Dr. C. Davison — British Earthquakes. 305 



and was compared to passing waggons, etc., in 27 per cent, of the 

 records, to thunder in 45 per cent., to the fall of a heavy body in 9, 

 and to miscellaneous sounds in 18 per cent. The beginning of the 

 sound preceded that of the shock in 86 per cent, of the records, and 

 coincided with it in 14 per cent. ; while the end of the sound preceded 

 that of the shock in 14 per cent, of the records, coincided with it in 

 28, and followed it in 57 per cent. 



Since the direction of the longer axis is parallel to that of the 

 isoseismal 8 of the earthquake of 1906, and the line joining the 

 epicentres of the two earthquakes is very nearly parallel to the longer 

 axis, it follows that the Swansea earthquake of 1907 was caused by a 

 slip of the fault that was in action the year before, the region of 

 maximum displacement being about two miles farther to the west. 



11. Ochil Earthquake : July bth, 1907. — Time of occurrence, 9.48 p.m. 

 A slight shock, consisting of a single vibration, felt at Menstrie. 



12. Ockil Earthquake : Jultj 21st or 28th, 1907.— A slight shock felt 

 early in the evening (between 5 and 7.30) at Menstrie. The day 

 was one of the last two Sundays in July, but which of the two, 

 unfortunately, cannot be ascertained, as the information was com- 

 municated some time after the occurrence of the shock. 



13. ' Ochil Earthquake : September I8th, 1907. — A very slight shock 

 felt at Menstrie at about 5.30 p.m. 



14. Malvern Earthquake : September 27th, 1 907. — Time of occurrence, 

 8.12 a.m.; intensity, 5; centre of isoseismal 5, in lat. 52° 6'6' jST., 

 long. 2° 16*8' W. ; number of records 107, from 40 places, and negative 

 records from 6 places. 



Of 89 estimates of the time of occurrence, 14 are regarded by their 

 observers as being accurate to the nearest minute, their average being 

 8.12 a.m. 



The isoseismal 5 is 9 miles long, 7 miles wide, and contains 48 

 square miles. Its centre lies 1-i- miles east of Great Malvern station, 

 and its longer axis is directed J^. 6° E. The outer isoseismal, 

 of intensity slightly less than 4, is 18 miles long, 14i miles wide, 

 and 206 square miles in area. The distance between the two 

 isoseismals is 3-1- miles on the west side and 4 miles on the east. 

 Outside the latter curve the earthquake was perceived at six places by 

 persons under favourable conditions, the shock and sound at Longworth 

 (8+ miles west of the isoseismal) and Preston (2i- miles south-west), 

 the sound only at Eedmarley D'Abitot {i mile south), and the shock 

 only at Elmbridge (65- miles north-east), Cheltenham (8 miles south- 

 east), and Charlton Kings (O-i- miles south-east). Thus the total 

 disturbed area must contain about 800 square miles. 



At most places the shock consisted of a single violent jerk, like that 

 caused by the fall of a heavy body or an explosion of dynamite. Close 

 to the centre the thud was followed by a slight vibration. At three 

 places (Mathon, "Welland, and Worcester) two vibrations were felt, the 

 second being the stronger. 'Near the boundary of the disturbed area 

 the shock was felt as a slight tremor or quiver. The mean duration of 

 the shock was 2 seconds. 



The sound-area coincides nearly with that contained by the outer 

 isoseismal, but overlaps it towards the west. The sound was heard by 



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