III. 



ROLLING AND FLYING MOVEMENT. 

 I. The Intelligent Billiard Balls. 



ARRANGE three billiard balls (A, B, C, Fig. 

 10) in a row along the cushion at the side of 

 a billiard table in close contact with one another. 

 Place another, D, at a distance of about six 

 inches from the end of the row, but in a similar 

 position beside the cushion. 



Now push the ball D lightly and smoothly 

 along the cushion in the direction of the other 

 balls, till it reaches a position near to them, 

 as at E, by which time it will have acquired a 

 certain speed. Let it run the rest of the dis- 

 tance along the cushion by itself and strike 

 the ball C a smart stroke full on the nearest 

 side. When all movement is over, the final 

 position of the balls will be as shown at a, b, c y 

 and d. D will have come to rest approximately 

 in the position in which it was at the moment 

 of striking the other balls, as at d. B and C 

 will remain apparently just as they were, 

 without the smallest movement, as at b and c. 

 A, however, will suddenly run away in the 

 direction of D's previous movement to a. It 

 will appear to start instantly at the moment 



36 



