ON IMPACT WITH A LIQUID SURFACE 199 



Such a conclusion, if established, would have practical importance in inany 

 mechanical processes. It could proljably be tested by a microscopic examination* of 

 specimens of the metal of the plate taken from the immediate neighbourhood of the 

 " splash," and it is interesting io recall in this connection the argument of Professor 

 POYNTINO in his paper on the Change of State : Solid Liquid (' Phil. Mag.,' July, 

 1881), that the rate of exchange of molecules across any surface will increase with 

 the pressure. 



* Since this was written Sir WM. ROBERTS-AUSTEN has most kindly examined for us specimens of the 

 metal token from the " burr " of such an armour-plate splash, and reports that he finds no traces of lique- 

 faction having occurred. It therefore appears that, even in this extremely rapid deformation, we may 

 have to attribute the plasticity and quasi-fluidity of the metal to the same slip along surfaces of cleavage 

 within the crystals of the material, which Professor EWINO and Mr. ROSEN HAiN't have shown to take 

 place when the deformation is much more slowly effected. (Note, October 8, 1899.) 



t ' Roy. Soc. Proc.,' May 25, 1899, vol. 65 ; ' Phil. Trans. K.S.,' Series A, vol. 193, 1899. 



