WORKING WONDERS WITH A TOP 



French physicist Foucault. But the practical ap- 

 plications of the principle, with which we are here 

 chiefly concerned, are triumphs of the science of our 

 own day. 



HOW THE GYROSCOPE WORKS 



What, then, is the gyroscopic principle" that can 

 work such wonders? Fundamentally, its basis is this 

 simple fact: A spinning top or heavy body of any kind 

 so placed that it can rotate on an axis tends always 

 in virtue of the momentum due to its rotation, to 

 maintain its axis in a fixed position. The rotating 

 body may be moved in a direct line in any direction 

 whatever quite as freely as if it were not rotating, 

 provided no attempt is made to change the direction 

 of its axis. But against any change in the direction 

 of the axis it manifests a resistance of which a non- 

 rotating body gives no evidence. 



The principle may be simply illustrated by spin- 

 ning a bicycle wheel on a hub held in the hand. It will 

 at once be evident that it may be moved upward or 

 downward or latterly or diagonally, quite as well in 

 motion as at rest, provided the axis of the hub is kept 

 always parallel with its original position. But the 

 moment an attempt is made to shift this axis, as by 

 bending the wrist, the resistance of the wheel will 

 be felt. The same principle may be exemplified in 

 an even more familiar way by rolling an ordinary 

 hoop, which owes its stability solely to its gyroscopic 

 action, and which, as every boy knows, resists an 

 attempt to overturn it in a very curious fashion. 



To demonstrate just what is the peculiar feature 



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