Vol. 5 2. J EASTERN CORNER OF ANGLESEY. 631 



extreme deflection to W.S.W.) would then come into play, and cause 

 the S.S.E. deflection. Moreover, the Llanfairfechan glacier, being 

 the feeblest, would be the first withdrawn, and the Aber glacier 

 would then rather aid the S.S.E. deflection than otherwise. 



VII. Summary. 



The south-eastern promontory of Anglesey consists chiefly (besides 

 the schists) of Ordovician and Carboniferous rocks, overlain by 

 extensive Glacial deposits; but there are also two small but im- 

 portant fragments of ancient formations at Careg Onen and Baron 

 Hill. 



The slates of Careg Onen rest unconformably upon the schists, 

 and appear to be separated by another strong unconformity from 

 the Ordovician shales. Whence it would appear, pending con- 

 firmation from other sections or direct fossil evidence, that the 

 slates (which contain sponge-spicules) must be of pre-Cambrian 

 age, and the schists themselves even older. 



The ashy grits aud bedded tuffs of Baron Hill appear to have 

 been moved somewhat from the N.E. along a plane of overt hrust. 

 They are traversed by planes of my Ionization, as well as isoclinally 

 folded, and in general much broken up. 



The Ordovician rocks consist chiefly of dark shales and mudstones, 

 sparingly fossiliferous, but contain a group of volcanic tuffs on the 

 horizou of the pisolitic ironstone. Another tract of Arenig beds, 

 with the pisolitic ironstone and graptolitic shales, lies concealed 

 beneath glacial drift at Llanddona. 



The Carboniferous rocks appear to be about 700 feet thick. They 

 contain 100 feet of conglomerates, sandstones, and shales, with 

 plant-remains, about the middle of the series. 



The glacial striae sweep round from S.S.W. at the northern to S.W. 

 and W.S.W. at the southern end of the district. In the Penmon 

 area there is cross-hatching with a series running S.S.E. , and it is 

 suggested that this is due to fluctuation in the power of the Caer- 

 narvonshire glaciers to deflect the ice coming from the north, 

 combined with the local influence of certain high ground. 



Discussion. 



Sir Archibald Geikie rose, not for the purpose of criticism, but 

 to congratulate the Society on the acquisition of a geological recruit 

 who, possessing leisure, enthusiasm, and capacity, was likely to 

 advance the progress of geology in this country. Notwithstanding 

 all that had been written regarding the geology of Anglesey, the 

 subject still bristled with difficulties. Unsolved problems presented 

 themselves in every part of the island. These could never be settled 

 by mere hurried holiday visits, but needed such patient investigation 

 as was demanded in the preparation of a geological map of the 

 district on a large scale. The present paper, and the little piece of 



