290 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1917. 



The chief terrace on the right bank of the Rhine lies at irregular 

 heights, but the normal highest points rise upstream as follows : Ding- 

 den, 54 meters; Wesel, 70 meters (or 54 meters above the Rhine); 

 Bottrop, 81.5 meters (60 meters above) ; Duisburg, 95 meters (73 

 meters) ; Diisseldorf, 120 meters (90 meters) ; Keulen, 144 meters 

 (106 meters) ; Bonn, 183 meters (136 meters above the Rhine). 



The breadth of the high terrace varies from 3.5 to 15 kilometers; 

 its western edge is always easy to follow as a clear slope, but rarely 

 as a definite cliff, except near Diisseldorf. 



The middle terrace lies with its upper surface at Sieg at 59 meters 

 and at Obercasscl, above Bonn, at 62 meters. 



The low terrace lies at Dingden at 30 meters, at Sterkrade at 31 

 meters, at Duisberg at 33 meters, at Diisseldorf at 40 meters, and at 

 Bonn at 52 meters. 



As a result of his studies of borings Lorie found evidence of nu- 

 merous changes of (lie channel of the stream, and of a considerable 

 sinking of the floor. 



The moraine of the maximum glaciation (lower diluvium of north 

 Germany) crosses the Rhine Valley only between Crefeld and 

 Nijmengen; here it underlies the gravels of the chief terrace (25, 20), 

 but overlies and disturbs gravels of an old delta of the Rhine and 

 Mouse (Van Baren, 1908). Farther north the gravels of the chief 

 terrace are mixed with marine shells as well as with northern bowl- 

 ders, indicating that at this point they are of fluvio-marine origin. 

 From this it follows that the chief terrace falls in the Eem inter- 

 glacial, between the lower and middle glacial of Germany, as well 

 as at the conclusion of the preceding or lower glacial. 



The equivalent of the middle glacial, the gray clay of the region 

 east of the Yssel, rests on and disturbs the terrace on the east bank 

 of this river corresponding to the chief terrace of the Rhine (20) ; 

 similarly the middle glacial rests on and disturbs the chief terrace 

 of the Rhine north of Crefeld, forming terminal moraines which 

 indicate the limit of the ice (25). 



When the chief terrace and the higher upper terraces are traced 

 northward through Holland, they converge and descend below sea 

 level, so that they lie in the same vertical sequence, and the chief 

 terrace, being the younger, overlies the equivalent of the upper 

 terraces. Between the two occur clayey beds and peat with a tem- 

 perate fauna and flora, well known under the term " Tegelen stage," 

 first described by E. Dubois (27) at Tegelen on the Meuse as an 

 interglacial formation overlain by fluvio-glacial gravels correspond- 

 ing to the chief terrace of the Rhine and underlain by still older 

 fluvio-glacial gravels. In the following years various Dutch and 

 German geologists found equivalents of the Tegelen stage at various 



