116 



REMARKS ON THE 



district of parallel strata, including the coal-fields of Warring- 

 ton and Wigan, and the great alluvial deposite of Cheshire. 

 These bring us to the neighbourhood of the Welch mountains, 

 which I believe are all of the same nature, some specimens ha- 

 ving been given me by a member of this Society, taken from 

 the summit of Snowden. Grauwacke, according to Mr Aik.n, 

 makes its appearance at Church Stretton in Shropshire * ; 

 and near Hay, on the border of Hereford, I observed it my- 

 self. 



A great part of Somerset, and, finally, the whole of Devon 

 and Cornwall, again excepting the granite, and a small por- 

 tion 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 ; al- 

 though it is probable, that at Mount Sorrel in Leicestershire, 

 some of the same series may be found. 



We are still less acquainted with the precise limits of its ex- 

 tent in Ireland : we know, however, that it occupies the coast, 

 from Belfast Lough to the mountains of Morne, which are of 

 oranite ; 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 appears to be the princi- 

 pal rock of the Kerry mountains, and I know it occurs in great, 

 abundance in the county of Cork. 



Hence, even with the little information we possess respect- 

 in a its exact limits, we have enough to know, that the transi- 

 tion rocks form a very large proportion of the superficial ex- 

 tent of Great Britain and Ireland, and also comprehend the 

 principal mining districts. 



Having 



* Geological Transactions, vol. i. p. 212. 



