72 Rev. A. Sedgwick on the Geological Relations and 



areat thickness. The lower part consists of the usual yellow sand and soft sand rock ; over them 

 arc various irregular false-bedded red masses containing concretions of reddle, and resembling the 

 most ordinary varieties of new red sandstone : and over these are beds of yellow sand and sand- 

 stone immediately supporting the limestone. 



Such are the mineralogical characters and geological relations of the lower 

 red sandstone, which I have given with the more detail, because no general 

 description of it has yet been published. Indeed before the appearance of 

 Mr. Smith's geological map of Yorkshire, it seems to have been almost over- 

 looked in our own country, though it occupies the precise place of the rothe- 

 todte-liegende, which has been so often described by the geologists of the 

 continent. By it we are, therefore, enabled, not merely to add a new member 

 to the series of English secondary formations, but to establish a new term of 

 comparison between the physical history of our own country, and that of the 

 remote parts of the European basin. 



During my two first visits to the county of Durham, I did not meet any- 

 practical men who appeared to have the least knowledge of the existence of 

 the remarkable formation I have been describing. But since the prosecution 

 of the great coal-works within the limits of the magnesian limestone, they have 

 become acquainted with the existence and continuity of the inferior sandstone; 

 and now count upon its appearance in the sinkings of the shafts like any of 

 the more regular strata of the district. Unfortunately, from its incoherent 

 nature, it affords so free a passage to the water, that we might assert, without 

 much exaggeration, that great subterranean rivers circulate in some parts of 

 the county between the limestone and the coal-measures. Through these 

 strata of incoherent sand and of water most of the coal-shafts must necessarily 

 pierce, which commence in the higher formation. To the success of opera- 

 tions of this kind one situation may be more favourable than another: the 

 inferior sandstone may be of inconsiderable thickness, or may perhaps be 

 wanting altogether ; but no one would be justified in anticipating such a result 

 before trial. And it is not I think too much to assert, that whoever shall under- 

 take to sink any coal-shafts on the east side of the limestone escarpment, 

 between Thrislington Gap and the Wear, must be prepared to encounter 

 very great difficulties, and to overcome an enormous discharge of water*. 



* The subject hinted at in the text is undoubtedly one of great practical importance. I there, 

 fore think it right to state one or two facts in support of the opinion I have advanced. 1. In the 

 sinking of the Hetton pit, though the lower sandstone was reduced to the thickness of a few feet, 

 there was a great discharge of water between the limestone and the coal-measures, which was 

 only reduced by iron tubs at an enormous expense. 2. At Eppleton pit (about three-quarters 

 of a mile N.E. of the former) the lower sandstone was 126 feet thick, and discharged water at 



