[ 175 1 



IV. Impact ivith a Liquid Surface studied by the aid of Instantaneous Photography. 



Paper II. 



By A. M. WORTHINOTON, M.A., F.R.S., and R S. COLE, M.A. 



Received March 21, Read May 4, 1899. 



[PLATES 2-3.*] 



IN a previous paper ('Philosophical Transactions,' A, 1897, vol. 189, p. 137) we have 

 drawn attention to the fact that the disturbance set up in a liquid by the impact of a 

 rough sphere falling into it, differs in a very remarkable manner from that which 

 follows the entry of a smooth sphere. In the present paper we describe further 

 experiments, made with the object of ascertaining the reason of this difference, and 

 give the conclusions reached. 



It appeared desirable, in the first place, to take instantaneous photographs of the 

 disturbed liquid below the water-line. These were easily obtained by letting the 

 splash take place in an approximately parallel-sided thin glass vessel (an inverted 

 clock-shade) illuminated from behind. The liquid surface when undisturbed was 

 about level with the middle of the camera-lens, which was focussed for the sphere 

 when under water. The general arrangement of the optical apparatus will be suffi- 

 ciently understood from the accompanying cut (fig. 1). The method of timing the 

 illumination was that already described (loc. cit.). 



Fig. 1. 



A, camera lens. 



BC, vessel with liquid. 



D, plate of finely roughened glaw. 



E, condenser taken from an optical lantern. 



F, spark-gap at centre of curvature of concave mirror. 

 M, concave silvered watch-glass. 



G, copper gauze to break the fall of the sphere. 



' The photographic illustrations accompanying the manuscript of this paper are silver prinU mounted 

 on ten sheets, which are referred to as " sheets " in the text. Certain figures from these sheets have been 

 selected for collotype reproduction, and are given on Plates 2 and 3. Others are given in the text. 

 When a figure is referred to which is not reproduced either by photography or by a cut in the text, the 

 No. of the figure is enclosed in [ ]. 



VOL. CXCIV. A 255 . 



