522 Reports and Proceedings — 



Scotland, with indications in North Ireland. Thus the coal-growth invested 

 the southern and western edges of Godwin- Austen's ' internal sea ' above- 

 mentioned, and extended westward by two outlets : one at its south-west 

 corner, by South Wales ; and the other on the north-west, by Central 

 Scotland, each into the Irish area, and thus roughly surrounding the 

 several older Palseozoic lands of Wales, Ireland, Cumbria, and South 

 Scotland. 



In Professor Eamsay's account of the denuded remnants of the Welsh 

 coal-fields ' the stretch of coal-growth along the border of the old Cambrian 

 land is clearly indicated in his statement, that — 



" One denuded edge of these accumulations now forms part of the 

 counties of Pembroke, Caermarthen, Glamorgan, and Monmouth, and is 

 elsewhere exhibited in the Forest of Dean, the narrow strips of Coal- 

 measures north of May Hill in Gloucestershire, the Clee Hills (outliers of 

 the Forest of Wyre and Coalbrookdale), the coal-fields south and west of 

 Shrewsbury, and that of Oswestry, Wrexham, and Mold. All these are 

 but fragments of one great original coal-field, once mantling round North 

 Wales and the older rocks west of the Severn and north of Bristol 

 Channel." 



Both north and south, however, of the old Cumbrian area are a few 

 seemingly isolated patches of coal ; but the Whitehaven field is really the 

 western portion of the North-of-Engiand coal-growth ; the coal of Anglesea 

 belongs to the westward extension of the Lancashire field ; and that of 

 Ingleton is a remnant of the northern part of the latter towards the 

 margin of the old Cumbrian land. 



5. Coal-field of South Wales: its extent, thickness, and constituent 

 strata. — The valuable coal-field of South Wales (estimated by some to 

 occupy 640,000 acres, and stated by others to be 906 square miles in 

 extent) forms an irregular oval basin or trough lying E. and W. (about fifty- 

 six miles long, from Pontypool to Caermarthen Bay), with a narrow 

 extension westward beyond Caermarthen Bay, through Pembrokeshire to 

 St. Bride's Bay (about seventeen miles long). The greatest width is about 

 sixteen miles. In 1881 there were 662 collieries at work (see Hull, 1881). 

 The strata of the whole area have been much undulated and broken ; on 

 the south they dip at an angle of 45°, and at about 12° on the north. 

 Great faults, approximately north and south, alter the levels from forty to 

 a hundred fathoms ; they are generally filled with clay ; but one, near 

 Swansea, many fathoms wide, is filled with fragments of the broken strata 

 (Trimmer). 



A strong anticline once passed along the middle of the trough (E. and 

 W.), with its complemental synclines, one on each side. These have been 

 somewhat shifted (the eastern moiety towards the S.W., and the other to 

 the N.E.) by a great ohMqne fault coincident with the valley of the Neath. 

 Except at Swansea and Caermarthen Bays, the outcrops of the lowest part 

 of the series of strata, of irregular width, are continuous around the coal- 

 field. About seven unequal patches of the upper measures have been 

 presei'ved from denudation in the synclines. Two of these areas are in the 

 eastern moiety ; both long, but the southern syncline retains only a narrow 

 and interrupted series of patches.^ The Ebbw, the Sirhowy, the Rhymney, 

 and the upper part of the Afon cross the former ; the Taff" and the 

 Rhondda, with their branches, cross both synclines ; and the Ely and Ogwa 

 cross the lower syncline. The respective valleys give local opportunities 

 for opening certain beds, and afibrd facilities for roads and railways from 

 the hills to the sea-coast. In the western moiety there are five circum- 

 scribed areas of the upper measures in the two synclines ; the united 

 Amman and Llwchwr River runs between four of them, and the Tawe 



1 Mem. Geol. Surv. vol. i. 1846, p. 314. 



"^ See Hull's ' The Coalfields,' etc., 4th edition, pp. 88, etc., and map. 



