176 MESSES. A. M. AVORTHINGTON AND R. S. COLE 



The first series of these photographs (see Sheet 1, from which a selection is repro- 

 duced on Plate 2) is, for the sake of clearness, called Series X., so as to keep the 

 numbering continuous with the previous paper. The photographs show what is going 

 on below the surface of the liquid while the phenomena of Series VIII. of the previous 

 paper are visible above the surface.* The sphere was a rough marble, freshly sand- 

 papered on each occasion. 



The photographs 1 and [2] show the sphere gradually entering the surface ; above 

 it is the inverted image of the part that has entered, formed by internal reflection on 

 the liquid surface. Higher up still (in fig. 1) and not quite in the same vertical line 

 (on account of a slight optical displacement due to the front of the vessel not having 

 been set quite perpendicular to the line of sight) is seen the top of the sphere. This, 

 however, is out of focus, for the camera was focussed on the part under water, which 

 is optically brought forward. 



In figs. [3, 4] and 5 it will be observed that the liquid already leaves the sphere along 

 a tangent, and from this point onward the sphere is followed by a bag or pocket of air 

 of gradually increasing depth. The wall of this pocket is not quite smooth, and the 

 summit of the sphere, as seen through it, is always somewhat distorted. The sharp 

 angle made with this wall by the oppositely sloping wall of the image tells in each 

 figure the position of the surface, and in several figures we see the lobed lip of the 

 crater that has been already photographed from above in Series VIII. The present 

 photographs show the exact height of this. It will be observed that the depth of 

 the crater or pocket below the surface is far greater than the photographs of Series 

 VIII. gave any reason to suspect, also that the upper part of the sphere is not wetted 

 at all. t 



We can find no trace of any reflecting layer of air between the lower part of the 

 sphere and the water, and have no reason to doubt that the lower part is thoroughly 

 wetted up to the place at which the liquid is seen to leave it. As the sphere 

 descends the position of the circular line of contact rises on the sphere and the liquid 

 does not always leave it along a tangent. The ripple-marks conspicuously visible in 

 fig. 9, and in many of the later figures, are indications of the flow of the liquid along the 

 walls of the cylinder of air. The long cylindrical hollow that is thus formed is not 

 a configuration of stable equilibrium, and, if we may leave momentum out of account, 

 its law of spontaneous segmentation will be the same as for a liquid column of the 



* This series of photographs, with the exception of the last two, was taken in June, 1896, and was 

 exhibited at the soiree of the Royal Society in June, 1897. 



t The present photographs, taken in conjunction with those of Series VIII. of Paper I., bring out a 

 point which had escaped us. For it is now evident that the hollow below the surface in such figures as 8, 

 9, and 10 of Seiies VIII. is far too deep and capacious to be filled by the small amount of liquid raised 

 above the general level at the edge of the water, and can, therefore, only be accounted for by a rise of the 

 general leixl, r extending to a very considerable distance from the splash. We showed that this phenomenon 

 accompanied the entry of a smooth sphere ; we now see it to be even more marked with a rough one. 



