118 i)k. ch. calla^vay on the r.ncojjeormities between 



4. The Geanitic Eocks. 



Prof. Blake appears to have discovered some new outcrops of the 

 granite. He says " there are two small patches of it in the midst 

 of the rhyolites near the south-eastern end of the Wrekin." But, 

 as the Wrekin is a narrow ridge trending JS'.E. and S.W., it cannot 

 have a " south-eastern end," and we are therefore left in the dark as 

 to the situation of the new masses. Wherever they are, they must 

 be very small. 



At Primrose Hill, the granite is thought by Prof. Blake to 

 " suggest a neck." He states that it " almost seems to pass into 

 rhyolite." I can find, however, no rhyolite near the granite. The 

 rock into which the granite really passes is fine-grained and com- 

 pact ; but, under the microscope, it is seen to be merely a crushed 

 state of the granite, as first suggested to me by Prof. Bonney. A 

 series of microscopic slides shows the actual stages of the crushing 

 process. 



There remains the difficult and obscure section at Ercal Hill. 

 Yery little is to be learned in the field. At one spot I once saw 

 a mass of felsite included in the granite ; but all the rock was too 

 much decomposed for satisfactory study. On the other hand, I hav^e 

 never found a vein of the granite in the felsite. The junction is 

 nearly a straight line, and is marked by some minute crushing. 

 There is some reason to suspect a fault. 



Since writing the above, I have received a note on the subject by 

 Prof. Bonney. He has examined a new junction-specimen of mine, 

 and re-examined several slides of his own. He says, " Certainly 

 there is nothing to show that the granite is intrusive in the felsite," 

 and he thinks there are signs of fault-brecciation. He cannot find 

 any distinct proof of the intrusion of the felsite in the granite. We 

 may then fairly conclude that Prof. Blake's opinion receives no 

 support from the study of the rocks, either in the field or under the 

 microscope, and the evidence from included fragments, given in the 

 last section, may be allowed its due weight. 



The pebbles of granite and schist in the Charlton-Hill conglome- 

 rates clearly prove the unconformity between the Uriconian and an 

 earlier rock-system. The nature of the break between the Uri- 

 conian and the Longmvndian will be more fullv explained in 

 Part III. 



III. The Helation between the Uriconiak and 



THE LoNGMTNBIAN. 



The age of the Longmynd rocks must be considered as suh judice. 

 The antique facies of tlie fauna of the Hollybush Sandstone and the 

 gap between that formation and the Upper Cambrian led me many 

 years ago to doubt the Upper-Cambrian age of the former, and I 

 have provisionally regarded it as Menevian. The obvious hiatus 

 between the quartzite underlying this sandstone and the Longmynd 

 Series rendered the Cambrian age of the latter highly improbable, 



