ,,souchong ,,tea ,,poison ,,flies8 ,a4 ,because it produces prussic acid1 which destroys their nervous system4 ,q4 ,why is strong ,,green ,,tea ,,unwholesome8 ,a4 ,because it contains prussic acid1 which destroys the nervous system4 ,q4 ,why is a ,,dead man ,,taller than a living man8 ,a4 ,because at death the ,,cartilages are relaxed4 ,so1 also1 after a night's rest1 a man is taller than when he went to bed4 ,q4 ,what is ,,sleep8 ,a4 ,sleep is the rest of the brain and nervous system4 ,q4 ,why can we not ,,see1 when we are asleep with our ,,eyes ,,open8 ,a4 ,because the ,,ret,,ina of the eye is inactive and at rest4 ,q4 ,why can we not ,,hear in sleep8 ,a4 ,because the drum or ,,tympanum of the ear is placid and at rest4 ,q4 ,why can we not ,,taste when we are asleep8 ,a4 ,because the nerves at the end of the tongue 7called papill7 are inactive and at rest4 ,q4 ,why can we not ,,feel when we are asleep8 ,a4 ,because the ends of the nerves 7called papill71 situated in the skin1 are inactive and at rest4 ,q4 ,why have persons in sleep no ,,will of their own1 but may be moved at the will of ,,any one8 ,a4 ,because the ,,cerebellum 7or posterior part of the brain7 is inactive and at rest4 ,q4 ,why have ,,dreamers no power of ,,judgment or ,,reason8 ,a4 ,because the ,,cerebrum 7or front of the brain7 is inactive and at rest4 ,q4 ,why are ,,dreams such ,,foolish and ,,inconsistent things8 ,a4 ,because the ,,pineal ,,gland is acting without the brain2 and the faculty of thinking exists in the ,,pineal ,,gland1 but the faculty of judgment in the ,,cerebrum of the brain4 ,the cerebrum of the brain occupies the top and front of the skull4 ,the ,,pineal ,,gland is a small conical gland 7about the size of a pea7 in the brain4 ,q4 ,why do some persons ,,lose all ,,power of ,,sensation8 ,a4 ,because the ,,cerebrum 7or front of their brain7 has been injured4 ,q4 ,why are many persons ,,idiots8 ,a4 ,because the ,,cerebellum of the brain has been removed by some accident1 or injured by some disease4 ,the cerebellum is all the posterior part of the brain4 ,q4 ,why does a person ,,feel when he is ,,touched8 ,a4 ,the ends of certain nerves 7called ,,papill7 situated in the skin erect themselves when touched1 and produce a nervous sensation called ,,feeling4 ,q4 ,why are persons able to ,,taste ,,different ,,flavours8 ,a4 ,because the ,,papill of the tongue and palate erect themselves when food touches them1 and produce a nervous sensation called ,,taste4 ,q4 ,why do very ,,old people ,,lose the power of ,,volition1 ,,sensation1 and ,,thought8 ,a4 ,because their brain ossifies2 and as the cerebrum 7or front of the brain7 goes1 they lose the power of sensation and reason2 and as the cerebellum 7or posterior part of the brain7 goes1 they lose the power of volition4 ,q4 ,why are ,,old people ,,unable to ,,walk8 ,a4 ,because their muscles become rigid4 ,,glossary4 ,,acetic ,,acid1 commonly called ,distilled ,vinegar4 ,,citric ,juice of ,lemons4 ,,nitric ,aqua ,fortis4 ,,oxalic ,salt of ,lemons4 ,,sulphuric ,oil of ,vitriol4 ,,sulphate ,,of ,,lime ,plaster of ,paris4 ,,magnesia ,epsom ,salts4 ,,soda ,glauber ,salts4 ,,zinc ,white ,vitriol4 ,,nitrate ,,of ,,silver ,lunar ,caustic4 ,,acetate ,,of ,,copper ,verdigris4 ,,muriate ,,of ,,soda ,table ,salt4 ,,tartrate ,,of ,,potash ,tartar ,emetic4 ,,carbonate ,,of ,,ammonia ,smelling ,salts4 ,,lime ,chalk1 ,marble1 c4 ,,super-,,acetate ,,of ,,lead ,sugar of ,lead4 ,,oxide ,,of ,,lead ,goulard4 ,,sublimates are chemical preparations1 the basis of which is quicksilver4 ,in ,,corrosive ,,sublimates1 the quicksilver is extinguished1 either by vitriol1 potter's clay1 or some other ingredient4 ,,sublimation is a similar process to distillation2 only solids7such as metals7 are employed1 instead of liquids4 ,thus the fine blue used by painters is a sublimate1 and made thus3--,take #b parts of quicksilver1 #c flower of brimstone1 #h sal ammoniac2 and 7having ground them7 put them with the quicksilver into a glass retort1 luted at the bottom2 place the retort in a sand-heat2 and 7when the moisture is given off7 you will have a splendid blue sublimate for painting4 ,,index4 ,,absorbers1 best1 #aib not conductors1 #ahe not reflectors1 #aib radiators1 #aig ,,absorption of ,,heat1 #ahd not conduction1 #ahd of light1 #cfd ,,accidental ,,colors1 #djg1 #djh ,acetate of lead1 #dbf ,acetic acid1 #dbf ,acid of drinks1 #bfi of fermentation1 #bfi ,activity affected by cold1 #ia by heat1 #ic ,aerated water1 #bfg ,aeronauts feel pain1 #bed ,age affects the sensation1 thought1 judgment1 #dbe power of walking1 #dbe ,,air1 #bdj always in motion1 #bic bad conductor1 #ac1 #agg1 #agh bad radiator1 #bai1 #bcg cold1 #agg colder than blood1 #aha composed of two gases1 #bg1 #bdj cooled by convection1 #bbj by rain1 #aei cools hot iron1 #bdf density diminished by rain1 #ccg descends when cold1 #bhi double current in a room1 #bij dries linen1 #afj elements of1 #cc expanded by heat1 #ajc full of smells1 #aeb gets fire up1 #ej healthful1 #beb heated1 #bai1 #bde1 #bdf1 #bhi not by sun1 #bij in a room1 #beb inflammable1 see hydrogen in summer1 #cac of cities unhealthy1 #bdc1 #bec of the country healthy1 #bdc1 #beb on land colder than on water1 #bbd on land cold at night1 #bcj preserved normal1 #bdd purified by lightning1 #bg rusts iron1 #beg still before a tempest1 #adf strong1 #ajh varies in temperature1 #cce ,aisles famous for echoes1 #dag ,alcohol1 #aji1 #bgj1 #bga ,,ale1 #aji bottled1 #bfh froth of1 #aji froth increased by heat1 #bfh ,alkali1 #de ,anenometer1 #cad ,anglers hate a magpie1 #aec ,angle of incidence1 #cgj of reflection1 #cgj ,animal heat1 #hc1 #he1 #bdc1 #bgg ,animals and vegetables co-dependent1 #bdd ,ants love honey-dew1 #bba ,appetite1 #hi1 #ij1 #ia 7,see hunger47 ,apples full of air1 #aje roasted1 #aje soft1 #ajf ,april showers1 #cjg ,aqua fortis1 #dbf ,argand lamps1 #hc ,arnott's stoves smell of sulphur1 #ef smoke1 #fi ,ascent in balloons painful1 #ade ,ashes soften water1 #cde ,asses bray in wet weather1 #adh ,aurora borealis1 #adb1 #bhe coloured1 #adc white1 #adb a prognostic1 #adc ,avenues1 #chj ,azote1 see nitrogen ,bales catch fire spontaneously1 #eg ,balloons1 #adf inflated1 #aji rise1 #aaj ,balls of fire1 #f ,banisters wet1 #baf ,barley malted1 #bgj ,,barometer1 #cag affected by cold1 #cbh frost1 #cbi heat1 #cbh thaw1 #cbi wind1 #cbg rules for its rise and fall1 #ccj sudden change in1 #ccj use of1 #cai varies most in winter1 #cbg least in summer1 #cbg when highest1 #cbh lowest1 #cbh ,barren land collects no dew1 #bji ,bass notes in music1 #dab ,bass preserves flowers from frost1 #bjf ,bathing1 danger of1 #chg with ether for inflammation1 #aeg ,beakers broken by hot water1 #abf ,beasts covered with hair1 #agf ,beds damp1 #aeg ,,beer1 fermentation of1 #bfi flat1 #bgc froth increased by bottling1 #bfh froth increased by heat1 #bfh raisins and raw meat improve it1 #bgc stale1 #bge soured by lightning1 #bg not old beer1 #bg spoiled1 if the vent-peg be left out1 #bgc yeast added to make it work1 #bga ,beer-vats dangerous1 #bfe ,bells heard at a distance1 #dab cracked1 sound harsh1 #daa silenced by a touch1 #daa ,bell-metal1 #daj ,bellows1 #ea ,bins purified1 #bff ,birds covered with feathers1 #agf ,,black1 #djb cloth warm1 #ahf eyes1 #aia glass for spectacles1 #djh hat turns red at the sea-side1 #cdd ,hole of ,calcutta1 #bej kid gloves1 #ahh lead1 #beh prevents rust1 #beh mist1 #add skin1 #aij tea-pot1 #aig used by cotters1 #aih set on a hob to draw1 #aih will never blister1 #aij ,blacks1 #fj none to railway engines1 #fj ,blacksmiths strike fire by nails1 #if ,bladders inflated by heat1 #ajc ,,blaze1 blue1 #df green1 #de yellow1 #df between the bars of a grate1 #de ,blazing coals burn quickly1 #ci ,blood red1 #bdb purple1 #bdb ,blowers1 #gj ,blowing cools broth1 #ahj1 #bdg1 #cab tea1 #bdh ,blue1 #dja glasses1 #djg sky1 #acb sublimate1 #dbf ,body warm1 #hg ,,boiling1 #bcd ,,water bubbles1 #aad1 #bhc makes it flat1 #bge is in a ferment1 #bcb rattles1 #aaf runs over1 #aae1 #bcc swells1 #aad one pot will not boil in another1 #aah retarded by a spoon1 #aag by salt1 sugar1 #aah ,bottled ale1 c41 #bfh ,brackish water unfit for railway engines1 #bfc ,bread heavy1 #bgf made with yeast1 #bgf ,breath exhaled1 #bdd visible in winter1 #bag ,breathing difficult on a mountain1 #bee previous to a storm1 #bee ,,breeze at watering places1 #caj evening1 #cji morning1 #cjh of islands1 #cji speed of1 #cac 7,see wind47 ,bricks for cold feet1 #agc ,brick stoves1 #agd ,bricklayers cannot work in a frost1 #cei cover new work with straw1 #cei ,brilliancy1 #cfd ,brine retards boiling1 #aai tested1 #cfa ,broth cooled by breath1 #bdg1 #cab by convection1 #bdg by stirring1 #bdg ,bubbles in tea1 #dai of boiling water1 #aad ,bulk for bulk1 #aaj ,burns cured1 #aeg ,burning glasses1 #b ,caloric1 #a ,cambric handkerchiefs cool1 #ahd ,cambridge1 rain of1 #cdj ,,candles1 #gd burn1 #gd blue1 #adh cotton1 not easily blown out1 #gi easily blown out1 #ea1 #gh and rekindled1 #ea1 #ee extinguished1 #gi flame hot1 #ge hollow1 #gf pointed1 #gg purple below1 #gf tends upwards1 #gg yellow1 #gf gas of1 #bha held at a door1 #bij hottest above the flame1 #gi give light1 #gf make glass damp1 #gh need snuffing1 #ha ,palmer's1 #hj prevent our seeing abroad1 #cgh reflected in a window1 #cgi rush1 easily go out1 #gi smoke1 #ha spirt1 #aee suddenly introduced give pain1 #cfe wax1 need no snuffing1 #ha ,candlestick rags catch fire spontaneously1 #eh ,capillary veins1 #hd ,captain ,ross1 #dad ,carbon1 #cc1 #gd ,carbonate of lime1 #dbf of soda1 #dbf ,,carbonic ,,acid ,,gas1 #cg1 #ajh1 #bdi1 #bfd deleterious1 #bej1 #bfd in human bodies1 #hd its presence detected1 #bfd ,,carburetted ,,hydrogen ,,gas1 #bgi1 #bhj ,carpets warm1 #afi ,carriage wheels catch fire1 #ii ,carriage windows misty1 #bac ,casks charred1 #gc ,cart grease1 #ajj ,cathedral aisles famous for echoes1 #dag ,,cats in wet weather1 #adg prowl by night1 #cfg rub their ears1 #aej see in the dark1 #cfg wink before a fire1 #cfg ,cattle uneasy in wet weather1 #adh ,caverns famed for echoes1 #daf ,ceilings sooty1 #ga ,cellars cold in summer1 #bef warm in winter1 #bef ,cerebellum1 #dbd ,cerebrum1 #dbd ,chalk1 #dbf ,,charcoal1 #gb bad conductor1 #aff fire1 #gb deleterious1 #bfe purifies water1 #gb removes the taint of meat1 #gb ,charring bread1 #gc casks1 #gc wood1 #gc ,,chemical ,,action1 #cj ,chestnuts crack when roasted1 #ajd not if slit1 #aje ,chimney pots1 #ga ,,chimneys ,,smoke1 if a room be too close1 #fa remedy1 #fb in vestries1 valleys1 #ff remedy1 #fg in wind1 #ff1 #aaa if too long1 #fb1 #aaf short1 #fb large1 #fi remedy1 #gj when the draught is slack1 #fc1 #fi when the door is on the same side1 #fh remedy1 #fh when it needs repairing1 #fh sweeping1 #fh when two fires are in one room1 #fe remedy1 #fe ,china broken by hot water1 #abe ,choke damp1 #bfd1 #bgi ,church bells heard at a distance1 #aea ,churchyards smell offensively1 #bhc ,chyle1 #bdb ,cider1 #bfi ,cinders1 #dc iron1 #dc will not blaze1 #dh ,cirro-cumulus clouds1 #acf ,cirro-stratus clouds1 #acd ,cirrus clouds1 #acd ,citizens pale1 #bdc ,citric acid1 #dbf ,city air unhealthy1 #bec ,clean kettles1 #ahf ,cleanliness connected with the dietary1 #ic ,clear day overcast1 #cjd ,clear nights exhilarating1 #add ,clocks heard1 at a distance1 #aea1 #dac ,close rooms unhealthy1 #bec ,cloth collects but little dew1 #bjh ,clothes gather damp in summer1 #baa wet1 #aeg ,clothing for workmen1 #afd promotes warmth1 #agf ,,clouds1 #abg cause of1 #abi classes of1 #acd colour of1 #acb compound1 #acf simple1 #acd differ from fog1 #abh1 #bbg dissipated1 #cjd distance from the earth1 #abi edges most luminous1 #cii electrical1 #aca fall in rainy weather1 #ccg float1 #abh height of1 #d1 #abj highest and lowest1 #acj intermediate1 #ace light1 #abj motion of1 #acc red1 #acb1 #cii round mountain tops1 #acg thickness of1 #acj how ascertained1 #acj vary in shape1 #abi1 #acj in colour1 #acc where most abundant1 #abi where least1 #abi use of1 #acg velocity of1 #cad wind affects them1 #abi1 #aca ,coal gas1 #bhj mines explode1 #bha ,coals black1 #djc ,,cold ,,weather affects the barometer1 #cbh makes us love fat1 #ij activity1 #ia out of doors1 #cab promotes hunger1 #ia ,collapsing1 #bhi ,colour of clouds1 #acb1 #acc ,colours vary1 #djj some warm1 some cold1 #ahg ,combining not mixing1 #be ,,combustion1 see fire1 #cc1 #he cause of1 #cf elements of1 #cf heat of1 #cg increased by wind1 #eh in the veins1 #hd ,,communication of ,,heat1 #afd ,compound clouds1 #acf ,compression1 #ajb ,,condensation1 #ih1 #ajb ,condensed air1 #bhi ,,conduction1 #afd not absorption1 #ahd ,,conductors1 best1 #afe worst1 #aff not absorbers1 #ahe of lightning1 #bb dangerous1 #bd ,,convection1 #bai1 #bca ,convective currents1 #bde cool broth1 #bdg cool iron1 #bdg ,cooking vessels with wooden handles1 #aff ,cooper applies hot hoops1 #abb ,copper sonorous1 #daj tarnishes1 #bei ,,copper-,,hole1 #fj roars1 #fj not when the door is open1 #fj ,cornea1 #chh ,corns ache in wet weather1 #bef ,corpse cold1 #ie ,corrosive sublimates1 #dbf ,cotton bales catch fire spontaneously1 #eg handkerchiefs hot1 #ahd ,countrymen ruddy1 #bdc ,cowls1 #fg1 #aaa ,crowds produce drowsiness1 #bea head-ache1 #bdi vitiate air1 #bdi unhealthy1 #bej ,culinary vessels have wooden handles1 #aff should be sooty1 #ga1 #bja ,cultivation promotes dew1 #baj warmth1 #afj ,cumulo-stratus clouds1 #acf1 #acg ,cumulus clouds1 #acd1 #ace ,cup in a pie1 #abj why full of juice1 #abd ,damp banisters1 #bag beds1 #aeh house1 #bag ,,danger ,,in ,a ,,storm1 #ab in attics and cellars1 #af a crowd1 #ah theatre1 c41 #ai before a fire1 #ae near a tree1 #ab river1 #ad flocks and herds are exposed to1 #ai those who bar shutters1 #ah lean against a wall1 #ag or carriage1 #bj who ring bells1 #ae1 #ag run1 #ae ,dark colours warm1 #ahf radiate heat1 #aig ,davy1 ,sir ,h41 #bha ,day-light produces hunger1 #hh ,dead bodies cold1 #ie taller than living1 #dbc ,deal snaps in fire1 #ajg ,decanting liquor1 #bgd spirting1 #bgd ,depression of spirits1 #ade ,descent in a diving bell painful1 #adf ,deserts hot and dazzling1 #dje ,,dew deleterious1 #bbj differs from rain1 #bbf distilled after a hot day1 #bai especially if the wind is westerly1 #bah unequally1 #bjg in open places1 #bjd in valleys and hollows1 #bjg on clothes1 #baa cultivated lands1 #baj grass1 #bji leaves1 c41 #bjh none beneath a tree1 #bjd1 #bje a flower awning1 #bje hedge or wall1 #bje none in a cloudy night1 #bjd in a windy night1 #bjg especially if easterly1 #bah none on stones1 cloth1 #bjh deserts1 gravel1 metal1 rocks1 wool1 #bji ,dew-drops round1 #bbc flattened1 #bbc roll on cabbages1 #bbc roses1 #bbd ,digging promotes warmth1 #afa ,digestion1 #ia ,dinner covers1 #bjb ,dirt warm1 #ic ,distant bells heard1 #dac clocks1 #aea objects appear small1 #cha1 #chb sight1 #cij spectacles for1 #cia ,distance makes things invisible1 #chd ,distilled vinegar1 #dbf ,divers suffer pain1 #bee ,diving bell1 #adf ,doors swell and shrink1 #aea ,dogs uneasy in wet weather1 #adg ,dough1 #bgd set before a fire to rise1 #bgf ,double concave glasses1 #chi convex glasses1 #cia ,draining lands promote warmth1 #afj ,,draught at a door1 #cad key-hole1 #cad window1 #cae slack1 #fc1 #fd1 #fi ,dreams1 #dbd foolish things1 #dbd ,drops of rain roll on dust1 #aee ,drowned men restored1 #aja ,drums1 #daa ,,dry ,,wood for kindling1 #dd burns best1 #ajg snaps about1 #ajg ,dryest months1 #cbh ,dublin1 rain of1 #cdj ,duck dry in water1 #bbd ,dunghills hot1 #bgg ,dusty shoes hot1 #aid ,dyeing changes a colour1 #dja ,ear-trumpets1 #dae ,,earth1 bad conductor1 #aha cool in summer1 #ahb cracks by frost1 #ceg crumbles in spring1 #ceh warm in whiter1 #aca ,earth-fog1 #bba ,earthen tea-pots1 #aig1 #aih set on a hob to draw1 #aih ,east wind cold1 #cjb dry1 #cjc prevents dew1 #bah ,eat more in cold1 #ij less in warm weather1 #ia ,echo1 #daf ,echoes1 two or more1 #dah ,,effervescence1 #bfi soon subsides1 #bge ,egg cracked when boiled1 #bci tested1 #agh1 #bci ,,electricity affects the clouds1 #aca1 #acc excited by friction1 #bi felt at the elbow joints1 #bg1 #bi hot1 #c of clouds1 #d positive negative1 #af ,,england grows warmer and warmer1 #afj ,,winds of1 #cjj east dry1 #cjb morning at watering places1 #caj most prevalent1 #cjj north cold1 #cab north-east dry1 #cje south rainy1 #cjc warm1 #cjc south-west rainy1 #cjd west rainy1 #cjd when highest1 #cja lowest1 #cja ,see ,march wind4 ,epsom salts1 #dbf ,esquimaux love blubber1 #ib ,equatorial current1 #bih ,,ether1 #dg boils1 #aai used for freezing1 #cfj used for inflammation1 scalds1 burns1 #aeg ,european skin white1 #aia ,,evaporation1 #aef freezes1 #cfj ,,evening ,,clouds1 #acb grey1 #adj red1 #ach1 #cii ,,evening ,,rainbow1 #ada ,evergreens frost-bitten1 #bcj ,ewers broken by frost1 #cdi ,,expansion by ,,heat1 #ajc ,extinguishers1 #gi made of paper1 #gi ,eyes1 two1 #cfh see single1 #cfi affected by blue glasses1 #djg fire-light1 #djg the sun1 #djg ,face soon scorched1 #aif ,fanning1 #agi1 #cac ,far sight1 #cij spectacles for1 #cia ,farriers apply hot shoes1 #abc ,fat men swim best1 #cfb ,feathers warm1 #agf ,feeling1 #dbe ,feet cold before a fire1 #ec wet dangerous1 #aeg ,,fermentation1 #bfi of dough1 #bgf ,fender and fire-irons cold1 #ahe ,fiddle-strings musical1 #daa snap from wet1 #cci ,fine weather braces1 #adg ,finger feels cold when wet1 #aeg ,,fire black and red1 #ch1 #dj blazes1 #ci not in frost1 #dh burns blue1 #adh cause of1 #cf charcoal1 #gb damp1 #bhj effect upon the eyes1 #djg extinguished1 #ed by water1 #ajg fiercest in winter1 #di out of doors1 #ej grotesque figures in1 #dj heat of1 #bhj how increased1 #fc hot1 #cg kindled at the bottom1 #db light dazzles1 #cff lighted with paper and wood1 #da luminous1 #df poker draws up1 #eb radiates heat1 #aif red hot1 #ch reflected on windows1 #cgi sun dulls it1 #di thaw dulls it1 #ej wind intenses it1 #ea ,see combustion4 ,fire-irons cold1 #ahe rust1 #beg prevented1 #beh ,fishes ascend and dive1 #cfc seem nearer than they are1 #chh cold1 #id ,,flame of a ,,candle1 #gf described1 #gg blown out easily1 #gh damp1 #gh hollow1 #gf hottest above1 #gi pointed1 #gg purple and yellow1 #gf smokes1 #ha ,flame of a fire between the bars of a grate blue1 #df green1 #de yellow1 #df1 #dg ,flannel warm1 #id used for foot-warmers1 #agc ,flash1 see lightning ,flat beer1 #bgc improved1 #bgc ,flavour discerned by the taste1 #dbe ,flint and steel1 #ig ,,flowing ,,water freezes slowly1 #ced makes rough ice1 #ced oscillates1 #cdh pure1 #cdg ,flower awnings arrest dew1 #bje purify air1 #bec ,flowers smell sweetest at night and before rain1 #aeb ,flues blacked1 #bch ,see chimney4 ,flutes1 #dab ,fly-poison1 #dbb ,,fogs1 #bbe1 #bbf arrest sound1 #dac1 #dad cause of1 #abi differs from cloud1 #abh1 #bbg mist1 #bbg dispersed by wind1 #bbh by sun1 #bbg frozen1 #bca in autumn1 #bbh in marshes1 #bbf valleys1 #bbh none in a frosty night1 #bbg ,food converted to blood1 #bdb cooled by the breath1 #cab ,foot-prints frozen1 #cej ,foot-warmers1 #agc ,forked lightning1 #e dangerous1 #e ,forests catch fire spontaneously1 #ajb ,france warmer than of yore1 #afb ,,freezing ,,mixtures1 #cfj ,,friction 7see rubbing71 #ih excites electricity1 #bi sets forests on fire1 #ajb ,frogs cold1 #id ,,frost affects barometer1 #cbi sound1 #dad braces1 #adg breaks ewers1 #cdi tiles1 stones1 rocks1 #cej pipes1 #cea cracks earth1 #ceg expands water1 #ceb prevents fog1 #bbg warm1 #cef ,froth of beer1 #bfi1 #cej ,frozen ruts and footprints1 #cej ,fruits cool the blood1 #ib fall to the earth1 #dai pleasant in summer1 #ib ,fuel for the body1 #hg ,fumigation for sick rooms1 #dba ,,fur1 bad conductor1 #aff for clothing1 #age warm1 #aga ,furnaces of brick1 #agd lined with clay1 #agd ,furr of kettles1 #bfb steam engines dangerous1 #bfc ,gallery hot1 #bdi1 #caf ,gas1 #aab of candles1 #bha ,gauze wire of safety lamps1 #bhb prevents explosion1 #bhb ,german silver tarnishes1 #bfj ,german tinder1 #ajb ,germany warmer than of yore1 #afb ,ghosts1 #bhf ,gideon's miracle1 #baa ,ginger pop1 #bfh acid1 #bfi ,,glasses broken by hot water1 #abe covered with mist1 #bad which soon subsides1 #bae dulled by a hot hand1 #bae by breath1 c41 #bae ,see spectacles4 ,glass a reflector1 #aid soon cools1 #bab ,see looking-glass4 ,glauber salts1 #dbf ,gloves1 black kid1 #ahh ,lisle thread1 #ahh ,glow-worms glisten by night1 #cfh ,,god',s ,,wisdom #ahb1 #bjh1 #baj1 #cjb1 #cjh1 #ceb1 #ceg ,gold never tarnishes1 #bfj ,goulard1 #dbf ,grapes never ferment1 #bgb ,grass promotes warmth1 #afa collects dew1 #bji ,grate1 see stove ,gravel collects no dew1 #bji ,gravity1 #dai ,gray morning1 sign of a fine day1 #adj ,,grease liked in cold weather1 #ij loathed in hot1 #ib prevents rust1 #beh used for wheels1 #ajj ,green colour1 #dja wood does not burn1 #ajg ,grottoes famous for echoes1 #daf ,ground frost1 #bbi ,growth promoted by moonlight1 #bbj ,gulls fly to sea1 #aed to land1 #aed ,gusty weather makes a smoky house1 #ga ,,hail1 #cca1 #ccd cause of1 #cce accompanied with thunder1 #cce falls in summer1 #cce ,hair1 bad conductor1 #aff covered with dew1 #bag ,halls famous for echoes1 #dag ,halo round the moon1 #adc ,hard work promotes hunger1 #hh ,hat covered with dew1 #bag turned red at the seaside1 #cdd ,hawks see near and far1 #cib ,hay-stacks catch fire spontaneously1 #eh ,haze round the sun1 #adc moon1 #adc affects sound1 #dad ,head aches in a crowd1 #bdi itches in wet weather1 #aej ,hearth-rug warm1 #afi ,hearth-stone cold1 #afi hot1 #agj ,,heat1 #a and light1 #dg affects barometer1 #cbh sound1 #dad animal1 #hc1 #he1 #bgg applied to the bottom of boilers1 #bcd effects of1 #b1 #d1 #ajc expands water1 #ceb from beaten iron1 #ie ,,latent1 #ca1 #ge1 #if of candles1 #ge dunghills1 #bgg fire1 #cg1 #bgg lime1 #bgh radiates1 #aif sources of1 #b ,heavy bread1 #afj ,hills larger in a fog1 #adh ,,hoar ,,frost1 #bbh not found on trees1 #bcj under shrubs1 c41 #bcj of frozen fog1 #bca on clear nights only1 #bbi on grass1 #bbi tombstones1 #ahi1 #bcj very partial1 #bbi ,,honey-,,dew1 #bbj ants fond of1 #bba effects of1 #bba injures plants1 #bba ,hot cloudy night oppressive1 #add ,hot weather abates activity1 #ic appetite1 #ij love for grease1 #ib ,hottest place at church1 #caf ,hoops used red hot1 #abb1 #abc ,horse shoes fitted hot1 #abc ,horses strike fire1 #ih snuff up air1 #aeb uneasy in dull weather1 #adh ,houses catch fire spontaneously1 #ef smoke in valleys1 #ff ,hunger1 #hh promoted by cold1 #ij day-light1 #hh singing1 speaking1 work1 #hh ,see appetite4 ,hydrogen gas1 #cd1 #gd ,,ice1 #cdi lighter than water1 #cdi grows thicker1 #cec dissolved by snow1 #ceg melted by sun1 #abf ,ice-bergs famous for echoes1 #dag ,idiots1 #dbd ,,ignis ,,fatuus1 #bhe cause of1 #bhf ,impure water purified1 #gb ,indian mode of striking fire1 #ii ,inflammable air1 #cd1 #gd ,insensible perspiration1 #bac ,intermediate clouds1 #ace ,,iron1 bad conductor1 #ahe cinders1 #dc contains latent heat1 #if cooled by air1 #bdf convection1 #bdf radiation1 #bdf matches1 #if rust1 #beg when most common1 #beh prevented1 #beh sonorous1 #daj stoves1 #agd ,ironing-box1 #aee ,islands equable in temperature1 #caa subject to wind1 #cji1 #caa ,itching in wet weather1 #aej ,jack o'lanthorn1 see ignis fatuus ,jet of flame through bars1 #de ,juice of lemons1 #dbf ,jungle of ,hindostan fatal1 #bff ,kendal rainy1 #cdj ,keswick rainy1 #cdj ,,kettle boils over1 #aae quickly when covered with soot1 #ahf slowly when clean1 #ahf when new1 #ahf bottom should be sooty1 #bjj cold when water boils1 #bjj inside white1 #bjj lid hot1 #bja furr1 #bfb holder1 #afg not full after boiling1 #aae runs over1 #bcc through the spout1 #aae sings1 #aac1 #bcc top bright1 #bjj ,kindling wet1 #dc ,lakes which never freeze1 #cee ,lamps1 #gd ,argand1 #hc smoke1 #hb1 #hc spirit1 #aee ,see candle4 ,lamp-glasses1 #hc ,land air cold1 #bbd1 #caa breeze unhealthy1 #cji ,laplanders clad in skin1 #ahc ,,latent ,,heat1 #ca1 #ge1 #if ,laziness promoted by want of food1 #hi by heat1 #ic ,lead tarnished1 #bei ,,leaves collect dew unequally1 #bjh green1 #djd light green in spring1 #djd in a pond1 #dai pale in dark places1 #djc promote cold1 #afa yellow in autumn1 #djh ,lid of kettles1 c4 hot1 #bja ,light bread1 #bgf ,,light1 #cfc composed of various colours1 #djj divided by a prism1 #cic from a flint1 #ig of candles1 #gf fire1 #df sun1 #cfc reflected1 #cfd speed of1 #cfd sudden painful1 #cfe ,,lightning1 #c balls1 #f barks and snaps trees1 #bg comes from clouds1 #af from earth1 #af conductors1 #bb dangerous1 #bd follows dry weather1 not wet1 #bh forked1 #e fuses metal1 #bg kills animals1 #g knocks down churches1 #bd maims1 #h passes down the outside of a tree1 #ad passes through the inside of animals1 #ad purifies air1 #bg rare in winter1 #bh sheet1 #f summer1 #aa common1 #bh straight1 #f turns beer sour1 #bg not old beer1 #bg milk sour1 #be ,see danger1 safety4 ,lilac steel rusts1 #bei prevented1 #bei ,,lime and water1 #bf1 #cj burned1 #bgh hot1 #bgg purifies bins1 #bff1 #dba sewers1 #bfg1 #dba ,lime-wash for rooms1 #dbb ,lincoln1 rain of1 #cdj ,linen cool wear1 #ahc dried1 #afj1 #caf ,linseed oil boils1 #aai ,,liquefaction1 #abf ,,liquids1 #aab bad conductors1 #agb1 #bcb cooled1 #bce ,lisle thread gloves1 #ahh ,liverpool1 rain of1 #cdj ,,london ,,fog1 #bbe rain of1 #cdj ,long flues1 #aaj grass promotes cold1 #afa ,log of wood1 #b two burn better than one1 #dd1 #eb ,looking-glass1 #cfi ,lucifer matches1 #bhd ,lunar caustic1 #dbf ,mackarel scales1 c41 #acf ,macintosh prevents cold1 #aeh ,madness from starvation1 #hf ,malt1 #bgj1 #bgb ,man a swimmer1 #cfb no bigger than a crow1 #chb ,manchester1 rain of1 #cdj ,magpies indicate weather1 #aec ,marble1 #dbf ,,march comes in like a lion1 #cjf goes out like a lamb1 #cjf dry good1 wet bad1 #cjf flowers undesirable1 #cjg wind dry1 #cje ,marsh damp1 #bhj ,marsupium1 #cib ,meat-covers1 #bjb ,,meat liked in cold weather1 #ij loathed in hot1 #ib taint removed1 #dbb tainted by moonlight1 #bbj ,,mechanical ,,action1 #ie ,mercury of barometer bright1 #bfj concave1 #cbe convex1 #cbe its rise and fall1 #cbe ,,metal collects no dew1 #bji feels colder than wood1 #afh hotter than wood1 #afg fused by fire1 #abg by lightning1 #bg good conductor1 #afe handles burn1 #aff reflectors1 #aic tea-pots1 #aig ,milk soured by lightning1 #be ,miners' danger1 #bhc prevented1 #bfe ,mirror1 #cfi ,,mist arrests sound1 #dad black1 #add cause of1 #bbd differs from cloud1 #abh dew1 #bbb fog1 #bbg seems to rise1 #bbb vanishes at sunrise1 #bbg white1 #add ,mixing not combining1 #be ,money hot in a pocket1 #afh ,monsoon1 #cjj ,months1 driest1 #cbh wettest1 #cbi ,,moon1 distance and size1 #chc largest at horizon1 #adi1 #cgh reflected in water1 #cgf in a well1 #cgd seems flat1 #chc larger than stars1 #chc ,moonlight makes plants grow1 #bbj taints meat1 #bbj ,,morning breeze1 #cjh gray1 #adj rainbow1 #ada red1 #aci1 #cii streaks1 #acb ,,mortar1 #bgh adhesive1 #bgi crumbles1 #ceh ,motes in a sun-beam1 #bdh ,mould hardened by sun1 #afc ,mouldiness prevented1 #dbb ,mountains cold1 #ajj1 #aie collect rain1 #cch famous for echoes1 #dag impede respiration1 #bee noiseless1 #daf ,muriate of soda1 #dbf ,musical instruments1 #daa flat1 #dab ,nails for matches1 #if ,naves fitted on hot1 #abb ,near-sight1 #chh1 #cia spectacles for1 #chi ,negative electricity1 #ff ,negroes1 why black1 #aij with black eyes1 #aij ,new kettles boil slowly1 #ahf ,night allays hunger1 #hh exhilarating1 #add oppressive1 #add produces cold1 #hi rainbow at1 #ada ,nimbus clouds1 #acg ,nitrate of silver1 #dbf ,nitric acid1 #bh1 #dbf ,nitrogen1 #cf ,north wind cold1 #cjb dry1 #cjc ,north-east wind dry1 #cje1 #cbj ,november rainy1 #cjh1 #cch ,oak attracts lightning1 #beg ,old people far-sighted1 #cij hold objects at a distance1 #cib lose their sensation1 thought1 volition1 #dbe lose their power of walking1 #dbe spectacles for1 #cia ,oil1 #gd linseed1 #aai of turpentine1 #aai of vitriol1 #dbf ,one pot will not boil in another1 #aah how to make it boil1 #aah ,oxalic acid1 #dbf copper1 #bei iron1 #beg ,,oxide of lead1 #bei1 #dbf platinum1 #bfa potassium1 #bfb silver1 #bfj sodium1 #bfb ,oxygen1 #cd of air1 #ig its use1 #bdj supports combustion1 #bdj sustains life1 #bdj ,out-of-door work produces hunger1 #hi ,owls prowl at night1 #cfg see in the dark1 #cfg sleep all day1 #cfg ,paleness1 #bdc ,palmer's candles1 #hj ,paper burns1 #da not always1 #dd1 #ec extinguishers1 #gi puckers from wet1 #cci used for kindling1 #da ,papill1 #dbe ,paris1 plaster of1 #dbf rain of1 #cdj ,parlours smell of smoke in summer1 #ga ,partition walls to arrest sound1 #dae ,pea-soup fog1 #bbe ,,percussion1 #ie ,perspiration1 #hi ,petals1 #djb ,petrels1 #aed ,phosphate of lime1 #bhd ,phosphorus1 #bhc1 #bhd ,,phosphuretted ,,hydrogen ,,gas1 #bhc ,piano-forte1 #dab ,pickle tested1 #cfa ,pie with a cup1 #abj full of juice1 #aba ,pin puts a candle out1 #ha ,pineal gland1 #dbd ,pipes broken by frost1 #cea ,piston1 #ajb ,,plants collect dew1 #bjh deleterious in bedrooms1 #dje grow out of walls1 #caf ,plaster of ,paris1 #dbf of stoves falls away1 #abd ,plasterers cannot work in frost1 #cei ,platinum1 #bfa its use1 #bfa never tarnishes1 #bfa ,plate warmer1 #ahh1 #aic ,ploughing1 promotes warmth1 #afa ,plumbago1 #beh prevents rust1 #beh ,poison for flies1 #dbb ,poker draws up fire1 #eb cold1 #agb1 #bch how to carry it when hot1 #bcg1 #bch rusts1 #beh prevented1 #beh ,polar current1 #bih ,poor averse to cleanliness1 #ic ventilation1 #id lazy1 #hi ,pores of wood1 #ajf ,porter1 froth of1 #aji set before a fire1 #aji stale1 #bge ,positive electricity1 #af ,potatoes1 green1 #dje yellow1 #djd ,potassium1 #bfb burns in water1 #bfb ,primrose1 #djb ,prisms divide light1 #cic ,pump handle cold1 #afh water hard1 #cfc ,purple steel rusts1 #bei its rust prevented1 #bei ,,putrefaction1 #bgg1 #bgh ,putrefying bodies smell1 #bhd1 #bhe ,quadrupeds swim1 #cfb ,,radiation1 #aie cools iron1 #bdg ,radiators are absorbers1 #aig ,rags catch fire spontaneously1 #eh ,railway steamers1 #bah ,,rain1 #cca1 #ccf affected by wind1 #ccg after lightning1 #aa arrests sound1 #dac cause of1 #cbf1 #ccf cools air1 #aei differs from dew1 #bbf falls in drops1 #ccf fertilizing1 #cjg1 #ccg from passing clouds1 #ccf heaviest in summer1 #cda least at the poles1 #cdb melts salt1 #cdf sugar1 #cde most in mountainous places1 #cch most in winter1 #cda near the equator1 #cda not salt1 #cdg on dust1 #bbc prognostics of1 #acg purifies air1 #cch sudden change1 #cbf ,,rainbow1 #cid1 #cig colours reversed1 #cif morning1 #ada night1 #ada two1 #cie ,rain drops1 #ccf vary in size1 #ccg ,rain-water smells offensively1 #cde soft1 #cdd stagnant1 #cdg ,rainy months1 #cjh parts of ,england1 #cdj ,rattling of kettle-lid1 #aaf ,ray of light divided1 #cic1 #djj ,reading aloud produces hunger1 #hh ,,red colour1 #dja rose1 #dja sky1 #acb1 #cii sun-rise1 #aci sun-set1 #aci ,reflected light1 #cfd ,,reflection of ,,heat1 #aib1 #cgj ,,reflectors1 #aib help the roast1 #aid keep kitchen cool1 #aid not absorbers1 #aib should be clean and bright1 #ahi1 #aib should not be painted1 #ahi ,,refraction1 #chf1 #cid ,refrangible1 #acb ,retina1 #chh ,reverberation1 #dag ,rice for food1 #ic ,,rivers flow slowest at sides1 #cdh freeze unequally1 #ced never frozen at bottom1 #ceb not wholly frozen1 #cec shallow freeze fastest1 #ced seem shallower than they are1 #chg warm when frozen1 #ced ,roast apples1 #aje soft1 #ajf chestnuts1 #ajd ,road dark from a light room1 #aid ,rocks collect no dew1 #bji broken by frost1 #cej ,room cooled1 #aei1 #cae ventilated1 #cge warmed by fire1 #bcg ,rose red1 #dja ,ross ,captain1 #dad ,rotting leaves promote cold1 #afa ,rubbing1 #ii hands to warm them1 #aja melts ice1 #aja restores suspended animation1 #aja ,see friction4 ,ruddiness1 #bdc ,ruins famed for echoes1 #daf ,running1 promotes warmth1 #hg ,running water freezes slowly1 #ced makes rough ice1 #ced oscillates1 #cdh promotes warmth1 #hg pure1 #cdg ,rush lights easily blown out1 #gi extinguished by a pin1 #ha ,,rust1 #beg prevented1 #beh when most troublesome1 #beh ,,safety ,,in ,a ,,storm abroad1 #bj at a slight distance from a tree1 #bj best to be wet1 #bb in a carriage1 #bj in bed1 #bb in-doors1 #ba ,safety lamp1 #bha1 #bhb ,sailors rarely catch cold1 #aeh ,st4 ,bride's church destroyed by lightning1 #bd ,,salt1 #dbf and snow cold1 #ceg and water1 #ca bad for washing1 #cdc crackles in a fire1 #dd dissolves ice1 #ceg by water1 #cdf especially hot water1 #cdf retards boiling1 #aah white1 #djc of lemons1 #dbf smelling1 #dbf water unfit for railway engines1 #bfc ,sand dazzling1 #dje ,saturday's kettle boils fastest1 #aii ,saucepan boils best when black1 #aii slowly when new1 #aii lids should be clean and bright1 #aii ,scald cured1 #aeg ,scum of fermentation1 #bgb ,sea-beach healthy in the morning1 #caj not healthy at night1 #caj ,sea before storm1 #adf heaves and sighs1 #adf not much heated by sun1 #bif ,sea-gulls1 #aed ,sea water easier to swim in than fresh1 #cfj rarely frozen1 #cee gives cold1 #aeh salt1 #cdf ,sea-waves1 #cab ,sedentary pursuits abate hunger1 #ij ,,seeing in a glass1 #cfi into a dark street1 #cff light room1 #cgh ourselves in a small mirror1 #cga the same object1 #cfe when used to darkness1 #cff ,sensation destroyed1 #dbd of feeling1 #dbe of taste1 #dbe ,sewers purified1 #bfg ,shade cool1 #ahc ,shadow in water1 #cga1 #cgb ,shadow larger as the object approaches a light1 #cgi ,sheen1 #dje ,sheep bleat1 #adh ,sheet lightning1 #f ,sheets wet1 #aeg ,ships out at sea1 #che ,shirts of linen1 #ahc ,shoes hot when dusty1 #aid ,sick rooms purified1 #dba ,sides of a pond covered with leaves1 #dai ,swimming1 #aab ,,silver meat-covers1 #bjb should not be chased1 #bjb tarnishes1 #bfj ,simple clouds1 #acd ,singing of a kettle1 #aac of boiling water1 #bcc produces hunger1 #hh ,single magpie unlucky1 #aec ,skin1 black does not scorch1 #aia white does1 #aia itches1 #aej ,sleep elongates the body1 #dbc body feels not in1 #dbe dreams in1 #dbd ears hear not in1 #dbc eyes see not in1 #dbc mind wills not in1 #dbd tongue tastes not in1 #dbc ,sleet1 #ccb ,slit chestnuts1 #aje ,smelling salts1 #dbf ,,smells in wet weather1 #aeb of church-yards1 #bhc of putrefying bodies1 #bhd ,,smoke1 #ci1 #ei curls1 #ei falls1 #aeb of fresh coals1 #ci lamps diminished1 #hc by a glass1 #hc rises1 #aaj useful in cooking1 #bja ,smoky chimneys1 #ei ,see chimney4 ,smoke-jacks1 #aab ,,snow1 #cca arrests sound1 #dac bad conductor1 #ccc cause of1 #cca falls in winter1 #ccb not in summer1 #ccd like wool1 #age nourishes the earth1 #ccc on mountains1 #ccd soon melts beneath a hedge or wall1 #bjf use of1 #ccb warm1 #ccb1 #ccc white1 #ccd1 #djb ,snow and salt cold1 #ca1 #ceg ,soap1 #cdd cleansing1 #cdd hard1 soft1 #cdd yellow1 #cdd ,soap-bubbles1 #cdh1 #cih change colour1 #cii ,soapy water bubbles1 #cdh ,soda water1 #bfh1 #bfi ,sodium1 #bfb decomposes water1 #bfb ,soft soap1 #cdd ,solids1 #aab ,soot in summer1 #ga on ceilings1 #ga ,sooty kettles1 #ahf ,,sound1 #dji affected by frost1 #dad heat1 #dad arrested by wet1 #dac velocity of1 #daj diminished by rarity of air1 #daf heard best by night1 #dad inaudible on mountains1 #adg ,south wind rainy1 #cjc1 #cbj warm1 #cjc ,south-west wind rainy1 #cjd ,sparks from a fire1 #ajf a flint1 #ig a horse-shoe1 #ih ,spectacles1 #chi black1 #djh blue1 #djg for aged1 #cij near sights1 #chi ,split bells1 #daa ,sponge swells when wet1 #cci ,,spontaneous ,,combustion1 #ef1 #eg1 #eh1 #he ,spoons become dull1 #bf in water1 #chg retard boiling1 #aag ,speaking promotes hunger1 #hh ,spring best late1 #cjg water cool1 #ahb sparkles1 #bfi ,springs prevent freezing1 #cef ,sprinkling to cool rooms1 #aei ,stagnant water1 #cdg full of worms1 #cdg ,stale beer1 c41 see beer1 #bge ,stars distance and size of1 #chc invisible by day1 #cfh seem flat1 #chd seen in a well1 #cfh1 #cgd seen on mountains1 #cgf twinkle1 #djf ,starvation1 #hf produces madness1 #hf ,,steam1 #abg engines burst1 #bcf invisible1 #aaf1 #bce of a kettle1 #bcf why visible1 #aag what becomes of it1 #aag ,,steel and flint1 #ig rusts1 #bei prevented1 #bei ,stillness before a storm1 #adf ,stirring cools broth1 c41 #bdg ,stockings difficult to draw on when wet1 #cdj ,,stones broken by frost1 #cej cold1 #afi collect no dew1 #bjh snap in fire1 #ajh unfit for fuel1 #dc ,,storms1 #adf direction of1 #bh places of danger in1 #ab safety in1 #bj ,straw covered over brickwork1 #cei over trees1 #cei water-pipes1 #cei ,street dark from a light room1 #aid ,,stoves crack1 when lighted1 #abc when cooling1 #abc of bricks1 #agd on a floor1 #eb1 #bcg rust1 #beg not often1 #beh prevented1 #beh settings fall away1 #abd warm a room1 #bcg ,strata of air1 #i ,stratus clouds1 #ace ,streets seem to meet at bottom1 #cha watered1 #aei ,stucco peels off in frost1 #ceh ,sublimates1 #dbf ,sublimation1 #dbf ,sudden light painful1 #cfe ,,sugar at top of tea melts quickly1 #dba left at the bottom of a cup melts slowly1 #dbj melted by water1 #cde especially by hot water1 #cdf retards boiling1 #aah stirred melts quickly1 #dbj white1 #djb of lead1 #dbf ,sulphate of lime1 #dbf magnesia1 #dbf soda1 #dbf zinc1 #dbf ,sulphuric acid1 #dbf and water1 #cj boils1 #aaj ,summer allays hunger1 #ij clothes for1 #ahg creates dislike of grease1 #ib love of fruit1 #ib lightning1 #aa ,sun-beams full of mites1 #bdh ,,sun affects eyes1 #djg dazzles1 #cfd dulls fire1 #dj largest at horizon1 #adi1 #cgg not seen in a well1 #cgc seems flat1 #chd source of heat1 #b reflected in water1 #cge ,sun-rise red1 #aci ,sun-set gray1 #adj red1 #ach yellow1 #aci ,super-acetate of lead1 #dbf ,swallows fly low1 #aeb ,swan dry in water1 #bbd ,swimmers sink1 #cfa ,swimming1 #bfb ,syrup boils1 #aai ,table salt1 #dbf ,tainted meat cured1 #gb1 #dbb water1 #gb ,tallow1 #gd ,tarnish1 #bei ,tartar emetic1 #dbf ,tartrate of potash1 #dbf ,tarts have a cup inside1 #abj full of juice1 #aba ,,tea cooled by blowing1 #bdh by stirring1 #bdg in a saucer1 #afc green deleterious1 #dbc poison for flies1 #dbc ,,tea-,,pot1 bright metal1 #aig tarnishes1 #bfj black earth1 #aig preferred by some1 #aih set on a hob1 #aih ,telescopes1 #che ,tempest1 #adf affects weather1 #cbf ,see storms4 ,thaumatrope1 #djf ,,thaw affects barometer1 #cbi cold1 #cbj1 #cef dulls fire1 #ej ,thermometer1 #cjg ,thick clothing unhealthy1 #afd ,,thunder1 #h after lightning1 #ab bolts1 #aa deep growl1 #aj irregular roar1 #i one crash1 #h rolling1 #aj ,see danger1 safety1 storm4 ,tigers prowl by night1 #cfg sleep all day1 #cfg see in the dark1 #cfg ,tiles broken by frost1 #cej ,timber charred1 #gc ,tin blowers1 #gj foot-warmers1 #agc reflectors1 #aic ,see reflectors4 ,tinder blown1 #ig ,toast and water1 #gc for the sick1 #gc ,tomb-stones frosted1 #bcj ,tongs rust1 #beh prevented1 #beh ,trade-winds1 #aih ,transparency1 #dje ,treble1 #dab ,,trees barked by lightning1 #bi collect dew1 #bjh covered with bass1 c41 #cei look more distant in a fog1 #adh promote warmth1 #afa purify air1 #bec shade of1 cool1 #ahc ,tumblers1 see glasses ,twilight1 #cii ,two eyes1 #cfh see single1 #cfi ,unslit chestnuts1 #ajd ,use of barometers1 #cag clouds1 #acg smoke in cooking1 #bja snow1 #ccb ,valley chimneys smoke1 #ff ,,vaporization1 #abf1 #abg ,vapour of a carriage1 #bad of a room1 #bab of sea not salt1 #afc ,vats fatal1 #bfe ,vegetable and animal life co-dependent1 #bdd ,vegetables collect dew1 #bjh cool the blood1 #ib ,velocity of clouds1 #cad light1 #cfd sound1 #daj wind1 #cac ,vent peg1 #bgc1 #bgd ,,ventilation1 #cae sought by the well-fed1 #id not by the ill-fed1 #id ,verdigris1 #dbf ,vertical sun1 #bic ,vestry chimneys smoke1 #ff ,violets blue1 #djb ,walls wet in winter1 #baf ,want connected with dirt1 #ic ,warm clothes1 #ahg some things more than others1 #afe ,wash-hand-basin1 #aga ,washing1 water for1 #bge should not be hard1 #cdc ,,water1 #ch1 #cdb and lime1 #cj and sulphuric acid1 #cj ashes soften1 #cde bad conductor1 #aga1 #bcd boiling1 #aai1 #bcb1 #bcd bubbles1 #aad1 #bcc rattles1 #aaf runs over1 #aae1 #bcc sings1 #bcc cleans dirty linen1 #cdd cold1 #agg converted to steam1 #abg1 #cdc cools slowly1 #bbe deep1 freezes slowly1 #cef dried up in summer1 #afb expands by frost1 #cea by heat1 #cea extinguishes fire1 #ed1 #ajg flat when boiled1 #bge fluid1 #cdb flowing1 pure1 #cdg for washing1 #bge freezes at the surface1 #bec hard1 #cdc unfit for washing1 #cdc how preserved cool1 #aia1 #bjb hot1 #aia heated1 #bcb intenses fire1 #ed mixed with salt1 boils slower1 #aai not heated above boiling1 #bce of a spring cool1 #ahb purified1 #gb purifies bins1 c41 #bfg salt1 bad for washing1 #cdc shallow1 freezes fastest1 #cee slackens flame1 #ee soft1 #cdd best for washing1 #cde sparkles1 #bfi stagnant1 #cdg full of worms1 #cdg stale1 #bge swells with boiling1 #aad will not bubble without soap1 #cdh warm when frozen1 #ced ,water pipes broken by frost1 #cea covered with litter1 #cei ,watering plants by the saucer1 #dbj streets1 #aei ,waves1 #cab ,wax1 #gd ,wax candles need no snuffing1 #ha ,weather affected by tempests1 #cbf prognostics of1 #acg told by barometer1 #cah rules1 #cai ,weather toys1 #cci1 #cdj ,well1 moon seen in1 #cgd stars seen in1 #cfh sun not seen in1 #cgc ,west ,wind promotes dew1 #bah rainy1 #cjd1 #cbj ,wet clothes cold1 #aeg feet dangerous1 #aeg finger cold1 #aeg kindling1 #dc1 #dd sheets1 #aeh summer1 cold winter1 #afj weather offensive1 #ade1 #adh ,wettest months1 #cbi ,wheels catch fire1 #ii greased1 #ajj kept cool by water1 #afb ,wheel-ruts frozen1 #cej ,wheelwright1 #abb ,,white1 #djb blisters1 #aij body linen1 #ahf crust on clothes1 #afc dresses for summer1 #ahf not fit for winter1 #ahg mist1 #add vitriol1 #dbf ,,wicks cotton1 need snuffing1 #ha have a knob when long1 #hj not upright when long1 #hj ,palmer's wicks need no snuffing1 #hj smoke1 #hb ,see candles4 ,will o' the wisp1 see ignis fatuus4 ,,wind1 #bhg affects barometer1 #cbg clouds1 #abi1 #aca after lightning1 #aa altered by clouds1 #bie by seas1 #bie1 #bif brings dry1 #cje rain1 #cje cause of1 #bhg1 #bib changes the shape of clouds1 #acb cold1 #aag1 #ahj1 #cab dispels clouds1 #aca1 #ach fog1 #bbh draws up fire1 #ea dries linen1 #caf feels hot sometimes1 #aha in ,england1 #cjj increases clouds1 #aca1 #ach makes barometer fall1 #cbj chimneys smoke1 #ff of a morning1 #cjh of an evening1 #cji prevents dew1 #bjf rate of travelling1 #cac regular1 #big ,see ,england1 monsoon1 north1 south1 west c41 trade-winds c4 ,winding passages famed for echoes1 #dag ,windows blazing with the sun1 #cgb not at noon1 #cgb covered with frost1 #bad mist1 #baa carriage1 dull1 #bac rattle1 #dah ,wine glasses1 see glasses ,wine made without yeast1 #bga ,winter clothing1 #ahg promotes hunger1 #ij ,,wisdom of ,,god1 #ahb1 #bjh #baj1 #ceb1 #ceg ,,wood burns1 #da spontaneously1 #ee charred1 #gc hot at one end1 cold at the other1 #afe ignited by friction1 #ii kindling1 #da dry1 #dd wet1 #ajg two logs burn best1 #dd1 #eb sends forth sparks1 #ajf will not melt1 #abg ,wooden handles1 #aff ,,wool bad conductor1 #aff collects no dew1 #bji warm1 #agf1 #ccc ,woollen clothing1 #age ,work produces hunger1 #hh ,yeast1 #bga makes light bread1 #bgf not used in wine1 #bga ,yellow flame gives best light1 #dg soap1 #cdd sun-set sign of wet1 #aci ,,finis ,,jarrold ,,and ,,sons1 ,,printers1 ,,norwich4 ,transcriber's ,notes3 ,archaic and inconsistent punctuation and spelling retained4 ,inconsistent question formats were regularized4