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Proceedings of the Royal Society of Edinburgh. [Sess. 
support. Under these circumstances the equilibrium position is that in 
which the axis of the flywheel is parallel to that about which the earth is 
spinning ; that is, the equilibrium position of the flywheel is that in which 
its axis points true north and south. In the experiment described above 
the armature of the motor-gyrostat represents the flywheel, and the vertical 
axis about which the ring is carried represents the axis of the earth. 
In fig. 7 the motor-gyrostat is shown fitted up as a gyrostatic pen- 
dulum. A support made of telescope tubing is attached to the apex of 
Fig. 8. — Motor-Gyrostat fitted up as “ Gray” stilt top. 
a triangular stand also made of telescope tubing, by means of a universal 
joint. The gyrostat is attached to the lower end of its supporting tube by 
means of a special cap provided with spring contact pieces to allow of the 
current being led into the the motor ; the leading-in wires are carried down 
the inside tube. Screwed to the lower side of the gyrostat is a pen 
attachment. 
By varying the speed of the motor and the initial inclination of the 
supporting tube to the vertical a large variety of designs may be obtained. 
Fig. 8 shows the motor-gyrostat fitted up to show an experiment due to 
