250 



Impact with a Liquid Surface. 



[Feb. 6, 



February 6, 1896. 



Sir JOSEPH LISTER, Bart., President, in the Chair. 



A List of the Presents received was laid on the table, and thanks 

 ordered for them. 



The following Papers were read : — 



I. " Impact with a Liquid Surface, studied by means of 

 Instantaneous Photography." By A. M. WORTHINGTON, 

 M.A., F.R.S., and R. S. Cole, M.A. Received September 

 25, 1895. 



(Abstract.) 



This communication is the first instalment of a review by the aid 

 of instantaneous photography of the ground covered by three previous 

 papers (' Roy. Soc. Proc.,' vol. 25, pp. 261 and 498, 1877, and ibid., 

 vol. 34, p. 217, 1882), in which the phenomena that accompany 

 various kinds of splashes are described. The advance made lies in 

 the unquestionable accuracy and fulness of detail of the information 

 now afforded. 



The photographs which illustrate the paper are 158 in number, and 

 were taken by 'means of a suitably timed Ley den-jar spark, whose 

 duration was less than 3/1,000,000 of a second. In the earlier parts 

 of a splash, when the changes of form are most rapid, the interval 

 between the consecutive stages photographed was made less than 

 2/1000 or even less than 1/1000 second. Each photograph was taken 

 from a separate splash. 



Interesting information is obtained as to the manner in which the 

 concentric outward-spreading ripples originate in the case of impacts 

 of small velocity (low falls), and as to the mode in which, with 

 higher falls, the crater thrown up closes and forms a bubble. 

 Specially remarkable is the difference in the disturbance set up by 

 the impact of a solid sphere, according as its surface is smooth, or, 

 on the other hand, rough or wet. A very smooth sphere becomes 

 sheathed with a thin film of liquid, before it is completely immersed, 

 but makes no immediate visible disturbance of the general flatness of 

 the surface, the level of which rises simultaneously, even at quite 

 distant places; from this flat surface, however, there subsequently 

 emerges a very considerable column, not to be accounted for by the 

 subsidence of any neighbouring wave, and which must be due to the 



