572 Reports and Proceedings — Geological Society of London. 



the unusually clear evidence that they furnish with regard to the 

 •origin of the double series of vibrations in one of the shocks, and to 

 the continuous displacement of the seismic focus along the surface of 

 the originating fault. The second earthquake — that of April 1st — 

 was the strongest of the series, and the account of it is based on 

 89 records from 56 different places. Two distinct shocks were 

 ij-ecorded at 25 places, the second being the stronger. The focus of 

 the first earthquake was about a mile in length ; that of the second 

 ■was probably not less than five miles, and its centre being about 

 a mile E, 3.'3° N. of the former, it probably included the focus of 

 the first earthquake. The focus of the third shock was probably, 

 included in that of the second. The strike of the rocks near 

 MuUion, a thrust-plane hading to the south-east, the strike of the 

 lodes near the epicentre, and several el van-courses — are all parallel 

 to the isoseismal axes, or nearly so. Besides the focal transference 

 along the strike of the fault-surface, the double series of vibrations 

 gives evidence of transference down the hade of the fault-surface, 

 (the focus of the earlier shock being at a higher level than that of 

 the second. 



2. " On the Geological Structure of Portions of the Malvern and 

 Abberley Hills." By Professor T. T. Groom, M.A., D.Sc, F.G.S. 



This paper is in continuation of one on the Southern part of the 

 Malvern Hills already published by the Geological Society. In it 

 descriptions are given of the exposed rocks of the Malvern Eange 

 from Swinyard Hill to North Hill, the district of Cowleigh Park, 

 Martley, Woodbury, Wallsgrove, and the neighbouring tract of Coal- 

 measures. The Silurian rocks west of the hills are almost invariably 

 inverted, and the Malvernian rock frequently can be found to be 

 •overthrust on to them. In several cases there is reason to suspect 

 that slips of Silurian rocks are caught in infolds among the 

 Malvernian rocks. The author concludes that the whole of this 

 ■district, May Hill, the Old Eed Sandstone tract to the west, the 

 coalfields of the Foi-est of Dean, South Wales, and Bristol, and the 

 Tortworth district, are traversed by a series of related folds, whose 

 axes run in two chief directions intersecting at a considerable angle : 

 the axial planes of one set tend to dip eastward, and of the other in 

 a southerly direction. Overfolding has taken place frequently from 

 the east, less frequently from the south ; and this inversion affects 

 the south as well as the middle and north of the Malvern range. 

 The Archaean rocks are thrust on to various members of the 

 Cambrian System in the south and of the Silurian System in the 

 north. The overthrusts are moi'e closely connected with a later 

 movement than with the first folding of the rocks, and while they 

 have not materially altered the nature of the rocks concerned, they 

 iiave in some cases resulted in the production of schists (mylonites). 

 In some cases a secondary folding has affected the thrust-planes. 

 The intensity of the folding diminished west of the old ranges. The 

 •chief movement appears to have progressed in sections from north to 

 south, and the western fronts of different sections show some 

 tendency towards convexity in the direction of movement. While 



