Rev. J. F. Blake — Precamhrian Geology. 485 



and if petrography can be shown in this case to be a safe guide, the 

 Moniau is certainly one. But on the next page (75) it is stated that 

 Dal radian is proposed for the "crystalline schists" alone. In a 

 note he says that the Monian includes Archeean gneiss. This it 

 does not do, for if the rocks which I suggested might be Archeean 

 gneiss were proved to be so, that fact would exclude them from the 

 Moniau ; and if they are not Archaean gneiss they are foliated 

 granite, and as such form no part of the system. Also that it 

 includes " strata, volcanic and fossiliferous, of undoubtedly Bala age." 

 But even if this could be proved, these strata could be eliminated 

 from the Monian without destroying its existence or making it 

 much smaller. 



1 now pass to the next paper by Dr. Callaway " On the Uncon- 

 formities between the Rock Systems underlying the Cambrian 

 Quartzite in Shropshire." 



The first question dealt w^ith is the age of the " Volcanic series " 

 or Uriconian. This I concluded to be younger than the Longmynd 

 shales. The evidence I brought forward for this was entirely 

 original, for Dr. Callaway never discussed the question at all, to my 

 knowledge, and even now he does not bring forward a shred of 

 positive evidence that it is older. He says they are faulted together, 

 in which case either might be the younger. The fact is he pi'oved 

 the Uriconian to be older than the Cambrian Quartzite, and assuming 

 the Longmynd shales to be Cambrian also, that carried the point. 

 Even now, I can scarcel}' regard its younger age as definitely proved; 

 it may be that they are more or less contemporaneous in spite of 

 any difference of strike. All I can say is that all the evidence 

 available is most in favour of the volcanic series being younger ; and 

 actually Dr. Callaway's own statements are prima facie to the same 

 effect. Thus he refers to a locality on the S. E. of Ragleth (which 

 after careful searching I failed to find) where shale like the Long- 

 mynd shale is overlaid by red felsite. Again, he states that near 

 Hazier cottages the Longmynd slate near its junction -with, the 

 Uriconian " has a burnt appearance and the cracks are injected with 

 red felspar." 



He next refers to the Pontesford Hill area, and says that the rocks 

 next the rhyolite are not altei'ed. Assuming that they are not, 

 though to my mind they certainly are, the section is still proved by 

 stratigraphy to lie above the whole of the Longmynd series. It is 

 difficult to understand the gist of the concluding sentence : " As 

 this crucial case breaks down on examination, I thought it needless 

 to re-examine the other masses of Uriconian which appear on the 

 line of the great Pontesford Linley fault." If it means that because 

 in his opinion I am in error about the alteration (in common with 

 Sir R. I. Murchison, who seems to have examined this district more 

 thoroughly than any one else), therefore I am unworthy of credence, 

 his paper might have conveniently stopped there. 



Turning next tO the unconformity in the middle of the Longmynd, 

 he selects for sole examination the section at Narnells rock. I give 

 the junction as it is actually seen, and this is what I say about it. 



