i6 PROCEEDINGS COTTESWOLD CLUB 1910 



OFFA'S DYKE 



On arriving at Chepstow (Plate III., fig. i), the Members were met 

 by Mr Butt, and having taken their places in two brakes and a waggonette, 

 were driven over the bridge which divides Monmouthshire from Gloucester- 

 shire, where was seen an excellent example of an anticline in the Carboniferous 

 limestone. I Offa's Dyke was passed through on the southern side of Sedbury 

 Park, and about this famous earth-mound the President had something 

 to say. He said that according to Sir John Maclean, the oldest monument in 

 England of which the date is known is Hadrian's Wall, 121 A.D. The next 

 was Offa's Dyke. 779 A.D. Offa reigned in Mercia from 755 to 794. There 

 were older boundary ditches in Wilts and elsewhere, but their dates were un- 

 known. This dyke was said to stretch from the Severn to the estuary of the 

 Dee. They were told that it was not a fortification, but a bank with a ditch 

 on each side. When perfect it was about 40 feet at the base, and 18 feet 

 4 inches in height. Mr Butt said that apparently on his own land what was 

 called Offa's Dyke was sometliing else. Ormerod, who li\ed at Sedbury 

 Park, said that Llancaut was joined Vjy a narrow neck of land to Tidcnham, 

 across which works ranged from cliff to cliff, consisting of two parallel 

 mounds, formed of fragments of limestone, with the convex side of the 

 curve and the ditch towards Mercia. It might be either British or an 

 entrenchment of Danish pirates. Ormerod inclined to the former. Sir John 

 Wintour intended to fortify and make good these entrenchments in 1644, but 

 was defeated and driven over the river. It was remarkable that they 

 had here Buttington Wood, with the precipice and the dyke resting on 

 the Severn, and precisely the same combination at Buttington, near Welsh- 

 pool, in Montgomeryshire. They knew that Offa was more than once 

 interrupted in the construction of his dyke by the incursions of the Britons, 

 and it is doubtful if it was ever completed. .\s far as his own personal 

 observation went, it could hardly be pos.sible that it ever formed a continuous 

 mound from here to Chester. One writer said that its condition very much 

 resembled an unfinished modern railway. One saw portions of the line com- 

 pleted, others in course of construction, and elsewhere on the line of route the 

 ground was untouched. One could to-day find no trace of the dyke in 

 or about Tutshill. It was really lost sight of from a point almost opposite 

 the end of the Norman walls of Chepstow till it reappears close to Mr 

 Yockney's house on the road leading to Lancaut from the main-road, running 

 from Tutshill to the Chase and St Briavels. Sir John Maclean, who traced 

 the course of the dyke throughout Gloucestershire, asserts that it has 

 invariably occupied a site removed from the river Wye about a quarter 

 or half mile, of which it in all cases commands a view. This was not 

 so on his (the speaker's) place— if the mound is Offa's Dyke — for the 

 end comes absolutely up to the edge of the cliff. [W.T.] 



THE GEOLOGY OF SEDBURY CLIFF 



At Sedbury Cliff, Mr Richardson gave a short lecture on the geology of 

 the country around Chepstow. 2 He said that, as they were aware, two great 

 subdivisions had been made of the great mass of fossiliferous rock that lies 

 above the Archaean, namely, the Pal.cozoic and Neozoic. Each of these had 

 been subdivided, the upper three systems of the Palaeozoic Group being 

 the Devonian, Carboniferous, and Permian, and the lower three of the 

 Neozoic, the Triassic, Jurassic, and Cretacic. In late Carboniferous times 

 the Paleozoic rocks were crumpled, and in the Chepstow district underwent 

 denudation, which produced hill and valley, until late Triassic or Keuper 

 times. Then it sank, and the waters of the Keuper inland sea slowly crept 



1 L.R., Proc. Cotteswold Nat. F. C, vol. xv., pt. i (1904), PP- •?, 18, and PI. I. 



2 L.R., Trans. Woolhope Nat. F. C, vol. for 1903, pp. 178-184. 



