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DR. CHARLES DAVISON ON 



[Feb. 1905, 



fig. 4, in which the synkinetic line intersects the area within which 

 the vibrations from the eastern focus are felt more strongly. It is 

 evident that there is no corresponding modification of fig. 5, for the 



Figs. 3-6, illustrating different cases of relative intensity in 

 twin-eariliquahes. 



Fig. 3. 



Fig. 4- 



Fig. 5- 



Fig. 6. 



boundary of the latter area is always nearer to the eastern than to 

 the western epicentre, while the synkinetic line is always nearer 

 the epicentre of the focus last in action. 



VI. Elements oe the Twin-Foci. 

 Distance between the Twin-Epicentres. 



The exact determination of the positions of the twin-epicentres 

 is a problem of some difficulty, and it is only in one or two cases 

 that it has been approximately solved. Major Dutton, in his 



