QUATERNARY DEPOSITS OF BRITISH ISLES — BROOKS. 289 



extent of the ice in Holland, is the equivalent of the lower glacial or 

 first glaciation, of the north German plain ; the gray clay overlying 

 the Eem bed is thus the representative of the middle glacial, or 

 second glaciation, while the ice of the upper glacial or third glacia- 

 tion does not appear to have reached Holland. 



F, Schucht (24) considers that the Lauenburg clay forms a good 

 horizon for the correlation of the German and Dutch Quaternary. 

 At various points in the Elbe valley and north toward Holstein the 

 oldest glacial deposits are covered by sand, passing up into a thick, 

 black clay, which he regards as a product of ice melting. Above this 

 conies the Eem zone and the middle glacial. The Lauenburg clay 

 can be traced into Friesland, where it occupies the same position be- 

 tween two bowlder clays. It helps to confirm the inferences drawn 

 from the position of the Eem beds. 



RELATIONS TO RHINE TERRACES. 



The relations of these two bowlder clays to the Rhine terraces 

 must now be worked out; they will be of considerable importance 

 later in correlating the Fennoscandian and Alpine glaciations. The 

 study of this question is not facilitated by the awkward nomenclature 

 given to the Ehine terraces by the German geologists. The best 

 classification appears to be the fourfold one adopted by Fliegel (25). 



1. Oldest Quaternary gravels, forming the highest terraces (sometimes 



two or three) more than 100 meters above the present Rhine bed. 



2. Chief terrace, sometimes termed " high terrace," especially by Dutch 



geologists, but higher than, and to be carefully distinguished from 

 the " high terrace " as defined by Steinmann. 



8. Middle terrace, including the terrace or terraces between the chief 

 terrace and the low terrace. Steinmann's " high terrace " is in- 

 cluded among these, as Fliegel considers it to have a pui-ely local 

 value. This inclusive term " middle terrace " seems most satis- 

 factory, as being least likely to lead to confusion. 



4. Low terrace, 8 to 30 meters above the Rhine bed. 



In the Ehine gorge near Coblentz the oldest gravels lie at a higher 

 level than the chief terrace, but farther north they descend to the 

 same level and are overlain by them. In the same way the continu- 

 ation of the high terrace is overlain by sands which upstream pass 

 into the low terrace ; the middle terrace, however, seems to die out. 



The Ehine terraces between Bonn and the sea were studied in 

 great detail l)y J. Lorie (26). We are only concerned here with 

 those on the right bank, which he describes as follows : 



The chief terrace is not the oldest, but above it, at Bonn, Pohlig 

 discovered in 1883 an older gravel, lying at 210 to 215 meters above 

 sea level ; it is very much broken up, and can not be traced south of 

 the Brohl Valley or north of the Ahr Valley. Near Brohl it lies at 

 260 to 270 meters. 



