192 THE SEASON WHY. 



" Children obey your parents in the Lord : for this is right. 



surfaces of its wing's to strike the air, produces the equivalent 

 effect of a wind from the earth blowing the top upwards. 



844. Why does the flying-top return to the earth when its 

 rotations are expended ? 



Because the reaction produced by its wings striking upon the 

 air, is insufficient to counteract the attraction of gravitation. 



Fig. 34 PLYItfG-TOP. Fig* 35. PEA AND PIPE. 



845. Why does a pea, into which a pin has been stuck, 

 dance in suspension upon a jet of air blown through a pipe ? 



Because the jet of air, being slightly compressed under the 

 convex form of the pea, by the weight of the pin, forms a concave 

 cup of air, in which the pea rests. 



In the case put, it is supposed that the pin is passed through the pea until its 

 head comes, in contact with it. The pin is dropped into the hole of the pipe, 

 and the breath is then applied, the pipe being held upright. The pea will rise 

 in the air, and be suspended upon the jet, while the point of the pin will rotate 

 around the stem of the pipe. There are other methods of fixing the pin which 

 alter the result, and require a different explanation to that given above. 



LESSON XL. 



846. Why does a mouse, painted upon one side of a 

 card, and a trap upon the other, represent to the eye a 



