Mr Vincent, Experiments on Impact. 



335 



a linear function of the velocity of approach. The removal of the 

 cloth raises the values of e, and the effect of puncturing the ball 

 after the cloth is removed is to lower e very little 1 . 



Fig. 3 gives the results of some experiments on a lawn tennis 

 ball of this season's make ; the two sets of readings were taken 

 on successive days. The difference is a temperature effect, pro- 

 bably on the material of the envelope and not on the contained 

 gas, as it is greater than one would expect puncturing to cause. 



Vel. of Approach in cms. a sec. 

 Fig. 3. Two sets of observations. 



The curves A on Fig. 4 were obtained from the same ball, 

 care being now taken to handle it as little as possible, and to 

 leave an interval of a couple of minutes between each experiment. 



Vel. of Approach hi cms. a sec. 

 Fig. 4. 



1 The gas escaping from the ball on puncturing smelt strongly of ammonia. 



