206 THE SPLASH OF A DROP AND ALLIED PHENOMENA. 



If we keep to tlie same size of drop and increase the fall to some- 

 thing over a yard no great change occnrs in the natnre of the splash 

 but the emergent column is rather higher and tliinner and shows a ten- 

 dency to split into drops. 



When, however, we double the volume of the drop and raise the 

 height of fall to 52 inches, the splash of Series IV is obtained (Plate VI), 

 which is beginning to assume quite a different character. The raised 

 rim of the previous series is now developed into a hollow shell of con- 

 siderable height, which tends to close over the drop. This shell or 

 dome is a characteristic feature of all splashes made by large drops 

 falling from a considerable height, and is extremely beautiful. In the 

 splash atpresentunder consideration itdoesnotalways succeed in closing 

 l)ermanently, but opens out as it subsides, and is followed by the emer- 

 gence of the drop (tig. 8). In fig. 9 the return wave overwhelms the drop 

 for an instant, but it ia again seen at the summit of the column in fig. 10. 



But on other occasions the shell or dome of figs. 4 and 5 closes per- 

 manently over the imprisoned air, the liquid then flowing down the sides, 

 which become thinner and thinner, till at length we are left with a large 

 bubble floating on the water (see Series V, Plate VI I). It will be 

 observed that the flow of liquid down the sides is chiefly along definite 

 channels, which are probably determined by the arras thrown up at 

 an earlier stage. The bubble is generally creased by the weight of 

 the liquid along these channels. It must be remembered that the base 

 of the bubble is in a state of oscillation, and that the whole is liable to 

 burst at any moment, when such figures as (J and 7 of the previous series 

 will be seen. 



Such is the history of the building of the bubbles which big rain- 

 drops leave on the smooth water of a lake, or pond, or i)uddle. It is 

 only the bigger drops that can do it, and reference to the number at 

 the side of fig. 5 of Series IV (Plate VI) shows that the dome is raised 

 in about two-hundredths of a second. Should tlie domes fail to close, or 

 should they open again, we have the emergent columns which any 

 attentive observer will readily recognize, and which have never been 

 better described than by Mr. II. L. Stevenson, Avho, in his delightful 

 Inland Voyage, speaks of the surface of the Belgian canals along which 

 he was canoeing, as thrown up by the rain into "an infinity of little 

 crystal fountains." 



Very beautiful forms of the same type indeed, but different in detail, 

 are those produced by a drop of water falling into the lighter and 

 more mobile licjuid, petroleum. 



It will now be interesting to turn to the splash that is produced 

 when a solid sphere, such as a child's marble, falls into water. 



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

 rate up to a height of fall of 4 or 5 feet, depends entirely on the state 

 of the surface of the sphere. A polished sphere of marble about O.G of 

 au iucli ift liii^uieter, rubbed very dry with a cloth just beforeUau4 ap4 



