92 Mr. J. Aitken on some Experiments on 



break. In order, therefore, to cause the chain to take up the 

 same velocity as the pulley, it was pressed against it by means of 

 the elastic pulley G, fig. 3, PL IV., with the following results. 



A. Fig. 1, PI. V., shows the effect when the chain is pressed 

 by G at o, on the descending side, at the point where it leaves 

 the pulley. There is 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 motion of the links. 



B. Fig. 2, PI. V., shows the effect when the chain is pressed 

 at the point p, a little higher up the pulley on the descending 

 side. In this case, the centrifugal force of the curved part of 

 the chain resting on op on the descending side of the pulley 

 being unbalanced by the tension, the chain rises from the pulley 

 and is shot away from it, as shown — the direction of its 

 motion where it leaves the pulley being a tangent to the pulley 

 at the point p, where it is pressed by the elastic pulley Gr. Of 

 course the curved part of the chain p q, resting on the ascend- 

 ing side of the pulley A, also tends to rise, but is kept in its 

 place by the tension produced by putting the chain in motion 

 after being stopped by the platform. 



C. Fig. 3, PI. V., shows the effect of pressing the chain at 

 q on the ascending side of the pulley. The centrifugal force 

 of the curved part of the chain resting on op q being un- 

 balanced by the tension, the chain rises up off the pulley in an 

 irregular curve, and only touches the pulley at the point q. 

 When the velocity is sufficient to cause the chain to rise up 

 to such a height that all the slack chain resting on the plat- 

 form R is taken up, then the conditions become altered. 

 When all the slack chain is taken up, then the centrifugal force 

 produces a tension in the lower part of the chain, and, unless 

 we can keep increasing the velocity of the chain, it can no 

 longer keep its elevated position, because the centrifugal force 

 is now balanced by the tension ; and as the gravitation is now 

 unbalanced, it gradually flattens the curve, till the chain again 

 comes to bear on the top of the pulley, and spreads itself out 

 on the platform. 



D. Fig. 4, PI. V. At the beginning of the previous experi- 

 ment, as there was no tension in the chain to balance the 

 centrifugal force of the part of the chain resting on the pulley, 

 the centrifugal force overcame the force of gravitation and 

 caused the chain to rise into the air. After all the slack chain 

 resting on the platform had been taken up, and a tension was 

 produced in the chain by the centrifugal force, the centrifugal 

 force of the upper part of the chain was balanced by the tension. 



