204 THE SPLASH OF A DROP AND ALLIED PHENOMENA. 



five times, and the figures seen were like those of Series X.J Of course 

 all tliat can be shown in this way is the outline, or rather a horizontal 

 section of the splash 5 but you are able to recognize some of the con- 

 figurations already described, and will be the more willing to believe 

 that a momentary view is after all sufticieut to give much information 

 if one is on the alert and has acquired skill by practice. 



The general features of the splash that we have examined are not 

 merely characteristic of the liquid mercury, but belong to all splashes 

 of a liquid falling onto a surface which it does not wet, provided the 

 height of fall or size of the drop are not so great as to cause complete 

 disruption,' in which case there is no recovery and rebound. Thus a 

 droj) of milk falling onto a smoked glass will, if the height of fall and 

 size of drop are properly adjusted, give forms very similar to those 

 presented by a drop of mercury. The whole course of the phenomenon 

 depends, in fact, mainly on four quantities only: (1) The size of the 

 drop; (2) the height of fall; (3) the value of the surface tension; (4) 

 the viscosity of the li(|uid. 



The next series of drawings illustrates the splash of a drop of water 

 falling into water. 



In order the better to distinguish the liquid of the original drop 

 from that into which it falls, the latter was colored with ink or with an 

 aniline dye, and the drop itself was of water rendered turbid with 

 finely divided matter in suspension. Finally, drops of milk were found 

 to be very suitable for the puri>ose, the substitution of milk for water 

 not producing any observable change in the phenomenon. 



In Series II the drop fell 3 inches, and was one-fifth of an inch in 

 diameter. (Plate IV.) 



[In most of the figures of this and of succeeding series the central 

 white patch rei)resents the original droj), and the white parts round it 

 represent those raised i)ortions of the liquid which catch the light. 

 The numbers at the side of each figure give the time interval in sec- 

 onds from the occurrence of the first figure, or of the figure marked 

 T = 0.] 



It will be observed that the drop flattens itself out somewhat, and 

 descends at the bottom of a hollow with a raised beaded edge (fig. 2). 

 This edge would be smooth and circular but for the instability which 

 causes it to topple into drops. As the droj) descends the hollow 

 becomes wider and deeper, and finally closes over the drop (fig. 3), 

 which, however, soon again emerges as the hollow flattens out, appear- 

 ing first near, but still below the surface (fig. 4), in a flattened, lobed 

 form, afterward rising as a column somewhat mixed with adherent 

 water, in which traces of the lobes are at first very visible. 



1 Readers "who wisli a more detailed account of a greater variety of splashes are 

 referred to papers by the author, Proc. Roy. Soc, Vol. XXV, pages 261 aud 498 (1877) ; 

 and Vol. XXXIV, page 217 (1882). 



