THE AUTOMATON TUMBLERS. 



plane, descends in the same way as the puppets. The laws of equilibrium 

 and displacement of the centre of gravity, are rigorously observed by 

 jugglers, who achieve many wonderful feats, generally facilitated by the 



Fig. 24. First position of the puppets. 



rotatory motion given to the bodies on which they operate, which brings 

 into play the centrifugal force. The juggler who balances on his forehead 

 a slender rod, on the end of which a plate turns round, would never succeed 

 in the experiment if the plate did not turn on its axis with great rapidity. 

 But by quick rotation the centre of gravity is kept near the point of 



Fig. 35. Second position of the puppets. 



support. We need hardly remark, too, that it is the motion of a top that 

 tends to keep it in a vertical position. 



Many experiments in mechanical physics may occur to one's mind. 

 To conclude the enumeration of those we have collected on the subject, I 

 will describe the method of lifting a glass bottle full of water by means of 

 a simple wisp of straw. The straw is bent before being passed into the 

 bottle of water, so that, when it is lifted, the centre of gravity is displaced, 



