242 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 22, 



have their analogues among the green slates which are associated 

 with the porphyries and ash-beds of the Lake-district. 



Dufton Piife (1578 feet), which is on the south side of Swindale 

 Beck, has, on its northern side, porphyries resembling those which 

 make up Knock Pike ; and these are not confined to the northern 

 slope of Dufton Pike, for they form the principal portion of this 

 hill. These porphyries are penetrated by a mass of fine-grained 

 granite, as seen in a field caUed Barky Close. This granite extends 

 westwards, and is also seen in the narrow road immediately below 

 the farm of Halsteads. It possesses many of the features of felstone, 

 and has crystals of mica disseminated through it. Its occurrence 

 here, and its nature, have been noticed by Dr. Buckland *. 



The porphyries which form the balk of Dufton Pike also make 

 up the mass of Brownber (1695 feet), a hill lying about half a mile 

 north-east of Dufton Pike. The north-eastern side of Brownbar 

 comes abruptly against the newer Palaeozoic rocks. Brownbar 

 is separated from Dufton Pike by a deep narrow valley, a continua- 

 tion S.S.E. of the valley which separates Knock Pike from Flagdaw. 



Although the great mass of Dufton Pike consists of hard por- 

 phyries, these are not the exclusive components of this hill. Its 

 south-east side exhibits rocks which are distinctly laminated, which 

 have a well-marked cleavage, and which are composed of felspathic 

 ashes. These ashy rocks have been partially quarried on the south- 

 east side of Dufton Pike. They mark a considerable change in the 

 nature of the rocks in this area ; and they are succeeded by other 

 rocks stiU further removed from the porphyritic series. 



Immediately south-east of the base of Dufton Pike is an area 

 having a very different outline from the conical-hill country just 

 aUuded to. This area possesses gently undulating features, and is 

 drained by small streams which alone afford exposures of rock. 

 One of these, named Pusgill, flows along the south-east base of 

 Dufton Pike, and the rocks intersected by this stream consist of 

 dark flaggy shales impressed with a distinct cleavage ; and these 

 shales, wherever they occur in the bed of the stream, are highly 

 fossiliferous along the laminas of deposition f. Rocks of the same 

 nature are also seen in the course of the small stream (Dufton Syke) 

 which suppMes the village of Dufton with water ; and the strata 

 here are even more fossiliferous than in Pusgill. The dark flaggy 

 fossiliferous shales also occur in Billy's Beck, where this stream in- 

 tersects Bale Moor ; and we have them still further to the south- 

 east, in the bed of Harthwaite Syke. 



These dark-coloured fossiliferous flaggy rocks, which have a S.S.E. 

 dip, occupy a zone, measured on their dip, of more than three- 

 quarters of a mile wide ; and, like the porphyries, they too pass 

 under the Newer Palaeozoic rocks on the north-east, and on the 

 south-west they are brought into contact with the Upper Permian 



* Trans. Geol. Soc. 1st series, vol. iv. p. 109. 



t My attention was first directed to the fossiliferous nature of the Pusgill 

 shales by Mr. Wallace, of Dufton, the author of ' The Mineral Deposits of 

 Alston Moor.' 



