78 
Proceedings of the Royal Society 
brought over the driving pulley, or removed to some distance 
from it, so as to be able to bring the centre of suspension over the 
centre of gravity of the chain, whatever shape the chain may be 
caused to take. The chain so suspended, when in rapid motion, 
retains for a considerable time whatever form we please to give it. 
It may be moulded into a most complicated series of curves, and 
though it resists any effort made to alter these curves, it has 
itself but little tendency to do so. If we observe the chain closely, 
we will however find that the disturbing forces, which I have 
already referred to, are acting on the chain, tending to change its 
curvature. For instance, if we keep the point of suspension over 
the centre of gravity of the chain, we will find after some time 
that the chain will take up a circular form. This is caused by the 
friction in the chain, and other causes. Again, the effect of the 
varying rate of rotation of the link on its own axis is also well 
marked, but is quite different from what wo get when the chain is 
hung over the driving pulley. When the chain is hung over the 
pulley, there is a tension due to the w r eight of the chain. This 
tension gives rise to the wave form which certain chains take up 
when in motion. The tension due to the centrifugal force has no 
such effect. When, therefore, the chain is suspended and gravita- 
tion removed, there is no tension preventing the chain from con- 
tinuing to curve always in the same direction; and if we use a 
chain specially prepared to show this effect, such as the one 
already referred to, the chain goes on bending further and further 
round till it comes against the part of the chain coming in the 
opposite direction and stops the motion, even though the chain 
at that point is also bending out of the way on account of the 
resistance offered by the links to rotation on their axis. 
