SHARPE DEVONIAN ROCKS. 23 



groups, — the Eifel limestone, Eifel fossiliferous schists, and the red 

 sandstones and conglomerates. The synchronism of the limestones 

 of South Devon and of the Eifel is now universally admitted. Each 

 of these limestone-groups is underlaid by a great formation of shale 

 and schist, occasionally fossiliferous, showing a complete accordance 

 of this part of the series in the two countries. 



The lowest division, or Poudingue, psammite et schiste rouge, pre- 

 sents exactly the mineral characters of the upper portion of our Old 

 Red Sandstone : where we saw it at Pepinster it consists of the fol- 

 lowing beds : — 



Red sandstone. 



Coarse red conglomerate, about 20 feet thick, made up of large and 

 small pebbles of quartz, jasper, Lydian stone, slate, &c. 



Red sandstone. 



Grey sandstone. 



The most remarkable bed is the conglomerate, which is quite ver- 

 tical at Pepinster, and crosses the hills in a ridge 20 or 30 feet high, 

 resembling an ancient fortification, from which it has obtained the 

 name of the Mur du Diable. The beds dip at high angles and the 

 thickness of the series is considerable. M. Rozet estimated it at 150 

 metres or about 500 feet, which cannot include all the series ; and 

 although this may appear trifling when it is compared to the enor- 

 mous development of the Old Red Sandstone in Shropshire and 

 Herefordshire, it is probably greater than the thickness of that 

 formation in Westmoreland. In 1829 M. Rozet published a paper 

 in the ' Annales des Sciences Naturelles' (vol. xix. p. 113) in which 

 he distinctly asserts that the Belgian red sandstone, seen between 

 Dinant and Namur (the continuation of the Pepinster bed), is the 

 equivalent of the English Old Red Sandstone, in which view he was 

 afterwards supported by M. C. Prevost*. In this identification I 

 entirely coincide. We thus separate the Old Red Sandstone from 

 the schists and limestones of South Devon, and regard it as a lower 

 independent member of the series ; and thus we are relieved from the 

 necessity of supposing that in the same sea two deposits were forming 

 at a short distance apart, the one of red sandstone and conglomerate, 

 the other consisting of grey schists and limestones, without there 

 being any interchange of characters between them, or any gradual 

 passage from one to the other. We might admit two such different 

 deposits to have been formed at the same time in different seas, but 

 between the Old Red Sandstone of South Wales and the schists of 

 Devonshire there is no trace of any axis of older rock which could 

 have divided the ocean at the time these deposits were being formed. 



There appears to be no limestone in the Old Red Sandstone series 

 of Belgium, nor have organic remains been found in it ; this will not 

 prevent our identifying it with the Old Red Sandstone of this country, 

 large districts of which have neither afforded any limestone nor any 

 such organic remains. 



* Bull. Soc. Geol. de France, vol. ix. p. 82, Dec. 1837. The same view was 

 taken in 1850 by M. Delanoue, Bull. Soc. Geol. de France, 2nd series, vol. vii. 

 p. 366. 



