QUATERNARY DEPOSITS OF BRITISH ISLES — BROOKS. 293 



posited. It was, however, still considerably above its present level, 

 especially in the north, where the ground moraine is succeeded by 

 peat deposits and not by clays with arctic Mollusca. After the cli- 

 mate had again become temperate, however, still further subsidence 

 occurred, and the Eem clays were deposited, characterized by Tapes 

 aureus var. eemiemis. The upper part of the chief terrace appears 

 to have been deposited during this submergence, as marine shells are 

 mixed with the gravels. In the Gelder this subsidence was followed 

 by elevation, for the Eem beds are overlain by peat, and this again 

 by a bowlder sand of glacial origin. (Lorie, 1906.) 



After the formation of the chief terrace there followed a consid- 

 erable period of elevation and denudation in the middle Rhine, dur- 

 ing which the river deepened its bed at Bonn by more than 100 

 meters. In the lower Rhine the elevation, though less marked, was 

 probably still noticeable, for there is a total absence of aqueous de- 

 posits between the Eem beds and a bed of sand equivalent to the 

 lower terrace. 



Third glacial. — The ice during this period failed to cross the 

 Yssel River, and in the western part of the country the glaciation is 

 represented only by occasional beds of sand. In the Yssel Valley 

 the terminal moraines of this glaciation rest on and disturb the ter- 

 race corresponding to the chief terrace of the Rhine, and according 

 to Van Baren, also rest on the equivalent of the middle terrace; we 

 may therefore consider the middle terrace as contemporaneous with 

 the first part of this glacial period, indicating subsidence at the be- 

 ginning, but elevation at the end of the period. 



No deposits are known in Holland belonging to the third inter- 

 glacial. The land ice of the fourth glaciation did not reach Holland 

 or the Rhine Valley, but by analogy with the chief and middle ter- 

 races, the lower terrace is attributed to this glaciation. 



This succession does not by any means agree with the classification 

 adopted by various Dutch and German geologists, so I will briefly 

 discuss the latter. 



Lorie, assuming that in north Germany the middle glaciation was 

 the greatest, correlates with it the maximum glaciation of Holland 

 and consequently also the Rhine chief terrace, thus making the 

 middle and lower terraces both correspond to the last glaciation, 

 and the lower Rhine diluvium to the lower glacial of Germany. The 

 position of the Eem beds is sufficient to disprove this scheme. 



P. G. Krause discovered at various points in the chief terrace clay 

 and sand beds containing a small mammalian and molluscan fauna, 

 which he regarded as interglacial and of the same age as the Tegelen 

 flora, so that the chief terrace represents both the first and second 

 glaciations of the Alps. Tesch, however, pointed out (31) that the 



65133°— sm 1917 20 



