458 Notices of Memoirs — British Association — 



themselves wholly free from such structures. The age of the 

 folding, cleavage, and extrusion of the granite is thus definitely 

 fixed as having been subsequent to the deposition of the Culm- 

 measures, but previous to that of the Permian rocks. 



But we may fix the age still more closely. A broad syncline of 

 Carboniferous rocks traverses Mid-Devon, and is succeeded north- 

 wards by an anticline and by an extrusion of granite at Lundy 

 Island, the age of which, however, has not yet been definitely 

 ascertained. Still further north in a series of folds and overthrusts 

 which traverse the southern margin of South Wales we can recognise 

 the last effects of the great Devonshire movement at a distance of 

 not less than 130 miles from the central axis, the ground-swell, 

 «o to speak, subsiding as it receded from the distant storm-area. 

 Here the higher Carboniferous rocks are involved, and thus prove 

 that this part at least of the Armorican disturbance was of post- 

 Carboniferous age. 



In Dorset, Somerset, and Gloucestershire the Palasozoic rocks pass 

 •eastwards under Secondary formations, and are seen no more in the 

 south of England. That the disturbance continues, however, is 

 inferred from the fact that it has been traced across a large part of 

 the continent of Europe in the one direction and across the south of 

 Ireland in the other. The determination of its position therefore, 

 and especially of the effects of its intersection with the Midland 

 disturbances, is of the greatest importance in view of the possible 

 occurrence of concealed coalfields under the Secondary rocks. One 

 such intersection is open to observation. 



The Malvern and Devonshire disturbances intersect in Somerset. 

 On investigating their behaviour as they approach we may notice in 

 the first place that the subsidiary axes which form the northernmost 

 part of the Devonshire disturbance in South Wales die away one 

 after the other towards the east. Thus an east and west disturbance 

 at Llanelly runs a few miles and disappears. The more important 

 Pontypridd anticline, which traverses the centre of the coalfield, 

 fades away near Caerphilly, while the coalfield itself terminates 

 a little further east, its place on the same line of latitude being taken 

 by the Usk anticline, which trends southwards and south-westwards. 

 So far it might be inferred that the east and west folds die away on 

 approaching the north and south Malvernian axis. But the Cardiff 

 anticline, which lies south of and was more energetic than those 

 mentioned, crosses the Bristol Channel and, emerging on the other 

 side in a complicated region near Clevedon and Portishead, passes 

 to the north of Bristol and holds its course right across the coalfield 

 at Mangotsfield. The coalfield, however, lies in what is part of the 

 Malvernian disturbance, for it occupies a syncline running north and 

 south along the west side of the main axis of the upheaval. Though 

 the interruption is local and the strata recover their north and south 

 strike to the south of it, yet the east and west axis obviously holds 

 its course right through the Malvernian structure. 



Still further south, in the direction in which the east and west 

 movements gradually increase in energy, a series of sharp folds is 



