Q.Why do fishes always seem to be nearer the surface of a river than they really are?A. Because the rays of light from the fish arerefractedas they emerge from theeye: and (as a bent stick is not so far from end to end as a straight one) so the fishes appear nearer our eye than they really are.
Q.Why do fishes always seem to be nearer the surface of a river than they really are?
Q.Why do fishes always seem to be nearer the surface of a river than they really are?
A. Because the rays of light from the fish arerefractedas they emerge from theeye: and (as a bent stick is not so far from end to end as a straight one) so the fishes appear nearer our eye than they really are.
A. Because the rays of light from the fish arerefractedas they emerge from theeye: and (as a bent stick is not so far from end to end as a straight one) so the fishes appear nearer our eye than they really are.
Q.Why are some personsnear-sighted?A. Because theCOR´NEAof their eye is soprominent, that the image of distant objects is reflectedbefore it reaches theret’ina; and, therefore, is not distinctly seen.N.B. The cor´nea shields thecrystalline lens, and is more or less convex according to the lens which it covers.
Q.Why are some personsnear-sighted?
Q.Why are some personsnear-sighted?
A. Because theCOR´NEAof their eye is soprominent, that the image of distant objects is reflectedbefore it reaches theret’ina; and, therefore, is not distinctly seen.N.B. The cor´nea shields thecrystalline lens, and is more or less convex according to the lens which it covers.
A. Because theCOR´NEAof their eye is soprominent, that the image of distant objects is reflectedbefore it reaches theret’ina; and, therefore, is not distinctly seen.
N.B. The cor´nea shields thecrystalline lens, and is more or less convex according to the lens which it covers.
Q.What is meant by the “cor’neaof theeye?”A. All theoutsideof the visible part of theeye-ball.The curve A B C is called thecor'nea.If this curve be too prominent (or convex), the eye is near-sighted.If too flat (or concave), the eye is far-sighted.
Q.What is meant by the “cor’neaof theeye?”
Q.What is meant by the “cor’neaof theeye?”
A. All theoutsideof the visible part of theeye-ball.The curve A B C is called thecor'nea.If this curve be too prominent (or convex), the eye is near-sighted.If too flat (or concave), the eye is far-sighted.
A. All theoutsideof the visible part of theeye-ball.
The curve A B C is called thecor'nea.If this curve be too prominent (or convex), the eye is near-sighted.If too flat (or concave), the eye is far-sighted.
Q.What is meant by the “ret’inaof theeye?”A. The net-work which lines theback of the eye, is so called.The net-work ABC is called the ret'ina, and the projecting part DEF is called the cor'nea.
Q.What is meant by the “ret’inaof theeye?”
Q.What is meant by the “ret’inaof theeye?”
A. The net-work which lines theback of the eye, is so called.The net-work ABC is called the ret'ina, and the projecting part DEF is called the cor'nea.
A. The net-work which lines theback of the eye, is so called.
The net-work ABC is called the ret'ina, and the projecting part DEF is called the cor'nea.
Q.What sort ofglassesdonear-sightedpersons wear?A. If the cor’nea betoo convex(or projecting), the person must wear doubleconcave glasses, to counteract it.
Q.What sort ofglassesdonear-sightedpersons wear?
Q.What sort ofglassesdonear-sightedpersons wear?
A. If the cor’nea betoo convex(or projecting), the person must wear doubleconcave glasses, to counteract it.
A. If the cor’nea betoo convex(or projecting), the person must wear doubleconcave glasses, to counteract it.
Q.What is meant by “double concave glasses?”A. Glasses hollowed inon both sides.The figure A is double concave, or concave on both sides.
Q.What is meant by “double concave glasses?”
Q.What is meant by “double concave glasses?”
A. Glasses hollowed inon both sides.The figure A is double concave, or concave on both sides.
A. Glasses hollowed inon both sides.
The figure A is double concave, or concave on both sides.
Q.What is meant by the “imageof objects being reflectedbeforeit reaches theret’ina?”A. If the cor’nea betoo convex, the image of a distant object is reflected (on the vitreous humours of the eye)before it reaches the ret’ina.Thus the image is reflected at DE, instead of on ABC (the ret'ina).
Q.What is meant by the “imageof objects being reflectedbeforeit reaches theret’ina?”
Q.What is meant by the “imageof objects being reflectedbeforeit reaches theret’ina?”
A. If the cor’nea betoo convex, the image of a distant object is reflected (on the vitreous humours of the eye)before it reaches the ret’ina.Thus the image is reflected at DE, instead of on ABC (the ret'ina).
A. If the cor’nea betoo convex, the image of a distant object is reflected (on the vitreous humours of the eye)before it reaches the ret’ina.
Thus the image is reflected at DE, instead of on ABC (the ret'ina).
Q.What is the use ofdouble concave spectacleglasses?A. Near-sighted spectaclescast the reflection further back;and the image (beingthrown upon the ret’ina) becomes visible.
Q.What is the use ofdouble concave spectacleglasses?
Q.What is the use ofdouble concave spectacleglasses?
A. Near-sighted spectaclescast the reflection further back;and the image (beingthrown upon the ret’ina) becomes visible.
A. Near-sighted spectaclescast the reflection further back;and the image (beingthrown upon the ret’ina) becomes visible.
Q.Why areoldpeoplefar-sighted?A. Because the humours of their eyesare dried up by age, and thecor’neasinks in, or becomes flattened.
Q.Why areoldpeoplefar-sighted?
Q.Why areoldpeoplefar-sighted?
A. Because the humours of their eyesare dried up by age, and thecor’neasinks in, or becomes flattened.
A. Because the humours of their eyesare dried up by age, and thecor’neasinks in, or becomes flattened.
Q.Why does theflatteningof thecor’neaprevent persons seeing objects which arenear?A. As the cor’neais too flat, the image of any near object is formedbehind theret’inaof the eye, and is not seen at all.The reflection is made at DE, instead of at ABC (the retina).
Q.Why does theflatteningof thecor’neaprevent persons seeing objects which arenear?
Q.Why does theflatteningof thecor’neaprevent persons seeing objects which arenear?
A. As the cor’neais too flat, the image of any near object is formedbehind theret’inaof the eye, and is not seen at all.The reflection is made at DE, instead of at ABC (the retina).
A. As the cor’neais too flat, the image of any near object is formedbehind theret’inaof the eye, and is not seen at all.
The reflection is made at DE, instead of at ABC (the retina).
Q.What sort ofglassesdooldpeoplewear?A. As their cor’nea isnot sufficiently convex, they must usedouble convexglasses, to enable them to see objects near at hand.
Q.What sort ofglassesdooldpeoplewear?
Q.What sort ofglassesdooldpeoplewear?
A. As their cor’nea isnot sufficiently convex, they must usedouble convexglasses, to enable them to see objects near at hand.
A. As their cor’nea isnot sufficiently convex, they must usedouble convexglasses, to enable them to see objects near at hand.
Q.What sort of glasses aredouble convex spectacle-glasses?A. Glasses whichcurve outwardson both sides.The figure A is double convex, or convex on both sides.
Q.What sort of glasses aredouble convex spectacle-glasses?
Q.What sort of glasses aredouble convex spectacle-glasses?
A. Glasses whichcurve outwardson both sides.The figure A is double convex, or convex on both sides.
A. Glasses whichcurve outwardson both sides.
The figure A is double convex, or convex on both sides.
Q.What is theuseofdouble convexspectacle-glasses?A. As the image of near objects is reflectedbehind theret’ina, these double convex glassesshorten the focus of the eye, and bring the imageinto the eye(upon the ret’ina).
Q.What is theuseofdouble convexspectacle-glasses?
Q.What is theuseofdouble convexspectacle-glasses?
A. As the image of near objects is reflectedbehind theret’ina, these double convex glassesshorten the focus of the eye, and bring the imageinto the eye(upon the ret’ina).
A. As the image of near objects is reflectedbehind theret’ina, these double convex glassesshorten the focus of the eye, and bring the imageinto the eye(upon the ret’ina).
Q.Why donear-sightedpersons bring objectscloseto the eye, in order tosee them?A. As the distance between thefront and back of their eye is too great, distant objects are reflectedbefore they reach the ret’ina; therefore, near-sighted persons bring the objectscloser, in order that the reflectionmay be cast further back, (to reach the ret’ina).
Q.Why donear-sightedpersons bring objectscloseto the eye, in order tosee them?
Q.Why donear-sightedpersons bring objectscloseto the eye, in order tosee them?
A. As the distance between thefront and back of their eye is too great, distant objects are reflectedbefore they reach the ret’ina; therefore, near-sighted persons bring the objectscloser, in order that the reflectionmay be cast further back, (to reach the ret’ina).
A. As the distance between thefront and back of their eye is too great, distant objects are reflectedbefore they reach the ret’ina; therefore, near-sighted persons bring the objectscloser, in order that the reflectionmay be cast further back, (to reach the ret’ina).
Q.Why dooldpeopleholdobjectsfurther off, in order to see them better?A. As the distance between thefront and back of their eye is not great enough, the reflection of near objects is thrownbeyond the ret’ina; therefore, they hold objectsa long way off, in order to bring their imagesforward(so as to cast it on the ret’ina).
Q.Why dooldpeopleholdobjectsfurther off, in order to see them better?
Q.Why dooldpeopleholdobjectsfurther off, in order to see them better?
A. As the distance between thefront and back of their eye is not great enough, the reflection of near objects is thrownbeyond the ret’ina; therefore, they hold objectsa long way off, in order to bring their imagesforward(so as to cast it on the ret’ina).
A. As the distance between thefront and back of their eye is not great enough, the reflection of near objects is thrownbeyond the ret’ina; therefore, they hold objectsa long way off, in order to bring their imagesforward(so as to cast it on the ret’ina).
Q.Why arehawksable to see such animmenseway off?A. Because they have a muscle in the eye which enables them toflatten their cor’nea, by drawing back the crystalline lens.This muscle is called the “marsupium.”
Q.Why arehawksable to see such animmenseway off?
Q.Why arehawksable to see such animmenseway off?
A. Because they have a muscle in the eye which enables them toflatten their cor’nea, by drawing back the crystalline lens.This muscle is called the “marsupium.”
A. Because they have a muscle in the eye which enables them toflatten their cor’nea, by drawing back the crystalline lens.
This muscle is called the “marsupium.”
Q.Why canhawksnot only see such a long way off, but also objects within half-an-inch of their eye?A. Because their eyes are furnished with a broad circular rim whichconfines the action of this muscle, and throws thecor’nea forward.
Q.Why canhawksnot only see such a long way off, but also objects within half-an-inch of their eye?
Q.Why canhawksnot only see such a long way off, but also objects within half-an-inch of their eye?
A. Because their eyes are furnished with a broad circular rim whichconfines the action of this muscle, and throws thecor’nea forward.
A. Because their eyes are furnished with a broad circular rim whichconfines the action of this muscle, and throws thecor’nea forward.
Q.Into how manypartsmay arayoflightbedivided?A. Into three parts:Blue,Yellow, andRed.N.B. These 3 colours, by combination, make seven. 1.—Red. 2.—Red and yellow formorange. 3.—Yellow. 4.—Yellow and blue makegreen. 5.—Blue. 6 and 7.—Shades of blue calledindigoandviolet.
Q.Into how manypartsmay arayoflightbedivided?
Q.Into how manypartsmay arayoflightbedivided?
A. Into three parts:Blue,Yellow, andRed.N.B. These 3 colours, by combination, make seven. 1.—Red. 2.—Red and yellow formorange. 3.—Yellow. 4.—Yellow and blue makegreen. 5.—Blue. 6 and 7.—Shades of blue calledindigoandviolet.
A. Into three parts:Blue,Yellow, andRed.
N.B. These 3 colours, by combination, make seven. 1.—Red. 2.—Red and yellow formorange. 3.—Yellow. 4.—Yellow and blue makegreen. 5.—Blue. 6 and 7.—Shades of blue calledindigoandviolet.
Q.How is itknown, that a ray of light consists of several different colours?A. Because, if a ray of light be cast upon a triangular piece of glass (called a prism), it will be distinctly divided into seven colours: 1.—Red; 2.—Orange; 3.—Yellow; 4.—Green; 5.—Blue; 6.—Indigo; and 7.—Violet.
Q.How is itknown, that a ray of light consists of several different colours?
Q.How is itknown, that a ray of light consists of several different colours?
A. Because, if a ray of light be cast upon a triangular piece of glass (called a prism), it will be distinctly divided into seven colours: 1.—Red; 2.—Orange; 3.—Yellow; 4.—Green; 5.—Blue; 6.—Indigo; and 7.—Violet.
A. Because, if a ray of light be cast upon a triangular piece of glass (called a prism), it will be distinctly divided into seven colours: 1.—Red; 2.—Orange; 3.—Yellow; 4.—Green; 5.—Blue; 6.—Indigo; and 7.—Violet.
Q.Why does aprism dividea ray of light intovarious colours?A. Because all these colours havedifferent refractive powers. Red is refractedleast, and blue themost; therefore, thebluecolour of the ray will be bent to thetopof the prism, and theredwill remain at thebottom.Here the ray AB received on a prism, would have the blue part bent up to C; the yellow part to D; and the red part no further than E.
Q.Why does aprism dividea ray of light intovarious colours?
Q.Why does aprism dividea ray of light intovarious colours?
A. Because all these colours havedifferent refractive powers. Red is refractedleast, and blue themost; therefore, thebluecolour of the ray will be bent to thetopof the prism, and theredwill remain at thebottom.Here the ray AB received on a prism, would have the blue part bent up to C; the yellow part to D; and the red part no further than E.
A. Because all these colours havedifferent refractive powers. Red is refractedleast, and blue themost; therefore, thebluecolour of the ray will be bent to thetopof the prism, and theredwill remain at thebottom.
Here the ray AB received on a prism, would have the blue part bent up to C; the yellow part to D; and the red part no further than E.
Here the ray AB received on a prism, would have the blue part bent up to C; the yellow part to D; and the red part no further than E.
Q.What is meant by therefractionof a ray?A.Bending itfrom its straight line.Thus the ray AB of the last figure is refracted at B into three courses, C, D, and E.
Q.What is meant by therefractionof a ray?
Q.What is meant by therefractionof a ray?
A.Bending itfrom its straight line.Thus the ray AB of the last figure is refracted at B into three courses, C, D, and E.
A.Bending itfrom its straight line.
Thus the ray AB of the last figure is refracted at B into three courses, C, D, and E.
Q.What is the cause of arainbow?A. When the clouds opposite the sunare very dark, and rain isstill fallingfrom them, the rays of the bright sunare divided by the rain-drops, as they would be by a prism.Let A, B, and C be three drops of rain; SA, SB, and SC three rays of the sun. SA is divided into the 3 colours; the blue and yellow are bentabovethe eye D, and theredenters it.br /> The ray SB is divided into the three colours; the blue is bentabovethe eye, and the red fallsbelowthe eye D; but theyellowenters it.The ray SC is also divided into the three colours. The blue (which is bent most) enters the eye; and the other two fall below it. Thus the eye sees the blue of C, and all drops in the position of C; the yellow of B, and of all drops in the position of B; and the red of A, &c.; and thus it sees a rainbow.
Q.What is the cause of arainbow?
Q.What is the cause of arainbow?
A. When the clouds opposite the sunare very dark, and rain isstill fallingfrom them, the rays of the bright sunare divided by the rain-drops, as they would be by a prism.Let A, B, and C be three drops of rain; SA, SB, and SC three rays of the sun. SA is divided into the 3 colours; the blue and yellow are bentabovethe eye D, and theredenters it.br /> The ray SB is divided into the three colours; the blue is bentabovethe eye, and the red fallsbelowthe eye D; but theyellowenters it.The ray SC is also divided into the three colours. The blue (which is bent most) enters the eye; and the other two fall below it. Thus the eye sees the blue of C, and all drops in the position of C; the yellow of B, and of all drops in the position of B; and the red of A, &c.; and thus it sees a rainbow.
A. When the clouds opposite the sunare very dark, and rain isstill fallingfrom them, the rays of the bright sunare divided by the rain-drops, as they would be by a prism.
Let A, B, and C be three drops of rain; SA, SB, and SC three rays of the sun. SA is divided into the 3 colours; the blue and yellow are bentabovethe eye D, and theredenters it.br /> The ray SB is divided into the three colours; the blue is bentabovethe eye, and the red fallsbelowthe eye D; but theyellowenters it.The ray SC is also divided into the three colours. The blue (which is bent most) enters the eye; and the other two fall below it. Thus the eye sees the blue of C, and all drops in the position of C; the yellow of B, and of all drops in the position of B; and the red of A, &c.; and thus it sees a rainbow.
Let A, B, and C be three drops of rain; SA, SB, and SC three rays of the sun. SA is divided into the 3 colours; the blue and yellow are bentabovethe eye D, and theredenters it.br /> The ray SB is divided into the three colours; the blue is bentabovethe eye, and the red fallsbelowthe eye D; but theyellowenters it.The ray SC is also divided into the three colours. The blue (which is bent most) enters the eye; and the other two fall below it. Thus the eye sees the blue of C, and all drops in the position of C; the yellow of B, and of all drops in the position of B; and the red of A, &c.; and thus it sees a rainbow.
Q.Doeseveryperson see thesamecolours from thesame drops?A. No;no two personssee thesame rainbow.To another spectator the rays from SB might beredinstead of yellow; the ray from SC, yellow; and the blue might be reflected from some drop below C. To athirdperson the red may issue from a drop above A, and then A would reflect the yellow, and B the blue, and so on.
Q.Doeseveryperson see thesamecolours from thesame drops?
Q.Doeseveryperson see thesamecolours from thesame drops?
A. No;no two personssee thesame rainbow.To another spectator the rays from SB might beredinstead of yellow; the ray from SC, yellow; and the blue might be reflected from some drop below C. To athirdperson the red may issue from a drop above A, and then A would reflect the yellow, and B the blue, and so on.
A. No;no two personssee thesame rainbow.
To another spectator the rays from SB might beredinstead of yellow; the ray from SC, yellow; and the blue might be reflected from some drop below C. To athirdperson the red may issue from a drop above A, and then A would reflect the yellow, and B the blue, and so on.
Q.Why are there oftentwo rainbowsat one and the same time?A. Inonerainbow we see the rays of the sunentering the rain-drops at the top, and reflected to the eyefrom the bottom.In theotherrainbow, we see the rays of the sunentering the rain-drops at the bottom, and reflected to the top, whence they reach the eye.Here the ray SA strikes the drop at A,—is refracted or bent to B,—is then reflected to C, where it is refracted again, and reaches the eye of the spectator.Here the ray SB strikes the drop at B,—is refracted to A,—is then reflected to C,—is again reflected to D, when it is again refracted or bent till it reaches the eye of the spectator.
Q.Why are there oftentwo rainbowsat one and the same time?
Q.Why are there oftentwo rainbowsat one and the same time?
A. Inonerainbow we see the rays of the sunentering the rain-drops at the top, and reflected to the eyefrom the bottom.In theotherrainbow, we see the rays of the sunentering the rain-drops at the bottom, and reflected to the top, whence they reach the eye.Here the ray SA strikes the drop at A,—is refracted or bent to B,—is then reflected to C, where it is refracted again, and reaches the eye of the spectator.Here the ray SB strikes the drop at B,—is refracted to A,—is then reflected to C,—is again reflected to D, when it is again refracted or bent till it reaches the eye of the spectator.
A. Inonerainbow we see the rays of the sunentering the rain-drops at the top, and reflected to the eyefrom the bottom.
In theotherrainbow, we see the rays of the sunentering the rain-drops at the bottom, and reflected to the top, whence they reach the eye.
Here the ray SA strikes the drop at A,—is refracted or bent to B,—is then reflected to C, where it is refracted again, and reaches the eye of the spectator.
Here the ray SA strikes the drop at A,—is refracted or bent to B,—is then reflected to C, where it is refracted again, and reaches the eye of the spectator.
Here the ray SB strikes the drop at B,—is refracted to A,—is then reflected to C,—is again reflected to D, when it is again refracted or bent till it reaches the eye of the spectator.
Here the ray SB strikes the drop at B,—is refracted to A,—is then reflected to C,—is again reflected to D, when it is again refracted or bent till it reaches the eye of the spectator.
Q.Why are thecoloursof thesecondbow allreversed?A. Because inonebow we see therays which enter at thetopof the raindrops,refracted from the bottom:But in theotherbow we see the rays which enter at thebottomof the raindrops (after two reflections),refracted from the top.Here A, B, C, represent three drops of rain in theprimary(or inner)rainbow.Theleastrefracted line isred, andbluethemost.So thered(orleastrefracted rays) of all the drops in the position of A,—theyellowof those in the position of B,—and theblue(or themostrefracted rays) of the lowest drops, all meet the eye D, and form a rainbow to the spectator.The reason why the primary bow exhibits the stronger colours is this—because the colours are seen afteronereflection andtworefractions; but the colours of the secondary (or upper) rainbow undergotworeflections andthreerefractions.Here also theleastrefracted ray isred, and themostrefractedblue(as in the former case); but the position of each is reversed.
Q.Why are thecoloursof thesecondbow allreversed?
Q.Why are thecoloursof thesecondbow allreversed?
A. Because inonebow we see therays which enter at thetopof the raindrops,refracted from the bottom:But in theotherbow we see the rays which enter at thebottomof the raindrops (after two reflections),refracted from the top.Here A, B, C, represent three drops of rain in theprimary(or inner)rainbow.Theleastrefracted line isred, andbluethemost.So thered(orleastrefracted rays) of all the drops in the position of A,—theyellowof those in the position of B,—and theblue(or themostrefracted rays) of the lowest drops, all meet the eye D, and form a rainbow to the spectator.The reason why the primary bow exhibits the stronger colours is this—because the colours are seen afteronereflection andtworefractions; but the colours of the secondary (or upper) rainbow undergotworeflections andthreerefractions.Here also theleastrefracted ray isred, and themostrefractedblue(as in the former case); but the position of each is reversed.
A. Because inonebow we see therays which enter at thetopof the raindrops,refracted from the bottom:
But in theotherbow we see the rays which enter at thebottomof the raindrops (after two reflections),refracted from the top.
Here A, B, C, represent three drops of rain in theprimary(or inner)rainbow.Theleastrefracted line isred, andbluethemost.So thered(orleastrefracted rays) of all the drops in the position of A,—theyellowof those in the position of B,—and theblue(or themostrefracted rays) of the lowest drops, all meet the eye D, and form a rainbow to the spectator.The reason why the primary bow exhibits the stronger colours is this—because the colours are seen afteronereflection andtworefractions; but the colours of the secondary (or upper) rainbow undergotworeflections andthreerefractions.
Here A, B, C, represent three drops of rain in theprimary(or inner)rainbow.Theleastrefracted line isred, andbluethemost.So thered(orleastrefracted rays) of all the drops in the position of A,—theyellowof those in the position of B,—and theblue(or themostrefracted rays) of the lowest drops, all meet the eye D, and form a rainbow to the spectator.The reason why the primary bow exhibits the stronger colours is this—because the colours are seen afteronereflection andtworefractions; but the colours of the secondary (or upper) rainbow undergotworeflections andthreerefractions.
Here also theleastrefracted ray isred, and themostrefractedblue(as in the former case); but the position of each is reversed.
Here also theleastrefracted ray isred, and themostrefractedblue(as in the former case); but the position of each is reversed.
Q.Why does asoap bubbleexhibit suchvarietyofcolours?A. The changing colour of the bubble depends upon the changingthickness of the filmthrough which the ray passes.
Q.Why does asoap bubbleexhibit suchvarietyofcolours?
Q.Why does asoap bubbleexhibit suchvarietyofcolours?
A. The changing colour of the bubble depends upon the changingthickness of the filmthrough which the ray passes.
A. The changing colour of the bubble depends upon the changingthickness of the filmthrough which the ray passes.
Q.How does thethicknessof thefilmaffect thecolourof the soap bubble?A. Because differentdegrees of thicknessproduce differentangles of refraction, and, therefore, different colours reach the eye.
Q.How does thethicknessof thefilmaffect thecolourof the soap bubble?
Q.How does thethicknessof thefilmaffect thecolourof the soap bubble?
A. Because differentdegrees of thicknessproduce differentangles of refraction, and, therefore, different colours reach the eye.
A. Because differentdegrees of thicknessproduce differentangles of refraction, and, therefore, different colours reach the eye.
Q.Why is thesoap bubbleso constantlychangingitsthickness?A. As the bubble issuspended, the water keepsrunning down from the topto the bottom of the bubble, till the crown becomes sothinas to burst.
Q.Why is thesoap bubbleso constantlychangingitsthickness?
Q.Why is thesoap bubbleso constantlychangingitsthickness?
A. As the bubble issuspended, the water keepsrunning down from the topto the bottom of the bubble, till the crown becomes sothinas to burst.
A. As the bubble issuspended, the water keepsrunning down from the topto the bottom of the bubble, till the crown becomes sothinas to burst.
Q.Why are the lateevening clouds red?A. Becauseredrays (being theleast refrangible) are thelast to disappear.Here it will be seen that the red ray PA, being reflected on the horizon at A, will be visible to us; but theyellowandbluerays will be hidden by the curve of the earth.
Q.Why are the lateevening clouds red?
Q.Why are the lateevening clouds red?
A. Becauseredrays (being theleast refrangible) are thelast to disappear.Here it will be seen that the red ray PA, being reflected on the horizon at A, will be visible to us; but theyellowandbluerays will be hidden by the curve of the earth.
A. Becauseredrays (being theleast refrangible) are thelast to disappear.
Here it will be seen that the red ray PA, being reflected on the horizon at A, will be visible to us; but theyellowandbluerays will be hidden by the curve of the earth.
Here it will be seen that the red ray PA, being reflected on the horizon at A, will be visible to us; but theyellowandbluerays will be hidden by the curve of the earth.
Q.Why are the earlymorningcloudsred?A. Becauseredrays (being theleast refrangible) are thefirst to appear.See last figure.—It is evident that PA (the red rays) will be reflected on the horizon before either the yellow or blue ones.
Q.Why are the earlymorningcloudsred?
Q.Why are the earlymorningcloudsred?
A. Becauseredrays (being theleast refrangible) are thefirst to appear.See last figure.—It is evident that PA (the red rays) will be reflected on the horizon before either the yellow or blue ones.
A. Becauseredrays (being theleast refrangible) are thefirst to appear.
See last figure.—It is evident that PA (the red rays) will be reflected on the horizon before either the yellow or blue ones.
Q.What becomes of theblueandyellowrays?A. They are refractedbelow the horizon, and are soon made invisible by thecurve of the earth. (See last figure.)
Q.What becomes of theblueandyellowrays?
Q.What becomes of theblueandyellowrays?
A. They are refractedbelow the horizon, and are soon made invisible by thecurve of the earth. (See last figure.)
A. They are refractedbelow the horizon, and are soon made invisible by thecurve of the earth. (See last figure.)
Q.Why are theedgesofcloudsmoreluminousthan theircentres?A. Because thebody of vapour is thinnestat the edges of the clouds.
Q.Why are theedgesofcloudsmoreluminousthan theircentres?
Q.Why are theedgesofcloudsmoreluminousthan theircentres?
A. Because thebody of vapour is thinnestat the edges of the clouds.
A. Because thebody of vapour is thinnestat the edges of the clouds.
Q.What is the cause of morning and eveningtwilight?A. When the sun is below the horizon, the rays (which strike upon the atmosphere or clouds)are bent down towards the earth, and produce a little light called twilight.See figure on p.399.—Here the rays of PA will givesomelight.
Q.What is the cause of morning and eveningtwilight?
Q.What is the cause of morning and eveningtwilight?
A. When the sun is below the horizon, the rays (which strike upon the atmosphere or clouds)are bent down towards the earth, and produce a little light called twilight.See figure on p.399.—Here the rays of PA will givesomelight.
A. When the sun is below the horizon, the rays (which strike upon the atmosphere or clouds)are bent down towards the earth, and produce a little light called twilight.
See figure on p.399.—Here the rays of PA will givesomelight.
Q.Why is a ray oflightcomposed ofvarious colours?A. If solar light were ofone colour only, all objects would appear ofthat one colour(or else black.)
Q.Why is a ray oflightcomposed ofvarious colours?
Q.Why is a ray oflightcomposed ofvarious colours?
A. If solar light were ofone colour only, all objects would appear ofthat one colour(or else black.)
A. If solar light were ofone colour only, all objects would appear ofthat one colour(or else black.)
Q.Why are some things ofone colour, and some ofanother?A. As every ray of light is composed of all the colours of the rainbow,somethings reflectone of these colours, and someanother.
Q.Why are some things ofone colour, and some ofanother?
Q.Why are some things ofone colour, and some ofanother?
A. As every ray of light is composed of all the colours of the rainbow,somethings reflectone of these colours, and someanother.
A. As every ray of light is composed of all the colours of the rainbow,somethings reflectone of these colours, and someanother.
Q.Why do some things reflectone colour, and someanother?A. Because thesurfaceof things is sodifferently constructed, both physically and chemically; and, therefore,somethings reflectoneray; sometwo rays; someallthe rays; and somenone.
Q.Why do some things reflectone colour, and someanother?
Q.Why do some things reflectone colour, and someanother?
A. Because thesurfaceof things is sodifferently constructed, both physically and chemically; and, therefore,somethings reflectoneray; sometwo rays; someallthe rays; and somenone.
A. Because thesurfaceof things is sodifferently constructed, both physically and chemically; and, therefore,somethings reflectoneray; sometwo rays; someallthe rays; and somenone.
Q.What mainly determines thecolourof any object?A. The fluid or gas eitherinthe body, or on itssurface.N. B. Nitrogen gives green,—Oxygen gives red,—Hydrogen gives blue colours.
Q.What mainly determines thecolourof any object?
Q.What mainly determines thecolourof any object?
A. The fluid or gas eitherinthe body, or on itssurface.N. B. Nitrogen gives green,—Oxygen gives red,—Hydrogen gives blue colours.
A. The fluid or gas eitherinthe body, or on itssurface.
N. B. Nitrogen gives green,—Oxygen gives red,—Hydrogen gives blue colours.
Q.Why doesdyinga silk, &c.changeitscolour?A. Because the materials used in dyeingalter the chemical constructionof the substance dyed.
Q.Why doesdyinga silk, &c.changeitscolour?
Q.Why doesdyinga silk, &c.changeitscolour?
A. Because the materials used in dyeingalter the chemical constructionof the substance dyed.
A. Because the materials used in dyeingalter the chemical constructionof the substance dyed.
Q.Why is arose red?A. Because the surface of a roseabsorbs the blue and yellowrays of light, andreflectsonly theredones.
Q.Why is arose red?
Q.Why is arose red?
A. Because the surface of a roseabsorbs the blue and yellowrays of light, andreflectsonly theredones.
A. Because the surface of a roseabsorbs the blue and yellowrays of light, andreflectsonly theredones.
Q.Why does a rose absorb the yellow and blue rays, and reflect thered?A. Because the action of the sun’s rays on the oxygen (accumulated in thepetals) produces anacidwhich turns themred.The leaves which compose a flower, are calledpetals.
Q.Why does a rose absorb the yellow and blue rays, and reflect thered?
Q.Why does a rose absorb the yellow and blue rays, and reflect thered?
A. Because the action of the sun’s rays on the oxygen (accumulated in thepetals) produces anacidwhich turns themred.The leaves which compose a flower, are calledpetals.
A. Because the action of the sun’s rays on the oxygen (accumulated in thepetals) produces anacidwhich turns themred.
The leaves which compose a flower, are calledpetals.
Q.Why is aviolet blue?A. Because the surface of the violetabsorbs the red and yellowrays of the sun, andreflectstheblueonly.
Q.Why is aviolet blue?
Q.Why is aviolet blue?
A. Because the surface of the violetabsorbs the red and yellowrays of the sun, andreflectstheblueonly.
A. Because the surface of the violetabsorbs the red and yellowrays of the sun, andreflectstheblueonly.
Q.Why do violets absorb the red and yellow rays, and reflect theblue?A. Because the petals of the violet contain analkali, which gives them apurple tinge.
Q.Why do violets absorb the red and yellow rays, and reflect theblue?
Q.Why do violets absorb the red and yellow rays, and reflect theblue?
A. Because the petals of the violet contain analkali, which gives them apurple tinge.
A. Because the petals of the violet contain analkali, which gives them apurple tinge.
Q.Why is aprimrose yellow?A. Because the surface of the primroseabsorbs the blue and redrays of solar light, andreflectstheyellowones.All plants which have much alkali in their ash, have blue or yellow flowers.Those which have acid in their ash, have orange, pink, or red flowers.N. B. Anti-acids (like soda) are calledalkalis.
Q.Why is aprimrose yellow?
Q.Why is aprimrose yellow?
A. Because the surface of the primroseabsorbs the blue and redrays of solar light, andreflectstheyellowones.
A. Because the surface of the primroseabsorbs the blue and redrays of solar light, andreflectstheyellowones.
All plants which have much alkali in their ash, have blue or yellow flowers.Those which have acid in their ash, have orange, pink, or red flowers.N. B. Anti-acids (like soda) are calledalkalis.
All plants which have much alkali in their ash, have blue or yellow flowers.
Those which have acid in their ash, have orange, pink, or red flowers.
N. B. Anti-acids (like soda) are calledalkalis.
Q.Why are some thingsblack?A. Because theyabsorb all the rays of light, and reflectnone.
Q.Why are some thingsblack?
Q.Why are some thingsblack?
A. Because theyabsorb all the rays of light, and reflectnone.
A. Because theyabsorb all the rays of light, and reflectnone.
Q.Why are some thingswhite?A. Because theyabsorb none of the rays of light, but reflect themall.
Q.Why are some thingswhite?
Q.Why are some thingswhite?
A. Because theyabsorb none of the rays of light, but reflect themall.
A. Because theyabsorb none of the rays of light, but reflect themall.
Q.Why arecoals black?A. Because theyabsorb all the rays of the sunwhich impinge upon them, and stifle their reflection.
Q.Why arecoals black?
Q.Why arecoals black?
A. Because theyabsorb all the rays of the sunwhich impinge upon them, and stifle their reflection.
A. Because theyabsorb all the rays of the sunwhich impinge upon them, and stifle their reflection.
Q.Why issnow white?A. Snow consists of a vast number of crystals (or small prisms), which separate the rays into their elemental colours; but as these crystals are very numerous, the coloursunite againbefore they meet the eye, andappear white.N. B. The combination ofallcolours makeswhite.
Q.Why issnow white?
Q.Why issnow white?
A. Snow consists of a vast number of crystals (or small prisms), which separate the rays into their elemental colours; but as these crystals are very numerous, the coloursunite againbefore they meet the eye, andappear white.N. B. The combination ofallcolours makeswhite.
A. Snow consists of a vast number of crystals (or small prisms), which separate the rays into their elemental colours; but as these crystals are very numerous, the coloursunite againbefore they meet the eye, andappear white.
N. B. The combination ofallcolours makeswhite.
Q.Why issugar white?A. Sugar consists of a vast number of small crystals, which separate the rays into their elemental colours; but as these crystals are very numerous, the coloursunite againbefore they meet the eye, and appearwhite.
Q.Why issugar white?
Q.Why issugar white?
A. Sugar consists of a vast number of small crystals, which separate the rays into their elemental colours; but as these crystals are very numerous, the coloursunite againbefore they meet the eye, and appearwhite.
A. Sugar consists of a vast number of small crystals, which separate the rays into their elemental colours; but as these crystals are very numerous, the coloursunite againbefore they meet the eye, and appearwhite.
Q.Why issalt white?A. Salt consists of a vast number of small crystals, which reflect the various rays of light from different points of the salt; and as these coloursunitebefore they meet the eye, the salt appears to bewhite.N. B. The combination ofallcolours makeswhite.
Q.Why issalt white?
Q.Why issalt white?
A. Salt consists of a vast number of small crystals, which reflect the various rays of light from different points of the salt; and as these coloursunitebefore they meet the eye, the salt appears to bewhite.N. B. The combination ofallcolours makeswhite.
A. Salt consists of a vast number of small crystals, which reflect the various rays of light from different points of the salt; and as these coloursunitebefore they meet the eye, the salt appears to bewhite.
N. B. The combination ofallcolours makeswhite.
Q.Why are theleavesof plantsgreen?A. Because thecarbonof the leaves is abluish olive, and thesapandtissue of the cells,yellow; when, therefore, theyellow sapflows into theblue carbon, it produces agreen leaf.
Q.Why are theleavesof plantsgreen?
Q.Why are theleavesof plantsgreen?
A. Because thecarbonof the leaves is abluish olive, and thesapandtissue of the cells,yellow; when, therefore, theyellow sapflows into theblue carbon, it produces agreen leaf.
A. Because thecarbonof the leaves is abluish olive, and thesapandtissue of the cells,yellow; when, therefore, theyellow sapflows into theblue carbon, it produces agreen leaf.
Q.Why are leaves alightgreen inspring?A. Because the young leaves of spring havemore sapthancarbon; and, therefore, theyellowof the green prevails.
Q.Why are leaves alightgreen inspring?
Q.Why are leaves alightgreen inspring?
A. Because the young leaves of spring havemore sapthancarbon; and, therefore, theyellowof the green prevails.
A. Because the young leaves of spring havemore sapthancarbon; and, therefore, theyellowof the green prevails.
Q.Why are leaves ayellowish browninautumn?A. Because thecarbonof the leaves isdying away, and the yellow tinge of thetissueandfalling sapprevails over the blue.
Q.Why are leaves ayellowish browninautumn?
Q.Why are leaves ayellowish browninautumn?
A. Because thecarbonof the leaves isdying away, and the yellow tinge of thetissueandfalling sapprevails over the blue.
A. Because thecarbonof the leaves isdying away, and the yellow tinge of thetissueandfalling sapprevails over the blue.
Q.Why are plants apale yellowwhen kept in thedark?A. Solar light is essential for the production ofcarbon; and as plants kept in the darklose their carbon, they lose theblue colourwhich should convert their yellow sap togreen.
Q.Why are plants apale yellowwhen kept in thedark?
Q.Why are plants apale yellowwhen kept in thedark?
A. Solar light is essential for the production ofcarbon; and as plants kept in the darklose their carbon, they lose theblue colourwhich should convert their yellow sap togreen.
A. Solar light is essential for the production ofcarbon; and as plants kept in the darklose their carbon, they lose theblue colourwhich should convert their yellow sap togreen.
Q.Why arepotatoes yellow?A. Potatoes are grownunderground, and, therefore, contain very littlecarbon(or blue colour); hence theyellow sapof the potato is not converted to green by carbon.
Q.Why arepotatoes yellow?
Q.Why arepotatoes yellow?
A. Potatoes are grownunderground, and, therefore, contain very littlecarbon(or blue colour); hence theyellow sapof the potato is not converted to green by carbon.
A. Potatoes are grownunderground, and, therefore, contain very littlecarbon(or blue colour); hence theyellow sapof the potato is not converted to green by carbon.
Q.Why are potatoes (which growexposedto the air and light)green?A. Because the sun-lightincreases their carbon; which (mingling with the yellow sap) turns the potatogreen.
Q.Why are potatoes (which growexposedto the air and light)green?
Q.Why are potatoes (which growexposedto the air and light)green?
A. Because the sun-lightincreases their carbon; which (mingling with the yellow sap) turns the potatogreen.
A. Because the sun-lightincreases their carbon; which (mingling with the yellow sap) turns the potatogreen.
Q.Why is itdangeroustosleepin a room which containsliving plants?A. Because theyexhale carbon in the darkin the form ofcarbonic acid gas, which is destructive to animal life.
Q.Why is itdangeroustosleepin a room which containsliving plants?
Q.Why is itdangeroustosleepin a room which containsliving plants?
A. Because theyexhale carbon in the darkin the form ofcarbonic acid gas, which is destructive to animal life.
A. Because theyexhale carbon in the darkin the form ofcarbonic acid gas, which is destructive to animal life.
Q.Why aresomethings (like glass)transparent?A. In transparent bodies (like glass) all the rays of lightemerge on the opposite side.
Q.Why aresomethings (like glass)transparent?
Q.Why aresomethings (like glass)transparent?
A. In transparent bodies (like glass) all the rays of lightemerge on the opposite side.
A. In transparent bodies (like glass) all the rays of lightemerge on the opposite side.
Q.Why aresomethingsshiningand splendid?A. Those objects whichreflect the most raysare the mostsplendid; and those whichabsorbthem most, aredull.
Q.Why aresomethingsshiningand splendid?
Q.Why aresomethingsshiningand splendid?
A. Those objects whichreflect the most raysare the mostsplendid; and those whichabsorbthem most, aredull.
A. Those objects whichreflect the most raysare the mostsplendid; and those whichabsorbthem most, aredull.
Q.Why aredesertssodazzlingin summer time?A. Because each separate grain ofsandreflects the rays of the sunlike a mirror.
Q.Why aredesertssodazzlingin summer time?
Q.Why aredesertssodazzlingin summer time?
A. Because each separate grain ofsandreflects the rays of the sunlike a mirror.
A. Because each separate grain ofsandreflects the rays of the sunlike a mirror.
Q.If you move a stick (burnt at one end)roundpretty briskly, it seems to make acircle of fire,—Whyis this?A. Because the eyeretains the imageof any bright object,after the object itself is withdrawn; and as the spark of the stick returnsbefore the image has fadedfrom the eye, therefore, it seems to form acomplete circle.
Q.If you move a stick (burnt at one end)roundpretty briskly, it seems to make acircle of fire,—Whyis this?
Q.If you move a stick (burnt at one end)roundpretty briskly, it seems to make acircle of fire,—Whyis this?
A. Because the eyeretains the imageof any bright object,after the object itself is withdrawn; and as the spark of the stick returnsbefore the image has fadedfrom the eye, therefore, it seems to form acomplete circle.
A. Because the eyeretains the imageof any bright object,after the object itself is withdrawn; and as the spark of the stick returnsbefore the image has fadedfrom the eye, therefore, it seems to form acomplete circle.
Q.If separate figures (as a man and a horse) be drawn on separate sides of a card, and the cardtwistedquickly, the man seems to be seated on the horse,—Whyis this?A. Because the image of the horseremains upon the eyetill themanappears.The Thaumatrope is constructed on this principle.
Q.If separate figures (as a man and a horse) be drawn on separate sides of a card, and the cardtwistedquickly, the man seems to be seated on the horse,—Whyis this?
Q.If separate figures (as a man and a horse) be drawn on separate sides of a card, and the cardtwistedquickly, the man seems to be seated on the horse,—Whyis this?
A. Because the image of the horseremains upon the eyetill themanappears.The Thaumatrope is constructed on this principle.
A. Because the image of the horseremains upon the eyetill themanappears.
The Thaumatrope is constructed on this principle.
Q.Why do thestars twinkle?A. Fixed stars areso far off, that their rays of light do not strike upon the eyein a continuous flow, but atintervals: when their raysreach the eye, the star becomesvisible, and then is obscuredtill the next batch of rays arrive; and thisperpetuallyoccurring, makes a kind oftwinkling.
Q.Why do thestars twinkle?
Q.Why do thestars twinkle?
A. Fixed stars areso far off, that their rays of light do not strike upon the eyein a continuous flow, but atintervals: when their raysreach the eye, the star becomesvisible, and then is obscuredtill the next batch of rays arrive; and thisperpetuallyoccurring, makes a kind oftwinkling.
A. Fixed stars areso far off, that their rays of light do not strike upon the eyein a continuous flow, but atintervals: when their raysreach the eye, the star becomesvisible, and then is obscuredtill the next batch of rays arrive; and thisperpetuallyoccurring, makes a kind oftwinkling.
Q.If we look at ared-hotfirefor a few minutes,whydoes every thing seemtingedwith abluish greencolour?A. Because bluish green is the “accidental colour” of red: and if we fix our eye uponany colour whatsoever, when we turn aside, we see every object tinged withits accidental colour.
Q.If we look at ared-hotfirefor a few minutes,whydoes every thing seemtingedwith abluish greencolour?
Q.If we look at ared-hotfirefor a few minutes,whydoes every thing seemtingedwith abluish greencolour?
A. Because bluish green is the “accidental colour” of red: and if we fix our eye uponany colour whatsoever, when we turn aside, we see every object tinged withits accidental colour.
A. Because bluish green is the “accidental colour” of red: and if we fix our eye uponany colour whatsoever, when we turn aside, we see every object tinged withits accidental colour.
Q.If we wearblue glasses, (when we take them off,) every thing appears tinged withorange,—Whyis this?A. Becauseorangeis the “accidental colour” of blue: and if we look throughblue glasses, we shall see its “accidental colour,” when we lay our glasses aside.
Q.If we wearblue glasses, (when we take them off,) every thing appears tinged withorange,—Whyis this?
Q.If we wearblue glasses, (when we take them off,) every thing appears tinged withorange,—Whyis this?
A. Becauseorangeis the “accidental colour” of blue: and if we look throughblue glasses, we shall see its “accidental colour,” when we lay our glasses aside.
A. Becauseorangeis the “accidental colour” of blue: and if we look throughblue glasses, we shall see its “accidental colour,” when we lay our glasses aside.
Q.If we look at thesunfor a few moments, every thing seems tinged with avioletcolour,—Whyis this?A. Becausevioletis the “accidental colour” ofyellowlight; and as the sun isyellow, we shall see its “accidental colour”blue, when we turn from gazing at it.
Q.If we look at thesunfor a few moments, every thing seems tinged with avioletcolour,—Whyis this?
Q.If we look at thesunfor a few moments, every thing seems tinged with avioletcolour,—Whyis this?
A. Becausevioletis the “accidental colour” ofyellowlight; and as the sun isyellow, we shall see its “accidental colour”blue, when we turn from gazing at it.
A. Becausevioletis the “accidental colour” ofyellowlight; and as the sun isyellow, we shall see its “accidental colour”blue, when we turn from gazing at it.
Q.Does not thedark shadow(which seems to hang over every thing after we turn from looking at the sun) arise from our eyes beingdazzled?A. Partly so: the pupil of the eye isvery much contractedby the brilliant lightof the sun, and does not adjust itself immediately to the feebler light of terrestrial objects; but, independent of this, the “accidental colour” of the sun beingdark violet, would tend to throw a shadow upon all things. (See p.366.)
Q.Does not thedark shadow(which seems to hang over every thing after we turn from looking at the sun) arise from our eyes beingdazzled?
Q.Does not thedark shadow(which seems to hang over every thing after we turn from looking at the sun) arise from our eyes beingdazzled?
A. Partly so: the pupil of the eye isvery much contractedby the brilliant lightof the sun, and does not adjust itself immediately to the feebler light of terrestrial objects; but, independent of this, the “accidental colour” of the sun beingdark violet, would tend to throw a shadow upon all things. (See p.366.)
A. Partly so: the pupil of the eye isvery much contractedby the brilliant lightof the sun, and does not adjust itself immediately to the feebler light of terrestrial objects; but, independent of this, the “accidental colour” of the sun beingdark violet, would tend to throw a shadow upon all things. (See p.366.)
Q.Why isblackglass for spectacles thebestfor wear?A. Becausewhiteis the accidental colour ofblack; and if we wearblack glasses, every thing will appearin white light, when we take them off.
Q.Why isblackglass for spectacles thebestfor wear?
Q.Why isblackglass for spectacles thebestfor wear?
A. Becausewhiteis the accidental colour ofblack; and if we wearblack glasses, every thing will appearin white light, when we take them off.
A. Becausewhiteis the accidental colour ofblack; and if we wearblack glasses, every thing will appearin white light, when we take them off.
Q.Why does every thing seem shadowed with ablack mist, when we take off our commonspectacles?A. Because the glasses arewhite, and black being its “accidental colour,” every thing appears in ablack shade, when we lay our glasses down.The accidental colour of red is bluish green.The accidental colour of orange is blue.The accidental colour of violet is yellow.The accidental colour of of black is white.And the converse of this is true:—The accidental colour of bluish green is red.The accidental colour of of blue is orange.The accidental colour of of yellow is violet.The accidental colour of of white is black.(The law of an accidental colour is this—The accidental colour is always half the spectrum. Thus, if we take half the length of the spectrum by a pair of compasses, and fix one leg in any colour, the other leg will hit upon its accidental colour.)N. B. The spectrum means the seven colours—Red, orange, yellow, green, blue, indigo, and violet, divided into seven equal bands, and placed side by side in the order just mentioned.
Q.Why does every thing seem shadowed with ablack mist, when we take off our commonspectacles?
Q.Why does every thing seem shadowed with ablack mist, when we take off our commonspectacles?
A. Because the glasses arewhite, and black being its “accidental colour,” every thing appears in ablack shade, when we lay our glasses down.The accidental colour of red is bluish green.The accidental colour of orange is blue.The accidental colour of violet is yellow.The accidental colour of of black is white.
A. Because the glasses arewhite, and black being its “accidental colour,” every thing appears in ablack shade, when we lay our glasses down.
The accidental colour of red is bluish green.The accidental colour of orange is blue.The accidental colour of violet is yellow.The accidental colour of of black is white.
And the converse of this is true:—The accidental colour of bluish green is red.The accidental colour of of blue is orange.The accidental colour of of yellow is violet.The accidental colour of of white is black.(The law of an accidental colour is this—The accidental colour is always half the spectrum. Thus, if we take half the length of the spectrum by a pair of compasses, and fix one leg in any colour, the other leg will hit upon its accidental colour.)N. B. The spectrum means the seven colours—Red, orange, yellow, green, blue, indigo, and violet, divided into seven equal bands, and placed side by side in the order just mentioned.
And the converse of this is true:—
The accidental colour of bluish green is red.The accidental colour of of blue is orange.The accidental colour of of yellow is violet.The accidental colour of of white is black.
(The law of an accidental colour is this—The accidental colour is always half the spectrum. Thus, if we take half the length of the spectrum by a pair of compasses, and fix one leg in any colour, the other leg will hit upon its accidental colour.)
N. B. The spectrum means the seven colours—Red, orange, yellow, green, blue, indigo, and violet, divided into seven equal bands, and placed side by side in the order just mentioned.
Q.What issound?A. The vibration of some sonorous substance produces motion in the air calledsound waves, which strike upon thedrum of the ear, and give the sensation of sound.
Q.What issound?
Q.What issound?
A. The vibration of some sonorous substance produces motion in the air calledsound waves, which strike upon thedrum of the ear, and give the sensation of sound.
A. The vibration of some sonorous substance produces motion in the air calledsound waves, which strike upon thedrum of the ear, and give the sensation of sound.
Q.What aremusical sounds?A. Regular and uniform successions of vibrations, which are always pleasing to the ear.
Q.What aremusical sounds?
Q.What aremusical sounds?
A. Regular and uniform successions of vibrations, which are always pleasing to the ear.
A. Regular and uniform successions of vibrations, which are always pleasing to the ear.
Q.Howfastdoessound travel?A. About 13 miles in a minute, or 1142 feet in a second of time.
Q.Howfastdoessound travel?
Q.Howfastdoessound travel?
A. About 13 miles in a minute, or 1142 feet in a second of time.
A. About 13 miles in a minute, or 1142 feet in a second of time.
Q.How fast doeslight travel?A. Light would go 8 times round the whole earth, while sound is going its 13 miles.
Q.How fast doeslight travel?
Q.How fast doeslight travel?
A. Light would go 8 times round the whole earth, while sound is going its 13 miles.
A. Light would go 8 times round the whole earth, while sound is going its 13 miles.
Q.Why aresomethingssonorous, and othersnot?A. The sonorous quality of any substance depends upon itshardness and elasticity.
Q.Why aresomethingssonorous, and othersnot?
Q.Why aresomethingssonorous, and othersnot?
A. The sonorous quality of any substance depends upon itshardness and elasticity.
A. The sonorous quality of any substance depends upon itshardness and elasticity.
Q.Why arecopperandiron sonorous, and notlead?A. Copper and iron arehard and elastic; but as lead is neither hard nor yet elastic, it isnot sonorous.
Q.Why arecopperandiron sonorous, and notlead?
Q.Why arecopperandiron sonorous, and notlead?
A. Copper and iron arehard and elastic; but as lead is neither hard nor yet elastic, it isnot sonorous.
A. Copper and iron arehard and elastic; but as lead is neither hard nor yet elastic, it isnot sonorous.
Q.Of what isbell-metalmade?A. Ofcopper and tinin the following proportions:—In every 5 pounds of bell-metal, there should be 1 lb. of tin, and 4 lbs. of copper.
Q.Of what isbell-metalmade?
Q.Of what isbell-metalmade?
A. Ofcopper and tinin the following proportions:—In every 5 pounds of bell-metal, there should be 1 lb. of tin, and 4 lbs. of copper.
A. Ofcopper and tinin the following proportions:—In every 5 pounds of bell-metal, there should be 1 lb. of tin, and 4 lbs. of copper.
Q.Why is this mixture of tin and copper used forbell-metal?A. Because it is muchharderand moreelasticthan either of the pure metals.
Q.Why is this mixture of tin and copper used forbell-metal?
Q.Why is this mixture of tin and copper used forbell-metal?
A. Because it is muchharderand moreelasticthan either of the pure metals.
A. Because it is muchharderand moreelasticthan either of the pure metals.
Q.Why is thesoundof a bellstoppedbytouchingthe bell with our finger?A. The weight of the fingerstops the vibrationsof the bell; and as soon as the bellceases to vibrate, it ceases to make sound-waves in the air.
Q.Why is thesoundof a bellstoppedbytouchingthe bell with our finger?
Q.Why is thesoundof a bellstoppedbytouchingthe bell with our finger?
A. The weight of the fingerstops the vibrationsof the bell; and as soon as the bellceases to vibrate, it ceases to make sound-waves in the air.
A. The weight of the fingerstops the vibrationsof the bell; and as soon as the bellceases to vibrate, it ceases to make sound-waves in the air.
Q.Why does asplit bellmake ahoarsedisagreeable sound?A. Thesplitof the bell causes adouble vibration; and as the sound-wavesclash and jar, they impede each other’s motion, and produce discordant sounds.
Q.Why does asplit bellmake ahoarsedisagreeable sound?
Q.Why does asplit bellmake ahoarsedisagreeable sound?
A. Thesplitof the bell causes adouble vibration; and as the sound-wavesclash and jar, they impede each other’s motion, and produce discordant sounds.
A. Thesplitof the bell causes adouble vibration; and as the sound-wavesclash and jar, they impede each other’s motion, and produce discordant sounds.
Q.Why does afiddle-stringgive a musical sound?A. The bow drawn across the stringcauses it to vibrate, and this vibration of the stringsets in motion the sound-waves of the air, and produces musical notes.
Q.Why does afiddle-stringgive a musical sound?
Q.Why does afiddle-stringgive a musical sound?
A. The bow drawn across the stringcauses it to vibrate, and this vibration of the stringsets in motion the sound-waves of the air, and produces musical notes.
A. The bow drawn across the stringcauses it to vibrate, and this vibration of the stringsets in motion the sound-waves of the air, and produces musical notes.
Q.Why does adrumsound?A. The parchment head of the drumvibratesfrom the blow of the drum-stick, and sets in motion the sound-waves of the air.
Q.Why does adrumsound?
Q.Why does adrumsound?
A. The parchment head of the drumvibratesfrom the blow of the drum-stick, and sets in motion the sound-waves of the air.
A. The parchment head of the drumvibratesfrom the blow of the drum-stick, and sets in motion the sound-waves of the air.
Q.Why domusical glassesgive sounds?A. Because the glassesvibrateassoon as they are struck, and set in motion the sound-waves of the air.
Q.Why domusical glassesgive sounds?
Q.Why domusical glassesgive sounds?
A. Because the glassesvibrateassoon as they are struck, and set in motion the sound-waves of the air.
A. Because the glassesvibrateassoon as they are struck, and set in motion the sound-waves of the air.
Q.Why doflutes, &c. produce musical sounds?A. The breath of the performer causes theair in the flute to vibrate, and sets in motion the sound-waves of the air.
Q.Why doflutes, &c. produce musical sounds?
Q.Why doflutes, &c. produce musical sounds?
A. The breath of the performer causes theair in the flute to vibrate, and sets in motion the sound-waves of the air.
A. The breath of the performer causes theair in the flute to vibrate, and sets in motion the sound-waves of the air.
Q.Why dopiano-fortesproduce musical sounds?A. Thekeys of the piano(being struck with the finger) lift up a little hammer whichknocks against a string; and the vibration thus produced, sets in motion the sound-waves of the air.
Q.Why dopiano-fortesproduce musical sounds?
Q.Why dopiano-fortesproduce musical sounds?
A. Thekeys of the piano(being struck with the finger) lift up a little hammer whichknocks against a string; and the vibration thus produced, sets in motion the sound-waves of the air.
A. Thekeys of the piano(being struck with the finger) lift up a little hammer whichknocks against a string; and the vibration thus produced, sets in motion the sound-waves of the air.
Q.Why aresomenotesbassand sometreble?A.Slowvibrations producebass or deep sounds; whereas,quickvibrations produceshrill or treble sounds.
Q.Why aresomenotesbassand sometreble?
Q.Why aresomenotesbassand sometreble?
A.Slowvibrations producebass or deep sounds; whereas,quickvibrations produceshrill or treble sounds.
A.Slowvibrations producebass or deep sounds; whereas,quickvibrations produceshrill or treble sounds.
Q.Why is an instrumentflatwhen thestringsareunstrung?A. Because the vibrations aretoo slow; in consequence of which, the sounds produced are notshrillorsharpenough.
Q.Why is an instrumentflatwhen thestringsareunstrung?
Q.Why is an instrumentflatwhen thestringsareunstrung?
A. Because the vibrations aretoo slow; in consequence of which, the sounds produced are notshrillorsharpenough.
A. Because the vibrations aretoo slow; in consequence of which, the sounds produced are notshrillorsharpenough.
Q.Why can persons living a mile or two froma townhearthebellsof the town-churchsome times, and not atothers?A. Fogs, rain, and snow, obstruct the passage of sound; but when the air iscold and clear, sound is propagated more easily.
Q.Why can persons living a mile or two froma townhearthebellsof the town-churchsome times, and not atothers?
Q.Why can persons living a mile or two from
a townhearthebellsof the town-churchsome times, and not atothers?
A. Fogs, rain, and snow, obstruct the passage of sound; but when the air iscold and clear, sound is propagated more easily.
A. Fogs, rain, and snow, obstruct the passage of sound; but when the air iscold and clear, sound is propagated more easily.
Q.Why can wenothear sounds (as distant church bells) inrainyweather, so well as infineweather?A. Because the falling raininterferes with the undulations of the sound-waves, and breaks them up.
Q.Why can wenothear sounds (as distant church bells) inrainyweather, so well as infineweather?
Q.Why can wenothear sounds (as distant church bells) inrainyweather, so well as infineweather?
A. Because the falling raininterferes with the undulations of the sound-waves, and breaks them up.
A. Because the falling raininterferes with the undulations of the sound-waves, and breaks them up.
Q.Why can we not hear sounds (as distant church bells) insnowyweather, so well as infineweather?A. Because the falling snowinterferes with the undulations of the sound-waves, and stops their progress.
Q.Why can we not hear sounds (as distant church bells) insnowyweather, so well as infineweather?
Q.Why can we not hear sounds (as distant church bells) insnowyweather, so well as infineweather?
A. Because the falling snowinterferes with the undulations of the sound-waves, and stops their progress.
A. Because the falling snowinterferes with the undulations of the sound-waves, and stops their progress.
Q.Why can weheardistant clocksmostdistinctly inclear coldweather?A. Because the air is mostuniformthen: there are nottwo currents of air(one up and one down) to interrupt the sound-waves.
Q.Why can weheardistant clocksmostdistinctly inclear coldweather?
Q.Why can weheardistant clocksmostdistinctly inclear coldweather?
A. Because the air is mostuniformthen: there are nottwo currents of air(one up and one down) to interrupt the sound-waves.
A. Because the air is mostuniformthen: there are nottwo currents of air(one up and one down) to interrupt the sound-waves.
Q.Why can persons hear thevoicesof men in conversation for amiledistant, near thepoles, in winter time?A. Because the air is verycold and very clear; in consequence of which, there are nottwo currents of air(one up and one down) to interrupt the sound-waves.Captain Ross heard the voices of his men in conversation, a mile and a half from the spot where they stood.
Q.Why can persons hear thevoicesof men in conversation for amiledistant, near thepoles, in winter time?
Q.Why can persons hear thevoicesof men in conversation for amiledistant, near thepoles, in winter time?
A. Because the air is verycold and very clear; in consequence of which, there are nottwo currents of air(one up and one down) to interrupt the sound-waves.Captain Ross heard the voices of his men in conversation, a mile and a half from the spot where they stood.
A. Because the air is verycold and very clear; in consequence of which, there are nottwo currents of air(one up and one down) to interrupt the sound-waves.
Captain Ross heard the voices of his men in conversation, a mile and a half from the spot where they stood.
Q.Why are notsounds(such as distant church bells) heard so distinctly on ahot dayas infrostyweather?A. Because there aretwo currents of air; the current ofhotairascending from the earth, and the current ofcolderairfalling towardsthe earth; and these two currentsbreak up the sound-waves.
Q.Why are notsounds(such as distant church bells) heard so distinctly on ahot dayas infrostyweather?
Q.Why are notsounds(such as distant church bells) heard so distinctly on ahot dayas infrostyweather?
A. Because there aretwo currents of air; the current ofhotairascending from the earth, and the current ofcolderairfalling towardsthe earth; and these two currentsbreak up the sound-waves.
A. Because there aretwo currents of air; the current ofhotairascending from the earth, and the current ofcolderairfalling towardsthe earth; and these two currentsbreak up the sound-waves.
Q.Why can we not hearsounds(such as distant clocks) so distinctly in a thickmistorhaze, as in aclearnight?A. Because the mistdiminishes the velocityof the sound-waves, and (by overburdening them with vapour)limits their length.
Q.Why can we not hearsounds(such as distant clocks) so distinctly in a thickmistorhaze, as in aclearnight?
Q.Why can we not hearsounds(such as distant clocks) so distinctly in a thickmistorhaze, as in aclearnight?
A. Because the mistdiminishes the velocityof the sound-waves, and (by overburdening them with vapour)limits their length.
A. Because the mistdiminishes the velocityof the sound-waves, and (by overburdening them with vapour)limits their length.
Q.Why do we hearsoundsbetter bynightthan byday?A. 1st—Night air ismore uniform, because the ascending currents of air(raised by the action of the sun’s rays)ceaseas the evening advances; and2ndly—Night is morestillfrom the suspension of business, and the cessation of the hum of men.
Q.Why do we hearsoundsbetter bynightthan byday?
Q.Why do we hearsoundsbetter bynightthan byday?
A. 1st—Night air ismore uniform, because the ascending currents of air(raised by the action of the sun’s rays)ceaseas the evening advances; and2ndly—Night is morestillfrom the suspension of business, and the cessation of the hum of men.
A. 1st—Night air ismore uniform, because the ascending currents of air(raised by the action of the sun’s rays)ceaseas the evening advances; and
2ndly—Night is morestillfrom the suspension of business, and the cessation of the hum of men.
Q.How shouldpartition wallsbe made topreventthe voices in adjoining rooms from beingheard?A. The space between the laths (or canvass) should be filled withshavings or saw-dust; and then no sound would ever pass from one room to another.
Q.How shouldpartition wallsbe made topreventthe voices in adjoining rooms from beingheard?
Q.How shouldpartition wallsbe made topreventthe voices in adjoining rooms from beingheard?
A. The space between the laths (or canvass) should be filled withshavings or saw-dust; and then no sound would ever pass from one room to another.
A. The space between the laths (or canvass) should be filled withshavings or saw-dust; and then no sound would ever pass from one room to another.
Q.Why wouldshavingsor saw-dustpreventthe transmission of sound from room to room?A. Because there would beseveral different mediafor the sound to pass through: 1st—the air;2ndly—the laths and paper;3rdly—the saw-dust or shavings;4thly—the air again: and everyvarietydiminishes thestrength of the sound-waves.
Q.Why wouldshavingsor saw-dustpreventthe transmission of sound from room to room?
Q.Why wouldshavingsor saw-dustpreventthe transmission of sound from room to room?
A. Because there would beseveral different mediafor the sound to pass through: 1st—the air;2ndly—the laths and paper;3rdly—the saw-dust or shavings;4thly—the air again: and everyvarietydiminishes thestrength of the sound-waves.
A. Because there would beseveral different mediafor the sound to pass through: 1st—the air;
2ndly—the laths and paper;
3rdly—the saw-dust or shavings;
4thly—the air again: and everyvarietydiminishes thestrength of the sound-waves.