BASAL CAMBRIAN ROCKS OF SHROPSHIRE. 393 



On leaving the Drift, west of Colliersley, we come upon some 

 rugged masses composed of purple-weathering slate in a nearly ver- 

 tical position, and with the usual jN'.N.E. strike. On reaching the 

 summit of the crest, the purple slate suddenly gives place to a great 

 mass of purple grit without bedding and full of large fragments of 

 slate. The line of junction is not very clearly seen, but seems to be 

 a little transverse to the line of strike in the slates. Other beds of 

 slate, however, in the road to the south strike directly at this mass. 

 There is slate on the other side of it in the road to the west, and 

 only a feeble indication of the grit is seen at the cross roads, appa- 

 rently superficial. Thus if the purple grit be not here unconform- 

 ably overlying the slate beds, it must be a local band within them. 

 But this last appears impossible, as it lies across their strike. From 

 this point it seems obvious that the junction sought is to be traced 

 at the base of the mass of purple grit. 



From the cross roads the purple grit may be traced towards the 

 S.W. by the farm of Queensbounty by the entire covering of the fields 

 with its fragments, till we reach the eastern slope of High Eank 

 Hollow, where quarries are worked in it, and crags of it are exposed 

 for a certain distance along the slope ; while to the base to the 

 south and on the western slope, there is nothing but the purple- 

 weathering slate, which lies below, many of the strikes of which, if 

 continued, would cut through the purple grit. These strikes are 

 everywhere nearly the same, and yet not in the direction of the 

 band of purple grit, which here is seen only on the higher parts of 

 the ground. The mass of purple grit, which we have thus traced 

 from near Colliersley, thus appears to be an isolated patch, not, 

 indeed, actually seen lying on the edges of the slate, but whose main 

 direction crosses the line of their strike ; it dies out along a nearlv 

 horizontal line at a high level, and is without any stratification, and 

 its basal portion, if it be horizontal, contains many slate fragments. 

 I cannot see how such a mass can be anything than unconformable. 



Prom this outlying patch it is some half a mile west before we 

 reach the main mass of the purple grit, on the western slope of 

 Hawkham Hollow. Here the line of junction, if not actually seen, 

 is strictly limited for a long distance within a j^ard or two of 

 breadth. It is not, however, a straight, but a crooked line, though the 

 bedded slates, as seen, arc everywhere nearly vertical, and parallel to 

 each other. If part of the line of junction coincides with the strike, 

 as it seems to do, the rest docs not and cannot; and in one place 

 there are two crags not many yards apart of which one is slate, 

 striking directly at the other which is unbedded grit. There is here 

 no evidence of either twisting or interbedding, but the junction 

 appears to be an irregular surface both vertically and horizontally. 



In these localities which lie on the valley-worn northern slopes, 

 the exposures are pretty clear ; but, when we get upon the rolling 

 summit of hill-country, the relations of the beds become obscure. 

 From the sigmoid curve depicted on the maj), it might be thought 

 that the irregularity of junction is thereby demonstrated, but it is 

 not so ; the necessity for this curve is one of the dithculties. All 

 that can be seen is on the surface of the road. As we walk along 



