93 



supports the whole system, apparently annulling the force of 

 ^gravitation. But not in reality, for were the force of gravita- 

 tion suspended there would be no rotation around the vertical 

 axis, even could the wheel retain its inertia. 



Let us examine a little farther. Suppose the support is 

 between me and the ring, the axis of the wheel pointing from 

 me, and the rotation of the wheel right handed, — if the farther 

 end of the axis be depressed, or dropped, the particles of the 

 wheel in the quadrant above the ring and to the left hand of 

 the axis, will be displaced more than the particles in the right 

 baud upper quadrant, if the axis drop in a vertical plane ; but 

 the system bei^ig free to • move around the vertical axis will 

 move a little to the left so that the displacements of all the 

 particles shall be equal — this then commences the revolution 

 jvbout the vertical axis. If I could now fall on my right side, 

 still looking at the instrument, it w^ould appear to be falling 

 from me — and this falling would tend to give it a motion to 

 the left of its apparent position, — which would amount to the 

 apparatus rising in a direction contrary to that in which it fell 

 an instant since : and now, henceforth the outer end of the 

 axis continues to rise and fall in a series of rap'id and short 

 undulations which last until its motion is destroyed. The outer 

 end of the axis describes a succession of cycloidal curves. That 

 this is the correct explanation may be proved by accelerating the 

 motions around the vertical axis, when the ring will immedi- 

 ately rise ; if, on the contrary, we retard the revolution of the 

 ring it will fall and these different motions may be repeated 

 at pleasure. 



If the ring have a counterpoise which is heavier than the 

 ring and wheel, the motion about the vertical axle will be in 

 the contrary direction. If the ring be sustained in gimbals, 

 as is usual with the mariner's compass, so that the axis of the 

 wheel can take any given direction while the wheel is rotating, 

 its axis will tend to remain parallel to itself. 



Many other highly interesting experiments may be made 

 with this apparatus, which each can perform at his pleasure. 



Note by the Author. A more full discussion of the principles of the Gyra- 

 scope, may be found in the July nvimber of the Amer. Jour. Sci. by Maj. J. G. 

 Barnard. Salem, Aug. 6. 



