262 



NORBURY AND LINLEY HILLS. 



As the copper veins penetrate equally the slate of the Cambrian System and the 

 overlying Caradoc deposit, it is clear that their formation took place not only after 

 these rocks were consolidated, but also subsequent to those dislocations by which 

 they were thrown into their present relations. Indeed, the evidences in this neigh- 

 bourhood enable us to go still further, and to infer that the veins were in some way 

 connected with, if not resulting from, the intrusion of igneous rocks among the strata : 

 for not only do we find the strata most veined and charged with ore when they are con- 

 tiguous to or included between such trap rocks, but we also see that the veins stop 

 where they meet with bosses of the latter, the ores of copper merely lining the adjacent 

 chinks and fissures. I particularly noticed this fact in certain quarries of green, granular, 

 and compact felspar north of the road between Wentnor and Norbury, and where, 

 besides the green and blue carbonates of copper, the cracks were coated with black oxide 

 of iron. 



We may now proceed to consider the structure of some of the other trap rocks of 

 this immediate district, or those which have burst out in fissures through the strata of 

 the Cambrian System. 



Norbury and Linley Hills. — These hills lie between the north-western face of the 

 Longmynd, with which it has been shown they are intimately united, and the remark- 

 able serrated and altered ridge called the " Stiper stones." 



The elevation on which the village of Wentnor stands, at the south -western termination of one 

 of the ridges, affords an instructive example of their composition. 



In the rugged road which ascends from the Walk Mill (Fuller's Mill) to the Church, the principal 

 mass consists of vertical, contorted, indurated beds of purplish-red sandstone and grit, of the same 

 nature as in the Longmynd ; and through their ends rise various wart-like bosses of trap, precisely 

 in the manner described in the Little Stretton Brook, (wood-cut, p. 259.) The trap is a greenstone, 

 in parts concretionary and amygdaloidal, but principally dark-coloured, and made up of compact 

 felspar and hornblende. The shale in contact has occasionally the aspect of Lydian stone, and the 

 sandstone is very hard and sometimes much veined. 



Near Gravenor Bridge is a dyke twelve to fourteen paces wide, of dark-coloured crystalline green- 

 stone, containing small concretions of white compact felspar ; the sandstone in contact with the trap 

 is indurated. Several other protuberances of more or less finely or coarsely granular greenstone jut 

 out on the sides of Gravenor and Norbury Hills, marking the south-western prolongation of those 

 outbursts, which are to be traced to the north-west on the sides of a small brook as far as the 

 Bridges. On the eastern flank of the Stiper Stones, nearly opposite the centre of the ridge, is a 

 prominent mass of trap, a part of which is called the "Calf Knolls." It is nearly a mile in length 



had coatings of grey copper. (See explanation of the origin of Llandrindod and other mineral sources in the 

 twenty-sixth chapter.) 



Dr. Du Gard, who analysed this water many years ago, found the chief ingredients to be the muriates of 

 soda, lime and magnesia, the first in much the greatest abundance ; with minute quantities of the carbonates 

 of lime, iron, and magnesia, and a trace of vegetable matter. The proportions of saline contents probably vary 

 in different seasons. 



