136 A CURIOUS GYROSCOPIC PHENOMENON. 
freely in the ring, and the ring revolves very freely on 
the two pins. Hence, if the disc be set in rapid motion 
on its axle, and the ring be made to revolve on the pins, 
we have the gyroscope continuously passing from one 
plane to another, and we should expect continuous re- 
sistance. i | 
On the lower pin isa sort of clutch-wheel, or pulley, 
which, ty help of a lever (not shown in the diagram), 
can be dropped or raised almost instantly, and so breaks, 
or makes, connection with the large driving wheel. 
First Experiment—I give the disc a high speed in the 
usual way—by help of a strong string wound on its axle 
—and time it. I find that friction brings it to rest in, 
say, five minutes. 
Second Experiment—I now let the disc alone. It has 
ceased to revolve on its horizontal axis. I raise the 
clutch-wheel as shown in the diagram, and turn the large 
wheel, and so make the gyroscope revolve very rapidly 
on the vertical axis. Then I let the clutch drop so as to 
be out of connection with the ring. The apparatus goes 
on from its momentum fora very considerable time. The 
motion is smooth and quiet, until the friction and air 
bring it to rest. The rotation around the vertical axis 
did not set the disc to revolve on the horizontal. Ap- 
parently it had no effect whateverin that sense. This is 
what we should expect from the well-known law that 
forces at right angles to each other neither increase nor 
diminish the effect of either. 
Third Experiment—I now raise the clutch, as in the 
diagram, and set the disc in very rapid motion on its own 
axis, and at the same moment attempt to turn the driv- 
ing wheel, but experience great resistance. While the 
resistance is still strong—say in fifteen or twenty seconds 
—I release the clutch-wheel, and almost instantly the 
horizontal rotation ceases. The disc, however, is still re- 
volving with no apparent decrease of speed. In the pre- 
se 
