499 



Table I. Comparison of N.A.O. calculations with fjrmul;i<: due II Herring and Bryant. 



It will Be seen that the comparison is quite satisfactory except tnat the figures for the rise 

 of the bubble are not correct, the approximate formula for the rise of the bubble giving too high a result. 

 Subject to this correction, it seems that the use of the approximate formulae In this region is quite 

 satisfactory, as a basis of comparison with experiment. The approximate formula tor the rise was 

 arrived at empirically, and the fact that it is incorrect in no way affects the validity of the remaining 

 ipproximt-.tions, which can n^w be used with confidence. 



4, Compari son of theory with 'Experiment . 



The following quantities suggest themselves for this purpose:- 



».l 



The radius of the bubble as a function 



of ti me: Careful comparisons have been made by Herring, 

 lutenant Campbell. Agreement is good except in the 



(using photographs 0' tained by Edgerton), and by 

 region near the minimum radius where there is reason to believe that the simple incompressible theory 

 breal<s down, due to radiation of acoustic energy and possibly to other causes also. The maximum radius 

 and periotf between explosion and first minimum have also been compared with expcrimriht by wright, Campbell 

 and senior, who find exceTTent agreement. The minimum value of the radius is hard to obtain from the 

 photographs, owing to the fact that motion is very fast in that neighbourhood, and also owing to the 

 obscuring effect of debris in the water. The further history of the bubble, after the first minimum 

 can also be accounted for satisfactorily, provided that it is assumed that there is a loss of energy 

 at each mi nimum. 



