liocJcs of North Devon^ ^c. 113 



other case, near Miuldlebritlge, I derived the unconformity 

 partly from observation, partly from inference. There the 

 Fremington limestone and shale form an arched curve, broken 

 at the surface, supporting on each side the sandstone of the 

 coal-measures, the latter being in mass on the southern side, 

 but appearing only as a remnant on the northern side ; in 

 the former case dipping 70° to the S. W. and in the latter 50° 

 to the N.E. The immediate contact of these carboniferous 

 strata with the subjacent Trilobite slates is not visible, but in 

 the nearest adjoining portion of the latter formation exposed 

 to our view, namely, in the Bickington quarries on the east, 

 we find the dip of the beds to be 60° to the southward. If 

 then we suppose, as we are justified in doing, that these beds 

 extend to the westward under the carboniferous strata near 

 Muddlebridge, the unconformity of the two formations be- 

 comes manifest. The nearest Trilobite slates seen on the 

 north show also a southerly dip. It was to illustrate these 

 relations that I constructed the diagrams of a plan and section 

 in the region of Muddlebridge, as laid before the Geological 

 Society. 



On the other hand, if we proceed to the southern side of 

 the Devonshire carboniferous trough, it is admitted that in 

 one case at least an unconformity is observable between the 

 carboniferous series and the subjacent schistose rocks*, al- 

 though a general coincidence or parallelism in the strike of 

 their respective strata may be apparent adjacent to their 

 boundary line ; but the culmiferous series in a part of its ex- 

 tent is said to rest also upon granite. Mr. Austen, however, 

 has repeatedly stated that the culmiferous measures in South 

 Devon rest unconformably upon a series of deposits belonging 

 to the transition system f ; and some of the remarks of Mr. 

 De la Beche in that quarter are much to the same effect J. 



That the carboniferous group of Devon should be directly 

 deposited on rocks of the transition epoch, without the inter- 

 vention of the Old Red Sandstone, should not surprise us, since 

 analogous occurrences may be noticed in other parts of the 

 island, e. g. in those portions of Pembroke, Westmoreland, 

 and Cumberland where the Old Red Sandstone is wanting; 

 so also in the South of Ireland. Nay, in some quarters of 

 the world coal tracts are found reposing immediately on gra- 

 nite, e.g. in France and in Virginia, U.S. From the mere 



* Proceedings of the Geological Society, May 1838, p. 681 ; and Lend, 

 and Edin. Pliil. Mag., vol. xiv. April 1839, p. 24G, note, 



t Proceedings of Geol. Society, Dec. 1837, pp. 586, 588 ; and Ibid. 

 April 34th, 1839. 



X Geol. Report on Cornwall, Devon, and W. Somerset, pp. 61 , 107, HI. 

 Fhil. Mag. S. 3. Vol. 15. No. 94. A\ig. 1839. I 



