180 MKSSKS. A. M. WORTHINGTON AND R. 8. COLE 



small and inconspicuous bubbles, afterwards when the height is increased, of large 

 and very visible bubbles. 



Thus the transition from " smooth " to " rough " is gradual. But the equilibrium 

 of the splash, if we may use the phrase, is very unstable and very much depends on 

 the condition of the surface of the sphere when dropped in. 



Thus a polished steel sphere 15 '9 millims. in diameter was found to give an airless 

 splash when falling into water from a height of 132 '5 centims. ; at 137 '5 centims. 

 there was much air taken down. This observation at 137 '5 centims. was repeated 

 three times, Observer C doing the polishing. Then Observer W polished, and the 

 splash was first nearly airless, then quite airless. Then, by persevering in the 

 rubbing, the height of fall was gradually raised to 162*5 centims., and a perfectly 

 airless splash was secured ; and even at 172 '5 centims. the record was " very little air 

 indeed." 



Again, a polished marble sphere 2 '57 centims. in diameter falling into water from a 

 height of 112 centims. was found to take " much air" when rubbed with clean 

 handkerchief, A, and " none at all, or only very little," when rubbed with clean 

 handkerchief, B. This result was confirmed four times with B, and five with A. 

 These handkerchiefs were subsequently examined under the microscope, but were 

 found to be extremely similar, and the cause of the difference remained for the time 

 beyond conjecture. 



On another occasion, of two similar nickel-plated steel spheres, each 19 millims. in 

 diameter, and each treated in exactly the same way, falling 22 centims. into paraffin 

 oil, one would always take down much air and the other little or none, and again 

 microscopic examination showed only a very slight difference in the surfaces. 



Influence of the Nature of the Liquid. 



The nature of the liquid employed has a great influence in determining whether at 

 a given height the splash shall be " rough " or " smooth." 



Thus with paraffin oil the maximum height that could be reached with an airless 

 splash with highly polished nickel-plated spheres, well rubbed on a selvyt cloth, was 

 found to be only 24'7 centims., but with water a fall of 160 centims. could be reached. 

 Whenever water was used as the liquid it was contained in a deep glass bowl, kept 

 brim-full and running over by means of an india-rubber supply pipe from the main, so 

 that the surface was kept perfectly clean. The Devonport water is drawn from a 

 granite country, and is very soft and pure. 



We shall revert later to the manner in which the physical constants of the liquid 

 come into play. 



Influence of Temperature. 



We then found that if the polished sphere was heated in boiling water, quickly 

 rubbed dry, and let fall while it was still hot, a very marked difference was produced. 



