502 A. Blytt on the probable Cause of 



English deposits as described by J. Geikie (' Great Ice Age,' 

 ed. 2, pp. 387 et seqq.) as our guide. 



Tiie Quaternary period commences with the retrogression 

 of the ice and with a considerable denudation. Then the sea 

 again rose and covered a grent part of the east of England. 

 The inland ice again extended itself and formed a bottom- 

 moraine, " the great chalky boulder-clay " (arc V). After 

 this glacial period an elevation of the land seems to have fol- 

 lowed, and the ice retreated. But a new depression followed 

 (Bridlington Crag) and a new glacial period (purple boulder- 

 clay, arc 2"). A frosh elevation seems to have followed, with 

 a new interglacial period. Then came a new depression, which 

 was very considerable, and which at Moel Tryfaen in Wales, 

 at Macclesfield, and in Ireland has left marine shells at heights 

 of 1000 to 1300 feet above the sea (nearly__approaching that 

 at which the old " seter " or beach-lines in Osterdalen, Ljssje, 

 &c. occur). Like the preceding depression, this was also 

 followed by a glacial period, the last (Hessle boulder-clay, 

 arc 3"). Finally the land rose and the ice melted. The 

 Postgbicial period came with its four peat-beds (the last 

 portion of 3 ' and 4"). To arc 4" corresponds a small oscil- 

 lation of the sea innnediately before the recent period. In 

 Scania, Garavallen,a raised beach-formation, rests upon peat; 

 in Gotland, in the British Islands (Carse Clay, &c.),and even 

 in North America, we may trace the same oscillation of the 

 sea ; it was no doubt too great to be capable of explanation by 

 local conditions, compression of peat-beds by shifting sand- 

 dunes, &c. 



We have already seen that the land (according to Howorth 

 and Suess) in many places under high latitudes rose consider- 

 ably in the Postglacial period, and that a corresponding 

 depression took place in the warm coral-seas. The last oscil- 

 lations therefore affected a great part of the earth. From this 

 we may conclude that this was the case also with the oscilla- 

 tions of former times, and that they have their cause in general 

 cosmical conditions. The small oscillation (arc 4'') forms 

 an interruption in this great upheaval under high latitudes. 

 A similar interruption of the depression, if our theory be 

 correct, must be exhibited under the tropics ; and in reality 

 in the equatorial parts both of America and the Old World, 

 there are numerous evidences of such a small postglacial 

 oscillation in coral-reefs, which have been upraised several 

 metres and are now lying dry (see Suess, AntUtz der Erde, 

 ii. pp. 630 et setjg.). These coral-reefs may date from the 

 same time when the northern peat-beds were submerged. The 

 sunken peat-beds with the marine deposits formed during the 



