Rigidity produced by Centrifugal Force. 105 



over the centre of gravity of the chain, then the form of the 

 chain changes and approaches that of a circle, and the chain 

 may again be made to take its original oblong form by moving 

 the point of suspension to its original position. The circular 

 form which the chain takes up when the centre of suspension 

 is kept over the centre of gravity is due to friction, length of 

 links, and other causes. 



The effect of the varying rate of rotation of the links on their 

 own axis is also well marked, especially if we give the chain a 

 quick curve at any point. The effect, however, is very dif- 

 ferent from what we get when the chain is hung over the 

 driving-pulley. When the chain is hung over the driving- 

 pulley, there is a tension in the chain due to gravitation ; this 

 tension, coupled with the rotation of the links, gives rise to 

 the wave-form which we saw certain forms of chain took up 

 when in motion, fig. 3, PL VII. The tension due to centrifugal 

 force has no such effect. When, therefore, in this experiment 

 the chain is suspended and the tension due to gravitation re- 

 moved, there is but little tension preventing the chain from 

 continuing to curve further in the same direction. The chain 

 therefore goes on bending further and further round until it 

 comes into collision with the part of the chain moving in the 

 opposite direction, and stops the motion, even though the 

 chain at this point is bending out of the way on account of 

 the resistance offered by the links at this part to rotation on 

 their axis. This effect is best shown by using a chain speci- 

 ally prepared for showing the effect of the varying rate of ro- 

 tation of the links, such as the one used in experiment IX. 



While these experiments illustrate the laws of motion, they 

 also in a somewhat rough way illustrate certain early specu- 

 lations on the structure of matter which have recently been 

 revived and founded on a scientific basis. In these experi- 

 ments, as in the well-known vortex-ring, motion confers cer- 

 tain properties which we are in the habit of associating with 

 the solid condition of matter. This, however, is a subject 

 alike beyond my province and my powers ; I must therefore 

 take leave of it, and conclude by expressing a hope that the 

 experiments may be useful to those engaged in the higher and 

 more difficult investigation of the subject. 



Darroch, Falkirk. 



