62 Prof. Sedgwick on the general Structure 



lations of the central carboniferous chain to the secondary zones of the great 

 cluster of the Cumbrian mountains. But there is still one difficulty to be 

 explained. Beyond Stainmoor, the western border of the central chain de- 

 flectSj as before stated, considerably towards the north-west, and rises into an 

 escarpment, partly made up of mural precipices, which overlooks the plain of 

 the new red sandstone in the vale of the Eden, and in the crest of Cross Fell 

 reaches the elevation of 2900 feet. On the contrary, the northern calcareous 

 zone of the Cumbrian system dips under the plain of the new red sandstone, 

 and along the course of the Eden, lies buried probably many hundred feet 

 below the surface. This relative position is explained in a transverse section 

 from the central mountains to the ridge of Cross Fell : and it seems impossible 

 to account for the collocation of the two carboniferous systems without the 

 intervention of 2l fault ranging somewhere near the base of the chain of Cross 

 Fell, and producing an enormous upcast to the north-east*. The misappre- 

 hension of this fault formerly introduced a great error into certain published 

 sections, in which the new red sandstone of the Eden was placed under the 

 whole system of Cross Fellf . 



Fortunately in this, as in the former case, we have better evidence than a 

 mere inference ; for in following the escarpment from any portion of the Cross 

 Fell chain to the foot of Stainmoor (the key of the whole position), we have 

 a manifestation of the true nature of the fault, and on a scale hardly to be 

 rivalled in any other part of our island J. A little before we reach Brough, 

 there commences a steep craggy mountain ridge, ranging parallel to the prin- 

 cipal escarpment ; from which it is separated by a ravine several hundred 

 feet in depth. On entering this ravine, we find ourselves on the very line of 

 an ancient convulsion, by which the whole craggy ridge has been torn off 

 from the escarpment, and tumbled over into the valley, in which it now stands 

 on edge ; every part of it being inclined at a very great angle. It is of vast 

 thickness, and probably includes nearly the whole calcareous system of Cross 

 Fell : but its upper beds are buried under the alluvion of the new red sand- 

 stone. 



These inclined beds (on a part of which stands the town of Brough) are 

 prolonged to the foot of Stainmoor, and thus brought into contact with the 

 dislocated beds thrown down from the opposite side of the valley by the great 



* See PI. V. fig. 6, 



t See a paper by Professor Buckland (Geol. Trans., First Series, vol. iv. p. 105), in which this 

 mistake is rectified. 



J There are some other places near the base of the carboniferous chain where we meet with in- 

 dications of the'nature of the Cross Fell fault. (See Geol. Trans., First Series, vol. iv. PL V. figs. 2 

 and 3.) But in none of them is the evidence comparable to that exhibited in the Brough section. 



