90 Olservalions on the Geology 



average thickness is about nine yards. Below this hmestone the 

 great mass of whinstone in some parts makes its appearance ; 

 the thickness is from sixteen to sixty yards. 



The lowest great limestone called the Melmerby scar lime- 

 stons is by far the most considerable, being 42 yards in thick- 

 ness. It is so called from its occurrence at Melmerby scar (or 

 cliff) in Cumberland. This bed nearly equals in thickness the 

 vast beds of limestone in Derbyshire, and Craven on the north- 

 west of Yorkshire. Some few beds of hmestone, but of miaor 

 importance, lie below the Melmerby scar limestone. The total 

 thickness of the strata between the latter and the red sandstone 

 is about one hundred and twenty yards. The red sandstone 

 called by the Germans the old red sandstone, or the first floetz 

 sandstone of Werner, I believe, has no where been directly sunk 

 through, nor is its exact thickness known. 



Mr. Forster's section comprises, as before stated, both the coal 

 and the metalliferous limestone districts, closing with the red 

 sandstone. I have extended the horizontal sketch beyond the 

 schistose and porphyritic mountains westward, where we again 

 meet with thick beds of stratified siindstone and coal dipping 

 into the Irish sea. 



It is foreign to the purpose of the present letter to enlarge the 

 account of this side of tlie island. I shall only observe tliat 

 the rocks which compose t^he mountains near the lalics are well 

 known to geologists to belong to that class whicli present few re- 

 gular features of stratification (and I maght add, with few excep- 

 tions,) nor any regular order of succession. T!ie beds and tabular 

 masses where these u;iouiitains are schistose are very elevated, or 

 nearly vertical. Mr. Forster, whose observation^ appear to have 

 been principally confined to stratified parallel rocks intersected 

 occasionally by perpendicular veins and dykes, describes the 

 whole mass of the Cumberland mountains cutting through the 

 stratified rocks, as an enormous dyke or vein of what lie calls 

 blue rock. *' The most remarkable dyke (he says) that wc find 

 in the north of England, is the great blue rock at Keswick, which 

 ill some places is ten or twelve miles wide, and may be traced 

 into Wales to the southward and into Scotland northward." Ex- 

 travagant as this description may at first appear, it coincides in 

 substance with the system of those geologists who suppose that 

 primary and transition mountains iiave been melted or softened by 

 subterranean fire, and thrust through the superficial covering of 

 the globe. I should not have thought it necessary to quote a 

 description involved in the language of hypothesis ; but I con- 

 sider the opinions of practical men on any department of nature 

 with which they are familiar, as deserving some attention, whether 

 such ojiinions coincide with or oppose the fashionable theories 

 of cabinet philosophers. The 



