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THE POPULAR SCIENCE MONTHLY. 



you saw, gyration is absolutely essential to the effect which Mr. 

 Boys thinks accounts for its stability. 



We may, I think, dismiss the top from further consideration ; 

 but there is another instrument apparently much closer in its re- 

 lation to the bicycle. I mean the gyroscope, or rather that form 

 of it which Sir William Thomson calls a gyrostat. Its wheel is 

 upright like the bicycle's (see Figs. 3 and 4). The lower part of 



Figs. 3 and 4. The Gyrostat. 



the ring which supports the wheel rests in a kind of trough, to the 

 bottom of which is attached crosswise a piece of metal (best seen 

 in Fig. 3) curved on the lower edge, and with two projecting wires 

 by which it may be drawn back and forth in the plane of the wheel. 

 I now set the wheel in rapid motion much more rapid than 

 any bicycle-wheel can go ; I place it on a smooth, hard surface I 

 have here a pane of glass and leave it to itself. It begins at once, 

 as you see, to revolve around a vertical axis. If it leans little, it re- 

 volves slowly ; if it leans much, it revolves faster. It will not fall 

 to the table, though I push it, or strike a hard blow. It resists 

 with remarkable force. I now take it by the projecting wires 

 and attempt to make it move in a straight course, as a bicycle 

 does when it spins along the road. Instantly it falls. The rota- 

 tion of the wheel on its axis was not in the slightest degree inter- 

 fered with, but the stability vanishes the moment the rotation 

 around the vertical axis ceases. Invariably it falls. Yet you ob- 

 serve the conditions are far more favorable for the effect of gyro- 

 static action than in the bicycle, for the mass of the rim of our 

 gyrostat is many times heavier in proportion to its size, and its 

 speed incomparably greater. I try the experiment over and over, 

 the result is always the same. No amount of skillful manage- 

 ment will make the instrument stay up for an instant if it has to 

 move in a straight line. I submit that these experiments are 

 proof positive that the sustaining power of the bicycle does not 

 come from any gyroscopic action. 



