Clare Island Survey — Geology. 7 19 



" head " or scree. The evidence does not preclude the possibility that in 

 the short time that elapsed between the formation of the beach and the 

 Glacial Epoch the land stood much higher than it does at present. Indeed, 

 as, at its present level, the " head " is being rapidly eroded by the action of 

 the waves, it is probable ; as suggested by Messrs. Wright and Maufe, that it 

 did stand higher while the deposit was being accumulated. 



Another reason for supposing that in late pre- Glacial times the sea and 

 land occupied about the same relative positions in the Irish area as they do 

 now, is the presence of marine shells in the boulder-clays of Clare Island, 

 north Mayo, and various localities in the east of Ireland. As the shells are 

 found, with respect to the main ice-current, only on the down-stream side of 

 existing arms of the sea, the inference is that during the period of maximum 

 giaciation, or, at least, at a short time previous to that episode, the sea still 

 •occupied the present basins. 



Whether the Irish land occupied a higher level when the giaciation was 

 most intense, no local evidence entitles us to say ; but such slender informa- 

 tion as is obtainable from the geological records in places outside this area 

 points to an elevation of the whole of north-western Europe at that time. 

 Many of the land valleys of this region, which run down to the existing 

 coast-lines, have been traced out to sea for considerable distances, and as the 

 portions of them now above the sea-level have obviously been fashioned into 

 their present form under aerial conditions, their submerged prolongations 

 must have been formed in the same manner. But although this considera- 

 tion shows that the area was considerably higher at some comparatively 

 recent period, it does not very definitely fix the date as that of the Glacial 

 Epoch. Surer evidence of such a glacial elevation is furnished by dredgings 

 of dead littoral shells from considerable depths in the seas round the British 

 Isles, Faroe Islands, and off the coast of Norway, and the distribution, at 

 great depths in the floor of the North Atlantic, of dead shells of the shallow 

 water arctic species associated with the Yoldia Clay deposit. 



The subsequent movements of the earth's crust in north-western Europe, 

 at the close of and since the Glacial Epoch, can best be studied in the Baltic 

 area, where so many natural records of the fluctuations of the relative level 

 of sea and land have been preserved. From the evidence there obtainable, it 

 would appear that the fading of the general ice-cap was accompanied by a 

 depression of the land in the Scandinavian area. The southern portion of 

 that peninsula sank and admitted the sea, which spread over a great part of 

 the Swedish plains. This sheet of water, known as the Yoldia Sea, connected 

 the Skager Bak with the Gulf of Bothnia, and extended over Finland as far 



