514 DR. C. CALLAWAY OIS T THE LONGMYNDIAN [Aug. I9OO, 



All the foregoing slides are grits, the materials of which are 

 mainly derived from gneissic and igneous rocks. The specimens 

 from the Woolhope Conglomerate differ from the Old Radnor Grit 

 only varietally, and in no greater degree than specimens of the Old 

 Radnor Grit differ one from the other. 



3. Pre-Cambrian Age of the Old Radnor Series. 



The great dissimilarity between these rocks and the May Hill 

 Sandstone which occurs near Presteign, at a distance of only 3 miles 

 to the north-east, is obvious at a glance ; and it was no doubt this 

 difference that led Murchison to infer that the Old Radnor rocks 

 had undergone metamorphism. The chief mass of the May Hill 

 Sandstone, as seen at Nash Scar, is highly quartzose, and sometimes 

 approaches a quartzite in composition and texture. The bedding is 

 quite distinct, and, in some localities nearer Presteign, fossils (such 

 as Petraia and Pentamerus) are abundant. 



Irrespective of this lithological dissimilarity, the (at least) pre- 

 Silurian age of the Old Radnor Series may be inferred from the 

 unconformity indicated by the Woolhope Conglomerate ; and the 

 close resemblance between the material of its pebbles and the grit 

 of the Old Radnor mass renders it highly probable that the hill is a 

 fragment of the land which margined the Woolhope sea. The Old 

 Radnor Series must therefore be regarded as pre-Silurian. If this 

 be admitted, its pre-Cambrian age becomes highly probable, and 

 the following considerations will, I think, convert probability into' 

 a very near approach to certainty. 



(a) Geological Position of the Series. 



The normal strike of the rocks of the Longmynd is south-south- 

 westerly, and this is steadily maintained from the northern end of 

 Haughmond Hill to the southern extremity of the Longmynd range, 

 a distance of 20 miles. If the Longmynd strata are continued for 

 19 l miles farther along the line of strike, some part of them would 

 coincide with the position of Old Radnor Hill. Purthermore, the 

 eastern boundary of the Longmynd massif is the Church -Stretton 

 Fault. This also is continued south-south-westward, and passes 

 very near the eastern margin of Old Radnor Hill, if not close to it 

 (see map, PI. XXVIII). The Old Radnor mass is therefore on 

 the western side of the fault, where my theory requires it to be. 

 The Longmynd Series in Shropshire is followed on the west by the 

 Ordovicians of the Stiper Stones area, which reappear on the 

 southern line of strike, 7 or 8 miles west of Old Radnor, at Builth 

 and Llandrindod. It is almost certain, therefore, that the Long- 

 myndian occupies its normal position in the Old Radnor district, and 

 that Old Radnor Hill is a mass of it jutting up amid Silurian strata. 

 It should be remembered also that the May Hill Sandstone of 

 Shropshire is a shore-deposit on the Longmynd Hills, just as is 

 the Woolhope Conglomerate at Old Radnor. 



1 The distance is only 16 miles from the inlier of grit at Hopesay. 



