56 Mr. A. M. Worthington on Calculating Surface-Tensions 



z=K-Jc 



observe that the value of the integral I - — is calculated 



on the assumption that the fraction r is small ; and, again, the 



1 -^ dz 



value of j is calculated on the assumption that -7- is small, 



even when x is large, i. e. that the drop is very flat, even far 

 from the vertex. Now the drop or bubble used by Prof. 

 Quincke was often far from satisfying these conditions. In 



some cases the diameter was so small that the fraction -p 



amounted to as much as |, and the curvature at the vertex 



was so considerable that the value of ? cannot be satisfactorily 



calculated in the way described. Thus in the first measure 

 of an air-bubble in water (Quincke, loc. cit. § 3, table III.) 



^ = •319 ; while in the case of drops of petroleum in water it 



is as much as *3768. 



I have therefore selected for correction only those measures 



for which the value of T was smallest, though the mean value 



lj 1 



of the observed quantity K— - h used in calculating— was 



generally taken from the whole of the measures given by Prof. 

 Quincke. 



Air-bubbles in Hyposulphite of Soda. 



D= 1-1248. 



No. 



L. 



K-k. 



1 



3282 1/ 



1 



V 



Grams 



per cm. 



S. tension 

 (Quincke). 



S. tension, 

 corrected. 



3. 

 4. 



141 



•3738 

 •3662 



I -2161 



•0492 \ 



•07856 

 •07541 



1 -06853 







Mean (of 4 measures 



i) 



•07903 



Quincke) 



By ca 



pillary tubes ( 



•07636 



(The mean of K— h used to calculate j- was -37485.) 



