20 Remarks on the Transition Rocks of Werner. 
same nature, some specimens having been given me by @ 
member of this society, taken from the summit of Snow= 
don. Grauwacke, according to Mr. Aikin, makes its ap- 
pearance at Church Stretton in Shropshire*; and near Hay, 
on the border of Hereford, I observed it myself. 
A great part of Somerset, and, finally, the whole of 
Devon and Cornwall, again excepting the granite, and a 
small portion of serpentine, and some other rocks, are all 
composed of transition strata. Thus, by extending a line 
almost due south, from Berwick to the English Channel, 
we shall find a large proportion of the country to the west 
composed of transition rocks; while, so far as I know, 
none occurs to the east of it; although it is probable that 
at Mount Sorrel in Leicestershire some of the same series 
may be found. 
We are still fess acquainted with the precise limits of its 
extent in Ireland: we know, however, that it occupies the 
coast from Belfast Lough to the mountains of Morne, 
which are of granite; it also extends westward as far as 
Monaghan, and probably much beyond that point. From 
what Mr. Weld states, in his account of Killarney, it ap- 
pears to be the principal rock of the Kerry mountains, and 
T know it occurs in great abundance in the county of 
Cork. 
Hence, even with the little information we possess re- 
specting its exact limits, we have enovgh to know, that 
‘the transition rocks form a very large proportion of the su- 
perficial extent of Great Britain and Ireland, and also com- 
prehend the principal mining districts. 
Having thus imperfectly chalked out the boundaries, or 
rather localities, of the transition districts in these islands, 
T shalt endeavour to show that some of the rocks of Corn- » 
wall are grauwacke, ‘in all respects similar to some of the 
south of Scotland; and if strata may be compared to the 
leaves of a book, a few decided and indisputable specimens 
are sufficient to characterize a district. 
It was in consequence of some observations during a 
tour through Cornwall and Devon last summer, that I was 
led to suspect this class stood in a different relation in point 
of period, with respect to granite, from that which I had 
hitherto conceived : greater experience, or perhaps sufficient 
attention to the writings of Dr. Hutton, might have pointed 
out this before. Had I looked more attentively into his 
description of the granite district of Galloway, and at the 
* Geological Transactions, vol. i. p. 212. 
same 
