124 AN EMPIRICAL STUDY OF GYRATING BODIES. 



prevented in some way of which we, as yet, have had no 

 inkling. For the only counteracting influences thus far 

 considered are friction and the resistance of the air. 

 These we have seen eliminated, and yet all the phe- 

 nomena were the same as before — except a little change 

 in rate, that is all. It would seem that there ought soon 

 to result a very considerable horizontal velocity. 



But it is found on trial that the horizontal motion is 

 very moderate, and, so long as the rotation is sensibly 

 uniform, there is apparently no acceleration. 



This is a very curious and important fact, that the 

 horizontal movement ought to be an accelerated one, and 

 yet it is not. 



Why not ? What becomes of the energy that ought to 

 be expended in sending the gyroscope with ever-in- 

 creasing rapidity around the supporting point \ How is 

 it expended % 



I answer : Accelerating the horizontal movement tends 

 to make the gyroscope rise ; it acts against, and, to that 

 extent, neutralizes gravity, and gravity, being thus 

 counteracted, there is less and less fall to produce the 

 acceleration ; and therefore that, too, grows less, till it 

 practically ceases, i. e., becomes exceedingly small if not 

 absolutely nothing. 



That accelerating the horizontal movement makes the 

 gyroscope rise, is proved by an experiment already 

 shown. I refer to that in which a string attached to the 

 free end of a gyroscope is pulled in various directions. 

 You all saw that when the string was pulled so as to 

 make the horizontal motion more rapid, the free end of 

 the instrument rose towards a vertical. This proof of 

 the law is absolute ; but we are now seeking to find the 

 reasons for all these things. Fig. 16 will help us in our 

 search. 



The observer is supposed to stand squarely facing the 

 wheel, and the weight on the arm (both arm and weight 



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