SHARPE — DEVONIAN ROCKS. 2/ 



deposits. In tliat case we must assume the upper member of con- 

 glomerate and sandstone to be either wanting in Devonshire, or con- 

 cealed below the Culm-measures, and the Ilfracombe group to repre- 

 sent the middle or marly division of the Old Red, and the Linton 

 red sandstones its lower division. The occurrence of the Upper Si- 

 lurian Tile-stones immediately beneath the Old Red Sandstone, 

 throughout the greater part of its course, favours this view, and there 

 is nothing in the mineral character of the North Devon rocks incon- 

 sistent with it. But it will be premature to attempt to decide the 

 question until we know more of the older rocks of South Wales, and 

 can ascertain whether there are in that district any "Rhenane" beds 

 below, and independent of, the Old Red Sandstone. 



The sandstone with CucuUceoi which occurs at Marw^ood in North 

 Devon, and has not been observed elsewhere, has no representative 

 in South Devon nor in Belgium ; it is doubtful whether this rock 

 should be regarded as a member of the Rhenane or of the Carbonife- 

 rous series. 



It is worthy of remark, that in the State of New York there is a 

 great series of beds characterized by Devonian fossils, below what is 

 considered to be the Old Red Sandstone * . These will now stand on 

 the parallel of the "Rhenane" group of Belgium. 



The section, fig. 2, from the Old Red Sandstone of Brecon to the 

 south of Devonshire, shows the relations of the different rocks upon 

 the scheme advocated in this paper. Their position offers several 

 anomalies ; — on the north we have the Old Red Sandstone of South 

 Wales dipping towards the Linton beds, which are supposed to be older 

 deposits. On the south of the Culm-basin, the fossiliferous beds of 

 S. Petherwin have not yet been well separated from the older deposit 

 of schists and limestones of South Devon, and a similar difficulty 

 occurs again where the Plymouth limestone dips south towards an 

 older group of " Rhenane " rocks. Yet these faults are not more 

 violent than those which M. Dumont has proved to exist in forma- 

 tions of similar ages in Belgium. And when the two sections, figs. 

 1 and 2, are compared, it will be found that the faults are so nearly 

 counterparts in the two districts, as to suggest the idea that they are 

 really continuous. 



Liege and Launceston stand nearly on the same parallel of latitude, 

 and in both districts the general direction of the faults approaches 

 east and west. In both districts we can trace an enormous move- 

 ment prior to the Carboniferous period, which produced great east and 

 west faults, and, by unequal elevation of the masses, brought rocks 

 of very different ages into contact on a common level : thus, the 

 "Rhenane" rocks, both of Linton and of the Hermitage du Sart, 

 form an arched ridge between younger deposits, and reappear to the 

 south less disturbed. These ridges of the older rocks stood above 

 the water in both districts, and the carboniferous beds were deposited 

 in the troughs between them. Somewhat later we find proofs of 

 another great movement along nearly the same lines, by which the 



* Sharpe on the Palaeozoic rocks of N. America, Quart. Journ. Geol. See. A'ol.iv. 

 p. 156. De Verneuil, Bull. Soc. Geol. Fr. 2 Ser. vol. iv. p. 646. 



