414 
Proceedings of the Royal Society of Edinburgh. [Sess. 
two gyrostats are spun rapidly and the arrangement placed as shown on a 
table. The large gyrostat spins on the table as an ordinary top, and, in 
consequence of friction at the pivots of the flywheel, the frame and the 
small gyrostat are carried round with it. For one of the two directions 
in which the small gyrostat may be spun it will rise up and assume the 
position shown in the figure. 
In figure 7 is shown a compound top made up of one large gyrostat and 
two small ones. A wire frame in which are carried, in sleeved joints as 
Fig. 7. — Acrobatic Top. 
shown, the two small gyrostats, is mounted in two sockets carried by the 
frame of the large gyrostat. The whole arrangement is suspended from a 
stand by means of a string terminating in a hook as shown. Now, suppose 
the large gyrostat to be spinning rapidly, and the small gyrostats to be 
spinning in opposite directions. If the arrangement is hung up so that its 
centre of gravity is vertically under the hook the small gyrostats will both 
remain in the lower positions. If, however, the hook is placed to one side 
as shown, the large gyrostat will precess round so that its axis turns in a 
plane which is nearly horizontal, carrying with it the small gyrostats. One 
