352 DE. CHAELES DAVISON ON THE [A.Ug. I907, 



June 27tb, about 8.15 a.m. : Ferryside. — A shock accompanied by a 

 heavy thud. 



June 27th, 10.14 a.m. : Ystalyfera. — A very slight shock. 



June 28th, 2.5 a.m. : Lower Cwintyrch (Swansea Valley). — A slight shock. 



June 30tb, 11.30 p.m. : Neath.— A slight shock. 



October 9th, 3.15 p.m. : between Pontardulais and Llanedy. — Two prolonged 

 sounds, separated by an interval of 2 minutes, and resembling distant 

 thunder, were heard ; with each a slight tremor was felt, as if a light 

 vehicle were passing on the road. A similar sound was heard in the 

 afternoon of this day at Growerton. 



II. The Eaethqttake of June 27th, 9.45 a.m. 



Intensity, 8; centre of isoseismal 8 in lat. 51° 38-0' N., long. 4° 0'3' W 

 Number of records, 1168, from 607 places, and 89 negative records from 

 84 places. 



Time of Occurrence. 



Excluding approximate estimates of the time of occurrence, the 

 total number of such records is 651, of which 108 are regarded by 

 their observers as being accurate to the nearest minute. Taking 

 account of the latter group of records only, the average of 21 records 

 from places within the isoseismal 8 is 9 h 45'2 m a.m., and of 87 

 records from places outside this isoseismal 9 h 45 # 6 m . The time at 

 the origin may, therefore, be taken as 9 h 45 m . 



Isoseismal Lines and Disturbed Area. 



On the map of the earthquake (PI. XXV) are drawn six 

 isoseismal lines, corresponding to intensities 8 to 3 of the Eossi- 

 Eorel scale. These are represented by continuous lines, broken in 

 the portions where their course is doubtful. 



The isoseismal 8 is an elongated ellipse, 26J miles long, 14 miles 

 wide, and 299 square miles in area, the longer axis being directed 

 E. 5° N. and "W. 5° S. The centre of the curve lies about 3 miles 

 west of Swansea, in lat, 51° 38*0' 1ST., long. 4° 0'3' W. Damage to 

 buildings, chiefly the fall of chimneys, is reported from 40 towns 

 and villages within the isoseismal line. 1 



The southern half of the isoseismal 7 traverses the Bristol 

 Channel, but the trend of the curve just before leaving land and 

 the close approach to intensity 7 at several places in North Devon 

 show that the course of this portion as drawn on the map cannot err 

 greatly from its true position. The isoseismal is 62 miles long, 

 43 miles wide, and 2120 square miles in area. Its distance from the 

 isoseismal 8 is 12 miles on the north side and 17 miles on the south, 

 13 miles on the west side and 23 miles on the east. The inequality 

 between the former pair of figures indicates that the originating 

 fault hades towards the south, while that between the latter pair 



1 The extent of the injury to property does not come within the range of 

 this paper, but it may be noticed that the number of chimneys thrown down 

 or damaged must amount to several hundred. At Swansea, the number is 

 estimated at not less than 120, at Neath 30, etc. Two men in Swansea 

 received scalp-wounds from falling bricks. 



