306 Dr. C. Davison— Britkh Earthquakes. 



94 per cent, of all the observers, by 95 per cent, within the isoseismal 

 5, and by 93 per cent, in the zone between the two isoseismals. 

 "Within the isoseismal 5, the sound is compared to passing waggons, 

 etc., in 29 per cent, of the records, to thunder in 9 per cent., to wind 

 in 5, to loads of stones falling in 12, to the fall of a heavy bodj- in 26, 

 and to explosions in 19 per cent. ; in the area between the isoseismals, 

 the sound is compared to passing waggons, etc., in 44 per cent, of the 

 records, to thunder in 11 per cent., to wind in 3, to loads of stones 

 falling in 17, to the fall of a heavy bodj- in 8, and to miscellaneous 

 sounds in 3 per cent. Thus, references are made to types of short 

 duration in 57 per cent, of the records within the isoseismal 5, and in 

 40 per cent, of the records in the surrounding zone. 



The beginning of tbe souud preceded that of the shock in 46 per 

 cent, of the records, coincided with it in 46, and followed it in 8 per 

 cent. ; while the end of the sound preceded that of the shock in 

 5 per cent, of the records, coincided with it in 58, and followed it in 

 37 per cent. The duration of the sound was greater than that of the 

 shock in 56 per cent, of the records and equal to it in 44 per cent. 



From the seismic evidence it may be inferred that the mean 

 direction of the originating fault is N. 6° E., that its hade (as 

 determined by the relative position of the isoseismals and the westerly 

 overlapping of the sound-area) is towards the east, and that the fault- 

 line passes a short distance to the west of the centre of the isoseismal 5, 

 i.e. not far from Great !Malvern. Now, the mean direction of the 

 fault that runs along the east side of the Malvern Hills is N. 4° E. near 

 Great Malvern, its hade is to the east, and it passes through Great 

 Malvern. 



There can thus be little doubt that the earthquake was caused by 

 a small slip of this fault in the neighbourhood of Great Malvern. That 

 the depth of the focus was small is shown by the sharp, abrupt character 

 of the shock near the central area, fading away to a tremor near the 

 outer margin. 



This is the only movement along the Malvern fault with which 

 I am acquainted, and certainly none of any consequence has taken 

 place during the last 1 9 years. ^ 



Earth-shahes in Minimj BidricU. — Earth-shakes resembling those 

 so frequently felt in mining districts were observed at and near 

 Abercarn (Monmouthshire) on February 11, 1904, Camborne on 

 September 5th, 1904, Eastwood (j^ottinghamshire) on September 17th, 

 1904, and Pendleton (near Manchester) on JN'ovember 25th, 1905. 

 The Pendleton earth-shake has been described in a recent paper in this 

 Magazine.^ 



Abercarn: Fehruary 11th, 1904. — A smart shock, accompanied by 

 a noise like a distant explosion, occurred at 2.30 a.m. In the colliery 

 districts it was thought that a disaster had occurred m one of the 

 mines. The shock was evidently local, for it was not felt at three 



1 I do not think that the occurrence of this slight earthquake lends any .support to 

 the suggestion (Quart. Jouru. Geol. Soc, vol. Ivi, 1900, p. 196) that perceptible 

 displacements have recentl}' occurred along the line of fault. 



' Geol. Mag., Dec. Y; Vol. Ill (1906), pp. 171-176. 



