On Sounds of Splashes. 773 



3. The 21*2 volts radiation ionizes abnormal helium pro- 



duced by 20'4 volts electron impacts, and with a 

 relatively high gas pressure the detected effects of 

 ionization may swamp those of radiation. This result 

 provides an explanation of the ionization of helium by 

 electrons having less than the normal ionizing velocity, 

 which is essentially different from that offered by 

 Compton. 



4. Both types of radiation can be absorbed and sub- 



sequently re-emitted by normal helium atoms, so that 

 they are passed from atom to atom throughout a 

 volume of the gas. 



5. For velocities below the normal ionizing velocity , the 



amount of ionization produced as the result of 

 electron impacts on abnormal helium atoms, under 

 the experimental conditions used, is small in com- 

 parison with that resulting from the ionizing action 

 of the 21' 2 volts radiation. 



The possibility of the presence of a small quantity of 

 impurity in the helium facilitating the production of radia- 

 tion at 20*4 volts has been investigated, but no evidence that 

 the impurity acts in this way has been obtained. 



It is con3luded that the significance of the experimental 

 results in connexion with theories of the arrangement of the 

 two electrons in the normal helium atom lies in the fact that 

 they indicate that the limitations of the selection principle 

 are not applicable to the fundamental displacements of the 

 outer electron of the helium atom. 



LXXXIII. On Sounds of Splashes. 

 By A. L. Narayan, M.A.* 



[Plate XXIII.] 



IN a previous paper Prof. C. V. Raman and Ashutosh Dey 

 investigated by a photographic method the " smooth " or 

 sheath splash and the " rough " or basket splash, in so far as 

 the splash depends on the condition of the surface of the 

 impinging sphere. 



In this connexion it may be noted that a smooth splash is 



* Communicated by the Author. 



