- 
Remarks on the Transition Rocks of Werner. 94 
same time attended to the nature of the stratified rock of 
which that country is principally composed, this fact would 
-not have been new to me now. There were other circum- 
stances, however, which severally contributed to prevent 
me from supposing that grauwacke could occur in this po- 
sition. ; 
First, the unlimited use to which Dr. Hutton applied the- 
term alpine schistus, left us quite uncertain with respect to 
the species of rock he meant: secondly, the alteration in- 
duced on grauwacke, near its junction with granite,—a cir- 
camstance so strikingly exemplified in Galloway, that [own 
it deceived myself; and, lastly, the assertion I have so 
often heard repeated by the Wernerian geognosts, that 
granite veins never occurred excepting in rocks formed of 
the same constituents, alluding to gneiss and rica-slate. 
Before I visited Cornwall, [ knew that granite abounded 
in the Stannaries, and that tin and wolfram, metals which 
are considered nearly of the highest antiquity, were there 
common productions. I therefore expected to mect with 
a perfect epitome of the Wernerian system, containing the 
usual series of primitive rocks, descending from granite, 
through gneiss, mica-slate, and clay-slate, with all the ef 
ceteras of serpentines, traps and porphyries; but in this 
I was mistaken. 
On my approach to Exeter through Somerset, I first ob- 
served the transition strata between Bridgewater and Taun- 
ton; (Nos. 1 and 2*) and from thence traced them, more 
or less distinctly, till {£ 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 
RO Means continuous, and im many places appear only ia 
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 
considerable display of strata, having all the external ap- 
pearance 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-gray: it was very tough un- 
der the hammer, it broke with a smooth and somewhat 
conchoidal fracture, and did not split into the thin laminz 
of the grauwacke-slate. This appearance puzzled me at 
first; the rock presented all the external characters of grau- 
* The numbers refer to the Appendix, at the end of this parer. 
B3 wacke, 
