Geological Society. 221 



the water ran off the Boulder-clay ; and when the impervious beds 

 overlying the limestone had been cut back by denudation, a 

 number of lines of swallow-holes marked the successive stages in 

 the process ; but there was not such evidence of the former exten- 

 sion of the drift up to the Norber boulders. 



5. The boulders themselves were not rounded and glaciated in 

 the same way as the masses of the same rock in the drift, but 

 resembled the pieces now seen broken out by weathering along the 

 outcrop of the rock close by. 



Having thus shown the improbability of these boulders having 

 been let down out of a mass of drift the finer part of which had 

 been removed by denudation, or of their having been masses floated 

 to their present position on shore-ice, he offered an explanation of 

 their peculiar position, which he thought was not inconsistent with 

 the view that they belong to some part of the age of land-ice. 



That they were to be referred to some exceptional local circum- 

 stances seemed clear from the rarity of such glaciated pedestals, 

 while boulders and other traces of glaciation were universal over 

 that part of the country. He therefore pointed out, in explanation, 

 that they occurred always where there was a great obstacle in the path 

 of the ice : — at Cunswick the mass of Kendal Pell curving round at 

 the south and across the path of the ice ; at Farleton the great 

 limestone escarpment rising abruptly from Crooklands ; at Norber 

 the constriction of the Crummack valley near Wharfe and the great 

 mass of Austwich grit running obliquely across its mouth. In all 

 these cases the ice had to force its way up hill ; and there would be 

 a time when it would just surmount the obstacle after a season of 

 greater snowfall, and fall back after warm seasons, until it fell back 

 altogether from that part. During the season of recession, boulders 

 would be detached below the ice-foot ; during the seasons of advance 

 they would be pushed forward ; and in those exceptional localities 

 of isolated hills from which the drainage from higher ground was 

 cut off, the boulders were left on a clean furrowed surface of lime- 

 stone, which was then acted upon by rain-water and the vegetation, 

 except where protected by the boulders. 



2. " On some derived Fragments in the Longmynd and newer 

 Archaean Rocks of Shropshire." By Dr. Charles Callaway, F.G.S. 



Further evidence was added to that given in the Author's previous 

 paper (Q.J.G.S. 1879, p. 661), to show that the Longmynd rocks of 

 Shropshire were chiefly composed of materials derived from the 

 Uriconian series, and that the Uriconian series itself (Newer 

 Archaean) was partly formed from the waste of pre-existing rocks. 

 This evidence consisted of (1) the presence, throughout the greatly 

 developed Longmynd conglomerates and grits, of purple rhyolite 

 fragments, recognized by microscopical characters as identical with 

 the Uriconian rhyolites of the Wrekin, and the occurrence of grains, 

 probably derived from the same rhyolites, in the typical green slates 

 of the Longmynd ; and (2) the existence of conglomerate beds con- 

 taining rounded fragments of granitoid rock in the core of the 



