296 J. G. Goodchild — The Coniston Limestone Series. 



Below the Upper Shale-and-limestone series, which represents 

 the Coniston Limestone Series of the areas to the west, there rises 

 a thick mass of rhyolitic tuffs, which form the Pikes of Dufton, 

 Knock, the north end of Eake Brow, Melmerby, and several other 

 smaller eminences in the district. They are quite conformable to 

 the overlying shales. Their base is not clearly seen anywhere here ; 

 but quite enough of them is exposed to show that they are not less 

 than 1100 feet in thickness. This, there is reason to believe, is not 

 far from their full vertical extent. Except that these rocks are (as 

 I believe) of pyroclastic origin everywhere in this area, they very 

 closely resemble the rhyolitic series that underlies the Coniston. 

 Limestone west of Shap, and there cannot be much doubt about 

 their actual contemporaneity. 



With the general distribution of these in the Cross Fell area wo 

 are not at present concerned. But their presence in the neighbour- 

 hood of Eoman Fell has been misinterpreted. Considering the 

 complicated nature of the geology there, this can hardly be wondered 

 at. The facts as they appear to me are of the following kind : — 

 Between the village of Helton and the flanks of Roman Fell, 

 Coniston Shales of the ordinary type are seen at many places from 

 Helton Beck southward. They are cut off on the south-west by the 

 Outer Pennine Fault, which brings the Bunter (or St. Bees) Sand- 

 stones and Shales directly against them. The Coniston Shales dip 

 towards the north-west at rather high angles. So that as their out- 

 crops are traced towards the south-east, their base is reached about 

 five hundred yards to the south-east of Helton Beck. Then rises 

 from beneath them here, as elsewhere in this part of England, a 

 mass of rhyolitic tuffs of exactly the same nature as those of Dufton 

 Pike, Knock Pike, etc. These form the small hill known as the 

 Seat. The Outer Pennine Fault runs close alongside this hill, and 

 cuts off these tuffs on the south-west, bringing the St. Bees Sand- 

 stones into direct contact with them for a distance of several hundred 

 yards, as may be seen in the course of Helton Sike. 



On the eastern side of the Seat ranges one of the Middle Pennine 

 Faults, which here brings up against the rhyolite tuffs a narrow 

 strip of the alternations of submarine tuffs and argillites, which 

 represent the seaward equivalents of the Borradale Series, and which 

 1 have named the Milburn Rocks. These in turn are cut off by 

 another fault ranging nearer to Roman Fell. The effect of this 

 fault is to let in a strip of volcanic rocks of yet a different type. It 

 is these with which we are specially concerned at present. Under 

 the name of the Roman Fell Volcanic Series, specimens collected 

 and fully labelled by myself were for several years from 1876 

 onward on exhibition in the Rock Collection at the Museum of 

 Practical Geology. I have reason to know that Mr. Marr has long 

 been acquainted with the specimens in question ; though I under- 

 stand from him that he has not actually seen them in situ. 



On the ground, these Helton Moor Volcanic Rocks may be readily 

 found by any one used to field geology, if he will cross the Moor 

 from the Smelt Mill at Helton along a direct line connecting that 



