Dr. C. Damson — British Earthquakes. 307 



places (Henllys, Machen, and Risca), which lie about 3 or 4 miles 

 from Abercara. 



Camlorne : September bth, 1904. — Time of occurrence, 1.55 a.m.; 

 intensity, 4 ; number of records 7, from 6 places, and negative records 

 from 3 places. 



The earth-shake was felt chiefly in the district between Camborne 

 and Redruth, but, owing partly to its occurrence shortly after midnight, 

 it was not so widely observed as the stronger shake of June 4th, 1902. 

 The boundary of the disturbed area is similar to that of the earth- 

 shake in 1902,^ but falls short of it by about half a mile towards the 

 north, west, and south. It is thus about 3|- miles long, 2\ miles wide, 

 and 7 square miles in area, its longer axis being roughly parallel to 

 that of the earlier shake, and consequently to the principal faults of 

 the district. The shock was brief, its duration being not more than 

 2 seconds, and was accompanied by a noise which was supposed by one 

 observer to be due to a fall of ground in Dolcoath Mine. 



Ea&twood : September nth, 1904. — At about 5.30 p.m. a shock was 

 felt at Eastwood, a mining village about 8 miles north-west of 

 Nottingham. The shock was strong enough to shake crockery and 

 make windows rattle loudly. It does not appear to have been felt at 

 other places in the surrounding district. 



Llwynypia : May 11 th, 1907. — Time of occurrence, 3.15 p.m.; 

 intensity, 5 ; centre of disturbed area in lat. 51° 38'2' JST., long. 3° 26-6' 

 W. ; number of records 22, from 13 places, and negative records from 

 7 places ; number of observations made in mines, 6. 



During the last twenty years earth-shakes have occurred in the 

 Rhondda valleys on June 22nd, 1889, April 11th and May 2nd, 1894, 

 October 16th, 1896, and May 17th, 1907, but many others in all 

 probability have escaped record. The epicentres in 1894 were situated 

 about three-quarters of a mile east of Porth, the other three in the 

 neighbourhood of Pentre and Llwynypia.^ 



The earth-shake of May 17th, 1907, occurred at 3.15 p.m. iN'ear 

 the centre of the disturbed area its intensity was 5, very nearlj^ 6. 

 The boundary of the disturbed area is an isoseismal of intensity 4, 

 and is very nearly circular in form, about 4 miles in diameter and 

 13 square miles in area. Its centre is situated half a mile east of 

 Llwynypia. 



The shock in all parts of the disturbed area consisted of a single 

 series of vibrations, lasting on an average for 1 1- seconds. Close to the 

 centre of the area, as at Llwynypia, it began with one or two strong 

 vibrations, followed by others rapidly decreasing in intensity ; while 

 near the boundary, at Gelli and Cymmer, only a tremulous motion was 

 felt. The sound was much louder near the centre of the area than 

 near the boundary ; at Llwynypia it was described as a violent report 

 and a great crash, or compared to a locomotive charging a building ; 

 near the boundary it was either not heard at all or described as a dull 

 thud or like a distant explosion. It was heard by 86 per cent, of the 

 observers. In 62 per cent, of the records it is compared to the fall 

 or banging of a heavy body or to an explosion or blasting ; in the 



1 Geol. Mag., Dec. V, Vol. II (1905), pp. 221-2. 



2 Ibid., Dec. Ill, Vol. VIII (1891), p. 371 ; Dec. V, Vol. VII (1900), pp. 124-5. 



