226 



Mr. A. M. Worthington. 



the sides, which thus became thinner and thinner till at last a large 

 bubble remained floating on the top of the water. Series IY shows 

 the formation of such a bubble. 



It will be observed that the flow of liquid down the sides is chiefly 

 along definite channels, which are probably determined by the arms 

 thrown out at an earlier stage. The bubble is generally creased by 

 the weight of the liquid in these channels. 



It must be remembered that the base of the bubble is in a state of 

 oscillation, and that it is liable to burst at any moment, when such 

 figures as (6) and (7) of Series III, &c, will occur. These figures are 

 in complete accord with the explanation lately given by M. J. Plateau* 

 of the phenomena presented by a bursting bubble. 



Such bubbles as those described are often seen when large rain- 

 drops fall into smooth water. No vortex ring is produced, and the 

 disturbance caused by such a drop is confined to a very small depth, 

 the liquid flowing off laterally in all directions down the compara- 

 tively gentle slope of the sides of the shell. 



Series Y shows the splash of a drop of milk *496 centim. in 

 diameter falling into olive oil from a height of 60 centims. The last 

 four figures are interesting, since they prove the lateral as well as 

 downward flow of the oil, which as it flows away from the vortex 

 drags with it the adherent milk, and, as it were, turns the drop inside 

 out till it recovers itself by irregular jerks under the influence of a 

 surface tension, which at length asserts itself. This jerky recovery 

 may be perceived by attentive observation in continuous light without 

 the aid of any apparatus. 



Impact of Solid Spheres. 



It has been already mentioned incidentally that an increase of 

 viscosity in the impinging drop, produced by the addition of glycerine, 

 has its effect on the character of the splash, and it now remains to 

 describe the splash produced by the impact of a solid sphere. 



To my great surprise I found that the character of the splash, at 

 any rate up to a height of fall of 150 centims., depends entirely on 

 the state of the surface of the sphere. 



A polished sphere of marble, l'28f centims. in diameter, rubbed 

 very dry with a cloth just beforehand, and dropped from a height of 

 62 centims. into water, gave the figures of Series YI, in which it is 

 seen that the water spreads over the sphere so rapidly that it is 

 sheathed with the liquid even before it is below the general level of 



* " Q.uelques Experiences sur les Lames Liquides Minces." "Bulletins de 

 l'Academie Royale de Belgique," 3me serie, tome II, No. 7, 1881. 



f This or^a similar sphere 1*55 centims. in diameter could be used indifferently. 



