112 Mr. Weaver on the Older Stratified 



appear also in the N.W. of Gloucestershire and adjacent parts 

 of Herefordshire*. Now, no one contends that these forma- 

 tions are of the same epoch, but quite the contrary : the Old 

 Red Sandstone here also, be it observed, containing no fossils 

 of the transition aera, nor any other except some vestiges of 

 vegetable remains. And if we refer to Ireland, similar ob- 

 servations maybe made: thus, for example, the same body 

 of Old Red Sandstone, which surrounds the Bilboa mountains, 

 lies near Newport unconformably, and at the outlet of the 

 Bilboa river conformably, on the subjacent clayslate; arising 

 in fact from the variable position of the clayslate strata, while 

 that of the Old Red Sandstone is more constant, being disposed 

 in extended overlying sheets t- It appears needless to multi- 

 ply instances. In all such cases unconformity must assuredly 

 be taken as the governing principle in deciding relative age. 



Now, to apply this to North Devon. While admitting 

 the generally apparent parallelism (namely, conformity of 

 strike, but not necessarily of dip) between the beds of 

 the carboniferous series and the subjacent Trilobite slates, 

 I have adduced two examples of what appeared to me non- 

 conformity; the one in Runson Lane on Rosa Hill, South of 

 Barnstaple, the other in the region of the Pill near Muddle- 

 bridge on the south side of the harbour. In Runson Lane 

 the relations on which I rely may not be very obvious to a 

 passing explorer, as they are not so directly apparent in the 

 road as in the bank above, and even there the relations are 

 partially concealed by soil and herbage, and require close in- 

 spection. Here the coarse shale, which abuts against the 

 Trilobite slate (both dipping south), is inflected to the north, 

 and forms an arched curve overlying the latter, and therefore 

 unconformable. The space exhibited is certainly not consi- 

 derable, yet seemed to me sufficient to determine the fact, 

 when duly examined; while the total dissimilarity in the cha- 

 racters, both mineralogical and zoological, of the coarse shale 

 and the Trilobite slate, is a corroborative. In this part of 

 the section laid before the Geological Society, I did not at- 

 tempt a finished drawing of the accompanying soil, herbage, 

 &c., but simply expressed the fact of unconformity. In the 



tions on parts of Gloucestershire and Somersetshire. § § G, 10, 17, with 

 the Map and Section, No. 2. 



* Geol. Trans. § §. 34. 35. and Section No. 4. Both these examples 

 of unconformity are admitted by Mr. Murchison ; see pp. 444, 456, of the 

 Sihirian system; a work, in the execution of which a most important con- 

 tribution has been made to geological science, affording ample evidence of 

 the unwearied zeal and diligence of the author. 



t Gcol. Trans., vol. v. Memoir on the East of Ireland, §. 139. 



