The Geology of Central Wales

Part I The following covnnaunication contains some of the results worked out in frequent field-excursions during three years9 stay at the University College of Wales, Aberystwyth. In many of these excursions I was accompanied by my students of the College ; and to them I am indebted for much help both in the museum and the field. Our principal field of work was, naturally, within a radius of some fifteen to twenty miles around the hewn of Aberystwyth ; and most of this country we have carefully searched and traversed through and through. The more distant areas to the south of Cader Idris, at Llanbrynmaer, Llandovery, Llandeilo, Cardigan, &e., have also been visited with a view to the determination of the extent and variation of the Cardiganshire rock-groups, and the discovery of their stratigraphical relations to other and better-known geological horizons. Little has yet been done by geologists to elucidate the structure of this part of Wales : while the most careful labours of our greatest authorities have been devoted to the study of the northern counties and eastern borders of Wales, and also, of late years, to the south inPembrokeshire, this barren and chaotic area of Mid Wales has been always neglected, and is even now very rarely touched with the geological hammer. For the bibliography of our subject we have therefore but little to say, the most important contributions being :—the work of our great leader Sedgwick, published in the Society9s Journal in the year 1847 (vol. iii