74 
Proceedings of the Royal Society 
allowed to fall on a platform, so that part of the chain lay loose on 
the platform, thus destroyed the tension produced by the centrifugal 
force at the lower part of the chain. The chain was made to take 
the same velocity as the driving pulley, by being pressed into 
contact with it by means of an elastic wheel. 
I. When the chain was pressed at the point where it leaves the 
pulley there was no alteration in the path of the chain, because 
the chain after it leaves the pulley is moving in a straight line, and 
as there is no deviating force, there is no centrifugal force, and 
therefore, removing the tension in the chain has no effect on the 
direction of the motion of the links. 
II. When the chain was pressed at a point a little higher up 
the pulley, then the centrifugal force of the curved part of the 
chain resting on the pulley at the descending side, being unba- 
lanced by the tension, rises from the pulley, and is shot in a direc- 
tion away to one side of the pulley. Of course the curved part of 
the chain on the other side of the pulley has also a tendency to 
rise, but is kept in its place by the tension produced by putting 
the chain in motion after being stopped by the platform. 
III. When the chain is pressed on the ascending side of the 
pulley, then the chain rises up off the pulley and forms itself into 
a somewhat irregular curve resting on the platform, and touching 
the pulley at only one point. When the velocity is sufficient to 
raise it to a certain height, the conditions become altered. The 
chain in rising takes up all the slack chain lying on the platform, 
and a tension is produced in the chain by the centrifugal force, and 
unless we keep increasing the speed of the chain, it can no longer 
keep in its elevated position, because the centrifugal force is now 
balanced by the tension, and as the force of gravitation is now 
unbalanced, it gradually flattens the curve till the chain again 
comes to rest on the top of the pulley and spreads itself out in an 
irregular curve on the platform. 
IV. At the beginning of the previous experiment the centrifugal 
force being unbalanced by the tension, it overcomes the force of 
gravitation and causes the chain to rise into the air. After all the 
slack chain has been taken up, and a tension is produced in the chain 
by the centrifugal force, then the centrifugal force is balanced by 
the tension and is no longer capable of opposing gravitation, and 
