1388 A CURIOUS GYROSCOPIC PHENOMENON. 
In the one-eightieth part of a second it will be carried 
up 90° to m’,* to the horizontal plane passing through the 
axle of the disc. Its horizontal velocity at m’ will be— 
suppose its radial distance to be two and a half inches— 
about twenty-five feet a second. This speed is not, at 
first sight, anything remarkable, but it has been attained 
in one- eightieth of a second. Gravity—7. e., a body’s 
weight—would impart a speed of only two-fifths of a 
foot in the same time. Hence the acceleration here is 
Fig.l 
iit 
omtmiad - *) 
A 
sixty-two and a half times that of gravity, according to 
the well-known law, that the accelerating force is pro- 
portional to the velocity imparted in equal times. 
The effect increases as the product of the number of 
revolutions in the two planes. 
Could we make them sixty and sixty, instead of twenty 
and twenty, the results would be nine times as great. 
It is fortunate that the time this acceleration acts, is so 
short that the actual velocity attained in our disc is only 
twenty-five feet in a second, for if it had been permitted 
to act for a whole second, its speed would be two thou- 
sand feet, or nearly twice that of a cannon ball—suffi- 
cient to destroy the instrument. 
* Unfortunately, the ‘and " on the middle and the upper m, Fig. 1, 
are too indistinct. The reader will please mark them with a pen. 
8s 
