CENTRAL OR CORNSTONE FORMATION, HEREFORDSHIRE, ETC. 177 



layers have been already alluded to as appearing in the face of the great escarpment of the 

 Blorenge- 



I refer the reader to the map to obtain a notion of the large tracts in Brecon and Monmouth, 

 where these limestones prevail. A good descending section of the whole system of Old Red, has 

 recently been laid open by making the new road from Chepstow to Usk, which runs directly across 

 the strata. On this road 3 the traveller first passes over the quartzose formation of sandstone and con- 

 glomerate, rising from beneath the lower carboniferous limestone shale ; next the marls and cornstone 

 in the bold escarpment of Golden Hill, and thence traversing sundry calcareous courses, he meets with 

 the Silurian Rocks in the hills north of Usk, throwing off upon their eastern slopes the marls and tile- 

 stones. (See PI. 36. fig. 21.) In the southern parts of Herefordshire (between Monmouth Cap and 

 Whitefield), are numerous courses of small round concretions, which not being firmly bound together 

 by the matrix, readily separate from the imbedding sand and clay, and are used as gravel for the 

 roads. In the same tract, however, are strong courses of very pure concretionary limestone, of 

 purple and green colours, one variety of which appears to have been formerly used as marble. 



To the north of the river Wye, the same system is prolonged in the central hills of Herefordshire ; 

 and traverses made across these hills from Hereford to the Vale of Weobly, afford good sections of 

 the cornstone group. The descending section of it may be thus enumerated, the beds dipping to 

 the S.E. or S.S.E. at angles of 12° and 15°. 



a. Slaty beds, quarried for tiles in the hills above Mr. Peploe's Park, (contain broken portions of vegetables, often in a 

 state of carbon). 



b. Marls, red and green. 



c. Cornstone, in parts semi-crystalline, seldom exceeding 4 to 5 feet in thickness. 



d. Argillaceous marls with impure limestone, fit only for road-mending. 



e. Great sandstone quarries (at Raven's Causeway, for example,) from 30 to 40 feet in depth, contain fine large flaggy 

 beds of light greenish colour, used for tombstones ; and strong beds of micaceous, fmely-grained sandstone, the lines 

 of deposit being sometimes marked by purple and light green stripes. This stone is of excellent quality for building. 



/. Argillaceous marls. 



g. Courses of impure concretionary limestone, appear here and there in the slopes and lower sides of the hills ; these 

 descend into the rich low grounds around Weobly. If powerful denudation had not destroyed the strata and covered them 

 with gravel, the valley of the Wye between Hereford and the Hay would doubtlessly have afforded similar sections, for the 

 same succession of argillaceous marl, sandstone, cornstone, and flagstone is displayed in the hills of Moccas on the south or 

 right bank of the Wye, as those described in the Weobly Hills. There can, indeed, be no doubt that the strata of these 

 two hilly ranges on the opposite banks of the river were once continuous, because whenever the gravel has been removed, 

 the cliffs exhibit the red argillaceous beds. 



Similar arrangements of strata are exhibited in the escarpments of all the hills ex- 

 tending from Weobly to Leominster, and thence to Tenbury and Bromyard ; the vast 

 thickness of the formation, including many masses of strong-bedded sandstone, being 

 remarkably well displayed in the hills crossed by the new road from Leominster to 

 Hereford. Wherever the marls have prevailed, the denudations have been most exten- 

 sive, as is remarkably exemplified in the lateral valleys on the sides of the Pyons, two 

 small conical hills, probably saved from destruction by the hardness of the concretionary 

 rock and gritty sandstones near their summits. 



Nearly the whole of the central and northern parts of Herefordshire, and the con- 

 tiguous parts of Salop and Worcestershire, are occupied by this formation, those hills 

 having best resisted denuding influences, which contain the hardest concretions of corn- 



