June 2, 1904] 



NA TURE 



113 



the rounded and smoothed surfaces of their sides. Their 

 floors are often rough with round shingle, which has un- 

 doubtedly been the material employed by nature in their 

 excavation. No one who has made himself familiar with 

 the roclc-platforms which at the present day are in course 

 of erosion by the sea along these same coasts can for a 

 moment doubt that the rock-platforms of the raised beaches 

 which, down to the minutest point, resemble them, have 

 likewise been eroded by the waves of the sea. 



That the daily oscillations of temperature invoked by 

 Prof. Suess in explanation of the Norwegian seter have had 

 their share in the erosion of these Scottish examples cannot 

 be doubted. But this share is evidently feeble in amount 

 now, although it may have been more considerable during 

 the Glacial period. More potent as a contributory influence 

 in the erosion of the older terraces was probably the action 

 -of floating ice, driven along the shores by winds and tidal 

 currents. Down to the time of the 50-foot beach, when 

 glaciers in the north of Scotland descended to the edge of 

 the sea, there may have been a good deal of such ice in 

 the more enclosed sea-lochs, where the water, freshened 

 by the discharge of melting snow-fields and glaciers, might 

 itself be covered with a cake of ice. And there was not 

 improbably a good deal more ice in the fjords of Norway. 

 The grinding and rasping action of such ice, driven by 

 gales ashore, has long been remarked. But in any case 

 we are justified in regarding the Scottish seter as examples 

 of truly marine erosion, and there appears to be no reason 

 why those of Norway should not have had the same origin. 

 It is at least clear that the statement that the characters of 

 seter " are absolutely irreconcilable with what we know 

 •of the action of the sea near its surface," cannot be sustained. 



Certain features of the extension of the raised beaches 

 throughout Britain appear to be of fundamental importance 

 in relation to the discussion of the problem of the emergence 

 of land. Though so persistent along both the western and 

 ■eastern coasts of Scotland, these beaches, as is now well 

 known, do not stretch northward into the Orkney and 

 Shetland Isles. Along precipitous sea-fronts we could not 

 ■expect to meet with them, but among these islands there 

 are endless sheltered inlets and bays which, had they in- 

 dented the shores of the mainland of Scotland, would un- 

 doubtedly have had their fringe of terraces. The conditions 

 for the development and preservation of the beaches were 

 so entirely favourable, that their absence can only be legiti- 

 mately accounted for on the supposition that they can never 

 have existed here. Still farther north, among the Fseroe 

 Isles, no trace of any raised beaches has been found among 

 the numerous natural harbours and creeks that break the 

 monotony of the vast ranges of basalt-precipice. Here, 

 again, we cannot suppose that any such beaches were ever 

 formed. 



In the southward extension of the Scottish raised beaches 

 these features begin to lose their distinctness as they are 

 traced into England. The loo-foot beach, which has not 

 been recognised along the northern coast of Sutherland or 

 in Caithness, appears also to fail before it reaches the 

 English coast. It is well marked in the estuaries of the 

 Clyde and Forth, whence in a fragmentary condition it 

 !ias been traced into Wigtonshire on the one side and to 

 the north of Berwickshire on the other. But no remnants 

 of it appear to have been detected in the North of England. 



The raised beaches of the north and east of England were 

 briefly referred to, and it was then shown that in England 

 and Wales the most continuous and best preserved examples 

 are to be seen on the coasts of the southern counties. The 

 lower raised beaches along the coasts of Dorset, Devon and 

 Cornwall have long been known, although their geological 

 age, their history, and their relation to the later phases of 

 Pleistocene time, have not yet been satisfactorily cleared 

 •up. William Pengelly, who devoted so much time to this 

 subject, clearly proved that these beaches do not stand now 

 at their original level, but that after their formation the 

 region was upraised to the amount, as estimated by him, of 

 not less than 70 feet, when the lowest sunk forests flourished 

 as land-surfaces, and that thereafter came a submergence 

 of certainly 40 and perhaps many more feet. 



Mr. Tiddeman has shown that, in Gower, on the coast 

 of Glamorgan, a raised beach which lies from 10 to 30 

 feet above the level of the modern beach, and contains 



NO. 1805, VOL 70] 



littoral shells of common species, is yet older than at least 

 some part of the Glacial period, for it is overlain by Glacial 

 drift. In this case, also, its present is probably not its 

 original level. There is evidence of considerable sub- 

 mergence, at a comparatively late period, farther east in 

 the same county and along the southern coast of England, 

 and the inter-Glacial or pre-Glacial raised beaches of the 

 whole of this region doubtless stood at one time higher 

 above the sea-level than they do now. 



The raised beaches of Ireland were alluded to, special 

 attention being directed to an ancient shore-line at Cork 

 Harbour, which has recently been traced by Messrs. Muff 

 and Wright, of the Geological Survey, not only within the 

 harbour, but for a long distance on the shore to the east 

 and west of that inlet. Though only a few feet above the 

 present high-water mark, this beach has been ascertained 

 to be older than the oldest Irish Boulder-clay, for it is 

 overlain by the so-called " shelly marl " which was brought 

 in upon the land from the sea-basin. The similarity of 

 position and antiquity between this beach and that under- 

 lying the drift in Gower is obviously as important as it is 

 interesting. A shore-line, which myst be of pre-Glacial or 

 inter-Glacial age, is traceable in the south of Ireland and 

 in South Wales. It has not only survived the erosive pro- 

 cesses of the Glacial period, but it appears to have outlived 

 some serious alterations in the relative levels of sea and 

 land, which have taken place since its formation. More- 

 over, we have to note the fact that neither at Cork nor in 

 Gower does any younger post-Glacial terrace appear to be 

 recognisable. If we might judge from the analogy of other 

 parts of these islands where the succession of raised beaches 

 is tolerably complete, we should infer that if ever any later 

 terrace existed here it must now be submerged — an inference 

 which, it will be observed, is supported by the evidence of 

 considerable submergence in South Wales and on the 

 southern coast of Hampshire. 



(ii.) Submergence. — Of the various kinds of proof of the 

 submersion of terrestrial surfaces furnished in these islands 

 only two were dealt with : first, the extension of land-valleys 

 beneath the sea, and, secondly, the existence of what are 

 known as sunk forests. 



(i) That the fjords of Norway, the sea-lochs of the west 

 of Scotland, and the harbours or inlets of the west of Ireland 

 were originally valleys on the dry land, although now 

 deeply submerged, has long been an accepted belief among 

 those geologists who have specially considered the subject. 

 The interval of time which has elapsed since this sub- 

 mergence has not sufficed to fill up with sediment these 

 submarine depressions. By a study of the sea-charts, we 

 can still trace the winding curves of the ancient valleys, and 

 can even here and there detect among them the basins 

 which, when the present sea-bottom was a land-surface, 

 were filled with fresh-water lakes. On the sea-floor to the 

 east of our own country and of Scandinavia, such relics of 

 subaerial denudation are less imposingly preserved, yet 

 evidence of the submergence of land-valleys has been noted 

 there also. It must of course be remembered that the land 

 on that side is of much lower altitude than on the western 

 coasts, that the ground slopes gently under the sea, and 

 that the valleys are comparatively insignificant depressions 

 on its general surface. Moreover, the more abundant 

 drainage on the longer slope east of the watershed, and the 

 much greater development of drift on that side, leads to a 

 far more copious discharge of sediment into the shallow 

 North Sea and the Gulf of Bothnia, and the submarine 

 prolongations of the old land-valleys are thus apt to be 

 buried under recent accumulations of detritus. There may, 

 however, perhaps be another cause for the contrast between 

 the profoundly indented and precipitous western coast and 

 the comparatively low and monotonous trend of the eastern 

 coast. The author had long been disposed to believe that 

 the submergence has been greater towards the west than 

 towards the east. In the prolongation of the West High- 

 land sea-lochs on the floor of the Atlantic outside, the 

 original land-surface sometimes lies 600 feet or more below 

 the present sea-level. If the submerged land-surface of 

 north-western Europe could be upraised some 600 feet, the 

 submarine prolongations of the sea-lochs would once more 

 become glens and straths, and their rock-basins would again 

 be turned into fresh-water lakes. 



