﻿Correspondence — Mr. W. Giinn. 139 



Silurian rock exposed. The north side of Murton Pike forms the 

 south side of the Gill here, and is almost entirely Silurian rock ; 

 indeed, the west side of this Pike is wholly Silurian up to its sum- 

 mit. Next, further up the Gill, is the Old Eed Sandstone. Then 

 still higher up occur the escarpments of the alternating limestones, 

 sandstones, and shales of the Carboniferous series, including the 

 Melmerby Scar Limestone, which is the thickest bed of limestone on 

 this part of the chain. Above this series, at the head of the Gill, we 

 come to the Whin Sill, where a considerable quantity of its debris 

 lies at its foot. More Carboniferous rocks take on above the Whin 

 Sill, and slope backward each way to form the summit of the ridge 

 on the north and south sides of the Nick. As to the thickness of 

 the strata from the base of the Carboniferous rocks, in this section, 

 to the bottom of the Whin Sill, I cannot do more than give a pro- 

 bable estimate, and will venture to put it down at about 1000 feet. 

 Should this thickness be near the truth, as I expect it may, and if 

 the same thickness, or nearly so, occurs from the base of the Car- 

 boniferous rocks to the bottom of the Whin Sill, at the old Pencil 

 Mill, then, I think it may be fairly concluded that, the Silurian-like 

 shale, at this place, is not real Silurian, but indurated carboniferous 

 shale, and, therefore, the base of the Carboniferous rocks must be 

 considerably below the bottom of the valley of the Tees at either 

 Falcon Clints or the old Pencil Mill. The section at High Force, 

 about two miles further down the Tees from this place, affords 

 additional evidence, corroborative of the soundness of the conclusion, 

 that the base of the Carboniferous rocks cannot be seen in Teesdale. 

 1 may here refer Mr. Dakyns, or any of your readers, to that brief 

 abstract of a paper on this section, by C. T. Ciough, Esq., B.A., 

 F.G.S., in the Geological Magazine for October, 1876, page 474. 



Before leaving the subject, I may, however, state that there is a 

 possibility of some peculiar positions of the strata, such as a great 

 upward bend, or the upcast of a considerable dislocation, bringing 

 the base of the rocks in question to view. The Burtree Ford dyke 

 has a course nearly north and south ; it ranges up the east Allen to 

 the west of Allenheads, thence through Weardale, at Burtree Ford ; 

 and Mr. Forster, in his section of the strata, states that it crosses the 

 Tees at Cronkley Scars. In Weardale this dyke brings rocks up 

 to view, which would not have been seen, had the dyke not existed. 



There is some probability that it might produce a similar effect 

 where it crosses through Teesdale ; but whether it does so or not, 

 will be known by those who are better acquainted with the rocks 

 in that part of Teesdale than I am. John Curey. 



BOLTSBURN, EaSTGATE, DaRLINGTON, 



February oth, 1877. 



IS THEEE A BASE TO THE CAEBONIFEROUS ROCKS IN TEESDALE ? 



Sir, — My friend Mr. Dakyns, in the last Number of your Magazize, 

 asks the question, " Is there a base to the Carboniferous rocks in 

 Teesdale?" Permit me, on behalf of my colleague Mr. Clough and 

 for myself, to answer the question in the affirmative. We cannot 



