C. 13. WARRING. 131 



is no gyration when the instrument is supported at both 

 ends, or when balanced. 



A reversal of all the motions occurs when the arm of 

 the gyroscope, fig. 2, is made to overbalance the wheel. 

 It is the same as if gravity pulled up instead of down ; 

 consequently the gyration is in the opposite direction. 



The tendency of the gyroscope to go in a direction 

 perpendicular to the force applied — as has been formu- 

 lated in the four laws — accounts for the squirming feel- 

 ing produced when one takes the instrument in his hands 

 and tries to twist it, or turn it, in various directions. 

 The rationale is easily seen. 



ANOTHER NEW PARADOX. 



I refer to the experiment in which I showed my 

 balanced gyroscope (fig. 2) rapidly moving around the 

 supporting-point, under the influence of a weight at- 

 tached by a thread to the free end ; and then I cut the 

 thread by bringing a blaze against it. The gyration in- 

 stantly ceased, as if the machine had run against an ob- 

 stacle. The momentum of such an instrument weigh- 

 ing, as mine does, several pounds, moving with very 

 considerable rapidity, is quite an amount, yet it disap- 

 peared in an instant. There was a tremor, a circling up 

 and down, and then rest, but no advance. 



I asked what had become of the momentum. Now 

 we can see. 



When the weight was flashed off it left the instru- 

 ment balanced. Neither side being the heavier, there 

 was, therefore, no fall of the gyroscope, hence no im- 

 pelling pjower. The instrument would have remained 

 perfectly stationary but for the momentum previously 

 gained. That acts in the same sense as the string (fig. 

 16) which we used for accelerating the horizontal move- 

 ment ; i. e., it makes the gyroscope go faster than the 

 velocity due, at that instant, to the fall (in this case zero, 



115 



