96 Mr. J. Aitken on some Experiments on 



the chain does not swing as a solid body or chain not in 

 motion would do, so as to bring the centre of gravity under 

 the suspending pulley H ; but the descending side keeps the 

 same position it had before E and F were removed, and the 

 CO form alone slowly descends, its shape altering as it falls. 

 The explanation given of experiment III. is also applicable to 

 this case. The peculiar balance of the chain in this experi- 

 ment reminds one slightly of the balance of the gyroscope. 

 3rd. At the moment the pulleys E and F are removed a quasi- 

 elasticity may be observed : the chain falls rapidly for a short 

 distance, then stops and rises a little, and then falls again, 

 making two or three vertical oscillations before it settles into 

 a steady descent. The oscillations are probably caused by the 

 unbalanced tension, due to the weight of the chain, on the 

 pulleys E and F, adjusting itself to the new conditions after 

 the pulleys have been removed. 



D. In making the next experiment, the chain while at rest 

 is passed round the pulley E, in the manner shown in fig. 3, 

 PI. VI., so as to form a circular loop near the top on the 

 ascending side of the chain. The chain is then put in motion 

 by means of the driving-pulley H. After the chain has acquired 

 sufficient velocity the pulley E is removed, which is easily 

 done by gently striking the chain in front, just below the pulley 

 E, and at the same time withdrawing the pulley. The loop 

 E being now free, slowly moves down the chain, slightly in- 

 creasing in size as it descends. Its successive positions are 

 shown by the dotted lines. At first sight it might be thought 

 that the descent of the loop E was entirely caused by its weight. 

 Such, however, is not the case. The downward motion of the 

 circular loop is a true wave motion ; and the velocity of its 

 descent depends on the tension produced by the weight of the 

 lower end of the chain. If we unfold the loop E, as shown 

 at 0, we see at once that it is a wave motion, similar to that 

 shown in fig. 2, PL VI. This wave motion may still further 

 be illustrated by making the circular loop on the descend- 

 ing side of the chain, when the loop will ascend the chain. 

 The upward motion on the descending side is not, however, so 

 successful, as the circular loop gets rapidly reduced in size, 

 and only travels a few feet before it is destroyed. This experi- 

 ment may be varied in another way. We may put a movable 

 pulley into the lower end of the loop at D, so as to enable us to 

 increase the tension in the chain, when we shall find that by 

 increasing the tension we can cause the circular loop to move 

 faster, in accordance with the laws of wave motion. 



E. The last experiment with this chain to which we need 

 refer is made in the following manner. The chain is put in 



