1911-12.] On Novel Illustrations of Gyrostatic Action. 415 
of these assumes the upright position as shown. If now the hook is trans- 
ferred to the left-hand side of the frame the precessional motion is reversed ; 
the small gyrostat, which previously assumed the upright position, now 
takes up a position in which its centre of gravity is vertically below its 
supporting joints, while the second small gyrostat assumes the upright 
position. 
Experiments carried out with ordinary gyrostats are far from satisfactory 
if the old-fashioned method of spinning them by means of a string is 
adopted. By means of the following method angular velocities of about 
12,000 revolutions per minute can be obtained. A leather disc is fitted on 
the spindle of an electric motor, and against this is pressed lightly the 
spindle of the gyrostat. After a little practice the operation of spinning 
becomes easy of accomplishment, and the experiments are rendered really 
beautiful. 
The author desires to thank Professor Gray for the practical interest he 
has taken in the gyrostatic experiments here described. 
(Issued separately October 31 , 1912 .) 
