480 R. HARKNESS AND H. A. NICHOLSON ON THE STRATA BETWEEN 



such it has its representatives well exposed under the Carboniferous 

 Limestones along the eastern margin of the Lake- district, and also 

 under the Pennine escarpment. 



A short distance east of the conglomerate a porphyry, having a 

 delicate purple tint and containing well-developed crystals of a 

 greenish white felspar, occurs. This porphyry is similar to that 

 which forms the bulk of Lambay. Its purple tint is doubtless 

 due to staining from the purple conglomerate which, in some 

 places, overlies it. 



Fragments of a similar purple porphyry are met with in the Lake- 

 district near Caldbeck ; and in some spots this porphyry is seen in 

 situ overlain by purple conglomerates, when it manifests the same 

 tint as the Portraine porphyry. 



The Portraine porphyry is succeeded by traps and ashes ; and 

 these are seen to occur to beyond the farm-house on the coast. 



At the farm-house the coast trends for a short distance south-east. 

 A little beyond this the ash-beds begin to exhibit trappean fragments 

 in them, the ashes assuming the nature of ash-breccias. The trap 

 fragments, however, are not the only substances which the ashes 

 contain ; calcareous nodules also make their appearance in them. 



Patches of black shale, which show no traces of volcanic origin, 

 are also associated with the ash-beds ; and these black shales afford 

 Graptolites (Climacograptus teretiusculus). These ash-breccias with 

 calcareous nodules and graptolitic shales prevail in greater abun- 

 dance higher in the series ; and in the cliffs under the Martello 

 tower they are seen to be succeeded by fine green- coloured shales 

 so much affected by cleavage that their bedding can scarcely be 

 made out. There are some small faults indicated by Mr. Du Noyer 

 as occurring between where the porphyry is seen and where the 

 green shales make their appearance. These, however, are not of 

 sufficient importance to render the section difficult to interpret. 

 The green shales contain limestone nodules in bands which, though 

 much contorted, indicate distinctly the lines of bedding of the shales, 

 these shales being, no doubt, of ashy origin. Fossils occur in these 

 nodules and also in those which are found in the ash-breccia ; and 

 these fossils are distinctly of a Bala type. 



The " conglomerates," before referred to as seen on the south-east 

 side of Lambay Island, are a portion of the ash-breccia series. They 

 afford the same fossils, and they have the same graptolitic shales 

 accompanying them. 



As regards the horizon in which the nodular ash-breccias occur, 

 as compared with the rocks of the north of England between the 

 Borrowdalc group and the Coniston Flags, it would seem that they 

 must be placed on a parallel with those of Style-End Grassing and 

 with the more amply developed Dufton shales. To the latter they 

 are in part allied by their black shales, and to the former by their 

 ashy nature. They indicate more violent volcanic activity in the 

 locality of their deposition than the Dufton shales, but less powerful 

 igneous influences than in the case of the Style-End Grassing ash- 

 beds, where no black shales occur. 



