188 Reports &. Proceedings — Geological Society of London. 



caused by mountain-masses such as Schiehallion and Arthur's Seat, 

 found reason to conclude that deflection was caused also by variations 

 in the specific gravity of underground rocks. 



There is some reason for believing that lines of equal gravity may 

 have some connexion with magnetic 'ridge-lines'. It has been 

 recently recommended that the Magnetic Survey of 1891 should be 

 repeated. It is suggested that a Gravity Survey is equally desirable. 

 The British Isles, in virtue both of their geographical position on 

 the margin of the European Continent, and in virtue of the form and 

 structure of the Palaeozoic platform, appear to constitute a region 

 eminently suited for such an investigation. 



The Ballot for the Council and Officers was taken, and the following were 

 declared duly elected for the ensuing year : — 



Officers: — President: Aubrey Strahan, Sc.D., F.E.S. Vice-Presidents: 

 Professor Edmund J. Garwood, M.A. ; Richard Dixon Oldham, F.R.S. ; 

 Clement Eeid, F.R.S. , F.L.S. ; Professor W. W. Watts, Sc.D., M.Sc, F.R.S. 

 Secretaries: A. Smith Woodward, LL.D., F.R.S. ; Herbert Henry Thomas, 

 M.A., B.Sc. Foreign Secretary: Sir Archibald Geikie, K.C.B., D.C.L., 

 LL.D., Sc.D., Pres.R.S. Treasurer : Bedford McNeill, Assoc. R.S.M. 



The other Members of Council elected were : — Henry A. Allen ; Henry Howe 

 Bemrose, J. P., Sc.D. ; Professor Thomas George Bonney, Sc.D., LL.D., 

 F.R.S. ; James Vincent Elsden, D.Sc. ; John William Evans, D.Sc, LL.B. ; 

 William George Fearnsides, M.A. ; Professor Owen Thomas Jones, M.A., D.Sc. ; 

 Herbert Lapworth, D.Sc, M.Inst.C.E. ; Horace W. Monckton, Treas.L.S. ; 

 Edwin Tulley Newton, F.R.S. ; George Thurland Prior, M.A., D.Sc, F.R.S. ; 

 Arthur Vaughan, M.A., D.Sc. ; William Whitaker, B.A., F.R.S. ; Rev. Henry 

 Hoyte Winwood, M.A. 



Febriiart/ 26, 19 1 o. — Dr. Aubrey Strahan, F.li.S., President, 

 in the Chair. 



The following communications were read : — 



1. " The Ueology of Bardsey Island (Carnarvonshire)." By Charles 

 Alfred Matley, D.Sc, F.G.S. ; with an Appendix on the Petrography 

 by John Smith Plett, M.A., D.Sc, F.G.S. 



Bardsey, an island a mile and three-quarters long, lies off the 

 promontory of the Lleyn (Western Carnarvonshire), and forms the 

 isolated extremity of the strip of pre-Cambriau rocks that borders 

 the western coast of the Lleyn from Nevin south-westwards. 



The rocks are principally gritty schistose slates, with many thin 

 and some thick bands of grit, quartzite, and limestone; and they 

 contain an horizon of variolitic lava and tufaceous shale, which 

 indicates that a volcanic episode took place during their formation. 

 Sills of albite-diabase also occur, as well as one or more sills of 

 a crushed granite. 



The rocks have been subjected to intense earth-pressure acting 

 mainly from the north-west, and are mostly in a cataclastic condition, 

 the harder rocks being almost always torn up into lenticles. The 

 beds are shown to be arranged on the whole in a number of isoclinal 

 folds, complicated by overthrustiug, shearing, and brecciation. 

 Stages in the formation of crush conglomerates are described. From 

 the nature of the bi-ecciation and the comparatively small amount of 

 mineral alteration that the beds have undergone, it is inferred that 



