THE SEASON WHY. 199 



' A wise son makes a glad father : but a foolish son is the heaviness of his 

 mother." PBOVEEBS x. 



it strikes; reflected motion, when it is turned by a body upon 

 which it impinges ; friction, as it rolls along the ground ; the 

 communication of force, when it sets another body in motion against 

 which it strikes ; gravitation, when it falls to the earth ; and inertia, 

 when it lies in a state of rest. 



868. Why do pith-tumblers always pitch upon one end? 



Because the lead B is specifically heavier than 

 the pith to which it is attached ; it therefore 

 always falls undermost ; and as the lead is rounded 

 off, just like the spill of a top, after the head has 

 oscillated a little, and expended the force of the 

 momentum of its fall, it will settle upon its centre 

 of gravity t or the point through which it is 

 attracted to the earth. 



869. Why do the figures upon the " Thau- 

 matrope" appear to dance, wlien they are 

 made to revolve before a mirror ? 



Because the eye, in looking through the holes in 

 Pig. 47. the card, towards the reflections in the mirror, 



PITH-TUMBLER. rece j v es a rapid succession of impressions. 

 As the figures upon the card are represented in a graduated 

 series of positions the first one standing upright, the second with 

 his knees a little bent, the third a little more bent, as in the act of 

 springing, and so on, the figure being in each case the same, but 

 the position slightly altered, imparts an impression to the mind, 

 through the eye, that one figure is passing through a series of 

 motions. 



Thaumatrope.T?roTOi two Greek words, meaning wonder and to turn. 



"We have said enough, we hope, to show that even the play -hours of children 

 may be made instructive to them ; and that the simplest toys may be used to 

 illustrate some of the grandest laws of nature* Nor may this kind of instruction 

 be confined to children alone. Grown-up people, whether participators in the 

 sports of youth, or simple observers of their games, may gain instruction for 

 themselves, and be the better teachers of their children, by taking an interest 

 in their enjoyments, and giving to their minds, through the attractiveness of 

 pastime, a taste for observing and estimating the varied phenomena which 

 present themselves. 



Moreover, we think that parental government acquires a greater power when 



