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comparative effects of a slight and of a very decided unconformity 

 along lines of the same length. The first figure may be supposed 

 to show (diagrammatically) the relations of the Permian and 

 Carboniferous rocks east of Rotherham. The second, their 

 relations south of Wigton. 



Now, it is obvious that everywhere near Rotherham Upper 

 Coal Measures form the surface, and that a boring there would 

 reach the more productive Middle Coal Measures sooner or later ; 

 while in Cumberland it might, though equally near the Permian 

 boundary, be entirely through Lower Carboniferous rocks. And 

 as the coal seams of the Lower Carboniferous rocks are very 

 inferior both in number and thickness to those of the Coal- 

 Measures proper, and are, indeed, seldom worth working, it is 

 evident that to ascertain the true geological horizon of the 

 red-stained rocks is a matter of very considerable practical 

 importance. But as no distinction of colour invariably separates 

 Coal-Measures from Lower Carboniferous rocks, the horizon to 

 which red-stained Carboniferous beds belong, in any given locality, 

 can only be made out after long and careful study of the whole 

 district. On the other hand, the colour-test distinguishing Car- 

 boniferous from Permian rocks has never hitherto been found to 

 fail. But as the older geological writers on the district missed the 

 true significance of the various colours, I will first give some 

 account of the older views, which are set forth in the valuable 

 paper by the late Mr. Matthias Dunn on the Coalfields of Cum- 

 berland, which was written more than twenty years ago.* 



When Dunn wrote, the evident unconformity of the Whitehaven 

 Sandstone to the ordinary Coal-Measures (at Whitehaven) had 

 caused it to be classed as Permian, or, as he prefers to term it, 

 "New Red Sandstone." In the neighbourhood of Rose Gill 

 Colliery (S.W. of Bullgill Railway Station), the Whitehaven Sand- 

 stone is shown in many quarries, and is called by Dunn the 

 "Lower Red Sandstone." He notices the difference of colour 

 between the " Lower" and " Upper" Sandstones, and writes : — 

 " The formation of the New Red Sandstone is comprised in two 

 * North Eng. Inst. Min. Eng., vol. viii., 1859-60. 

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