ON SEISMOLOniCAL INVESTIGATIONS. 



73 



above considered are out at sea. It will be interesting to note whetbor 

 there is a difference between sea and land epicentres in the matter of Y ; 

 but this examination has not 3ret l)een made. 



In this connection such earthquakes as that of July i, 1914, may- 

 be significant. It is noted in the Shide Bulletin that 



a shock at 17 h. 46 m. 30 s. was followed some 100 seconds later by 

 another at another epicentre (12° away) ; but the curious thing is 

 that the nearer stations (Manila, Batavia, &c.) have recorded the 

 second quake and not the first. 



B 



The suggestion now offered is that the first focus was on or even 

 above the surface ; that the path of waves from it has a limiting (mini- 

 mum) depth, and therefore a limiting (minimum) radius for affected 

 stations, while the second focus was below the surface and was not 

 restricted. If such limits do exist, their application to the possible 

 formation of Y is tolerably obvious. 



XI. Coneclinv of Tables deferred. 



Provisionfil corrections to the tables for P and S were given at the 

 end of the last Report and are repeated above (p. 67). But the tables 

 printed on the last page of the Shide Bulletins will be used for the present, 

 until a fuller discussion has been made. Meanwhile, the above pro- 

 visional corrections are made use of in determining epicentres, and they 



