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NA TURE 



\_Nov. 25, I J 



lobes of ice and also often mark the line separating the glaciated 

 from the non-glaciated areas. 



The paper began with a sketch of recent investigations upon 

 tVie glaciation of North America, with special reference to the 

 significance of the terminal moraines discovered within the last 

 few years. The principal characters of these moraines were 

 given, and a map was exhibited showing the extent of the gla- 

 ciated areas of North America, the course of the interlobate 

 and terminal moraines, and the direction of striation and glacial 

 movement. It was shown that, apart from the great ice sheet 

 of North- Eastern America, an immense lobe of ice descended 

 from Alaska to Vancouver's Island on the western side of the 

 Rocky Mountains, and that from various separate centres in the 

 Cascade, Sierra Nevada, and Rocky Mountains there radiated 

 smaller local glaciers. 



The mountains encircling the depression of Hudson Bay 

 seemed to be the principal source of the glaciers which became 

 confluent to form the great ice-sheet. In its advance, this ice- 

 sheet probably met and amalgamated with a number of already 

 existin:; local glacial systems, and it was suggested that there 

 was no necessity for assuming either an extraordinary thickness 

 of ice at the Pole, or great and unequal elevations and depres- 

 sions of land. 



Detailed studies made by the author in Ireland in 1885 had 

 shown remarkably similar glacial phenomena. 



The large ice-sheet which covered the greater part of Ireland 

 was composed of confluent glaciers, while distinct and local 

 glacial systems occurred in the non-glaciated area. The prin- 

 cipal ice-sheet resembled that of America in h.aving for its centre 

 a great inland depression sun-ounded by a rim of mountains. 



These .appear to have given rise to the fii'st glaciers, which, 

 after uniting, poured outwards in .all directions. Great lobes of 

 this ice-sheet (lowed westward out of the Shannon and out of 

 Galway, Clew, Sligo, and Donegal Bays, northward out of 

 Loughs Swilly and Foyle, and south-eastwar'd out of Dundalk 

 and Dublin Bays ; while to the south the ice-sheet abutted 

 against the Mullaghareirk, G.alty, and Wicklow iMountains, or 

 died out in the plains. 



Whether it stopped among the mountains or in the lowlands, 

 its edge was approximately outlined by unusual accumulations of 

 drift and boulders, representing the terminal moraines. As in 

 America, this outer moraine was least distinct in the lowlands, 

 and w.as often bordered by an outer "fringe" of drift several 

 miles in width. 



South of an east and west line extending from Tralee to Dun- 

 garvan is a non-glaciated zone free from drift. Several local 

 systems of glaciers occur in the South of Ireland, of which by 

 far the most important is that radiating from the Killarney 

 Mountains, covering an area of 2000 square miles, and entitled 

 to be called a local ice-sheet. Great glaciers from this Killarney 

 ice-sheet flowed out of the fjord-like parallel bays which indent 

 the south-western coast of Ireland. At the same time the Dingle 

 Mountains, the Knockmeaklown and Comeragh Mountains, and 

 those of Wexford and Wicklow furnished small separate glaciers, 

 each sharply defined by its own moraine. 



No evidence of any g eat marine 'ubmergencewas discovered, 

 although the author had explored the greater part of Ireland, 

 and the eskers wer'e held to be phenomena due to the melting of 

 the ice and the circulation of sub-glacial waters. The Irish ice- 

 sheet seemed to have been joined at its north-eastern coi-ner by 

 ice coming fi-om Scotland 'across the North Channel. All the 

 evidence collected indicates tiiat a mass of Scotch ice, reinforced 

 by that of Ireland and England, filled the Irish Sea, over-riding 

 the Isle of Man and Anglesey, and extending at least as far 

 south as Bray Head, south of Dublin. A map of the glaciation 

 of Ireland was exhibited in which the ob ervations of the Irish 

 geologists and of the author were combined, and in which was 

 shown the central sheet, the five local glacial systems, all the 

 known strife, and the probable lines of movement as indicated 

 by moraines, stria:, and the tr-ansport of erratics. 



The glaciation of Wales was then considered. Wales was 

 shown to have supported three distinct and disconnected local 

 systems of glaciers, while at the same time its extreme 

 northern border was touched by the great ice-lobe filling the 

 Irish Sea. The most extensive local glaciers were those radiat- 

 ing from the Snowdon and Arenig region, while another set of 

 glaciers radiated from the Plinlimmon district and the mountains 

 of Cardiganshire, and a third system originated among the 

 Brecknockshire Beacons. The glaciers from each of these centres 

 transported purely local boulders and formed well-defined 



terminal moraines. The northern iice lobe, bearing granite 

 boulders from Scotland and shells and flints from the bed of the 

 Irish Sea, invaded the northern coast, but did not mingle with 

 the Welsh glaciers. It smothered Anglesey and part of Car- 

 narvonshire on the one side and part of Flintshire on the other, 

 and heaped up a terminal moraine on the outer flanks of the 

 North Welsh mountains. This great moraine, filled with far- 

 travelled northern erratics, is heaped up in hummocks and 

 irregular ridges, and is in many places as characteristically deve- 

 loped as anywhere in America. It has none of the characters of 

 a sea-beach, .although often containing broken shells brought 

 from the Irish Sea. It inay be followed from the extreme end of 

 the Lleyn Peninsula (where it is full of .Scotch gr.anite erratics), 

 in a north-easterly direction through Carnarvonshire past Moel 

 Tryfan and along the foot of the mountains east of Menai Strait 

 to Bangor, where it goes out to sea, re-appe.aring further east at 

 Conway and Cohvyn. It turns south-eastward in Denbighshire, 

 going past St. Asaph and Halkin Mountain. In Flintshire it 

 turns southward, and is m.agnificently developed on the ea tern 

 side of the mountains, at an elevation of over looo feet, between 

 Minera and Llangollen, south-west of which place it enters 

 England. There is evidence that, where the ice-sheet abutted 

 .against Wales, it was about 1350 feet in thickness. This is 

 analogous to the thickness of the ice-sheet in I'ennsylvania, 

 where the author had previously shown that it was about 1000 

 feet thick at its extreme edge, and 2000 feet thick at points some 

 8 mile> back from its edge. The transport of erratics coincides 

 with the direction of strioe in Wales as elsewhere, and is at 

 right angles to the terminal moraine. 



The complicated phenomena of the glaciation of England, 

 the subject of a voluminous liter-ature and discordant views, had 

 been nf high interest to the author, and had led him to redouble 

 his efforts for its solution. He had found that it w.as possible 

 to accurately map the glaciated areas, to separate the deposits 

 made by land ice from those due to icebergs or to torrential 

 rivers, and to trace out a series of terminal moraines both at the 

 edge of the ice-sheet and at the edge of its confluent lobes. 

 Perhaps the finest exhibition of a terminal moraine in England 

 is in the vicinity of Ellesmeie, in Shropshire. A great mass of 

 drift several miles in width, and full of erratics from Scotlan'l 

 and from Wales, is here heaped up into conical hills which inclose 

 " kettle holes " and lakes, and have .all the characters of the 

 " kettle-moraine " of Wisconsin. Like the latter, the Elles- 

 mere moraine here divides two great lobes of ice, one coming 

 from Scotland, the other fr'om Wales, This moi'aine may be 

 traced continuously from Ellesmere eastward through Madeley, 

 Macclesfield, to .and along the western flank of the Pennine 

 Chain, marking throughout the southern edge of the ice-sheet of 

 northern England. From Macclesfield the same moraine was 

 traced northward past .Stockport and Staleybridge to Burnley, 

 and thence to .Skipton in Yorkshire. North-east of Burnley it is 

 banked .against the Boulsworth Hills up to a height of 1300 feet 

 in the form of mounds and hummocks. South and east of this 

 long moraine no signs of glaciation were discovered, while north 

 and west of it there is every evidence of a continuous ice-sheet 

 covering land and sea alike. The strise and the transport of 

 boulders agree in proving a southerly and south-easterly direc- 

 tion of ice-movement in Lancashire and Cheshire. 



From Skipton northward the phenomena are more complicated. 

 .\ tongue of ice surmounted the watei'shed near Skipton, and pro- 

 truded down the valley of the Aire as far as Bingley, where its 

 terminal moraine is thrown across the valley like a great dam, 

 reminding one of similar moraine dams in several Pennsylvania 

 valleys. A continuous moraine was traced around this Aire 

 glacier. Another great glacier, much larger than this, de- 

 scended Wensleydale and reached the plain of York. The 

 most complex glacial movements in England occurred in the 

 mountain region about the Nine Standards, where local glaciers 

 met and were overpowered liy the greater ice-sheet coming 

 down from Cumberland. The ice-sheet itself w.as here divided, 

 one portion going southward, the other in company with local 

 glaciers and laden with the well-known boidders of " Shap 

 granite " being forced eastward across Stainmoor Forest into 

 Durham and Yorkshire, finally reaching the North Sea at the 

 mouth of the Tees. The terminal moraine runs eastward 

 through Kirkby Raven-.\\ orth, toward Whitby, keeping north 

 of the Cleveland Hills, and all Eastern England south of 

 Ilolderness appears to be non-glaciated. On the other hand, all 

 England north of Stainmoor Forest and the River Tees, except 

 the very highest points, was smothered in a sea of solid ice. 



