ANNIVERSARY ADDRESS OF TITE PRESIDICNT. 87 



ancient prc-Cambriau ridge ; and ho i)roposed for the volcanic 

 group the name of Uriconian, from the name of the ancient lloman 

 town which stood not far to the west of them *. Mr. Blake, in 

 subsequently criticizing some of Dr. Callaway's conclusions, and 

 in endeavouring to establish an unconforraability in the middle 

 of the Longraynd rocks, has contended that the volcanic rocks of 

 the Wrekin district are of later date than the Longmynd slates, and 

 he suggests that they may even be part of the Cambrian series of that 

 neighbourhood f. Professor Lapworth, as is well known, at least 

 to his friends, has devoted his leisure for some years past to the 

 detailed investigation of the older rocks of Western England, and 

 has mapped them with minute care upon the six-inch maps of the 

 Ordnance Survey, some of which were exhibited at the International 

 Geological Congress in 1888. He has not yet published more than 

 brief allusions to some of his principal results, such, for instance, 

 as the detailed sequence of the Arenig-Bala formations, his 

 discovery of the OleneUus-ioMna,, marking the lowest known fossi- 

 liferous Cambrian zone in the Wrekin district, and his recog- 

 nition of Cambrian fossils under the Coal-measures of Warwick- 

 shire X. When he learnt that I proposed to make a personal 

 examination of a portion of the ground, he not only most gene- 

 rously offered me the use of his unpublished six-inch maps and 

 furnished me with copious notes for my guidance, but he even 

 accompanied me over some of the typical sections, and enabled me 

 to see for myself certain critical parts of the evidence. 



For my present purpose it will be sufficient for me to state very 

 briefly the nature of the volcanic rocks which are claimed by 

 Dr. Callaway as pre-Cambrian in the Shropshire area, and how 

 far I think that the evidence of so high antiquity for them is trust- 

 worthy. 



These igneous masses form the core of the ancient ridge which 

 extends from near Wellington through the Wrekin, Caer Caradoc, 

 and other hills until it sinks beneath the Upper-Silurian formations. 

 They consist partly of lavas, partly of volcanic breccias and fine 

 tuffs. The lavas are thoroughly acid rocks of the felsitic or rhyo- 

 litic type. One of them, about 100 feet thick, which forms a pro- 



* OjJ. at. vols. XXX. (1874) p. 196, xxxiv. (1878) p. 754, xxxv. (1879) p. 643, 

 xhi. (1886) p. 481. 



t Op. cit. vol. xlvi. (1890) p. 386. Dr. Callaway has replied to these objections 

 in a paper not yet pubHshed. 



+ Geol. Mag. (1882) p. 563 ; (1886) p. 319 ; (1887) p. 78 ; (1888) p. 484. 



VOL. XLVII. g 



