196 Mr. Maclauchlan's Notes to accompany a Geological Map 



supplied much information and many extensive boundaries ; but, as these obser- 

 vations as well as his own, were made in the course of duty, it is not presumed 

 that they are so precise, as if undivided attention had been given to the subject. 

 The greater portion of the outline from Mitcheldean to Penhow, was traced 

 by Mr. John R. Wright and Mr. R. Wright. 



Old Red Sandstone. 



The old red sandstone, which constitutes so large a portion of Hereford- 

 shire, and passes under the coal-field of the Forest of Dean, may be divided 

 into three portions. 



The lowest*, containingbedsofcornstone, occupies the flat district between 

 Hereford and Kenderchurch, stretching on the north-west from Wormbridge 

 to the east of the Black Mountain, and by Hay and Talgarth to Brecon : on 

 the north-east it extends from Wormbridge by Devvsall and Aconbury, and 

 crosses the Wye, near Fownhope, towards Sellershope, where the strata are 

 thrown up by the outcrop of the transition series. Along the course of the 

 Wye, to the south of Hereford, these beds are overlaid by diluvium; and to the 

 south-west as far as Thruxton. The sandstone, however, may be observed at 

 intervals ; and the occurrence of a bed at Brandon Hill, near Bullingham, 

 dipping to the north, renders it probable, that a line of elevated strata ranges 

 from Kender-church, in an irregular direction, to Shucknell Hill, to meet the 

 anticlinal line which extends from May Hill to the apex of the Bristol coal- 

 field. The same line of elevation is supposed to pass from Kenderchurch, 

 southward by Clytha (where the transition beds are thrown up) to Usk. 



The next bed, which from its position may be called the middle, is a con- 

 glomerate, and may be easily distinguished by its elevated position, forming 

 the northern escarpment of the hills, from the Graig at Grosmont, where it 

 attains the height of 1380 feet, by Garway Hill and Aconbury, at which 

 point its dimensions are much diminished, to Capler Camp on the Wye. This 

 conglomerate, it is presumed, may be an outlier of that which occurs at the 

 Doward Hill on the Wye, near Monmouth (Map, PI. XV.) ; and the pre- 

 sumption is strengthened by a want of connexion between the beds at a lower 

 elevation, as far as has been observed ; and by a coincidence of opinion with 

 Mr. Mushet of Coleford. 



It is supposed that this bed of conglomerate, occupies the elevated summit 

 of Trelloch Beacon ; and that it passes by Wye Wood Common, and Chep- 



* The district occupied by this division, and the greater part of that, by the second or middle, 

 are not included in the map. 



