460 Notices of Memoirs — Prof. Boyd-Bmvldns — 



it is continued to the east through. Tunbridge Wells and Tenterden 

 to the sea to the south of Hythe. 



These three folds have no bearing on the range of the Coal-fields 

 in the drainage area of the Thames. The fourth, or Pembroke- 

 Mendip anticline, and the fifth, or South Welsh syncline, are the 

 two great tectonic folds which remain for consideration. 



The Pembroke-Mendip anticlinal range, highly faulted and folded, 

 is traceable westwards into South Ireland, and eastwards through 

 Pembroke and the peninsula of Gower, to the south of Cardifi", 

 through Weston-super-Mare and the Mendip Hills. Throughout 

 this area it forms the southern margin of the Coal-fields. Near 

 Frome it plunges beneath the Oolites. It is, however, clearly 

 marked by the Upper Greensand anticline of the Vale of Pewsey, 

 and by the Upper Greensand inliers of Ham and Kingsclere. 

 Thence it passes along the line to the high downs past Basingstoke 

 and Farnham to Peasemarsh, south of Guildford, where it is seen 

 in an inlier of Weald clay. It is carried still further to the east 

 by similiar inliers south of Westerham, and at Wateringbury and 

 Maidstone. From Maidstone it sweeps to the south-east, through 

 Otham and Ashford, arriving at the coast close to Hythe. In the 

 eastern portion of its course it has, in my opinion, been the chief 

 factor causing the south-eastern trend of the North Downs in the 

 district of Maidstone. It forms also the southern boundary of the 

 south-eastern Coal-field discovered in the boring at Dover, and of 

 the Coal-fields of northern France and Belgium. 



The South Welsh syncline, only two miles wide at St. Bride's 

 Bay, in the anthracite district of Pembroke, widens out into the 

 Coal-field of South Wales, twenty miles in width. As it approaches 

 the upper estuary of the Severn it is represented by the outlying 

 Coal-field of the Forest of Dean, and the three partially or wholly 

 covered fields to the north of the Mendip Hills, distributed through 

 an area measuring forty-five miles from north to south. The wedge- 

 like syncline with its more or less connected Coal-fields continues to 

 widen eastwards, its northern boundary being probably represented 

 by a line drawn from the northern rim of the South Welsh Coal- 

 field to the north of the Forest of Dean, and continued due east 

 beneath the Secondary and Tertiary rocks to some point between 

 Walton-on-the-Naze and the mouth of the Black water. It passes 

 through Gloucester, Eissington in the valley of the Windrush, 

 Blenheim, Kirtlington, Quainton, Luton, Bishop's Stortford, Dun- 

 mow, Braintree, and Colchester. The width of this great tectonic 

 syncline between Colchester and Dover is about fifty miles, and it 

 occupies nearly the whole of the London Tertiary basin, which, it 

 must be noted, is of the same wedge shape, widening to the east. 



The boring recently described by Mr. Whitaker at Culford, near 

 Bm-y St. Edmunds, in which a slate rock, probably of Silurian or 

 pre-Silurian age, was struck at a depth of 637 feet 6 inches from 

 the surface, shows that in all probability that area is an anticlinal 

 area. About forty-two miles to the south, in the deep boring at 

 Harwich, the Yoredale shales come in. Both these points are, be it 



