ANNIVERSARY ADDRESS OF THE PRESIDENT. 89 



to be tlireefold. In the first place, the qiiartzite contains fragments 

 of the volcanic rocks. I do not think much stress can be laid on this 

 fact. What struck me most in the composition of the quartzite 

 was its singularly pure quartzose character, and the comparative 

 scarcity of felsite-pebbles in it. Any deposit laid down conform- 

 ablj^ upon the top of the breccias and tuffs might obviously contain 

 some of these materials, while, if laid down unconformably, it might 

 reasonably be expected to be full of them. In the second place, 

 this quartzite is alleged to pass transgressively across the edges 

 of successive sheets of the volcanic group, and thus to have a quite 

 discordant dip and strike. I failed to find satisfactory evidence of 

 this unconformability in the northern part of the district. But in 

 the Caer-Caradoc area the quartzite does appear to steal across the 

 outcrops of the older rocks which plunge at nearly right angles in 

 an opposite direction. In the third place, the felsitic volcanic 

 group is believed by Professor Lapworth to pass upwards into the 

 Longmynd rocks. Obviously, if this group lies at the very bottom 

 of the vast Longmynd series, the discordance between it and the 

 quartzite must be enormous, and the date of the volcanic eruptions 

 must be placed vastly farther back in geological antiquity. Though 

 the evidence does not seem to me to amount to clear proof, I am 

 disposed, in the meantime, to accept it as affording the most pro- 

 bable solution of the difficulties presented by the structure of the 

 ground. 



If, then, the volcanic group underlies the whole of the Longmynd 

 series, and if, as it now appears, that series is older than the 

 Olenellus-zone of the Lower-Cambrian rocks, we can hardly include 

 the volcanic rocks of the AVrekin and Caer Caradoc in the Cambrian 

 system. They must belong to a stiU older geological formation, 

 and I think we cannot do better than adopt for them Dr. Callaway's 

 name, Uriconian. 



There are still, however, many problems to be solved before the 

 geological history of that region is fully understood. The rocks of 

 the Longmynd must be more fully worked out. It is incredible 

 that strata which look so likely to yield fossils should for ever 

 prove barren. The lower half at least may be hopefully searched, 

 although the upper massive reddish sandstones and conglomerates 

 offer less prospect of success. On the west side of the Longmynd 

 above Po;itesbury there occurs a small area of volcanic rocks like 

 those of the Wrekin district, including a well-marked nodular felsite 

 and fine tuffs. These rocks have been regarded by Dr. Callaway 



