CHARLES B. WARRING. 139 
It is no wonder that, when conical bearings (shown in 
Fig. 2) were used, the pressure upon them forced the 
ring back so far that the disc was very Fig.2 
apt to fly out of its place—in fact, with I 
conical bearings, very little acute (say 
60°), and with very high speed, this 
always occurred. ‘The bearings at first 
were all of this shape. I found it necessary to change 
them, and to make them cylinders. After that the disc 
never flew out. 
In this we have answer to the first question. The re- 
sistance comes from the inertia of the successive mole- 
cules passing from zero velocity at bot om and top of the 
disc to maximum velocity as they come to the horizontal 
plane passing through the horizontal axis. 
As to the second question : Why does the disc come to 
rest more quickly when the ring is in rapid motion ? 
It is simply a case of increased friction, produced thus: 
Fasten your mind on a molecule at m’. It is moving to 
the right. Its other motion (that in the vertical plane) 
being at right angles, neither hastens nor retards it, 
consequently m’ endeavors, all the time it is going to the 
top (m”), to tilt that quadrant toward the right, a ten- 
tency which results in a pressure or push upon the pin 
A. The same thing occurs in the opposite quadrant. In 
the other two quadrants, as the parts pass from zero ve- 
locity to the maximum, there is a downward pull on A 
and an upward one on B, so that really all four quad- 
rants act in the same sense, and pressure always increases 
friction. The effect of such increase is seen when I 
tighten slightly the pins A and B. The time of rotation 
falls from six minutes to much less than one, and this 
when the horizontal motion is not going on. 
Lastly : What becomes of the additional energy ex- 
pended to make the ring revolve, when the disc is also 
revolving % 
so 
