166 AN EMPIRICAL STUDY OF GYRATING BODIES. 



against the finger accelerates the gyration and by onr 

 first law, causes the weight to rise ; while the reaction on 

 the other side retards the gyration, and, therefore, 

 causes the weight to fall. 



All through it is the same story as was told about the 

 gyroscope. In fact, the Bohnenbergher is really a gy- 

 roscope, whose point of support is at the centre of 

 gravity. It presents no difficulties not easily solved by 

 one who has mastered that instrument. 



The "four laws" apply to both, and are as easily 

 verified for the one as for the other. 



THE EARTH AS A GYROSCOPIC BODY. 



Whatever be the value of the explanation which I 

 have offered of the curious imenomena which we have 

 been studying ; whether it will or will not bear the test 

 of analysis, it at least has great advantages as a working 

 hypothesis. It seems to account for all the paradoxical 

 behavior of gyroscopic bodies ; and it certainly enables 

 us to predict what they will do in new and untried con- 

 ditions. 



But, should this explanation prove to be incorrect or 

 insufficient, and be brushed aside as worthless, yet there 

 will still remain a body of curious results resting upon 

 no theory, but upon the solid ground of experience. 

 Among these is the following law : 



If a body revolving upon an axis passing through its 

 centre of gravity, be acted upon by a force tending to 

 make it revolve around another axis perpendicular to the 

 first, it will, if perfectly free, take two movements or 

 rotations ; one in the direction of the applied force, and 

 the other at right angles to it. There will be no 

 change in what may be called the geographical position 

 of the first axis, and the body will continue to revolve 

 about it with its angular velocity unaffected. 



150 



