Because the surfaces of the feathers fall upon the air _obliquely_, or slantingly, and therefore, as the shuttlecock descends, it turns in the air. [Verse: "Come ye children, hearken unto me, I will teach you the fear of the Lord."--PSALM XXXV.] [Illustration: Fig. 32.--BATTLEDORE AND SHUTTLECOCK.] 837. _Why do we hear a noise when we strike the shuttlecock with the battledore?_ Because the _percussion_ of the shuttlecock upon the parchment of the battledore causes it to vibrate, and the vibrations are imparted to the air. 838. _Why is the sound a dull and short one?_ Because the vibrations of the parchment are _not very rapid_, therefore there is _little intensity_ in the vibrations of the air. 839. _Why does the exercise, afforded by playing battledore and shuttlecock, make us feel warm?_ Because it makes us breathe _more freely_, and causes the _blood to flow faster_; we, therefore, inhale more _oxygen_, which produces heat by combining with the _carbon_ of our _blood_. 840. _Why does a kite rise in the air?_ A kite rises in the air by the force of the wind, which _strikes obliquely_ upon its _under surface_. The string is attached to the "belly-band" in such a manner that it is nearer the _top_ than the _bottom_ of the band: this causes the bottom of the kite, when its surface is met by the wind, to recede in the direction of the wind: the top is accordingly _thrown forward_, and the kite is made to _lie obliquely_ upon the current of air moving against it. The kite then being _drawn by the string in one direction_, and _pressed by the air in another direction_, moves in a line which _describes a medium between the two forces acting upon it_. [Verse: "Be ye therefore followers of God, as dear children; and walk in love, as Christ also hath loved us."--EPHESIANS V.] [Illustration: Fig. 33.--DIAGRAM EXPLAINING THE FLIGHT OF A KITE.] 841. _Why does the kite-string feel hot when running through the hand?_ Because the _rapid friction_ sets free the _latent heat_ of the _string_, attracts the heat of the _hand_ to the spot where the friction occurs, and sets free the latent heat of the _air_, which follows the _string_ through the hand, and is compressed by the friction. 842. _Why does running with the kite cause it to rise higher?_ Because it _increases the force_ with which the wind strikes upon the surface of the kite. If a person were to _run with a kite at the rate of five miles an hour, through a still air_, the effect would be _equal to a wind flying at the rate of five miles an hour_ against a kite held by a _stationary string_. 843. _Why does the flying-top rise in the air?_ Because its wings _meet the air obliquely_, just as the surface of the kite does. And the _twirling of the top_, causing the oblique surfaces of its wings to strike the air, produces _the equivalent effect of a wind from the earth blowing the top upwards_. [Verse: "Children obey your parents in the Lord: for this is right."]