482 DE. C. CALLAWAY Olf UERIVED FRAGMENTS IN THE 



is very probable, as you suggest, that the materials "' (of this slate) 

 " may have been partly derived from old rhyolites." 



The following is a condensed description of a series of slides cut 

 from typical varieties of rocks of the Longmynd series, usually 

 regarded as Lower Cambrian, and certainly not younger. The 

 quotations are from notes furnished by Prof. Bonney : — 



201. Pebble of conglomerate at Oak's Hill, near the western 

 margin of the Longmynd area. Purple rhyolite, " devitrified, fluidal 

 structure well shown." 



202- Pebble from the conglomerate at the summit of the Long- 

 mynd, S.E. of Ratlinghope. Devitrified rhyolite, crowded with 

 spherulites, " traces of perlitic structure (anterior to devitrification) 

 exhibited here and there in the interspaces of the groups of spheru- 

 lites." 



203. Pebble from conglomerate, Haughmond Hill, N.E. of 

 Shrewsbury. Occurring in association with a great majority of 

 pebbles of the purple rhyolite. Pale-green compact felsite. 

 Regarded as probably a " devitrified obsidian." 



204. Pebble from same conglomerate as Ko. 202. Pale-green 

 quartz-felsite, with perlitic structure. Prof. Bonney notices " indi- 

 cations of flow-brecciation." 



205. Coarse purple grit above great conglomerate, Haughmond 

 Hill. Composed of bits of quartz, purple rhyolite, mica- schist, and 

 felspar. " Pull of fragments of volcanic materials, many of them 

 bits of scoria," the majority of the fragments belonging to the 

 '' acid series of volcanic rocks." 



206. Purple grit, Aston-on-Clun. Mostly quartz, but a few bits 

 of felspar and of rhyolite. Largely derived from granitoid rocks. 

 " One fragment resembles a chip of mica-schist." 



207. Very typical plum-coloured grit from the head of Cardingmill 

 Glen, west of Church Stretton. " Volcanic materials of the usual 

 type abundant." Prof. Bonney also agrees with me that bits of 

 mica-schist are probably present. I may add that I have found 

 pebbles of mica-schist in the overlying conglomerates. 



208. Speckled grit. West of Hopesay Common. Composed of 

 quartz, felspar, and a small proportion of volcanic fragments. 



209. Pale-green grit, Haughmond Hill. Bits of quartz and 

 felspar, with mica and a small proportion of felsite. " Suggests 

 partial derivation from a mica-schist." 



211. Typical pale-green slate, Haughmond Hill. Noticed above 

 (p. 481). 



It may be safely concluded that, during the deposition of the 

 Longmynd series, the adjacent lands were largely composed of 

 purple rhyolites, pale-green felsites and quartz-felsites, granitoid or 

 gneissic rocks, and mica-schists. The Archaean age of the Wrekin 

 volcanic series, to say nothing of the metamorphic rocks, thus receives 

 ample confirmation. As the strike of the Uriconian is almost 

 uniformly east and west, while the strike of the Longmynd rocks is 

 steadily totheS.S.W., there would appear to be a considerable break 

 between the Archaean and Longmynd periods. 



