118 REMARKS ON THE 



productions. I therefore expected to meet with a perfect epi- 

 tome of the Wernerian System, containing the usual series of 

 primitive rocks, descending from granite, through gneiss, mica- 

 slate, and clay-slate, with all the et cceteras of serpentines, traps 

 and porphyries ; but in this I was mistaken. 



On my approach to Exeter through Somerset, I first obser- 

 ved the transition strata . between Bridgewater and Taunton ; 

 (Nos. 1. &2.*) and from thence traced them,more or less distinct- 

 ly, till I crossed the river Teign, which bounds Dartmore on 

 the east. Thus far great part of the country is very flat, some of 

 it extremely hilly as a road, but none of it mountainous. The 

 transition strata are by no means continuous, and in many 

 places appear only in small projections above the surface. 



On the right bank of the Teign, the road winds up the side 

 of a steep hill ; and where the rock is cut, there is a consider- 

 able display of strata, having all the external appearance of 

 grauwacke. On examining it, I found some of the strata 

 coarser than others ; but, in general, the grain was extremely 

 fine, (Nos. 5, 6, 7.) the texture solid and compact, the colour 

 very dark-grey : it was very tough under the hammer, it broke 

 with a smooth, and somewhat conchoidal fracture, and did 

 not split into the thin laminae of the grauwacke-slate. 

 This appearance puzzled me at first ; the rock presented 

 all the external characters of grauwacke, and yet internal- 

 ly it was different. I had not proceeded many paces, how- 

 ever, when I came upon Granite, (No. 8.) the proximity 

 of which, as before mentioned, is always marked by a 

 very material alteration in the consistence of the adjoin- 

 ing rock. This alteration, I observe, was not unnoticed by 

 Dr Berger, in his interesting paper f on the physical structure 



of 



* The numbers refer to the Appendix, at the end of this paper, 

 f Geological Transactions, vol. i. p. 112. 



