-1:08 PKOF. J. F. BLAKE ON THE MONIAN AND 



which rock. Unfortunately it leaves the matter doubtful after all. 

 The line runs in general along the face of the quarry, turning 

 westwards towards the southern end ; but slips, for the most part, 

 cover it. The rhyolite below has irregular flow-lines, and contains 

 clastic portions, so that it does not look like intruding on anything. 

 In one spot beneath a tree the solid eurite and compact rhyolite are 

 brought side by side with a vertical dividing line, but the line is so 

 decayed that nothing can be made of it. Hard by are soft bedded 

 shales, evidently of rhyolitic material, which rest on and enter 

 the wide cracks of the eurite, and contain numerous nodules of the 

 latter of all sizes and shapes, which have evidently decayed in situ. 

 If we could only persuade ourselves that these shales are rhyolite 

 tuff, the question would be settled ; but they are not in the least 

 like the rocks anywhere else, and are scarcely consolidated. I take 

 them therefore to be merely stratified debris, probably first formed 

 within the fault, and therefore proving nothing. I did, however, 

 obtain a specimen on a former visit, under the guidance of Dr. 

 Callaway, which seemed to me an intrusive junction of the eurite, 

 but I cannot confirm the observation. From all available evidence, 

 it would, on the whole, appear that it is highly improbable that the 

 eurite is the older, and highly probable that it is, on the contrary, 

 intrusive in the rhyolite, but I cannot absolutely prove it. 



I must next pass to the conglomerates and grits which are met 

 with in these hills, the age of which is of supreme importance in 

 connection with the general interpretation of the district. In several 

 spots they have been noticed by Dr. Callaway, but have been taken by 

 him to be part of the volcanic series, and to prove the clastic origin of 

 the latter. If we commence on the south, we must probably consider 

 the conglomerate and grit of Hopesay Common the first member of 

 this group, for the summit of Wartle Knowl, at its termination, is 

 composed of a mass of rhyolite, with which a dolerite is associated 

 after the manner of an intrusive rock. This association of two 

 kinds of igneous rock, which recalls what we see universally in 

 these volcanic hills, and the position of this elevation in relation 

 to them and to the boundary-fault, indicate that we have in Wartle 

 Knowl the summit of a hidden Caradoc, enveloped by undenuded 

 Cambrian grit. The next hill is Ragleth ; along the western slope 

 of this is seen a red grit of rather mixed character, but recalling 

 very closely the Cambrian purple grit. It does not run trans- 

 versely to the hill, as the dark shales do when pushed aside, but 

 forms a longitudinal patch, which, from its easily determined limi- 

 tations, must be superficial and deposited where we find it. On 

 Cardington Hill there are two patches ; one is noticed by Dr. Calla- 

 way on the slopes of the Gaer Stones, and the other is a large one 

 at a lower elevation, situated to the east, where the hill is crossed by 

 the footpath. The exposures of this and of the surrounding rocks are 

 numerous, and the exact limit of the red grit can be easily traced. 

 It is seen to be superficial. Besides these two masses of grit, there 

 is on the same range, near the summit called Willstoue HiU (see 

 fig. 5), a very small and local patch of conglomerate occupying 



