774 Mr. A. L. Narayan on 



a silent one taking down no air, while a rough or basket 

 splash is noisy, taking down much air and throwing up a 

 tall and very conspicuous jet, as can be very easily seen from 

 the many beautiful instantaneous photographs taken by the 

 late Professor Wortliington and given in his interesting book 

 'A Study of Splashes/ pp. 97 and 103. 



The transition from a smooth splash to the rough splash 

 depends on : — 



1. Condition of the surface of the falling sphere. 



2. Velocity of entry of the falling sphere. 



3. Nature of the liquid. 



4. Temperature of falling sphere. 



The present investigation is undertaken with a view to 

 study photographically the transition from the " airless " 

 to the " airy " splash in so far as it depends on the second 

 condition, viz,, velocity of entry of the falling sphere, i. e., the 

 height from which the sphere is dropped. 



The method by which the photographic records of the 

 splashes are obtained in this communication is almost exactly 

 the same as was adopted by the authors of the previous 

 paper (Phil. Mag. No. 229, Jan. 1920, pp. 146-147). 



For the benefit of the readers, a brief description of the 

 apparatus is given here. It consists of an ordinary gramo- 

 phone horn at the end of which a thin mica disk is fixed. 

 From the centre of this disk, a thin steel blade projects 

 normally from the disk, and this projecting blade presses 

 on a fine steel needle supported horizontally on two props. At 

 one end of this steel needle a minute fragment of a galvano- 

 meter mirror is cemented. Thus when sound waves enter the 

 horn, the thin mica disk and along with it the projecting steel 

 spring vibrates, and thus the steel needle rolls on the supports 

 and the mirror fragment rotates about a horizontal axis. 

 It is interesting to note in this connexion that as experience 

 showed there is a greater freedom of movement for the steel 

 needle, the supporting blocks in this case are two small steel 

 knife-edges, which are at the same time slightly curved 

 so as to ensure that the needle always remains parallel to 

 itself. 



The sphere used in this investigation is mostly a highly- 

 polished nickel-plated steel sphere, about -J inch in diameter, 

 as used for ball-bearings. In some experiments a polished 

 brass sphere also is used. In all these cases, the height 

 of fall is gradually increased each time, rubbing the 

 sphere well on a clean handkerchief and then polishing it by 



