C. B. WARRING. L25 



are invisible) to be so placed that it just balances the 

 wheel. However rapidly the wheel is made to revolve. 

 there will be no gyration. But now I pull the string 

 horizontally to the right. The right hand side, a, moves 

 (a little) from the observer, and the other side, d, to- 

 wards him. (The same movements that are shown in 

 fig. 15 by the arrows x and y, on! y there they happen to 

 be reversed). But the wheel is revolving on its axis ; 

 when, therefore, a comes to the top, its motion from the 

 observer (which has not in any way been reduced) tends 

 to push the upper edge in that direction, or, in other 

 words, tends to tilt the instrument upwards. What is 

 true of a is also true of d, only it goes down instead of up. 



If c is pulled downward, b will tilt towards the ob- 

 server, and when the wheel has gone 90° of a revolution, 

 it will still tend to move towards him, and consequently 

 tend to send the instruments to the right, i. e., in the 

 direction of the lower arrow. 



In the same way we can determine the result when c 

 is pulled upwards ; or when it is pulled to the left. 1 



Now I move the weight towards the gyroscope so that 

 the end towards the observer is the heavier, and again 

 set the wheel, to revolving in the same direction as before. 

 At once, C begins to go to the right. Then pull the 

 string in the same direction as before. 



The results are embodied in these four laws : 



1. Accelerating the gyration causes an upward tend- 

 ency, greater, equal to, or less than the effect of gravity 

 according to the extent of acceleration. 



2. Decreasing the gyration causes more rapid fall. 



3. Pulling the free end upward causes a retardation, 

 or even a reversal, of the gyration. 



4. Pulling the free end downward quickens the 

 gyration. 



1 Clearness of conception will be greatly promoted by going through these movements 

 with a tee-square. It is easier for the mind and eye to follow it than to follow the gyroscope. 



109 



