The Rev. D.Williams on theGeology of Devon Sf Cornwall. 61 



south-west of Callington, with those which had been pro- 

 cured from the fine culm shales near Bideford. I believe it 

 to be an impossibility, on account of the same coarseness of 

 the matrix in the great outlier, as exists everywhere, that I 

 have seen, in the rocks of the floriferous series generally, 

 where I have never met with clearly defined specimens, ex- 

 cept in the finer culm-shales just mentioned. All I am pre- 

 pared to prove then is, that about St. Mellion and Pillaton, 

 between Callington and Plymouth, plants in the same imper- 

 foot condition are found in precisely the same slates and 

 shales^ which are parted by thick beds of the same sandstone, 

 and in intimate association with that singidarly characterized 

 and unique formation the Coddon Hill grit ; there is the same 

 triple association of the same rocks, and in the same order of 

 succession, that we witness in the base line of the floriferous 

 series along the north and south borders of the trough, and 

 where on earth could they come from if not from the same 

 sources which supplied the constituents of the same rocks 

 elsewhere in the same county ? The only deviation on the 

 S. and S.W. of Callington from the normal types of the flo- 

 riferous series elsewhere, is frequent intercalations in it of 

 undoubted killas, and beds of a composite or neutral charac- 

 ter, constituted of moieties of killas and Coddon Hill grit, or 

 of killas and floriferous, round the confines of the outlier; 

 seen not only in repeated alternation, but in other instances, 

 their wedge-shaped extremities interlocking into each other 

 like the teeth of a rat-gin. Here, as elsewhere along the con- 

 fines of these two vast formations, Nos. 9 and 10, whether 

 we advance towards the floriferous area on the one hand, or 

 towards the killas on the other, we distinctly observe the one 

 becoming thinner and evanescent as the other augments into 

 unity and fulness. 



Nature has manifestly conducted her operations of deposi- 

 tion and elevation in this region on a vast scale, and if her 

 works be not regarded in their just proportions, we never 

 shall arrive at the truth : thus as we explore the confines of 

 Nos. 9 and 10, we are startled almost at the vastness of the 

 ties and adjustments by which they are indissolubly united, 

 till we reflect that they are only in a ratio to the magnitude 

 and dimensions of their respective masses ; that it is only the 

 same transition and alternation on a larger scale, that we ob- 

 serve throughout Exmoor between the several members from 

 No. 2 to No. 9, on a smaller ; for while I hesitate as to the 

 diameter of No. 9 ; No. 10, I repeat, is upwards of eight 

 miles, measured according to Professor Playfair. Thus again, 

 if we take a coup d'ceil view of this country from one channel 



