1894.] Prof. A. M. Worthington on the Splash of a Drop, &c. 289 



WEEKLY EVENING MEETING, 



Friday, May 18, 1894. 



Sir Frederick Bramwell, Bart. D.C.L. LL.D. F.R.S. Honorary 

 Secretary and Vice-President, in the Chair. 



Professor A. M. Worthington, M.A. F.R.S. 



The Splash of a Drop and Allied Phenomena, 



The splash of a drop is a transaction which is accomplished in the 

 twinkling of an eye, and it may seem to some that a man who pro- 

 poses to discourse on the matter for an hour must have lost all sense 

 of proportion. If that opinion exists, I hope this evening to be able 

 to remove it and to convince you that we have to deal with an 

 exquisitely regulated phenomenon, and one which very happily 

 illustrates some of the fundamental properties of fluids. It may be 

 mentioned also that the recent researches of Lenard in Germany and 

 J. J. Thomson at Cambridge, on the curious development of electrical 

 charges that accompanies certain kinds of splashes, have invested 

 with a new interest any examination of the mechanics of the 

 phenomenon. It is to the mechanical and not to the electrical side 

 of the question that I shall call your attention this evening. 



The first well directed and deliberate observations on the subject 

 that I am aquainted with were made by a schoolboy at Rugby some 

 twenty years ago, and were reported by him to the Rugby Natural 

 History Society. He had observed that the marks of accidental splashes 

 of ink-drops that had fallen on some smoked glasses with which he 

 was experimenting, presented an appearance not easy to account for. 

 Drops of the same size falling from the same height had made always 

 the same kind of mark, which when carefully examined with a lens 

 showed that the smoke had been swept away in a system of minute 

 concentric rings and fine striae. Specimens of such patterns, obtained 

 by letting drops of mercury, alcohol and water fall on to smoked 

 glass, are thrown on the screen, and the main characteristics are easily 

 recognised. Such a pattern corresponds to the footprints of the dance 

 that has been performed on the surfaee, and though the drop may be 

 lying unbroken on the plate, it has evidently been taking violent 

 exercise, and were our vision acute enough we might observe that it 

 was still palpitating after its exertions. 



A careful examination of a large number of such footprints showed 

 that any opinion that could be formed therefrom of the nature of 

 the motion of the drop must be largely conjectural, and it occurred 

 to me about eighteen years ago to endeavour by means of the illumi- 



Vol. XIV, (No. 88.) x 



