XXI. — Notice of Two Models and Sections of about Eleven Square 

 Miles, forming a part of the Mineiml Basin of South Wales, in the 

 Vicinity of Pontypool, and presented to the Geological Society by 

 Richard Cowling Taylor, Esq., F.G.S. 



[ReadJune 18th, 1830.] 



IHE object of the author in preparing the models^ was to employ to advan- 

 tage a considerable accumulation of local details relating to the structure and 

 contour of this district, and thus to exhibit, in the most instructive form, a 

 faithful representation of a part of the South Welsh Coal Field. To avoid 

 confusion, and to convey a distinct iliuetration of geological arrangement, as 

 well as of natural features and artificial characters, two models appeared in- 

 dispensable. One of these, therefore, exhibits the external or pictorial cha- 

 racters of the area selected ; the other, which is more immediately interesting 

 to the geologist, develops the internal structure, and the position and inclina- 

 tion of the various mineral and coal strata*. 



Elevation. — The lowest point shown, is about 330 feet, and the highest 

 1563 feet above the high- water level of the Usk at Newport. The summit 

 level of the Monmouthshire canal is stated to be 447 feet above the basin 

 at Newport. The Pen Twyn iron-works are situated 179 feet, and the Aber- 

 sychan furnace 256 feet, higher than the canal summit; and from the latter 

 works to the top of Blaen Sychan the rise is about 900 feet more. The point 

 called Pen Rhiw Ffranch, by spirit level was found to be 890 feet, and by 

 barometrical observation 881 feet, above the canal. 



The district offers a characteristic specimen, in miniature certainly, of an 

 extensive range of similarly constructed country. Amongst its most striking- 

 features are the regular form of the Pens, or promontories, which project from 

 the principal mountain ranges, and the deeply eroded ravines which descend 

 into the adjacent valleys, off'ering to the speculative some elucidation, not the 

 less instructive because on a small scale, of the action of water. The 



* Plate XLII. represents the second of these models, but the direction of the ravines being shown 

 by the rivulets, and the form of the Pens by the range of the strata, the shading of the Iiills has 

 been omitted. 



It is necessary to premise that the north-east and south-west angles of the models have been 

 filled up from comparatively imperfect observation, the autlior being in possession of less abundant 

 data. These points must be received as approximations, introduced to preserve the general effect. 



