Mr Vincent, Experiments on Impact. 357 



(5) The volume of the dent is proportional to the energy of 

 motion of the sphere just before impact. This was found also to 

 apply even when the material of which the impinging sphere 

 was changed. 



For steady loads the square of the diameter of the dent is 

 proportional to the load. The pressure (P) between the surfaces 

 in contact is constant, and in the case of lead is about one-half 

 of p. 



(6) The time of impact is directly proportional to the diameter 

 of the impinging ball if other things are constant. 



Conclusion, 



The result (5) is in accord with Martel's 1 work on the inden- 

 tation produced by a pyramidal steel tool driven into a metal 

 block by a falling weight. He showed that the volume of the 

 indentation was nearly proportional to the work of the falling 

 weight. The volume was also nearly the same for tools of some- 

 what different form. 



Unwin 1 suggests that P and p would be found to differ. 



In conclusion I wish to thank Prof. J. J. Thomson for many 

 valuable suggestions. 



1 From Unwin, Testing of Materials of Construction. He gives the reference to 

 Martel's work as Commission des Methodes d'Essai des Materiaux de Construction, 

 Tome ii. p. 261. 



VOL. X. PT. VI. 26 



