THE AKCHjRAN ROCKS 57 



glomerate in the middle, (2) hard purple slates, and (3) purplo 

 and reddish-brown grits with lenticular beds of conglomerate. It 

 is uncertain whether this is a true succession, for it is just possible 

 that the double set of reddish grits and conglomerate IB a 

 reduplication. 



The relation of the western series to the eastern series IB also a 

 point of dispute. Professor Blake believed the former to be un con- 

 formable to the latter and to be of the same age as some of the 

 grits in the Uriconian Group. In his view the eastern or grey 

 series is the oldest rock-group in the district and the Uriconian is 

 newer. In favour of this view it may be remarked that the basal 

 Cambrian sandstones have only been found in contact with the 

 Uriconian and not upon any part of the Longmyndian. On the 

 other hand, numerous fragments of the Uriconian rhyolites occur 

 not only in the conglomerates of the western series, but also 

 occasionally as small fragments in the grits of the eastern series. 

 The evidence of actual unconformity is considered very dubious 

 by Dr. Callaway, who also points out that the strike of the two 

 Longmyndian Series is parallel (from N.N.E. to S.S.W.), while 

 that of the Uriconian is quite different (from east to west). 24 



The balance of evidence seems to be in favour of Dr. Callaway's 

 view, in which case the order of succession would be (1) Uriconian, 

 (2) Eastern Longmynd Series, (3) Western Longmynd Series. In 

 this connection it may be mentioned that this last (the red series) 

 has a close lithological resemblance to the Torridon sandstones, 

 and it will be remembered that the conglomerates of the latter 

 contain pebbles of a Uriconian rhyolitic type. This tends to 

 confirm Dr. Callaway's opinion and suggests a comparison between 

 the Longmyndian as a whole and the Torridonian of Scotland. 



Malvern Hills. The oldest rocks of the Malvern Hills are also 

 pre-Cambrian, and are interesting because the greater part cunikli 

 of highly crystalline gneissic rocks, which are probably altered 

 igneous rocks, and are comparable to the Hebridean gneisses of 

 Scotland and Ireland. This group is known as the Malvernian. 

 Side by side with these is a small tract of rocks comparable with 

 the Uriconian of Shropshire, and consisting of rhyolites, andesites, 

 basalts, and felspathic tuffs. 26 There is nothing here comparable 

 to the Longmyndian Series, but the district has undergone an 

 enormous amount of compression with plication, shearing, and 

 faulting, as will be seen from the section, Fig. 8. 



Charnwood Forest. Small tracts of volcanic tufls and 

 breccias, resembling those of the Uriconian, occur at Barnt Green 

 near Birmingham and at Caldecote near Nuneaton, and are in both 

 cases covered unconformably by Cambrian strata. A larger tract 



