THE BASAL ROCK-GROUPS OF SHROPSHIRE. 125 



tained that the source of supply of the Longmynd Series vras the 

 Caer Caradoc volcanic group. There was no indication of a volcanic 

 group in the Longmynd rocks, and it was much more likely that the 

 volcanic rocks existed previously to their deposition. He as yet saw 

 no reason for separating the Longmynd Series from the Cambrians. 

 The Author had difficulty in understanding Prof. Blake's theory 

 of extrusion as distinguished from intrusion. The rocks at Lyd's 

 Hole were important, because it was the only locality where 

 Prof, lilake affirmed the existence of contact- alterations. With 

 regard to the apparent conformity produced by squeezing, he would 

 ask why the outliers were not also conformable. He could not 

 follow Prof. Blake's arguments concerning the conglomerates on 

 Charlton Hill ; because the outcrops were circumscribed, it did not 

 follow that the patches were Cambrian, and, as a matter of fact, the 

 rocks have a dip and strike conformable with that of the associated 

 rhyolites. The Cambrian occurs on the west side of the Longmynd, 

 under the Stiper Stones ; for the Shineton shales are seen there, and 

 there is also a fault, cutting out the Lower-Cambrian rocks. 



Q.J.G.S. No. 186. K 



