248 



REPORTS ON THE STATE OP SCIENCE, ETC. 



1918-1924, which the British Association kindly printed in connection with the last 

 report. 



The following cases of abnormal focal depth recently added to those may be noted 



i 



I 



The cases of abnormaUy deep focus noticed in the years 1918-0-1926^25 are distri- 

 buted as follows. The unit of depth is 0^010 radius of 40 miles. Occasionally the 

 depth is estimated to ^005 ; these cases have been assigned half to each of the neigh- 

 bouring groups : — 



Distribution of focal depths. (D) 

 (Unit of D is 0-010 radius.) 



D= 1 



6 



8 



9 



At one time it seemed possible that there were certain critical depths near which 

 the foci were hkely to occur ; but ■with the accumulation of more cases this hypothesis 

 is not supported. The figures (which are the observations) suggest rather a regular 

 faUing-ofI according to some exponential of the focal depth. The three lines below 

 it are calculated from the formulae 



log Ci=222-0^23D. 

 logC.2=r60-0-018 D-^. 

 log C3 =-r41 -0^0020 D-\ 



