1 24 The Rev. D. Williams's Proofs that the Devonian 



thesis, in lithological characters and common associations, we 

 are somewhat prepared to expect that superposition, the only 

 law we possess, may add the force and authority of its posi- 

 tive proofs to the abundant plausible reasons we have met with, 

 and dissipate this cabinet hypothesis into its original elements, 

 by confirming the respective independence and individuality 

 of the several formations which it has been attempted to class 

 in common. 



I presume if I show by abundant evidences afforded in 

 nearly all parts along the confines of the killas and culm 

 rocks (from one extremity to the other an irregular line of 

 about seventy miles), that the killas overlies the culm-Jield — a 

 great truth, which is proved everywhere and contradicted no- 

 vohere — it will sufficiently demonstrate that neither the killas 

 slates of Devon and Cornwall, nor anything below them can 

 possibly be the equivalent of the Old Ked Sandstone; that the 

 floriferous series, or so called culm-measures, can in no sense 

 represent the great English coal-field ; and that the Coddon 

 Hill grit with its Posidonia limestones, which underlie them 

 both, never can be raised to the parallel of the mountain 

 limestone. 



I was occupied for as much time as I could spare of two 

 years, in taking observations along those confines, and I state 

 it without affectation, that at times I was in an agony of em- 

 barrassment at the facts I met with, till I discovered at Ashton 

 and Doddiscomb Leigh, on the north of Chudleigh, the Cod- 

 don Hill grit with its Posidonia limestone brought up in a 

 broad anticlinal line, entailing a permanent northern dip on 

 the floriferous beds to the north of it, and an equally perma- 

 nent southern dip on the floriferous rocks, with their included 

 coral limestones and killas on the south of it. 



I may here observe, that beyond an a priori view which had 

 commonly been entertained of the paramount high antiquity 

 of the killas (with which atone time I was as much impressed 

 as any one), founded on its supposed inorganic character, and 

 its metalliferous and mineral peculiarities, no reason could be 

 assigned for it, drawn from undisputed evidences of its infra- 

 position ; it was a sort of problem which had been solved by 

 common consent, although no one had troubled himself to 

 discuss the elements. 



It is necessary here that I refer your readers to a section 

 I gave of this region from the Bristol to the British Channel, 

 in your Journal for January 1840, page 60 ; if they could re- 

 fer to the Ordnance or any good map, also, I should be better 

 understood. In that section it will be seen that No. 8, the 

 Coddon Hill grits, which constitute the lower division or base 



