J. G. Barnard on the Motion of the Gyroscope. 71 
The discrepaney here exhibited between the motion proper to 
our theoretical solid of revolution and the experimental gyro- 
Scope is due to the division of the latter into two distinct masses, 
one of which rotates, with friction, upon points or surfaces in the 
axis of the disk. But the mounting is perfectly free to turn 
about the vertical axis through the point of support, though not 
about any other. If we decompose, therefore, the rotation which 
Would be impressed upon the mounting into two components, 
ee ation due to gravity, and adds to it; if the axis is below the 
orjzontal, the component is the reverse of the natural gyration, 
and diminishes it, 
But I have shown that the axis soon acquires, independent of 
. 
series of agencies. : ‘ 
The phenomenon may be best illustrated in the following man- 
ner, Let the outer extremity of the common gyroscope, i 
its axis inclined above the horizontal, be supported by a thread 
tached to some fixed point vertically above the point of support, 
at gyration shall be free. Here gravity is eliminated, and 
the axis of our theoretical solid of revolution would remain per- 
fectly motionless; but the gyroscope starts off, of itself, to gy- 
Th Mm the same direction that it would were its extremity free. 
his 
€ point of su ort, (the action of the deflecting force being 
“re reversed, ) Rt tae supporting itself on the ape 
