ORDINARY MEETING.* REV. JOHN TUCKWELL, M.R.A.S., IN THE CHAIR. The Minutes of the previous Meeting were read and confirmed. The following candidates were put forward by the Council : MEMBER-George Benson Clough, Esq., Barrister-at-Law. The following paper was read by the Author : ON THE AGE OF THE LAST UPRISE OF THE BRITISH ISLES. (With Map.) By Professor EDWARD HULL, M.A., LL.D., F.R.S. (Secretary). CONTENTS. PART I. PRE-HUMAN OSCILLATIONS OF LAND IN POST-TERTIARY TIMES. 1. Introduction :-Numerous oscillations of land in British Isles in the Post-Tertiary Period, divisible into Pre-Human, Pre-Historic and Historic, as follows:- Pre-historic or Pre-human period. Human Period. (1. Great elevation of land during the first glacial epoch, or Great Ice Age. 2. "The Great Submergence" or inter-glacial 3. Re-elevation of the second glacial epoch. raised beaches. PART II. RAISED BEACHES OF THE HUMAN PERIOD IN BRITAIN. 2. Description of the raised beaches along the coast of Scotland and of North-East Ireland, their levels and enclosed works of human art, etc. 3. Special interest of the works of art made of iron. 4. Gildas' description of the Picts during the Roman occupation and its historic interest. * Monday, March 7th, 1904. 5. Indications of the partial submergence of Scotland during the Roman occupation. Evidence derived from the Roman Wall (Vallum). Views of Sir Archibald Geikie. Statement of Gildas. PART III. DATE OF EMERGENCE OF THE LAND. 6. Inferential date; that the final elevation took place well within the Christian Era. PART IV. CONCLUSION. Introduction. Whatever may have been the length of time between the Pliocene Tertiary and the historic periods,generally included in the term " Post-Tertiary "-it cannot be denied that it included several remarkable oscillations of the land of Western Europe-indeed we might say, of the Atlantic sea-board on both sides. Oscillations which have left their impress upon the physical features of the lands, and in this way have powerfully influenced the social character of the present inhabitants. We begin with the first of these terrestrial movements of Post-Pliocene times-namely, that of the first glacial elevation to which Professor James Geikie has given the generally accepted name of "The Great Ice Age." We here recognise a movement of elevation of land reaching a height of several thousand feet above the present surface of the ocean, during which the Continental platform now covered by the waters of the sea was upraised, its surface abraded, and traversed by channels (or cañons) of the existing rivers, to their outlets on the floor of the abyssal ocean at depths of 6,000 to 7,000 feet below the present surface. Having already described in the pages of the Journal of the Institute the position and character of these "drowned river channels," I need not further allude to them here, except to reassert my conviction that in the great elevation of the continental lands of Europe and Africa of which these submerged river-valleys are evidence, we have a sufficient cause for that vast extension of extreme arctic conditions shown by the glacial phenomena of a past time in Scandinavia, the Alps, Pyrenees and Atlas mountains, extending far beyond the limits of existing glaciers, as also in the British Isles from which the glaciers have altogether passed away.* Succeeding to the epoch of the great Ice Age came that of the "Interglacial stage," in which the British Isles were depressed beneath the ocean to varying depths, of which the maximum was 1,200 feet in Central England, North Wales, and central *Trans. Vict. Inst., vols. xxx, xxxi, and xxxii. Ireland. This level being indicated by raised beaches with sea shells of existing species in Denbighshire, Carnarvonshire (Moel Tryfaen), and the Wicklow Mountains.* From this maximum level of depression the amount diminished both to the north and south. In Lancashire these gravels rise along the banks of the Irwell to about 600 feet, in Scotland to about the same. On the other hand, in Gloucestershire, the level of submergence was determined by myself many years ago to be 600 feet in the Cotteswold Hills, being that to which rolled quartzite pebbles are to be found scattered over the tableland formed of Jurassic limestone, these pebbles having been derived from the New Red conglomerate of the Midland Counties and drifted to their places by marine currents. This determination was fully confirmed by the late Professor Phillips in his Geology of Oxford.† Extending our observations still further south, we find the gravels of this period forming plateaus resting on the Bagshot Sands at Englefield Green and Windsor Forest southwards, and finally, in the Isle of Wight, forming the terraces of St. George's Down and Headon Hill, at a level of 400 feet above the sea. Such, in brief, are some of the localities at which the interglacial gravels may be observed. They are everywhere later than the newest Tertiary strata, and the deposits are consequently referable to the Great Ice Age. The rudely stratified clays with glaciated pebbles and erratic blocks to be observed along the valleys of the Irwell and Ribble and other parts of Lancashire resting on the interglacial sand and gravel indicate a recurrence of sub-glacial conditions, when the waters of the sea were clouded with glacial mud, and floats of ice carrying blocks from the glaciers entered the sea. This epoch need not detain us, as it was probably of short duration; and the deposits resulting from it do not appear to have extended into the centre and southern parts of England. We, therefore, pass on to the consideration of the subject which more immediately concerns us, and to The fact of these beaches occurring at nearly the same level along a west to east tract of about 100 miles is clear evidence of their marine origin, although attempts have been made to prove they owe their formation to "the great ice-sheet" which filled the Irish Sea. An icesheet never could have produced beds of stratified sand and gravel with shells, some of which are but little injured; an ice-carriage would have ground them to powder. + Page 457. The gravels were first described by Dr. Kidd and Dean Buckland. Phillips gives the extent of submergence as 1,500 feet-somewhat excessive. |