ON SEISMOLOGICAL INVESTIGATIONS. 



247 



The increase in the work may also be indicated by tbe number of epicentres dealt 

 with. Monthly counts of these were given in the last report, but the totals for the 

 year were omitted by oversight. For the seven years 1918-1924 they are 372, 323, 

 324, 258, 310, 542, 473. [The total 542 for 1923 is unduly exaggerated by the number 

 of aftershocks following the great Japanese earthquakes of 1923, September 1-2.] 

 The total for 1925 is 481. The monthly totals are :— 



The seven years 1918-24 showed a decided and rather sudden maximum in 

 September, even when the exceptional year 1923 was excluded. There is no trace 

 of this maximum in 1925. 



Deep Focus. 



It was mentioned in the last report that a paper showing the cases (a dozen or 

 more) in which indications of deep focus had been reached independently at Oxford, 

 and by Mr. Wadati in Japan, had been sent to him for pubhcation in the Tokio 

 Geophysical Magazine, in which his own paper (showing an independent method of 

 detecting deep foci) appeared. Nothing, however, has been received or heard in 

 reply up to the present, and inquiry is being made as to the fate of the paper. 



The cases of abnormal focal depth determined at Oxford are of course not confined 

 to the neighbourhood of Japan like those of Mr. Wadati. They have been given in 

 detail in the Summary, and are indicated briefly in the Catalogue of Earthquakes 



