130 AN" EMPIRICAL STUDY OF GYRATING BODIES. 



of fig. 17, representing the composition of the two forces, 

 B P and P A, at the instant of reversal of the section or 

 tee. Their resultant passes through P. 



Perhaps, however, the ability of two opposite equal 

 forces. acting on the ends of the arms of a tee-square to 

 transfer the weight to the end of the axis, will be more 

 clearly seen by the non-mathematician by the help of fig. 

 18. A and B are two projecting pins made, we will sup- 

 pose, by means of friction rollers, or otherwise, so that 

 the arms of the tee can move against them without sen- 

 sible friction. 



Place the tee-square as in the diagram. Nothing 

 keeps it from falling except the pressure of the two pins. 

 The spring-balance will show the weight of the whole 

 tee-square just as if it hung suspended on it alone. 



Fig. 17 explains also why one feels so much resist- 

 ance when pressing down the free end of the gyroscope. 

 By the curious transfer of force, he really presses against 

 a fixed point. This, of course, is on condition that there 

 is freedom to move laterally. For I showed by experi- 

 ment that if the horizontal or lateral motion is pre- 

 vented, or if it is stopped after commencing, the gyro- 

 cope will no longer sustain itself. Why ? 



The staying up depends upon the right and left 

 motion of the end of the tee (fig. 6) being in full opera- 

 tion at the instant of complete reversal. This is im- 

 possible unless they continue to move while they are 

 passing through the horizontal position; and it is the 

 right and left moving of the arms while horizontal that 

 makes the horizontal revolution. Consequently, if this 

 is stopped, the right and left movement stops, and no 

 force remains when the reversal is completed to counter- 

 act gravity. 



It goes without saying, that if there is no downward 

 movement there will be no gyration. Also that there 



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