308 Br. C. Davison — The Stafford Earthquakes of 1916. 



duration for the above districts are respectively 47, 64, 77, 73, and 

 77 ; showing that as the distance increases from the origin, the 

 sound becomes smoother and more monotonous. This is especially 

 noticeable in the case of references to the third type, that of 

 wind. 



Time-Relations of the Sound and Shock. — In the following table the 

 figures under the letters p, c, and f indicate the number of records 

 per cent in which the beginning or end of the sound preceded, 

 coincided with, or followed, the corresponding epoch of the shock ; 

 and those under the letters g, e, and 1 show the number of records 

 per cent in which the duration of the sound was greater than, equal 

 to, or less than, that of the shock : — 



It will be seen that the percentages for the beginning and end lend 

 no support to the view, sometimes expressed on insufficient observa- 

 tions, that the sound travels more rapidly than the waves which 

 form the shock. Had this been the case, the figures for the precedence 

 of the sound would have shown a very rapid increase with the 

 distance from the origin. 



After- S hock : January 15. 



Time of occurrence, 10.45 a.m.; intensity, 4; number of 

 records, 7, from 7 places. 



A slight shock was felt at Alsager, Cheadle, Coton Hill (near 

 Stone), Croxden (near Uttoxeter), Horseley (near Eccleshall), 

 Huntley (near Cheadle), and Stone. "With one exception, these 

 places lie within the isoseismal 6 of the principal earthquake 

 (Fig. 2). Alsager lies one mile to the north. From the distribution 

 of these places, it seems probable that the epicentre is not far from 

 the centre of the isoseismal referred to, and therefore lies between 

 the two epicentres of the principal earthquake. The shock was 

 a slight one, and consisted of a single series of vibrations. 



Origin of the Earthquakes. 



From the forms and relative positions of the isoseismal lines, we 

 obtain the following elements of the originating fault : (1) its mean 

 direction lies between E. 22° S. and E. 28° S., or about E. 25° S. ; 

 (2) its hade is to the north ; and (3) the fault-line must pass within 

 a short distance (about a mile or two) on the south side of the centre 

 of the isoseismal 7. This position for the fault-line is, however, 

 given on the supposition that the fault-surface is a plane. If the 



