A. Stmhan — The Age of the Vale of Clioyd. Ill 



The illustrations accompanying Mr. S. Ryan's specimens are : — 



1. Map of the country between the Transvaal and the Indian Ocean from 25° 30' 

 to 27°. 



2. Section across the country from Steynsdorp to the Indian Ocean. 



3. Fig. 1. — Plan of the Forbes Reef Gold-mining Company's property in Swazi- 

 land, including the lines of Sections Z and T, and Section X in the Eyan Tin-mining 

 Company's property at Darkton. (See p. 106.) 



4. Fig. 2. — The Sections T and Z in the Forbes Eeef Gold-mining Company's 

 property. (See p. 108.) 



0. Fig. 3. — The Section X in the Eyan Tin-mining Company's property (p. 109). 



III. — The Age of the Vale of Clwyd. 

 By A. Strahan, M.A., F.G.S. 



FOE many years the New Ked Sandstone of the Vale of Clwyd 

 was shown upon the maps as resting generally on Carboniferous 

 Liuiestone, but frequently overlapping it so as to pass on to the 

 surrounding Silurian strata. No faults were indicated, and the 

 structure of the Vale, as represented, suggested that a pre-Triassic 

 syncline here existed, within which a remnant of Carboniferous 

 rocks had been preserved from denudation and which had formed 

 a bay in the Triassic coastline. 



In 1880, however, when Sir A. Eamsay was engaged upon the 

 second edition of his Memoir on North Wales (vol. iii of the 

 Memoirs of the Geological Survey), doubts had arisen respecting 

 the correctness of the map, and I received instructions to make 

 a preliminary examination of the margins of the Vale. This I did 

 in company with Mr. Aveline, and the results were used by Eamsay 

 in writing chaptei's xxxii and xxxiii of the memoir referred to. 



Subsequently the resurvey of Flintshire on the six-inch scale, 

 which was then in progress, was carried so far as to include the 

 whole of the Vale except its extreme southern end and a portion 

 of its western side lying south of Denbigh. The western side north 

 of Denbigh was surveyed by Mr. Tiddeman, and the remainder by 

 myself. A description of the geology appeared in the Memoir on 

 Ehyl, etc. (1885), so far as related to Quarter-sheet 79 N.W., and 

 in the Memoir on Flint, etc. (1890), so far as related to Quarter- 

 sheet 79 S.E. The Quarter-sheets 79 S.W. and 74 N.E. were also 

 brought up to date in 1895, so far as was possible without a complete 

 resurvey. 



Briefly stated, the results of the resurvey went to show : — That 

 . two subdivisions of the Carboniferous system were represented in the 

 Vale, namely, the Carboniferous Limestone and some purple sand- 

 stones and shales lying conformably upon it^ : — That these strata 



1 Although Ijing outside the subject of the present paper, the history of these strata 

 deserves a brief notice. They were first distinguished from the Trias in 1865 by 

 G. Maw (Geol. Mag., Vol. II, pp. 380, 523, and Eep. Brit. Assoc, for 1865, 

 Sections, p. 67), but erroneously described as Permian. In the same year D. C. Davies 

 suggested that they would probably prove to be Carboniferous (Geol. Mag., Vol. II, 

 p. 476). Dming the resurvey of 1881 it was readily seen that the purple measures 

 lay directly and conformably upon the limestone, but were unconformably overlapped 

 by the Trias. They were known, moreover, to contain thin seams of coal, and to 

 include strata indistinguishable in tint or character from Coal-measures. Their 



