60 



Dr. C. Davison on Earthquake- Sounds. 



relatively to the disturbed area, is displaced towards the 

 line of fault. 



Place of Earth-Sounds in an Earthquake-Series. 

 In an admirable memoir, Prof. Omori has shown how the 

 after-shocks of a great earthquake are subject to a gradual 

 but fluctuating decline in frequency and average intensity*. 

 At first sight, it might appear that earth-sounds which, as 

 we have seen, are merely earthquakes too weak to be felt, 

 should be relatively more frequent towards the end of an 

 * "On the After-Shocks of Earthquakes," Journ. Coll. Sci. Imp. 

 Univ. Japan, vol. vii. pt, 2, pp. 111-200. 



